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Luciaphorus perniciosus Rack is one of the most serious pests of several cultivated mushroom species including Ganoderma lucidum (Fr.), Flammulina velutipes Karst., Auricularia polytricha (Mont.) Saac., Lentinus polychrous Lev., and Lentinus squarrosulus (Mont.) Singer in Thailand. Adult female Lu. perniciosus produce offspring inside their physogastric hysterosomas, with all embryos developing through to the adult stage while remaining in the abdomen. Once the abdomen ruptures, the female parent dies and the offspring consisting of mostly fertilized female adults along with a few male adults continue to emerge from the cadaver of the mother for a period of several days. This peculiar type of reproduction after the death of the mother is a special case for life table analysis and has not been discussed previously in demographic analyses. In this study, the life table data of this mite fed on Le. squarrosulus were collected at 25, 30, and 35 °C and analyzed by using the age-stage, two-sex life table. The standard errors of population parameters were estimated by using the bootstrap technique (200,000 bootstraps). At 25, 30, and 35 °C, females started reproduction at ages 9, 5, and 3 d, respectively; the net reproductive rates (R0) were 192.27, 253.81, and 234.11 offspring. Due to their rapid development and high fecundity, the r values were as high as 0.4189, 0.8653, and 1.0892 d–1 at 25, 30, and 35 °C, respectively. Computer projection indicated that the mushroom mites Lu. perniciosus is capable of a threefold daily increase at 35 °C.
Sericulture was developed in China in ancient times. Antheraea pernyi Guérin-Méneville was domesticated at least 2,000 yr ago, and Chinese farmers developed artificial rearing of A. pernyi before the 17th century. Today, >60,000 tons of cocoons are produced in China each year, which accounts for 90% of the world production. Despite the widespread utilization of A. pernyi in China and a long history of domestic research, the knowledge of A. pernyi outside China is limited. Therefore, we have in this paper summarized the production, usage, and breeding of A. pernyi. The foremost usage of A. pernyi is as silk producers; however, about 55–70% is used for other purposes. In this paper, we give examples of how the different developmental stages are used as a food source for human consumption and in traditional Chinese medicine, both directly in different preparations and also as a nutrient source for rearing medicinal fungi.
Preservation of honey bee (Apis mellifera L., Hymenoptera: Apidae) sperm, coupled with instrumental insemination, is an effective strategy to protect the species and their genetic diversity. Our overall objective is to develop a method of drone semen preservation; therefore, two experiments were conducted. Hypothesis 1 was that cryopreservation (–196 °C) of drone semen is more effective for long-term storage than at 16 °C. Our results show that after 1 yr of storage, frozen sperm viability was higher than at 16 °C, showing that cryopreservation is necessary to conserve semen. However, the cryoprotectant used for drone sperm freezing, dimethyl sulfoxide (DMSO), can harm the queen and reduce fertility after instrumental insemination. Hypothesis 2 was that centrifugation of cryopreserved semen to reduce DMSO prior to insemination optimize sperm quality. Our results indicate that centrifuging cryopreserved sperm to remove cryoprotectant does not affect queen survival, spermathecal sperm count, or sperm viability. Although these data do not indicate that centrifugation of frozen-thawed sperm improves queen health and fertility after instrumental insemination, we demonstrate that cryopreservation is achievable, and it is better for long-term sperm storage than above-freezing temperatures for duration of close to a year.
A genetic stock identification (GSI) assay was developed in 2008 to distinguish Russian honey bees from other honey bee stocks that are commercially produced in the United States. Probability of assignment (POA) values have been collected and maintained since the stock release in 2008 to the Russian Honey Bee Breeders Association. These data were used to assess stability of the breeding program and the diversity levels of the contemporary breeding stock through comparison of POA values and genetic diversity parameters from the initial release to current values. POA values fluctuated throughout 2010–2016, but have recovered to statistically similar levels in 2016 (POA(2010) = 0.82, POA(2016) = 0.74; P= 0.33). Genetic diversity parameters (i.e., allelic richness and gene diversity) in 2016 also remained at similar levels when compared to those in 2010. Estimates of genetic structure revealed stability (FST(2009/2016) = 0.0058) with a small increase in the estimate of the inbreeding coefficient (FIS(2010) = 0.078, FIS(2016) = 0.149). The relationship among breeding lines, based on genetic distance measurement, was similar in 2008 and 2016 populations, but with increased homogeneity among lines (i.e., decreased genetic distance). This was expected based on the closed breeding system used for Russian honey bees. The successful application of the GSI assay in a commercial breeding program demonstrates the utility and stability of such technology to contribute to and monitor the genetic integrity of a breeding stock of an insect species.
The conservation of bee populations for pollination in agricultural landscapes has attracted a lot of recent research interest, especially for crop industries undergoing expansion to meet increased production demands. In Canada, much growth has been occurring with commercial cranberry production, a field crop which is largely dependent on bee pollination. Wild bee pollinators could be negatively impacted by losses of natural habitat surrounding cranberry fields to accommodate increased production, but growers have little insight on how to manage their lands to maximize the presence of wild bees. Here, we described a 2-yr study where bee diversity and species composition were investigated to better understand the dynamic between natural habitat and cranberry fields. Bees were sampled using pan-traps and hand netting both within cranberry fields and in one of the three adjacent natural habitat types once a week during the crop flowering period. We found that bee community composition among cranberry fields did not differ based on the respective adjacent habitat type, but fields bordered by meadows were marginally less diverse than fields bordered by forest. As one would expect, field and natural habitat communities differed in terms of species composition and species richness. There was no evidence that one type of natural habitat was more favorable for the bees than another. Future agrobiodiversity studies should simultaneously examine bee diversity comprised in both crop fields and adjacent natural environments to better understand the species dynamics essential to the preservation of pollination services.
Plant viruses may indirectly affect insect vector behavior and fitness via a shared host plant. Here, we evaluated the host-mediated effects of Squash vein yellowing virus (SqVYV) on the behavior and fitness of its whitefly vector, Bemisia tabaci (Gennadius) Middle East-Asia Minor 1, formerly biotype B. Alighting, settling, and oviposition behavioral assays were conducted on infected and mock-inoculated squash (Cucurbita pepo L.) and watermelon [Citrullus lanatus (Thunb) Matsum and Nakai] plants. Developmental time of immature stages, adult longevity, and fecundity were measured on infected and mock-inoculated squash plants. For adult longevity and fecundity, whiteflies were reared on infected and mock-inoculated squash plants to determine the effects of nymphal rearing host on the adult stage. More whiteflies alighted and remained settled on infected squash than on mock-inoculated squash 0.25, 1, 8, and 24 h after release. No such initial preference was observed on watermelon plants, but by 8 h after release, more whiteflies were found on mock-inoculated watermelon plants than on infected plants. Whiteflies laid approximately six times more eggs on mock-inoculated watermelon than on infected watermelon; however, no differences were observed on squash. Development from egg to adult emergence was 3 d shorter on infected than mock-inoculated squash plants. Females lived 25% longer and had higher fecundity on infected squash plants than on mock-inoculated plants, regardless of infection status of the rearing host. The host-mediated effects of SqVYV infection on whitefly behavior differ on two cucurbit host plants, suggesting the potential for more rapid spread of the virus within watermelon fields.
Long-term feeding effects of the almond pollen on the life table parameters of Neoseiulus californicus McGregor were assessed after 5, 10, and 20 generations after introduction in the rearing arena. Furthermore, to evaluate behavioral characteristics of the mass-reared predator (strain A) in face with the real prey, functional and numerical responses of the predator to different densities of the twospotted spider mite nymphs were determined, and the obtained data were compared with those reared on twospotted spider mite (strain T). Long-term rearing did not significantly affect total fecundity of N. californicus (ranged from 37.79 to 41.91 eggs). Nevertheless, preadult duration in the 5th generation was significantly longer than the 10th and 20th generations. The intrinsic rate of increase (r) in the 10th (0.2056 d–1) and 20th (0.2201 d–1) generations had not significant difference together. However, the r value slightly dropped in the 5th generation (0.1706 d–1) because of the irregular offering of fresh pollen to the rearing colonies before that. Both strains of N. californicus exhibited a type II functional response; however, the N. californicus reared on the almond pollen (strain A) had a higher attack rate (a) and shorter handling time (Th). The individuals reared on the almond pollen had a greater size than those reared on twospotted spider mite; its higher predation potential is probably due to this characteristic. Consequently, the rearing of N. californicus on the almond pollen positively affected its attributes including high survivorship, body size, and fecundity, and subsequently higher potential to control twospotted spider mite.
In several insect systems, fungal entomopathogens synergize with neonicotinoid insecticides which results in accelerated host death. Using the Asian longhorned beetle, Anoplophora glabripennis (Motschulsky), an invasive woodborer inadvertently introduced into North America and Europe, we investigated potential mechanisms in the synergy between the entomopathogenic fungus Metarhizium brunneum Petch and the insecticide imidacloprid. A potential mechanism underlying this synergy could be imidacloprid's ability to prevent feeding shortly after administration. We investigated whether starvation would have an impact similar to imidacloprid exposure on the mortality of fungal-inoculated beetles. Using real-time PCR to quantify fungal load in inoculated beetles, we determined how starvation and pesticide exposure impacted beetles' ability to tolerate or resist a fungal infection. The effect of starvation and pesticide exposure on the encapsulation and melanization immune responses of the beetles was also quantified. Starvation had a similar impact on the survival of M. brunneum-inoculated beetles compared to imidacloprid exposure. The synergy, however, was not completely due to starvation, as imidacloprid reduced the beetles' melanotic encapsulation response and capsule area, while starvation did not significantly reduce these immune responses. Our results suggest that there are multiple interacting mechanisms involved in the synergy between M. brunneum and imidacloprid.
The mitogen-activated protein kinases (MAPKs) are conserved signal transduction pathways and broadly responsible for bacterial infection from yeast to mammals, and virus, fungi, and bacteria, specifically Bacillus thuringiensis, to insects. But little is known about the MAPK pathways in antibacterial responses in Chilo suppressalis (Walker), an important lepidopteran pest of rice. In this study, we used the bacteria of Bacillus thuringiensis, Escherichia coli, and Staphyloccocus aureus to infect C. suppressalis larvae, and the responses of MAPK pathways were analyzed. The results showed that E. coli infection induced the up-regulated expression of Csp38 and CsERK1 at 24 h postinfection (pi). Meanwhile, injection of B. thuringiensis and S. aureus resulted in strong activation of CsJNK phosphorylation at 3 h pi. These results suggest that MAPK signaling pathways play important functional roles in antibacterial responses in C. suppressalis larvae.
This study describes four multiple nucleocapsid nucleopolyhedrovirus isolates recovered from infected larvae of beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), on crops in two different geographical regions of Mexico. Molecular and biological characterization was compared with characterized S. exigua multiple nucleopolyhedrovirus (SeMNPV) isolates from the United States (SeUS1 and SeUS2) and Spain (SeSP2). Restriction endonuclease analysis of viral DNA confirmed that all Mexican isolates were SeMNPV isolates, but molecular differences between the Mexican and the reference isolates were detected using PCR combined with restriction fragment length polymorphism (RFLP). Amplification of the variable region V01 combined with RFLP distinguished the two Mexican isolates, SeSLP6 and SeSIN6. BglII digestions showed that the majority of the isolates contained submolar bands, indicating the presence of genetic heterogeneity. Amplification of the variable regions V04 and V05 distinguished between American and the Spanish isolates. Biological characterization was performed against two laboratory colonies of S. exigua, one from Mexico, and another from Switzerland. Insects from the Mexican colony were less susceptible to infection than insects from Se-Swiss colony. In the Se-Mex colony, SeSP2 was the most pathogenic isolate followed by SeSIN6, although their virulence was similar to most of the isolates tested. In Se-Swiss colony, similar LD50 values were observed for the five isolates, although the virulence was higher for the SeSLP6 isolate, which also had the highest OB (occlusion body) yield. We conclude that the Mexican isolates SeSIN6 and SeSLP6 possess insecticidal traits of value for the development of biopesticides for the control of populations of S. exigua.
Exorista larvarum (L.) is a tachinid parasitoid native to the Palearctic region, known as an antagonist of lepidopterous defoliators. This species is suitable to be cultured in vitro, and yields of fecund adults, approaching those usually attained in host larvae, have been previously achieved on artificial media. Direct oviposition by E. larvarum on media has not yet been obtained, and the eggs for the in vitro rearing are routinely removed from parasitized host larvae. However, many eggs are usually laid throughout the cage by captive females and can be retrieved by placing them on artificial media. Storage at low temperatures provides a method for prolonging the development of insects and stockpile them when not needed immediately. We studied the effects of storage at 20 °C (for 5 d or until pupation) or 15 °C (for 5 d or until egg hatching) on the in vitro development of E. larvarum. Lower temperatures were excluded, because previous studies showed a strong negative impact on hatching when the eggs were stored at 5 °C or 10 °C. For the experiments, eggs were removed from hosts and placed on an artificial medium. The results suggested that it is possible to delay the development of the in vitro-reared E. larvarum, which eventually reached the adult stage, although some negative effects on fly quality (i.e., longevity and fecundity) were also observed. Because quality is not an absolute concept, all the situations tested in this study could be appropriate according to the current requirements.
The genetically modified strain of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) VIENNA 8 1260, was developed from the genetic sexing strain VIENNA 8. It has two molecular markers that exhibit red fluorescence in the body and green fluorescence in testis and sperm. These traits offer a precise tool to discriminate between mass-reared and wild males, increasing the effectiveness of sterile insect technique. The reproductive performance of the VIENNA 8 1260 and VIENNA 8 D53- (without the D53 inversion introduced to prevent recombination) was compared at different irradiation doses. The general effect of irradiation on VIENNA 8 1260 followed the same patterns documented in previous publications for VIENNA 8 D53-. Irradiation doses of 80 Gray or greater reduced fertility and induced high levels of sterility in wild females. Fecundity reduction was higher in VIENNA 8 1260 than in VIENNA 8 D53- females. Vertical transmission of the fluorescence gene was confirmed up to the F4 generation. Substerilization in the VIENNA 8 1260 could jeopardize the usefulness of the transgenic strain due to the possible vertical transfer of the fluorescence transgene from the sterile males to the wild flies. A biologically safe higher irradiation dose could result in reduced competitiveness of the VIENNA 8 1260 strain. Mating and remating experiments suggest that Mediterranean fruit fly females exhibit a relative precedence in the use of the sperm: though both sperms are mixed, sperm from the remating is spent first. Results suggest a lower fitness of VIENNA 8 1260 sperm, when compared with sperm from a nonfluorescent bisexual strain, which is consistent with the lower reproductive performance documented for the VIENNA 8 1260 strain.
Roger I. Vargas, Steven K. Souder, Joseph G. Morse, Elizabeth E. Grafton-Cardwell, David R. Haviland, John N. Kabashima, Ben A. Faber, Bruce Mackey, Eddie Nkomo, Peter J. Cook, John D. Stark
Degradation models for multilure fruit fly trap dispensers were analyzed to determine their potential for use in large California detection programs. Solid three-component male lure TMR (trimedlure [TML], methyl eugenol [ME], raspberry ketone [RK]) dispensers impregnated with DDVP (2, 2-dichlorovinyl dimethyl phosphate) insecticide placed inside Jackson traps were weathered during summer (8 wk) and winter (12 wk) in five citrus-growing areas. Additionally, TMR wafers without DDVP, but with an insecticidal strip, were compared to TMR dispensers with DDVP. Weathered dispensers were sampled weekly and chemically analyzed. Percent loss of TML, the male lure for Ceratitis capitata (Wiedemann) Mediterranean fruit fly; ME, the male lure for Bactrocera dorsalis (Hendel), oriental fruit fly; RK, the male lure for Bactrocera cucurbitae (Coquillett), melon fly; and DDVP was measured. Based on regression analyses for the male lures, TML degraded the fastest followed by ME. Degradation of the more chemically stable RK was discontinuous, did not fit a regression model, but followed similar seasonal patterns. There were few location differences for all three male lures and DDVP. Dispensers degraded faster during summer than winter. An asymptotic regression model provided a good fit for % loss (ME, TML, and DDVP) for summer data. Degradation of DDVP in TMR dispensers was similar to degradation of DDVP in insecticidal strips. Based on these chemical analyses and prior bioassay results with wild flies, TMR dispensers could potentially be used in place of three individual male lure traps, reducing costs of fruit fly survey programs. Use of an insecticidal tape would not require TMR dispensers without DDVP to be registered with US-EPA.
The black soldier fly, Hermetia illucens (L.), shows potential as a resource for animal feed. However, industrial production in regions where the insect is not native, like northwestern Europe, could lead to permanent establishment, which might entail environmental risks. In temperate climates, establishment depends on the insect's ability to overwinter. This study assessed the insect's cold hardiness by determining the supercooling point (SCP) and lower lethal time at 5 °C (LTime10,50,90) for different life stages. As diet or acclimation can influence cold hardiness, prepupae reared on different substrates and acclimated prepupae were tested in separate experiments. The SCP ranged from –7.3 °C for late-instar larvae to –13.7 °C for pupae. Prepupae reared on a highly nutritional substrate had a lower SCP compared with a control diet composed of chicken feed (–14.1 °C vs. –12.4 °C, respectively), whereas the SCP was unaffected by acclimation. Based on the LTime, prepupae and pupae were the most cold hardy life stages. Acclimated prepupae were most cold tolerant, with a LTime50 of 23 d. Based on an empirical relationship between LTime50 and field survival of various arthropods, it was predicted that H. illucens would survive about 47 d in the field during northwestern European winters. The results from this laboratory study suggest that H. illucens is rather unlikely to overwinter in northwestern Europe. However, caution is warranted given that diet and acclimation can influence the insect's cold hardiness and in the field the insect may survive in a diapausing state or in protected hibernacula.
This field study of codling moth, Cydia pomonella (L.), response to single versus multiple monitoring traps baited with codlemone demonstrates that precision of a given capture number is alarmingly poor when the population is held constant by releasing moths. Captures as low as zero and as high as 12 males per single trap are to be expected where the catch mode is three. Here, we demonstrate that the frequency of false negatives and overestimated positives for codling moth trapping can be substantially reduced by employing the tactic of line-trapping, where five traps were deployed 4 m apart along a row of apple trees. Codling moth traps spaced closely competed only slightly. Therefore, deploying five traps closely in a line is a sampling technique nearly as good as deploying five traps spaced widely. But line trapping offers a substantial savings in time and therefore cost when servicing aggregated versus distributed traps. As the science of pest management matures by mastering the ability to translate capture numbers into estimates of absolute pest density, it will be important to employ a tactic like line-trapping so as to shrink the troublesome variability associated with capture numbers in single traps that thwarts accurate decisions about if and when to spray. Line-trapping might similarly increase the reliability and utility of density estimates derived from capture numbers in monitoring traps for various pest and beneficial insects.
The Euwallacea sp. near fornicatus (Euwallacea sp. 1 hereafter) feeds on many woody shrubs and trees and is a pest of avocado, Persea americana Mill., in several countries including Israel and the United States. Quercivorol baits are commercially available for Euwallacea sp. 1 females (males do not fly), but their attractive strength compared to other pheromones and potential for mass trapping are unknown. We used sticky traps baited with quercivorol released at 0.126 mg/d (1×) and at 0.01×, 0.1×, and 10× relative rates to obtain a dose–response curve of Euwallacea sp. 1 attraction. The curve fitted well a kinetic formation function of first order. Naturally infested limbs of living avocado trees had attraction rates equivalent to 1× quercivorol. An effective attraction radius (EAR) was calculated according to previous equations for each of the various baits (1× EAR = 1.18 m; 10× EAR = 2.00 m). A pole with six sticky traps spaced from 0.25–5.75 m in height had captures of Euwallacea sp. 1 yielding a mean flight height of 1.24 m with vertical flight distribution SD of 0.88 m (0.82–0.96 m, 95% CI). The SD with specific EAR was used to calculate EARc, two-dimensional EAR (1× EARc = 0.99 m; 10× EARc = 2.86 m), for comparison with other insect pheromone traps and for use in simulations. The simulation methods described previously were performed with combinations of 1–16 traps with 1–50 aggregations per 9-ha plot. The simulations indicate mass trapping with quercivorol could be effective if begun in spring before Euwallacea sp. 1 establishes competing sources of attraction.
Different concentrations of sucrose were used to investigate how survival and feeding was affected in four species of aphids (Hemiptera: Aphididae). Seven sucrose concentrations were evaluated in feeding chambers fitted with parafilm membranes and infested with nymphs of Aphis glycines Matsumura, Diuraphis noxia Kurdjumov, Myzus persicae Sulzer, or Schizaphis graminum Rondani at 25 °C and a photoperiod of 14:10 (L:D) h. Survival on each diet was recorded 1, 3, 5, 7, 9, and 11 d. Diet volumes (µl) consumed and amounts of honeydew produced were then determined. Aphid survival differed significantly by concentration, time (d), and aphid species. Aphis glycines survival was highest (83.8%) on 30% sucrose although percent survival in the 70's occurred on concentrations ranging from 15–25%. Diuraphis noxia survival was highest on the 15 and 20% sucrose concentrations. Survival for Myzus persicae was optimal on 20% sucrose (92%) but did not differ that much (5%) on concentrations of 15–35%. Schizaphis graminum survival (93.0–93.6%) was highest on sucrose concentrations ranging from 20–30% sucrose. Myzus persicae and S. graminum, which feed on a wide-range of host plants, were overall more adapted to feeding on a wider range of sucrose concentrations than the more host-restricted aphid species, A. glycines. Diet consumption by A. glycines did not vary on the sucrose concentrations, but D. noxia and M. persicae exhibited increased consumption on diets that provided optimal survival. Results will aid in the design of short-term studies using sucrose-only diets to evaluate effects of bioactive materials on aphid survival for up to 11 d.
Commercial production of Amblyseius swirskii Athias-Henriot based on storage mites needs both space and labor to maintain large cultures of these prey, and also may lead to health problems for workers. Therefore, the accessibility of a suitable artificial diet could eliminate the mentioned problems; however, the artificial diets must support the persistent production of high quality progeny. This study endeavored to find a more easily available and cheaper nutrient that may further reduce the cost of diet production for A. swirskii. The predator's performance was determined when it was fed on a basic artificial diet (AD1) composed of honey, sucrose, tryptone, yeast extract, and hen egg yolk, and on eight other artificial diets consisting of 80% AD1 enriched with different nutrients including maize pollen (AD2), hemolymph of Plusia gamma L. (AD3), Ephestia eggs (AD4), Artemis cysts (AD5), Ephestia last-instar larvae (AD6), multivitamin syrup (AD7), bovine serum albumin (AD8), and bull sperm (AD9). The lowest development time was on AD2. The highest value of fecundity and oviposition period were observed on AD5, followed by AD2 and AD4. The intrinsic rate of increase (r) and the finite rate of increase (λ) reached the maximal value on AD5. Feeding on AD2 and AD5 resulted in highest value of R0 (net reproductive rate). Our results indicated that Artemia cysts and maize pollen had better potential to be used as nutrient in artificial diet for mass production of A. swirskii. Overall, it seems that AD2 is the most cost effective than others.
Temperature has significant effects on the development, survival, and reproduction of ectothermic organisms. In this study, we examined the effect of temperature on the demographic characteristics of two predatory mite species, Neosciulus womersleyi (Schicha) and N. longispinosus (Evans), reared on Tetranychus urticae Koch. The developmental and reproductive traits of both species were examined at 10 constant temperatures between 15 °C and 37.5 °C. The preadult development time of N. womersleyi and N. longispinosus decreased with increasing temperature until 32.5 °C and 35 °C, respectively. The lower developmental threshold (T0) and thermal constant (K) estimated by using a linear model were 11.61 °C and 69.36 DD for N. womersleyi and 11.92 °C and 61.5 DD for N. longispinosus, respectively. Total preoviposition period and total longevity of females and males of N. womersleyi and N. longispinosus decreased with increasing temperature. The mean generation time (T) first decreased with temperature until 32.5 and 35 °C for N. womersleyi and N. longispinosus, respectively, and then increased at higher temperatures. The R0 and r values first increased with temperature until 32.5 and 30 °C for N. womersleyi and N. longispinosus, respectively, and then decreased at higher temperatures. The R0 and r values for N. longispinosus at 37.5 °C were 0.3 offspring and –0.143 d–1, respectively. These results show that N. longispinosus is less fit than N. womersleyi at 37.5 °C.
Recent concerns regarding the impact of traditional synthetic pesticides on nontarget organisms have generated demand for alternative products with lower environmental impact. This demand has led to increasing focus on plant essential oils as sources of new biopesticides. In this study, we demonstrate that the essential oil of the Alaskan yellow cedar, Cupressus nootkatensis (D. Don) Spach, has activity against hybrid imported fire ant workers, Solenopsis invicta Buren × Solenopsis richteri Forel. In digging assays, ants were repelled by nootka oil and digging continued to be suppressed by nearly 50% in nootka oil-treated sand aged 6 mo in the laboratory. Higher worker mortality was also observed in contact and fumigation assays compared to control checks. In a field drench test, mortality of mounds treated with nootka oil lagged behind mounds treated with bifenthrin treatment for 7 wk, but both nootka oil and bifenthrin had higher mortality than the untreated check at the end of the 12-wk evaluation period. In a band application evaluation, nootka oil plots maintained a 90–95% reduction in fire ant mounds from the 2nd to 17th wk, when new mounds began to intrude on the field plots. The quarantine-approved bifenthrin band treatment maintained 100% control from the 2nd to 24th wk. Although the formulation tested here did not perform to Federal Imported Fire Ant Quarantine standards, other formulations may enable this product to reach 100% control. In addition, nootka oil could be beneficial in situations where ant suppression rather than complete quarantine elimination is the management goal.
Sweet orange oil fractions were prepared by molecular distillation of cold-pressed orange oil from sample A (Citrus sinensis (L.) ‘Hamlin' from America) and sample B (Citrus sinensis Osbeck ‘Newhall’ from China) respectively, and their fumigant activities against medium workers of red imported fire ants (Solenopsis invicta Buren) were investigated. The volatile composition of the orange oil fractions was identified and quantified using GC–MS. Fractions from sample A (A1, A2, and A3) contained 23, 37, and 48 chemical constituents, and fractions from sample B (B1, B2, and B3) contained 18, 29, and 26 chemical constituents, respectively. Monoterpenes were the most abundant components, accounting for 73.56% to 94.86% of total orange oil fractions, among which D-limonene (65.28–80.18%), b-pinene (1.71–5.58%), 3-carene (0.41–4.01%), b-phellandrene (0.58–2.10%), and linalool (0.31–2.20%) were major constituents. Fumigant bioassay indicated that all orange oil fractions exerted good fumigant toxicity against workers of fire ants at 3, 5, 10, and 20 mg/centrifuge tubes, and B1 had the strongest insecticidal potential, followed by A1, B2, A2, B3, and A3. The fractions composed of more high volatile molecules (A1 and B1) showed greater fumigant effects than others. Compounds linalool and D-limonene, which were the constituents of the orange oil, exhibited excellent fumigant toxicity against red imported fire ant workers. Linalool killed red imported fire ant workers completely at 5, 10, and 20 mg/tube after 8 h of treatment, and D-limonene induced >86% mortality at 8 h of exposure.
A 2-yr study in cotton (Gossypium hirsutum L.) was conducted to determine the abundance and species composition of thrips (Thysanoptera: Thripidae) on different plant parts throughout the season in Alabama, Georgia, North Carolina, South Carolina, and Virginia. Plant parts sampled included seedlings, terminals with two expanded leaves, leaves from the upper, middle, and lower sections of the canopy, white flowers, and medium-sized bolls. Adult thrips were significantly more abundant on seedlings and flowers in 2014, and on flowers followed by seedlings and leaves from the middle canopy in 2015. Immature thrips were significantly more abundant on seedlings, followed by flowers in 2014, and on seedlings followed by leaves from the lower canopy and flowers in 2015. Across locations and plant parts, thrips consisted of Frankliniella tritici (Fitch) (46.8%), Frankliniella fusca Hinds (23.5%), Frankliniella occidentalis (Pergande) (17.1%), Neohydatothrips variabilis (Beach) (7.4%), Thrips tabaci (Lindeman) (1.8%), and other species (3.4%). Frankliniella fusca represented 86.7% of all thrips on seedlings, while F. tritici was more abundant on terminals (51.6%), squares (57.5%), and flowers (75.1%). Across all leaf positions, F. fusca was the most abundant species (28.8%), followed by F. tritici (19.2%), N. variabilis (18.8%), F. occidentalis (12.9%), and T. tabaci (5.2%), as well as other species (15.0%). As neonicotinoid insecticides remain a primary tool to manage seedling infestations of F. fusca, our data indicate that mid- to late-season applications of neonicotinoid insecticides targeting other insect pests will intensify selection pressure for resistance on F. fusca, the primary pest of seedling cotton.
The conservation of natural enemies is an important tactic to promote biological control of arthropod pests. The earwig Doru luteipes (Sccuder) is the most important predator of the fall armyworm Spodoptera frugiperda (J.E. Smith) in corn fields. One way of conserving these predators in the field is by using only selective insecticides when the pest population reaches the economic threshold. Some recent insecticides such as azadirachtin, chlorantraniliprole, and novaluron have been claimed to pose reduced risk for natural enemies. Nevertheless, there is a dearth of information regarding the selectivity of these insecticides upon earwigs in specific. In this study, we carried out a series of laboratory assays to examine the survivorship and locomotory behavior of D. luteipes after exposure to fresh dry residue of azadirachtin, chlorantraniliprole, and novaluron. Our results show a significant survival reduction for D. luteipes nymphs exposed to fresh residues of chlorantraniliprole and novaluron. In the behavioral studies, adults of D. luteipes stopped more often, spent more time resting (inactive), and moved more slowly immediately after exposure to chlorantraniliprole residue. These results suggest that chlorantraniliprole may mediate an impaired movement and a behavior arrestment of earwigs after contact with this insecticide fresh residue. This could translate into reduced foraging efficiency, and increase exposure and insecticide uptake. Although chlorantraniliprole and novaluron showed a potential to undermine the biological control provided by earwigs, it is yet essential to conduct field trials in order to confirm our laboratory results.
The Mythimna (=Leucania) loreyi (Duponchel) has recently emerged as a major pest of grain crops in China. Little is known about its basic biology and ecology, making it difficult to predict its population dynamics. An age-stage, two-sex life table was constructed for this insect when reared on maize in the laboratory at five constant temperatures (18, 21, 24, 27, and 30 °C). Both the intrinsic rate of increase (r) and finite rate increase (λ) increased as temperature significantly increased and mean generation time (T) decreased significantly with increasing temperature. The highest values for net reproductive rate (R0) and fecundity were observed at 24 °C. However, M. loreyi was able to develop, survive, and lay eggs at all temperatures tested (18–30 °C). Development rates at different temperatures for the egg, larval, pupal, as well as for a total preoviposition period, fit a linear equation. The lower threshold temperatures of egg, larval, pupal, preoviposition, and total preoviposition period were 8.83, 10.95, 11.67, 9.30, and 9.65 °C, respectively. And their effective accumulated temperatures were 87.64, 298.51, 208.33, 66.47, and 729.93 degree-days, respectively. This study provides insight into the temperature-based phenology and population ecology in M. loreyi. The results will benefit population dynamics monitoring, prediction, and management of this insect pest in the field.
A previously unknown bark beetle species, Acanthotomicus sp., has emerged as a lethal pest of American sweetgum (Liquidambar styraciflua) in China. Our survey of nursery records from around Shanghai suggests that American sweetgum have been under heavy attack since at least 2013, resulting in the death of > 10,000 trees. Mass attacks of the apparently sweetgum-specific Acanthotomicus sp. can be diagnosed by accumulation of resinous exudates on the trunk, wilted foliage, and eventual numerous exit holes of the new generation. A Chinese native sweetgum Liquidambar formosana can also be colonized by Acanthotomicus sp. This pest is of concern not only as a killer of sweetgum in the Chinese nursery trade but also as a potentially destructive invasive pest of sweetgum in North America. This discovery suggests that global preinvasion assessment of pests is warranted.
The invasive redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), vectors the fungal pathogen (Raffaelea lauricola) that causes laurel wilt, a disease responsible for widespread mortality of trees in the Lauraceae in the southeastern United States. Early detection of incipient vector populations may allow for management practices that could successfully mitigate damage. Developing new, highly effective attractants is a priority for improving sensitivity of early detection efforts. In this study, two field tests were conducted to evaluate combinations of commercially available bark and ambrosia beetle lures for enhanced attraction of host-seeking female X. glabratus. In addition, lures were compared for capture of nontarget scolytine beetles. In the first experiment, traps baited with a combination of cubeb oil, conophthorin, chalcogran, and ethanol captured greater numbers of X. glabratus than cubeb oil alone, the current standard attractant. However, this combination lure resulted in higher nontarget scolytine captures than with the cubeb lure. In the second field test, an oil enriched in the sesquiterpene α-copaene caught significantly more X. glabratus than other lures currently available for monitoring this pest. There were no differences in efficacy between cubeb oil lures produced by two different manufacturers, and a combination lure containing copaiba and cubeb oils did not increase captures over the cubeb lure alone. Results of these two tests suggest that increased sensitivity for detection of X. glabratus may be achieved with a multicomponent lure that incorporates α-copaene, spiroketals, and low release of ethanol.
The Coryphodema tristis (Drury) is an important pest of Eucalyptus nitens (Deane and Maiden) plantations in South Africa. The gregarious larvae of this pest cause damage by feeding on the tree sapwood, and adults emerge in spring each year. The aim of this study was to optimize pheromone traps for operational use in management programs. This was achieved by investigating different pheromone blend combinations and trap types for efficacy under field conditions. Our results confirm that the cross vane bucket funnel trap baited with a 95:2.5:2.5 volumetric blend of Z9-14:OAc, Z9-14:OH, and 14Ac was superior to similarly baited standard bucket funnel and delta traps. We also estimated the release rate and ratios of the pheromone compounds loaded into an artificial permeation dispenser through solid-phase microextraction sampling. Results showed that the released blend of pheromone compounds mirrored the dispensed ratios relatively accurately and that release rates are affected by temperature.
A recently discovered ambrosia beetle with the proposed common name of polyphagous shot hole borer (Euwallacea sp., Coleoptera: Curculionidae: Scolytinae), is reported to attack >200 host tree species in southern California, including many important native and urban landscape trees. This invasive beetle, along with its associated fungi, causes branch dieback and tree mortality in a large variety of tree species including sycamore (Platanus racemosa Nutt.). Due to the severity of the impact of this Euwallacea sp., short-term management tools must include chemical control options for the arboriculture industry and private landowners to protect trees. We examined the effectiveness of insecticides, fungicides, and insecticide–fungicide combinations for controlling continued Euwallacea sp. attacks on previously infested sycamore trees which were monitored for 6 mo after treatment. Pesticide combinations were generally more effective than single pesticide treatments. The combination of a systemic insecticide (emamectin benzoate), a contact insecticide (bifenthrin), and a fungicide (metconazole) provided some level of control when applied on moderate and heavily infested trees. The biological fungicide Bacillus subtilis provided short-term control. There was no difference in the performance of the three triazole fungicides (propiconazole, tebuconazole, and metconazole) included in this study. Although no pesticide combination provided substantial control over time, pesticide treatments may be more effective when trees are treated during early stages of attack by this ambrosia beetle.
In-field management of Bactrocera tryoni (Froggatt) and Zeugodacus cucumis (French) (Diptera: Tephritidae) in fruiting vegetable crops has relied almost exclusively on organophosphate cover sprays. Laboratory and semifield trials were performed to compare a number of alternative insecticides for efficacy against these species. A novel semifield method was used whereby the insecticides were applied to crops as cover sprays under field conditions, and treated plants bearing fruit were transferred to large cages and exposed to fruit flies. Efficacy was assessed in terms of numbers of pupae developing from treated fruit. A laboratory cage method was also used to assess effects on adult mortality and comparative effects of 1- and 3-d-aged residues. The neonicotinoids clothianidin and thiacloprid were very effective against B. tryoni and Z. cucumis. Clothianidin was the only insecticide other than dimethoate to affect adult mortality. The synthetic pyrethroid alpha-cypermethrin was also very effective, particularly in semifield trials, although higher incidence of aphid and whitefly infestation was observed in this treatment compared to others. Cyantraniliprole was effective against B. tryoni, but less effective against Z. cucumis. Imidacloprid, bifenthrin, spinetoram, and abamectin were all relatively less effective, although all demonstrated a suppressive effect.
Bradysia odoriphaga is frequently subjected to heat shock during the summer in China. Although the effects of heat shock on insect ecology and physiology have been widely explored, the effects of heat shock on the life history parameters of Bradysia odoriphaga are largely unknown. In the present study, we investigated the effects of heat shock on B. odoriphaga survival and reproduction as well as on offspring development and sex ratio. We exposed adult B. odoriphaga to 31, 33, 35, or 37 °C for different durations (from 0 to 120 min). The results showed that the survival of both sexes declined with the increase in temperature and exposure time, especially at 33, 35, and 37 °C. Longevity was markedly greater for males than females across all treatments. Fecundity generally declined as temperature and exposure time increased, and no eggs hatched when females were exposed to 37 °C for >75 min. The development of offspring larvae was significantly delayed when the parent female and male had been exposed to ≥31 °C for ≥30 min. In addition, the sex ratio of F1 progeny derived from heat-shocked parental adults was increasingly skewed to female as exposure time and temperature treatment increased. Overall, the results indicate that heat shock negatively influences B. odoriphaga.
Zebra chip is a potato disease transmitted by the potato psyllid Bactericera cockerelli (Šulc) and distributed across several regions of the United States. Because of its potentially devastating effects, the disease represents a threat to the potato production and the industry particularly in the Pacific Northwest, where it was first detected in 2011. Efforts to control the disease primarily focus on managing the vector using pesticides. In this study, the effectiveness of two pesticide spray programs in 2012 (“FULL” and “REDUCED”) and three in 2013 (“FULL 1,” “FULL 2,” and “REDUCED”) against the potato psyllid was evaluated. Yellow sticky cards were used to monitor the adults, whereas immatures were evaluated by sampling the leaves. Overall, the vector infestation level in both years was low. The mean total number of adults per trap in 2012 was 1.5, 5, and 12 for “FULL,” “REDUCED,” and the control, respectively, while in 2013 was 10.3, 20.7, 17.7, and 52 for “FULL 1,” “FULL 2,” “REDUCED,” and the control, respectively. For each particular year, season-long regimes were most effective at controlling the pest than targeted applications; however, there was no statistical difference among regimes (“FULL” or “REDUCED”) after early July, when the first psyllids were detected, until mid-August. Moreover, this number was similar to the control. Also, psyllid density was uniform across sticky traps, and no clear relationship was found between the proportion of Lso-infective psyllids and zebra chip disease intensity.
Drosophila suzukii (Matsumura) is an invasive species that is a devastating pest of soft-skinned fruit crops. Although much effort has been directed toward developing traps and attractants to monitor for D. suzukii, current monitoring tools do not reliably predict fruit infestation. The objective of this study was to determine if D. suzukii females at different developmental stages are differentially attracted to monitoring traps with fermentation-based baits and ripe fruits. Females were collected on the surface of traps, within traps, and on ripe fruits during three experiments at field locations in North Carolina, USA, and were dissected to determine their reproductive status. In general, females collected on ripe fruits were more likely to have mature eggs present in their ovaries and had higher numbers of mature eggs than females collected on the surface of or within monitoring traps. The results of this study have implications for D. suzukii monitoring and the development of effective baits for use in integrated pest management programs.
Fluorescent dyes are commonly used in the sterile insect technique (SIT) for marking insects for a proper identification after recapture. However, the quality of the mark must be balanced against insect performance, because dyes can negatively affect some parameters of insect performance and reduce their effectiveness in control with the SIT. We determined the visibility and persistence and the effect of dyes on the quality of Anastrepha obliqua (Macquart) and Anastrepha ludens (Loew) (bisexual and genetic sexing strains) by testing four concentrations of a dye (Day-Glo) from 0 to 2.5 g dye/kg of pupae. Visibility and persistence of the mark were positively affected by dose and negatively affected by the length of time the samples were kept in a solution of 75% alcohol. However, upon dissection, even the lowest dose of dye was visible under a fluorescence microscope. Between dyed and undyed pupae (control), no significant differences were observed in rates of emergence, fliers and flight ability, and survival in two tests, with water and without food and without water and food, at any of the concentrations tested. Furthermore, no significant difference in mating competitiveness was detected between control pupae and those dyed at 1.0 and 2.5 g dye/kg pupae. We discuss our results with the possibility of reducing the dose of dye in these three flies, because the heads are large enough to capture sufficient particles to permit identification with the current methods of detection.
Few efforts have been made in Mexico to monitor Rhagoletis pomonella (Walsh) (Diptera: Tephritidae) in commercial hawthorn (Crataegus spp.) crops. Therefore, the main objectives of this study were to evaluate infestation levels of R. pomonella in feral and commercial Mexican hawthorn and to assess the efficacy of different trap-lure combinations to monitor the pest. Wild hawthorn was more infested than commercially grown hawthorn at the sample site. No differences among four commercial baits (Biolure, ammonium carbonate, CeraTrap, and Captor + borax) were detected when used in combination with a yellow sticky gel (SG) adherent trap under field conditions. However, liquid lures elicited a slightly higher, although not statistically different, capture. Cage experiments in the laboratory revealed that flies tended to land more often on the upper and middle than lower-bottom part of polyethylene (PET) bottle traps with color circles. Among red, orange, green, and yellow circles attached to a bottle trap, only yellow circles improved fly captures compared with a colorless trap. A PET bottle trap with a red circle over a yellow background captured more flies than a similar trap with yellow circles. An SG adherent yellow panel trap baited with ammonium carbonate was superior to the improved PET bottle trap (red over a yellow background) baited with different liquid proteins, but a higher proportion of females and no differences in fly detection were measured in PET traps baited with protein lures. These trials open the door for future research into development of a conventional nonadherent trap to monitor or control R. pomonella.
This study was conducted to better understand the life history of Parthenolecanium corni (Bouché) and Parthenolecanium quercifex (Fitch) (Hemiptera: Coccidae), and to develop degree-day models for crawler emergence of the two soft scale species in Georgia, North Carolina, South Carolina, and Virginia. Both species were univoltine in the southeastern United States. In South Carolina, eggs hatched from mid-April to early June; second instars began to appear in September and migrated to twigs to overwinter in October; and third instars and adults appeared in mid-March to early April. Each parthenogenetic female produced on average 1,026 ± 52 eggs. Fecundity was positively correlated to the fresh weight, length, width, and height of gravid females. Gross reproductive rate (GRR) was 695.98 ± 79.34 ♀/♀, net reproductive rate (R°) was 126.36 ± 19.03 ♀/♀, mean generation time (TG) was 52.61 ± 0.05 wk, intrinsic rate of increase (rm) was 0.04 ♀/♀/wk, and finite rate of increase (λ) was 1.04 times per week. Crawlers first occurred across Georgia, North Carolina, South Carolina, and Virginia in 2011–2013 when 524–596 Celsius-degree-days (DDC) had been accumulated with the single sine estimation method, or 411–479 DDC with the simple average method, at the base temperature of 12.8 °C and the start date of 1 January. These regional models accurately predicted the date of crawler emergence within 1 wk of the actual emergence in 2014.
We investigated kin relatedness and kin-recognition abilities of the Argentine ant, Linepithema humile (Mayr), an invader from North America that has pervaded Japan for 20 yr, using genetic analyses and behavioral bioassays. From these data and interactions among factors, we formulated an eradication and management time-scale pattern diagram. Relatedness within a colony using microsatellite markers was effectively zero, whereas relatedness estimated by multilocus DNA fingerprinting markers was relatively high. Specifically, relatedness of recently invaded populations was estimated at nearly 0.3. From the results of behavioral bioassays on the invading populations of the Argentine ant, all colonies except the Kobe supercolonies did not show clearly aggressive behaviors toward workers belonging to other colonies, even when distantly located. Because they are critical factors for eradicating and managing invasive organisms, we assessed the relationships among kin relatedness using multilocus DNA fingerprinting and microsatellite markers, with aggressiveness, in 2011 and 2012, including the establishment durations, and distances among supercolonies. A generalized linear model (GLM) analysis, with establishment durations as an explanatory variable, strongly contributed to explaining estimated relatedness from the two methods. Specifically, models using kin relatedness for both multilocus DNA fingerprinting and microsatellite markers provided the strongest contribution to explaining the establishment durations. Within 3 yr after establishment in a native area, eradication is possible because of their low genetic diversity and small colony size. After 15 yr, eradication will be more difficult, but it is preferable to just monitor the impact for a nonnative ecosystem.
The Dolichoderus thoracicus (Smith) has seriously infested urban, village, and agricultural environments in Taiwan. To develop optimal bait for the effective control of D. thoracicus, we investigated the feeding preferences of this ant at different sugar and amino acid concentrations in a laboratory setting. The number of feeding workers was significantly higher for 20% sucrose compared with that for other sugars at 10% and 20% concentrations. Furthermore, among all tested concentrations of monosodium glutamate (MSG; 1%, 3%, 5%, and 10%), the highest number of ants were attracted by 1% MSG with 20% sucrose. The consumption of each bait solution was also measured, and the results were similar to those for ant number. Regarding toxicants, the toxicity and repellency of 3% boric acid and borax bait were evaluated individually. Both 3% boric acid and borax demonstrated no repellency against D. thoracicus workers. The LT50 of the 3% boric acid bait was 4.87 d, whereas that of 3% borax bait was only 1.56 d. Thus, 3% boric acid showed further delayed action, facilitating workers spreading the toxicant to their nestmates through trophallaxis. In combination with our unique bait station, we propose an optimal bait formulation comprising 20% sucrose, 1% MSG, and 3% boric acid as a promising candidate for controlling D. thoracicus.
The dispersal flight activity (“swarming”) of two invasive subterranean termite species, Coptotermes gestroi (Wasmann) and Coptotermes formosanus Shiraki, was monitored in metropolitan southeastern Florida, where both species are now sympatric and major structural pests. Historical records of alates collected in the area showed that the two species have distinct peaks of flight activity, from mid-February to late April for C. gestroi, and from early April to late June for C. formosanus. However, an overlap of the two dispersal flight seasons has been observed since at least 2005. The daily monitoring of dispersal flight events in southeastern Florida in 2014, 2015, and 2016 confirmed that simultaneous flights occurred several times each year. In addition, environmental conditions for favorable flights were identified, and it was established that low temperature was the primary factor inhibiting both species from dispersal flights, while all other factors had little impact on the occurrence of major dispersal flight events. However, both species shared similar temperature requirements for favorable dispersal flight conditions despite distinct peaks of activity over time. The analysis of sex ratios and average weights of the alates suggests that intrinsic colony factors are important for the timing of the maturation of alates, and that once a cohort of individuals is ready to disperse, a flight may occur as soon as the environmental conditions are favorable.
Bistrifluron, a benzoylphenyl urea compound, was evaluated for efficacy against Coptotermes lacteus (Froggatt), a mound-building species in southern Australia. Bistrifluron bait (tradename Xterm) was delivered as containerized pellets inserted into plastic in-ground feeding stations implanted in the sides of mounds. Termites actively tunneled in the gaps between pellets and removed bait from the canisters. Two separate trials were conducted, one commencing on 22 September 2011 and the second commencing on 30 November 2011. In trial 1, all 13 treated colonies (seven single and six double treatments) were eliminated within 19 wk, while all five untreated colonies remained healthy. In trial 2, all four treated colonies were eliminated within 14 wk. In trial 1, bait consumed or removed in treated mounds averaged 105 g for single treatments and 147 g for dual treatments, and overall ranged from 7 to 309 g (70–3,090 mg bistrifluron). In trial 2, the four treated colonies removed an average of 85 g of bait. At the time mounds were dismantled, all showed signs of inattention: external cracking, delamination, and general external weathering. Mound repair and temperature profile data indicate that colony decline commenced much earlier than 19 wk and 14 wk, respectively, for trials 1 and 2, from as early as 4 wk onward. The ability of colonies to repair mound damage was impaired as early as 4 wk in some colonies, and mean internal mound temperatures in treated mounds began declining from 8 wk onward and clearly diverged from mean temperatures of untreated mounds thereafter.
Insect pests, including the German cockroach, Blattella germanica (L.), are prone to the development of physiological resistance when exposed to a number of insecticide sprays, and cross-resistance is frequently observed. Toxic baits are often used as a primary method of controlling German cockroaches, also resulting in heavy selection pressure from insecticidal baits. In response to this pressure, cockroach populations have developed aversion to specific inert ingredients in bait. Here, we examined the effect of exposure to baits containing fipronil, indoxacarb, or hydramethylnon on the development of physiological resistance to the same and other insecticides in a number of German cockroach strains. We found that prolonged exposure to baits containing fipronil or indoxacarb increased physiological resistance to these compounds. However, no increase in physiological resistance against any insecticide was observed in response to exposure to hydramethylnon bait. Additionally, we found that exposure to fipronil bait increased cross-resistance to indoxacarb. On the other hand, exposure to indoxacarb bait did not increase cross-resistance to fipronil. Neither fipronil nor indoxacarb bait exposure increased resistance to hydramethylnon. Interestingly, the development of insecticide resistance in response to bait exposure was strain-dependent and influenced by bait palatability. Our results demonstrate that exposure to toxic baits, particularly those containing fipronil, plays a significant role in the development of insecticide resistance, including cross-resistance, in German cockroaches. Further, although insecticide resistance in response to baits is mediated by exposure through the oral route, the molecular mechanisms at play are likely different for each insecticide.
The common bed bug (Cimex lectularius L.) (Hemiptera: Cimicidae) is an obligate blood-sucking insect that has been resurging in many countries. Researching this pest's behavior will help design more effective control methods. In this study, we evaluated the effect of feeding history and time elapsed from field collection on bed bug movement behavior and response to chemical lure or carbon dioxide stimulation in the laboratory. After CO2 was released, bed bugs unfed for 3 d began to return to harborages; in contrast, the ones unfed for 2 and 4 wk spent significantly more time outside their harborages during the first 1 h after than the 1 h before CO2 release. After CO2 release, there was an increase in activity (time spent moving outside harborage) in all bed bugs with different feeding history or time elapsed from field collection. During the 8-h observation period when CO2 was present, bed bug males unfed for 4 wk spent significantly more time exploring outside harborages than the ones unfed for 3 d, 1 wk, and 2 wk. Nymphs collected 1–2 wk and 1 yr ago spent significantly more time exploring outside harborages than the ones collected 43 yr ago. Bed bug's exploratory activity (the total percentage of bed bugs trapped in both baited and unbaited interceptors) was significantly affected by their time elapsed from field collection and their exploratory activity level was 1–2 wk > 6 mo > 5 and 43 yr. Both feeding history and time elapsed from field collection significantly affected bed bug movement, whereas bed bug's response to chemical lure or CO2 (the percentage of bed bugs trapped in the baited interceptor, summarized as the number of bed bugs trapped in the baited interceptor divided by the total number of trapped bed bugs in both baited and unbaited interceptors) was unaffected by the time elapsed from field collection.
The relationship between colony size and foraging distance was examined in extended foraging arenas with juvenile colonies of the Formosan subterranean termite, Coptotermes formosanus Shiraki. Our results showed that as long as royal pairs are present, larger colonies foraged at longer distances, and the oldest workers distributed farther away from the central nest. The results agree with the scaling model that predicts a large foraging range for animals of larger body size. An analysis of published data from population survey studies and field trials of bait toxicants showed that field colonies of the eastern subterranean termite, Reticulitermes flavipes (Kollar), follow the scaling model, while C. formosanus colonies were inconsistent with the model prediction. Reasons for the inconsistency with field data of C. formosanus are discussed.
Effects of ecdysone, 20-hydroxyecdysone (20E), and an ecdysone agonist, halofenozide, were tested against the Formosan subterranean termite, Coptotermes formosanus Shiraki, and the eastern subterranean termite, Reticulitermes flavipes (Kollar), in a 12-d no choice assay. Approximately 22–26% of R. flavipes and C. formosanus exhibited symptoms of hyperecdysonism, that is, “jackknife” position, when exposed to ecdysone and 20E at 1,000 ppm, respectively. High mortalities were recorded for both termite species in ecdysone and 20E at 100 and 1,000 ppm, but only at 10,000 ppm for halofenizide. Termites are known to move back to the central nest before the onset of ecdysis, and those that ingested lethal doses of chitin synthesis inhibitors (CSIs) die near the royal pairs, which partially accounts for the success of CSI baits to eliminate subterranean termite colonies. Because ecdysteroids and their agonists induce molting in termites, incorporation of these compounds into baits could potentially achieve the same colony elimination. This study showed that lethal time (12 d) of ecdysteroids and ecdysone agonist is shorter than that of a CSI (45 d); hence, the baiting time should be reduced by more than a month when they are incorporated in termite baits.
Insecticides are the dominant pest management method in fruit and vegetable crops worldwide owing to their quick effect, low cost, and relatively easy application, but they bear negative effects on human health and the environment. Insecticide mode of action (MoA), target species, and sex are variables that could affect insecticide-induced mortality. We recorded the mortality caused by three neurotoxic insecticides with different modes of action (chlorpyrifos [organophosphate, acetylcholinesterase inhibitor], λ-cyhalothrin [pyrethroid, sodium channel modulator], and thiacloprid [neonicotinoid, nicotinic acetylcholinesterase receptor agonist]) applied topically to adult males and females of three economically important tortricid species [Cydia pomonella (L.), Grapholita molesta (Busck), and Lobesia botrana (Denis & Schiffermüller)] that strongly depend on insecticide use for their control. Concentration and dose–mortality curves were recorded at 24 and 48 h postapplication. Large mortality differences between insecticides (maximum 7,800-fold for LD50) were followed by much lower, yet important, differences between species (maximum 115-fold), and sexes (maximum 41.5-fold). Significant interactions between the three factors indicate that they are not independent from each other. Interestingly, with the organophosphate chlorpyrifos, males of the three species were less susceptible than females, which was unexpected, as females are larger than males. Higher female sensitivity to organophosphates has been reported previously but only in G. molesta, not in other moth species. Our results highlight the importance of taking into account sex in dose–mortality studies with adult moths.
The green peach aphid, Myzus persicae Sulzer (Hemiptera: Aphididae), is an important sap-sucking pest of many crops, including Chinese cabbage, Brassinca oleracea L. The neonicotinoid insecticide thiamethoxam has been used as an effective insecticide to control M. persicae in cabbage fields. In this study, we assessed the effects of sublethal concentrations of thiamethoxam on demographic parameters of M. persicae. In leaf-dip bio-assays, thiamethoxam showed a relatively high toxicity against M. persicae with an LC50 of 6.80 mg liter–1. The duration of the preadult stage was not significantly affected in the sublethal bioassay. Additionally, the longevity and adult preoviposition period were not significantly affected by sublethal thiamethoxam. However, sublethal thiamethoxam significantly increased fecundity (LC10) and prolonged the total preoviposition period (LC40). Consequently, the finite rate of increase (λ) and the intrinsic rate of increase (rm) of aphids exposed to the LC40 were significantly lower than those of control aphids, whereas the net reproductive rate (R0) was higher, and the generation time (T) and the population doubling time (DT) were longer in the treated group. Based on these results, hormesis was induced by sublethal thiamethoxam in M. persicae, with the population growth of M. persicae negatively affected at higher sublethal concentrations of thiamethoxam. Therefore, our study indicated that the possible effects of thiamethoxam on aphids require further study to develop optimized integrated pest management strategies.
Frankliniella occidentalis (Pergande) is an economically important pest of agricultural crops. High resistance has been detected in field populations of F. occidentalis against the insecticide spinosad. In this study, we compared life history traits, body sizes, and feeding behaviors (recorded via an electrical penetration graph) of spinosad-susceptible (Ivf03) and spinosad-resistant (NIL-R) near-isogenic lines of F. occidentalis. Life table analysis showed that NIL-R had reduced female longevity and reduced fecundity. The relative fitness of NIL-R (0.43) was less than half that of Ivf03. NIL-R individuals were smaller than Ivf03 individuals, both in body length and body width at every stage. The number and duration of feeding activities were significantly reduced in NIL-R, with the exception of total duration of long-ingestion probes. These results suggest that there is a fitness tradeoff associated with spinosad resistance in F. occidentalis, and that the development of resistance in this pest species may be reduced by rotating spinosad with other pesticides lacking cross-resistance.
The green peach aphid, Myzus persicae (Sulzer), is a significant agricultural pest that has developed resistance to a large number of insecticides globally. Within Australia, resistance has previously been confirmed for multiple chemical groups, including pyrethroids, carbamates, organophosphates, and neonicotinoids. In this study, we use leaf-dip and topical bioassays to investigate susceptibility and potential cross-resistance of 12 field-collected populations of Australian M. persicae to three recently registered insecticides: sulfoxaflor, spirotetramat, and cyantraniliprole. Despite all 12 populations carrying known resistance mechanisms to carbamates, organophosphates, and pyrethroids, and two populations also exhibiting low-level metabolic resistance to neonicotinoids, we found little evidence of variation in susceptibility to sulfoxafor, spirotetramat, or cyantraniliprole. This provides further evidence that cross-resistance to spirotetramat, cyantraniliprole, and sulfoxaflor in M. persicae is not conferred by the commonly occurring resistance mechanisms MACE, super-kdr, amplification of the E4 esterase gene, or enhanced expression and copy number of the P450 gene, CYP6CY3. Importantly, this study also established toxicity baseline data that will be important for future monitoring of insecticide responses of M. persicae from both broadacre and horticultural crops.
Bacillus thuringiensis (Bt) corn producing the Cry1F protein was the first highly efficacious Bt corn deployed against the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) in Brazil, but reduced efficacy of this technology against the fall armyworm has been reported in some regions of the country. Here, we surveyed Cry1F resistance allele frequency and susceptibility of eight S. frugiperda populations collected in 2013 from non-Bt fields in different regions of Brazil. In F1 screen experiments, the overall frequency of the Cry1F resistance alleles in Brazilian populations was estimated at 0.24, with 95% credibility interval between 0.18 and 0.25. In concentration–response bioassays, five of the eight populations surveyed exhibited significant resistance levels, which were over 32 times higher than that of the standard susceptible laboratory strain. The estimates of Cry1F resistance allele frequency were positively correlated with those of median effective or lethal concentrations (i.e., EC50 or LC50). These results show that the allelic frequency and the magnitude of Cry1F resistance are high in field populations of S. frugiperda in Brazil, indicating a challenging situation for resistance management.
Helicoverpa armigera sterol carrier protein-2 (HaSCP-2) is a validated target for development of novel insecticides due to its divergent protein structure and function from the vertebrate SCP-2. HaSCP-2 is important for normal development and fertility in Helicoverpa armigera (Hübner). The discovery of chemical inhibitors of HaSCP-2 through a structure-based virtual screening is reported here. Bioassay indicated that H1 and H14 had inhibitory effect on the growth of H. armigera larvae. The results suggest that H1 and H14 are promising as useful lead compounds for further optimization and development of novel SCP-2-specific pesticides.
As a newer cis-nitromethylene neonicotinoid pesticide at present, cycloxaprid has good industrialization prospects, including the management of imidacloprid-resistant populations, because this chemical have an excellent efficiency against rice planthoppers. Sogatella furcifera (Horváth) is the most economically important pest of rice worldwide and has developed resistance to many insecticides. This study focused on the expression change of these resistance genes, induced by cycloxaprid, involved in metabolic detoxification and receptor protein. Twenty-two differentially expressed genes (DEGs) that may be related with the insecticide resistance were found in the transcriptome of S. furcifera, including 2 cytochrome P450 genes, 2 glutathione S-transferase (GST) genes, 1 acid phosphatase (ACP) gene, 12 decarboxylase genes, 2 glycolipid genes, 1 cadherin gene, and 2 glycosyltransferase genes, which were up- or downregulated in response to an exposure of cycloxaprid. Furthermore, two P450 genes (CYP4 and CYP6 family, respectively), two decarboxylase genes, and one glycosyltransferase gene were validated by qRT-PCR. Expression differences of these genes verified successfully by qRT-PCR in response to different concentrations and times treated with cycloxaprid could explain the insecticide resistance mechanism under cycloxaprid stress in S. furcifera.
The annual bluegrass weevil, Listronotus maculicollis (Kirby), is a major pest of golf course turf in eastern North America and has become particularly problematic owing to widespread development of insecticide resistance. As an alternative option to manage resistant adult L. maculicollis, we explored combinations of the pyrethroid insecticide bifenthrin with an emulsifiable oil formulation of the entomopathogenic fungus Beauveria bassiana strain GHA (Bb ES). Combinations synergistically enhanced mortality in both insecticide-susceptible and insecticide-resistant L. maculicollis adults in the laboratory when bifenthrin was used at LC50s for each population. To determine the component behind the synergism, technical spores of B. bassiana GHA and the emulsifiable oil carrier in the fungal formulation were tested separately or in combination with bifenthrin. In both separate and combined applications, the emulsifiable oil carrier was responsible for high mortality within 3 d after treatment and interacted synergistically with bifenthrin, whereas fungus-induced mortality started later. Strong synergism was also observed in three field experiments with a relatively resistant L. maculicollis population. Combinations of Bb ES and bifenthrin hold promise as an effective L. maculicollis management tool, particularly of pyrethroid-resistant populations.
Catalase (CAT) is an important antioxidant enzyme that protects organisms against oxidative stresses by eliminating hydrogen peroxide. In this study, we cloned and characterized a full-length cDNA of CAT from Chilo suppressalis (CsCAT) and examined the influence of environmental stresses on CsCAT expression and enzyme activity. The cDNA contains a 1659-bp open reading frame encoding a polypeptide of 553 amino acids most closely related (90.14%) to Papilio polytes catalases. The CsCAT was expressed in all developmental stages with the highest expression in the fat body, and the CsCAT enzyme activity closely mirrored its observed mRNA expression patterns. The CsCAT mRNA was up-regulated when the larvae were exposed to high temperature (≥30 °C), insecticides (abamectin and chlorantraniliprole), chemicals (H2O2, CHP, CdCl2, and CuSO4), and a dead-end trap plant (vetiver grass), and the CsCAT enzyme activity again mirrored the observed CsCAT expression patterns. These results suggest that up-regulation of CsCAT may enhance the defense response of C. suppressalis by weakening the effects of environmental stresses, and provide insight into the role of CsCAT during development of C. suppressalis.
In insects, odorant-binding proteins (OBPs) and chemosensory proteins (CSPs) are primary peripheral olfactory proteins playing critical roles in odorant detection. In this study, we present the first identification of OBPs and CSPs from the transcriptome of grape phylloxera Daktulosphaira vitifoliae Fitch, an important pest that damages both roots and leaves of grapes. The OBPs contained six conserved cysteine residues and the CSPs contained four conserved cysteine residues in this insect. Phylogenetic analysis showed that most of the olfactory proteins were closely related to OBPs and CSPs from other aphids. However, DviOBP7 and DviCSP9 were different because they were classified into different independent branches, respectively. Real-time polymerase chain reaction (RT-PCR) was used to examine the tissue expression of these transcripts. DviOBP1, DviOBP6, and DviOBP7 were uniquely or primarily expressed in antennae and not in the body. DviOBP2 was more abundantly expressed in the body than in the antennae. The expression levels of OBPs and CSPs of phylloxera varied depending upon where they were expressed in different body tissues.
The whitefly species Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood) are worldwide agricultural pests and virus vectors. Bemisia tabaci, in particular, is often transported internationally via trade routes leading to potential introductions of exotic whiteflies or plant viruses. Quick identification of agriculturally important whiteflies can facilitate interventions that prevent these cross-border introductions. Polymerase chain reaction (PCR) primers were designed to amplify the mitochondrial cytochrome oxidase I gene (mtCOI) sequence of members of the B. tabaci complex, MEAM1, MED, and NW, and T. vaporariorum. Primers incorporated an A/T-rich overhang sequence at the 5′ terminus (5′ flap) to test for increased primer sensitivity and assay efficiency. Single-target and multiplex endpoint PCR assays with the eight primer sets were performed using genomic DNA template extracted from individual adult whiteflies. Resultant PCR amplicons obtained for B. tabaci MEAM1, MED, and NW, and T. vaporariorum primers with the 5′ flap were 559-, 717-, 353-, and 258-bp, respectively, and without the 5′ flap were 550-, 712-, 329-, and 252-bp in length, respectively. In single-target and multiplex reactions, specific amplification was achieved using both the unmodified and 5′ flap-modified primers. Sequencing and phylogenetic analysis confirmed primer-target amplification specificity. Using these primer sets in single-target or multiplex PCR allows for quick discrimination and specific identification of B. tabaci complex members and T. vaporariorum, and the addition of 5′A/T-rich overhang sequences increases the sensitivity and amplification of some primer sets.
Oedaleus asiaticus B. Bienko is a persistent pest occurring in north Asian grasslands. We found that O. asiaticus feeding on Stipa krylovii Roshev. had higher approximate digestibility (AD), efficiency of conversion of ingested food (ECI), and efficiency of conversion of digested food (ECD), compared with cohorts feeding on Leymus chinensis (Trin.) Tzvel, Artemisia frigida Willd., or Cleistogenes squarrosa (Trin.) Keng. Although this indicated high food utilization efficiency for S. krylovii, the physiological processes and molecular mechanisms underlying these biological observations are not well understood. Transcriptome analysis was used to examine how gene expression levels in O. asiaticus gut are altered by feeding on the four plant species. Nymphs (fifth-instar female) that fed on S. krylovii had the largest variation in gene expression profiles, with a total of 88 genes significantly upregulated compared with those feeding on the other three plants, mainly including nutrition digestive genes of protein, carbohydrate, and lipid digestion. GO and KEGG enrichment also showed that feeding S. krylovii could upregulate the nutrition digestion-related molecular function, biological process, and pathways. These changes in transcripts levels indicate that the physiological processes of activating nutrition digestive enzymes and metabolism pathways can well explain the high food utilization of S. krylovii by O. asiaticus.
The ant genus Linepithema is widely known, thanks to the pest species Linepithema humile (Mayr), which is easily mistaken for Linepithema micans (Forel) due to their morphological similarity. Like L. humile, L. micans is associated to the main grapevine pest in Brazil, Eurhizococcus brasiliensis (Wille), also known as ground pearl. Therefore, the present study uses mtDNA fragments to expand the knowledge of haplotype diversity and distribution of L. micans in the state of Rio Grande do Sul (Brazil), to understand the genetic differences of the populations identified in this study. We identified 15 haplotypes of L. micans spread across different localities. Twelve of these haplotypes were new for the species. The high haplotype diversity uncovered in Rio Grande do Sul (Brazil) for this species was predictable, as L. micans is in its native environment. Additional studies that take gene flow into account may reveal interesting aspects of diversity in these populations.
The codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), is a major pest of pome fruit worldwide. Incorporation of semiochemicals, including the main sex pheromone (codlemone), into codling moth IPM programs has drastically reduced the amount of chemical insecticides needed to control this orchard pest. Odorant receptors located in sensory neuron membranes in the antennae are key sensors in the detection of semiochemicals and trigger downstream signaling events leading to a behavioral response. CpomOR1 is an odorant receptor belonging to the pheromone receptor subfamily in codling moth, and is a prime candidate for being a codlemone receptor based on its high expression levels in male antennae. In this study, the CpomOR1 gene was targeted using CRISPR/Cas9 genome editing to knockdown functional OR1 protein production to determine physiological function(s). By injecting early stage eggs, mutations were successfully introduced, including both deletions and insertions. When attempting to create stable populations of codling moth through mating of males with females containing mutations of the CpomOR1 gene, it was found that fecundity and fertility were affected, with edited females producing nonviable eggs. The role of CpomOR1 in fecundity and fertility in codling moth is unknown and will be the focus of future studies.
The filbert aphid Myzocallis coryli (Goeze) is a serious pest of hazelnut in North America, Italy, Spain, and Turkey. To evaluate the resistance of hazelnut to this insect, aphids were reared on five major cultivars (‘Tombul,' ‘Palaz,' ‘Çakıldak,' ‘Foşa,’ and ‘Mincane') under laboratory conditions. The developmental times of preadult and adult stages, total longevity, reproduction, and life table parameters were analyzed according to age–stage, two-sex life table theory, in which the stage differentiation and variable developmental rates among individuals could be described. The intrinsic rate of increase (r) and finite rate of increase (λ) varied among the cultivars. The highest values were found for aphids reared on Çakıldak (r = 0.2019 d–1, λ = 1.2238 d–1), which did not differ significantly from Mincane (r = 0.1957 d–1, λ = 1.2161 d–1), whereas these parameters were lowest for Palaz (r = 0.1622 d–1, λ = 1.1761 d–1) and Foşa (r = 0.1677 d–1, λ = 1.1826 d–1). Based on longer preadult development time, shorter adult longevity, shorter reproductive period, together with the demographic parameters, Palaz and Foşa provide a relatively unfavorable environment for the filbert aphid. The results obtained from demographic data together with estimates of pest growth potential generated by computer projection based on age–stage, two-sex life table theory, demonstrate that both Palaz and Foşa are resistant cultivars for M. coryli and can be considered in hazelnut integrated pest management and hazelnut breeding programs.
Alisha J. Johnson, Hossam E. M. Abdel Moniem, Kathy L. Flanders, G. David Buntin, Francis P. F. Reay-Jones, Dominic Reisig, Jeffery J. Stuart, Subhashree Subramanyam, Richard H. Shukle, Brandon J. Schemerhorn
Mayetiola destructor (Say) is a serious pest of wheat, Triticum aestivum L., in North America, North Africa, and Central Asia. Singly deployed resistance genes in wheat cultivars have provided effective management of Hessian fly populations for >50 yr. Thirty-five H genes have been documented. Defense mediated by the H gene constitutes strong selection on the Hessian fly population, killing 100% of larvae. A mutation in a matching Hessian fly avirulence gene confers virulence to the H gene, leading to survival on the resistant plant. As the frequency of virulence rises in the population, the H gene loses its effectiveness for pest management. Knowing the frequency of virulence in the population is not only important for monitoring but also for decisions about which H gene should be deployed in regional wheat breeding programs. Here, we present a novel assay for detecting virulence in the field. Hessian fly males were collected in Alabama, Georgia, North Carolina, and South Carolina using sticky traps baited with Hessian fly sex pheromone. Utilizing two PCR reactions, diagnostic molecular markers for the six alleles controlling avirulence and virulence to H13 can be scored based on band size. Throughout the southeast, all three avirulence and three virulence alleles can be identified. In South Carolina, the PCR assay was sensitive enough to detect the spread of virulence into two counties previously documented as 100% susceptible to H13. The new assay also indicates that the previous methods overestimated virulence in the field owing to scoring of the plant instead of the insect.
Bemisia tabaci biotype B (Gennadius) is one of the most important soybean pest worldwide. Herein, 15 soybean genotypes were evaluated, to characterize the occurrence of antixenosis to B. tabaci biotype B. Initially, a multiple-choice test with all genotypes was carried out, evaluating the settling and oviposition preference at 3 d after infestation, and the colonization by nymphs after 48 d of infestation. Subsequently, a no-choice test, using 14 genotypes, was conducted with infested plants individually, and the number of eggs was counted after 72 h. Then, 10 genotypes were selected (indicative of resistance and susceptibility), which were evaluated for whitefly settling 24, 48, and 72 h after infestation and for oviposition 72 h after infestation. The trichomes of the leaflets were characterized for density, size, and inclination to establish possible correlations with the settling and oviposition in the genotypes. In the first multiple-choice test, involving 15 genotypes, ‘IAC-17,' ‘IAC-19,' and UX-2569-159 expressed antixenosis against B. tabaci. ‘Jackson,' ‘P98Y11,' and PI-229358 exhibited the same behavior in the no-choice test. In the multiple-choice test, ‘Jackson,' ‘P98Y11,' and ‘TMG1176 RR' were the least attractive and least used for oviposition. The antixenosis shown by ‘Jackson,' ‘P98Y11,' and PI-229358 may be related to the characteristics of the trichomes (lower density and inclined). Based on the experiments carried out, ‘IAC-17,' ‘IAC-19,' ‘Jackson,' ‘P98Y11,’ PI-229358, TMG1176 RR, and UX-2569-159 are considered promising for resistance to B. tabaci biotype B and may be exploited in soybean breeding programs for resistance to insects.
The performance and preference of Mahanarva spectabilis (Distant) for feeding on different forage species were evaluated. The survival and duration of the nymphal period, longevity and fertility of adults, and food preferences (free choice) of adults of M. spectabilis were evaluated in a greenhouse trial, and food preferences of adults were also evaluated in laboratory tests without a choice of host plant. In the field, the numbers of plants with spittle masses were evaluated by forage sampling. Lower levels of nymph survival were observed in the greenhouse on Molasses grass, Jaraguá, Tanzânia, and Makueni. The duration of the nymphal period did not differ significantly on different forage species; however, the longevity and fertility of adults were significantly lower on Cynodon and Brachiaria decumbens Stapf. In the free-choice preference test, adult insects were attracted most strongly to B. decumbens and Jaraguá, with intermediate attraction to Brachiaria brizantha (Hochst ex A. Rich) Stapf and Pioneiro. In the test without host choice, insects exhibited lower excretion rates on Tanzânia, Cynodon, Jaraguá, B. brizantha, and Molasses grass, and those fed on Cynodon, Jaraguá, Molasses grass, and Makueni also exhibited reduced body mass. In the field, Pioneiro had the highest number of spittle masses, followed by Roxo de Botucatu. Thus, Molasses grass, Tanzânia, Makueni, and Jaraguá plants are less suitable food sources for M. spectabilis nymphs and adults. Additionally, although Jaraguá was less favorable to nymphs, it attracted food-seeking adults; hence, these plants have potential for use in control of M. spectabilis.
The bird cherry-oat aphid (Rhopalosiphum padi L.) is a global pest of wheat and vectors some of the most damaging strains of barley yellow dwarf virus (BYDV). In years of heavy R. padi infestation, R. padi and BYDV together reduce wheat yields by 30–40% in Kansas and other states of the U.S. Great Plains wheat production area. Cultivation of wheat cultivars resistant to R. padi can greatly reduce production costs and mitigate R. padi–BYDV yield losses, and increase producer profits. This study identified cultivars of hard red and soft white winter wheat with R. padi resistance that suppress R. padi populations or tolerate the effects of R. padi feeding damage. ‘Pioneer (S) 25R40,' ‘MFA (S) 2248,' ‘Pioneer (S) 25R77,' and ‘Limagrain LCS Mint' significantly reduced R. padi populations. MFA (S) 2248, Pioneer (S) 25R40, and ‘Limagrain LS Wizard’ exhibited tolerance expressed as significantly greater aboveground biomass. These findings are significant in that they have identified wheat cultivars currently available to producers, enabling the immediate improvement of tactics to manage R. padi and BYDV in heavily infested areas. Secondarily, these results identify cultivars that are good candidates for use in breeding and genetic analyses of arthropod resistance genes in wheat.
Population growth parameters of the Dysaphis pyri (Boyer de Fonscolombe) (Hemiptera: Aphididae) were evaluated on four different cultivars (Coscia, Ankara, Williams, and Santa-Maria) of pear (Pyrus communis L.) under field conditions in the Van region of Turkey. Aphids were kept on leaves of 10-yr-old pear trees in Plexiglas clip-cells (20 mm in diameter and 10 mm in height, with the upper side covered with muslin). For the description of the stage differentiation during population growth, we analyzed raw data of developmental time, survival, and fecundity using the age-stage, two-sex life table to take the variable developmental rate among individuals into account. Results indicated that the Coscia and Ankara cultivars are less favorable hosts for D. pyri because of the longer preadult developmental time, higher preadult mortality rate, and lower total fecundity on these cultivars. The intrinsic rate of increase (r), the net reproduction rate (R0), and the finite rate of increase (λ) values were lower on the Coscia and Ankara cultivars. We discussed the application of the Weibull function, polynomial model, and Enkegaard model in life table studies. Because these models are often inaccurate in describing survival and reproduction parameters, we suggest that their application in life table research should be reevaluated.
Aphid species, such as the potato aphid, Macrosiphum euphorbiae Thomas, and the green peach aphid, Myzus persicae Sulzer, are routinely considered the most important pests of potatoes. Potato aphid, green peach aphid, and more recently, other aphids such as the bird cherry-oat aphid Rhopalosiphum padi L. have been identified as vectors of multiple plant pathogenic viruses in potatoes. Since 2006, an area-wide trapping network consisting of ∼60 sites was developed through collaboration between researchers, extension faculty, and stakeholders, to monitor aphid populations in the Columbia Basin of Oregon (Umatilla and Morrow counties) and in northeastern Oregon (Union and Baker counties). Over a 9-yr period (2006 to 2014), aphid specimens were collected weekly using yellow bucket traps and specimens were then identified and counted to determine population levels during the growing season (May–September). Thus, aphid population data were compiled and subjected to spatial and temporal distribution analysis. Weather data, obtained from an established network of weather stations located in the monitoring areas, were used in a nonparametric multiplicative regression analysis to determine which abiotic variables may impact aphid populations. Weather conditions were characterized using confidence intervals (CIs) established based on weather data from 1999 to 2005 for each environmental variable. Aphid populations were found to have a heterogeneous distribution in most years; a few sites had high aphid populations while low numbers were observed at most sites; aphids were also found to correlate with several abiotic variables, namely, elevation, previous season temperature, and previous season dew point.
Two species, the cigarette beetle Lasioderma serricorne (F.) and the drugstore beetle Stegobium paniceum (L.), are particularly important stored-product pests because they damage dry food. A previous study showed that L. serricorne adults are attracted more to ultraviolet (UV) and blue light wave ranges more than others such as turquoise, green, yellow, red, and warm white. However, the previous study did not equalize the amounts of light. The study also evaluated the attractiveness by the numbers of L. serricorne individuals that were lured to LED lights in a small box in the laboratory. In some storehouses, damage by S. paniceum is more serious and establishment of an effective monitoring tool is required. Therefore, in the present study, attractions of these beetles to UV and blue light traps were compared to develop a tool to monitor the beetle pests. First, adult L. serricorne and S. paniceum beetles were provided with UV- and blue-LED panels whose light intensities were equalized in the laboratory, and the walking and flying paths of each adult were recorded and measured. As a result, adults were clearly attracted to the side of UV-LED panel by walking compared to the blue one. Second, we compared the numbers of cigarette beetles collected by sticky sheets that were set in the back of UV or blue-light LED traps in a real storehouse. The results showed that these beetles were significantly more attracted to UV than blue-light LED traps, indicating the UV-LED trap is a powerful tool to monitor these two pest species.
The khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is a polyphagous pest that infests many stored grains and products. The effect of nine maize hybrids including 704, AR 89, AS 71, AS 77, BC 678, KSC 703, PL 472, SC 704, and Simax was studied on biology and life table parameters of T. granarium at controlled conditions (33 ± 1 °C, 65 ± 5% RH, and a photoperiod of 14:10 [L:D] h). According to the results of this study, the immature period was the longest on BC 678 (56.79 ± SE: 1.51 d) and the shortest on PL 472 (39.90 ± 0.48 d). The highest values of fecundity and fertility were observed on PL 472 (67.95 ± 1.23 eggs and 74.81 ± 0.68%, respectively) and the lowest values were on BC 678 (40.00 ± 1.63 and 48.24 ± 1.35, respectively). The net reproductive rate (R0) of T. granarium ranged from 10.40 ± 0.11 offsprings on BC 678 to 30.43 ± 0.20 offsprings on KSC 703. The highest intrinsic rate of increase (rm) was for T. granarium reared on KSC 703 (0.0773 ± 0.0001 d–1), and the lowest was on BC 678 (0.0390 ± 0.0002 d–1). According to the obtained results, BC 678 is an unfavorable hybrid for population increase of T. granarium, which can be recommended to be grown in regions where the damage of T. granarium is considerable to minimize maize infestations by this pest.
The almond moth, Cadra cautella (Walker) (Lepidoptera: Pyralidae), is a serious worldwide pest of dates and other crops, both in the field and in storage. Infestation by this pest significantly limits the sale and export of dates. Modified atmospheres, the temperature manipulations, are the best eco-friendly alternatives in stored product protection. We examined temperature regulation as an ecologically friendly method of pest management in stored food commodities, in particular, its effects on characteristics of C. cautella biology, including development time, oviposition period, fecundity, fertility, and longevity of adults reared on date cultivar ‘Khodari,’ at temperatures of 15, 25, and 35 ± 1 °C, with 65 ± 5% relative humidity and a photoperiod of 15:9 (L:D) h. Six larval instars were recorded at each temperature. Larval development was sluggish at 15 °C; therefore, daily observations were terminated after 180 d of the larval span for this temperature. Total larval spans of 48.95 ± 0.76 and 32.12 ± 1.08 d were recorded at 25 °C and 35 °C, respectively. A mean ovipositional period of 5.80 ± 0.44 d yielding 213.60 ± 13.41 eggs per female, with hatchability of 85.94 ± 2.97%, was recorded at 25 °C, whereas at 35 °C, a mean ovipositional period of 1.60 ± 0.26 d yielded 19.80 ± 5.11 eggs per female, with no hatchability. These differences were highly significant. Our observations of poor development at 15 °C, lower numbers of eggs and absence of hatchability at 35 °C, together with head capsule measurements and growth ratios, can be of benefit when planning management strategies to reduce C. cautella infestation.
Volatile chemicals from waste artificial larval media as well as from bovine blood inoculated with bacteria isolated from screwworm-infested wounds attract gravid females of Cochliomyia hominivorax Coquerel and Cochliomyia macellaria (F.). Chemicals identified from volatiles are dimethyl disulfide, dimethyl trisulfide, phenol, p-cresol, and indole; a blend of these attracted females to oviposit. Present studies investigated the effectiveness of these compounds, either in a blend or individually as potential oviposition attractants. Tests were conducted to determine the effects of gender, ovarian age, and the color and type of substrates on attraction response and oviposition of C. macellaria adults. Results showed that substrates treated with dimethyl trisulfide (DMTS) alone or the five-compound blend alone attracted significantly more gravid females than other chemicals. Black substrates treated with DMTS attracted more gravid flies than did the yellow substrates. Yellow substrates treated with indole attracted more males and nongravid females. In oviposition tests, females deposited significantly more eggs on meat-based substrates than those without meat. These findings suggest that several factors have to be considered for developing an effective oviposition attractant that should include effectiveness of individual chemicals used, the ratio of the chemicals in a blend, and their concentrations. Also, an effective trap design will need to consider using suitable color which will selectively attract gravid females.
We examined the suitability of cultivated olive, Olea europaea L., as a host for emerald ash borer, Agrilus planipennis Fairmaire. In a bioassay using cut stems from a field-grown olive tree (cv. ‘Manzanilla') we found that 45% of larvae that had emerged from eggs used to inoculate stems, were recovered alive, many as larvae or prepupae, during periodic debarking of a subset of stems. Three intact stems that 19 larvae successfully entered were exposed to a simulated overwintering treatment. Four live adults emerged afterwards, and an additional pupa and several prepupae were discovered after debarking these stems. Cultivated olive joins white fringetree as one of the two species outside of the genus Fraxinus capable of supporting the development of emerald ash borer from neonate to adult.
Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) and brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), are global economic pests that may co-occur on small fruits. We investigated whether fruit recently exposed to H. halys affected subsequent host use by D. suzukii. Laboratory no-choice and choice tests presented D. suzukii with H. halys-fed and unfed raspberries and blueberries immediately or 3 d after H. halys feeding. Resulting D. suzukii eggs, or larvae and pupae, were counted. The number of D. suzukii immatures among fed and unfed fruit was not significantly different in lab studies. There was no relationship between the intensity of H. halys feeding, as estimated by the number of stylet sheaths, and D. suzukii oviposition on blueberry. Lastly, field studies compared D. suzukii infestation between H. halys-fed and unfed raspberries. Raspberries were previously exposed to H. halys for 3 d or simultaneously exposed to both pests for 7 d. Natural infestation by D. suzukii in the field was similar among raspberries previously or simultaneously exposed to H. halys compared to control fruit.
American sweetgum trees (Liquidambar styraciflua L. [Altingiaceae]) in China are being killed by a newly discovered wood-boring beetle “sweetgum inscriber” (Acanthotomicus sp.). It has not been detected in the United States yet, but given the extent of trade with Asian countries, eventual arrival of this beetle is a serious concern. The American sweetgum is one of the main hardwood species in the southern United States, and provides several economic and ecological benefits to society. We present the first economic analysis of the potential damage from sweetgum inscriber (SI) to timber-based land values in the southern United States. We modeled economic impacts for a range of feasible SI arrival rates that reflect policy interventions: 1) no efforts to prevent arrival (scenario A, once every 14 and 25 yr), 2) partial prevention by complying with ISPM 15 standards (scenario B, once every 33 and 100 yr), and 3) total prevention of arrival (scenario C, zero transmission of SI). Our results indicated much lower land values for sweetgum plantations without the prevention on SI establishment (scenario A, US$1,843–US$4,383 ha–1) compared with partial prevention (scenario B, US$5,426–US$8,050 ha–1) and total eradication of SI (scenario C, US$9,825). Across the region, upper bound timber-based economic losses to plantation owners is US$151.9 million (US$4.6 million annually)—an estimate that can help inform policy decisions.
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