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The potential contributions of B vitamins by a yeast associate to the nutrition of the carpenter ant Camponotus vicinus Mayr was examined as part of an effort to develop a chemically defined diet. This diet was used to test the effects of individual B vitamin and other nutrient deletions on larval development. The chemically defined diet contained amino acids, vitamins, minerals, and other growth factors in a liquid sucrose matrix. C. vicinus worker colonies with third- and fourth-instar larvae were fed a complete artificial diet or that diet with a component deleted for a 12-wk period. There was a significant effect of diet on larval growth and number of adult worker ants produced in the overall nutrient deletion test, but ant development was often better on incomplete diets with one B vitamin deleted compared with the complete holidic basal diet. Thiamine deletion resulted in significantly higher brood weights compared with the complete diet. Diets of sugar water plus all B vitamins, sugar water only, or a diet minus all B vitamins and cholesterol were associated with significantly lower brood weights. Significantly more adult worker ants were produced by worker colonies fed diets minus cholesterol, choline, thiamine, or riboflavin compared with the complete basal diet. The results suggest that the diet, while suitable for rearing, could benefit from further study to better define component levels. The potential relationship of C. vicinus with yeast associates is discussed in relation to further studies.
In 2001, the red imported fire ant (Solenopsis invicta Buren) was identified in Brisbane, Australia. An eradication program involving broadcast bait treatment with two insect growth regulators and a metabolic inhibitor began in September of that year and is currently ongoing. To gauge the impacts of these treatments on local ant populations, we examined long-term monitoring data and quantified abundance patterns of S. invicta and common local ant genera using a linear mixed-effects model. For S. invicta, presence in pitfalls reduced over time to zero on every site. Significantly higher numbers of S. invicta workers were collected on high-density polygyne sites, which took longer to disinfest compared with monogyne and lowdensity polygyne sites. For local ants, nine genus groups of the 10 most common genera analyzed either increased in abundance or showed no significant trend. Five of these genus groups were significantly less abundant at the start of monitoring on high-density polygyne sites compared with monogyne and low-density polygyne sites. The genus Pheidole significantly reduced in abundance over time, suggesting that it was affected by treatment efforts. These results demonstrate that the treatment regime used at the time successfully removed S. invicta from these sites in Brisbane, and that most local ant genera were not seriously impacted by the treatment. These results have important implications for current and future prophylactic treatment efforts, and suggest that native ants remain in treated areas to provide some biological resistance to S. invicta.
Maria Saponari, Giuliana Loconsole, Daniele Cornara, Raymond K. Yokomi, Angelo De Stradis, Donato Boscia, Domenico Bosco, Giovanni P. Martelli, Rodrigo Krugner, Francesco Porcelli
Discovery of Xylella fastidiosa from olive trees with “Olive quick decline syndrome” in October 2013 on the west coast of the Salento Peninsula prompted an immediate search for insect vectors of the bacterium. The dominant xylem-fluid feeding hemipteran collected in olive orchards during a 3-mo survey was the meadow spittlebug, Philaenus spumarius (L.) (Hemiptera: Aphrophoridae). Adult P. spumarius, collected in November 2013 from ground vegetation in X. fastidiosa-infected olive orchards, were 67% (40 out of 60) positive for X. fastidiosa by polymerase chain reaction (PCR) assays. Euscelis lineolatus Brullé were also collected but tested negative for the pathogen. Transmission tests with P. spumarius collected from the Salento area were, therefore, conducted. After a 96-h inoculation access period with 8 to 10 insects per plant and a 30-d incubation period, PCR results showed P. spumarius transmitted X. fastidiosa to two of five periwinkle plants but not to the seven olive plants. Sequences of PCR products from infected periwinkle were identical with those from X. fastidiosa-infected field trees. These data showed P. spumarius as a vector of X. fastidiosa strain infecting olives trees in the Salento Peninsula, Italy.
Spathius galinae Belokobylskij and Strazenac (Hymenoptera: Braconidae) is a recently discovered gregarious idiobiont larval ectoparasitoid currently being evaluated for biological control against the invasive emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) in the United States. To aid in the development of laboratory rearing protocols, we assessed the influence of various emerald ash borer stages on critical fitness parameters of S. galinae. We exposed gravid S. galinae females to emerald ash borer host larvae of various ages (3.5, 5, 7, and 10 wk post egg oviposition) that were reared naturally in tropical (evergreen) ash (Fraxinus uhdei (Wenzig) Lingelsh) logs, or to field-collected, late-stage emerald ash borers (nonfeeding J-shaped larvae termed “J-larvae,” prepupae, and pupae) that were artificially inserted into green ash logs. When exposed to larvae in tropical ash logs, S. galinae attacked 5 and 7 wk hosts more frequently (68–76%) than 3.5 wk (23%) and 10 wk (12%) hosts. Subsample dissections of the these logs revealed that 3.5, 5, 7 and 10 wk host logs contained mostly second, third, fourth, and J-larvae, respectively, that had already bored into the sapwood for diapause.NoJ-larvae were attacked by S. galinaewhennaturally reared in tropical ash logs. When parasitized by S. galinae, 7 and 10 wk hosts produced the largest broods (≈6.7 offspring per parasitized host), and the progenies that emerged from these logs had larger anatomical measurements and more female-biased sex ratios. When exposed to emerald ash borer J-larvae, prepupae, or pupae artificially inserted into green ash logs, S. galinae attacked 53% of J-larvae, but did not attack any prepupae or pupae. We conclude that large (fourth instar) emerald ash borer larvae should be used to rear S. galinae.
Cashew (Anacardium occidentale L.) is a very important source of income for more than 200,000 farmer households in Vietnam. The present cashew productivity in Vietnam is low and unstable, and pest damage is partly responsible for this. Cashew farmers rely on pesticides to minimize the damage, resulting in adverse impacts on farm environment and farmers' health. Weaver ants (Oecophylla spp) are effective biocontrol agents of a range of cashew insect pests in several cashewgrowing countries, and these ants are widely distributed in Vietnam. The aim of this study is to evaluate the potential of weaver ants in cashew orchards in Vietnam. Field surveys and field experiment were conducted in five cashew orchards from July 2006 to January 2008 in Binh Phuoc, Dong Nai, and Ba Ria Vung Tau provinces, Vietnam. Based on the field surveys, the most important pests that damage flushing foliar and floral shoots and young cashew fruits and nuts were mosquito bugs, brown shoot borers, blue shoot borers, and fruit-nut borers. The damage caused by each of these pests was significantly lower on trees with weaver ants compared with trees without the ants, showing that the ants were able to keep these pest damages under the control threshold. Regular monitoring of the field experiment showed that weaver ants were similar to insecticides for controlling mosquito bugs, blue shoot borers, fruit-nut borers, leaf rollers, and leaf miners. Aphids did not become major pests in plot with weaver ants. To manage insect pest assemblage in cashew orchards, an integrated pest management using weaver ants as a major component is discussed.
The red palm weevil, Rhynocophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) has become the most important pest of the date palm trees in the world. It has been reported in the kingdom of Saudi Arabia since 1987 and in Egypt since 1992. Studies were conducted to compare preferences among red palm weevil life stages for infection by 12 entomopathogenic nematodes (EPNs), under no choice and five stage choice experiments, and curative trials by some of EPNs isolates. All EPN isolates proved to be pathogenic for the first instars of red palm weevil larvae. Some of the test EPNs exhibited a preference for larvae over pupae, and a lesser degree of preference for adults. In contrast some strains showed no preference for any stage. The local Egyptian isolates ofEPNs were most efficient nematodes against red palm weevil than foreign strains. Field assessments using trunk injection resulted in a substantial decline in the population of red palm weevil after two successive applications within 3 wk. Efficacies ranging 48–88% were achieved in the curative assay resulting in a significant increase in palm survival compared with the untreated control. In conclusion, there is a great potential for the use of EPNs, in particular the Steinernema sp. (EGG4), against the red palm weevil when injected in the date palm.
Delia radicum L. or cabbage maggot is an important pest for Brassicaceous crops. There are currently no registered chemical control agents for its control in Slovenia. Fungal control agents for cabbage maggot were therefore sought among nine rhizosphere-compatible and plant growth-promoting, soil-adapted, and entomopathogenic species to cabbage maggots and were assayed in in vitro and soil laboratory bioassays. In the in vitro tests, the conidial suspensions were applied directly to cabbage maggot eggs. The soil tests mimicked pathways of natural exposure of various insect life stages to the fungal strains. Conidial concentrations used in soil tests were comparable to economic rates for in-furrow application. The following fungi were tested: Trichoderma atroviride P. Karst. (2 isolates), Trichoderma koningiopsis Samuels, C. Suarez & H.C. Evans (1), Trichoderma gamsii Samuels & Druzhin. (3), Beauveria brongniartii (Saccardo) Petch (1), Beauveria bassiana (Balsamo-Crivelli) Vuillemin (2), Metarhizium robertsii J.F. Bisch., Rehner & Humber (1), Metarhizium anisopliae (Metschn.) Sorokin (4), Purpureocillium lilacinum (Thom) Luangsa-ard, Houbraken, Hywel-Jones & Samson (2), and Clonostachys solani f. nigrovirens (J.F.H. Beyma) Schroers (2). Abbott's corrected mortality in the in vitro tests ranged from 0.0 ± 18.9 to 47.6 ± 9.0% and in the soil test from 2.4 ± 13.0 to 68.2 ± 21.5%. Seven isolates (B. hassiana [isolate 1174], C. solani [1828], M. anisopliae [1154 and 1868], T. atroviride [1872], T. koningiopsis [1874], and T. gamsii [1876]) caused significant cabbage maggot mortality in either in vitro or soil tests. The importance of fungal ecology as a criterion during the screening of potential biological control agents is discussed.
Postharvest quarantine treatments (irradiation or vapor heat) are used to control fruit flies and other pests in mangosteen (Garcinia mangostana L) exported to the United States and Japan from Thailand. No-choice tests were conducted in the laboratory to determine whether Thai mangosteen is a host for Bactrocera dorsalis (Hendel) (oriental fruit fly) and Bactrocera carambolae Drew & Hancock (carambola fruit fly). Ripe commercial quality fruit (1 wk after harvest) that were either undamaged or damaged by puncturing or peeling the pericarp were exposed to a high density of gravid flies in screen cages and then held for 10 d and dissected to inspect for immature life stages. Undamaged mangosteen fruit were not infested by B. dorsalis and B. carambolae. Partially damaged fruit with shallow punctures in the pericarp that did not extend to the aril also were not infested. Both fruit flies could infest damaged fruit if the pericarp damage allowed oviposition in the aril. Results suggest that natural infestation of mangosteen by B. dorsalis and B. carambolae can only occur if fruit exhibit physical cracks or mechanical injury. Resistance appears to be due to the pericarp hardness and thickness as well as latex secretion. Nonhost status could be used without additional quarantine measures to achieve quarantine security against B. dorsalis and B. carambolae in mangosteen exported from Thailand.
Studies were conducted in 2013–2014 to quantify attraction, feeding, and mortality of male oriental fruit flies, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), to STATIC SpinosadME a reduced-risk male annihilation treatment (MAT) formulation consisting of an amorphous polymer matrix in combination with methyl eugenol (ME) and spinosad compared with the standard treatment of Min-U-Gel mixed with ME and naled (Dibrom). Our approach used a behavioral methodology for evaluation of slow-acting reduced-risk insecticides.MEtreatments were weathered for 1, 7, 14, 21, and 28 d under operational conditions in California and Florida and shipped to Hawaii for bioassays. In field tests using bucket traps to attract and capture wild males, and in toxicity studies conducted in 1-m3 cages using released males of controlled ages, STATIC Spinosad ME performed equally as well to the standard formulation of Min-U-GelMEwith naled for material aged up to 28 d in both California and Florida. In laboratory feeding tests in which individual males were exposed for 5 min to the different ME treatments, mortality induced by STATIC Spinosad ME recorded at 24 h did not differ from mortality caused by Min-U-Gel ME with naled at 1, 7, 14, and 21 d in California and was equal to or higher for all weathered time periods in Florida during two trials. Spinosad has low contact toxicity, and when mixed with an attractant and slow release matrix, offers a reduced-risk alternative for eradication of B. dorsalis and related ME attracted species, without many of the potential negative effects to humans and nontargets associated with broad-spectrum contact insecticides such as naled.
Light brown apple moth, Epiphyas postvittana (Walker), is a quarantined pest in most countries. Its establishment in California and potential spread to other parts of the state and beyond make it urgent to develop effective postharvest treatments to control the pest on fresh commodities. Fumigation with cylindered phosphine at low temperature has emerged to be a practical methyl bromide alternative treatment for postharvest pest control on fresh commodities. However, its use to control E. postvittana eggs on sensitive commodities such as lettuce is problematic. E. postvittana eggs are tolerant of phosphine and long phosphine treatment also injures lettuce. In the current study, E. postvittana eggs were subjected to oxygenated phosphine fumigations to develop an effective treatment at a low storage temperature of 2°C. In addition, soda lime as a CO2 absorbent was tested to determine its effects in reducing and preventing injuries to lettuce associated with phosphine fumigations. Three-day fumigation with 1,000 ppm phosphine under 60% O2 achieved 100% mortality of E. postvittana eggs in small-scale laboratory tests. In the presence of the CO2 absorbent, a 3-d large-scale fumigation of lettuce with 1,700 ppm phosphine under 60% O2 resulted in a relative egg mortality of 99.96% without any negative effect on lettuce quality. The 3-d fumigation treatment without the CO2 absorbent, however, resulted in significant injuries to lettuce and consequential quality reductions. The study demonstrated that oxygenated phosphine fumigation has the potential to control E. postvittana eggs and the CO2 absorbent has the potential to prevent injuries and quality reductions of lettuce associated with long-term oxygenated phosphine fumigation.
Research on insect control should be conducted in a manner that mimics as closely as is feasible its commercial application in all of its practicably conceivable forms. When significant deviations from commercial application are used in research, the effect of the deviations on efficacy should be evaluated. Pest control techniques are sometimes based on research that used untested assumptions about variables that might affect efficacy. For example, some phytosanitary treatments are based on research done with diet-reared larvae inserted into holes bored in fruits, although the effect of this manipulation has not been evaluated. This research compares this type of infestation of grapefruit with Mexican fruit fly, Anastrepha ludens (Loew), third instars with a more natural infestation technique whereby females were allowed to oviposit on picked grapefruit in laboratory cages and third instars were reared inside the fruit. Although the results did not show statistically significant differences between infestation techniques, tendencies in the data caution against researchers making assumptions about efficacy without testing them when experimental techniques stray from more natural situations for which the research is designed.
Linepithema micans (Forel) (Hymenoptera: Formicidae) is the main ant species responsible for the spread of Eurhizococcus brasiliensis (Wille) (Hemiptera: Margarodidae), a soil scale that damages vine plants in southern Brazil. The daily foraging activity of L. micans and its seasonal preference for protein- and carbohydrate-based foods were evaluated. The study was carried out in a greenhouse using seedlings of the Paulsen 1103 rootstock (Vitis berlandieri × Vitis rupestris) planted individually in pots and infested with colonies of L. micans. To determine the daily foraging activity and seasonal preference, a cricket (Gryllus sp.) and a 70% solution of inverted sugar and water were offered once a month for 12 mo. The ants foraging on each food source were counted hourly for 24 h. L. micans foraged from dusk until the end of the next morning, with higher intensity in the spring and summer. Workers of L. micans showed changes in food preference during the year, with a predominance of protein-based food during winter and spring and carbohydrate-based food during autumn. The implications of this behavior for control of the species with the use of toxic baits are discussed.
Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a fruit pest of Asian origin that invaded North America in 2008. Despite the widespread economic impact of this species, much of the biology and general life history of this pest remains largely unknown. Under optimal laboratory conditions (22°C, ≈25% relative humidity),wemeasured development, survival, fecundity, hatch rate, and sex ratio of a North American ecotype of D. suzukii. Life history traits were used to construct a life table and reproductive schedule, and to calculate the intrinsic rate of population increase. The mean (±SE) total lifespan (egg to adult mortality) was 86.1 ± 4.25 d, with a maximum value of 153.7 d. On average, females produced 5.7 ± 0.24 eggs per day, with a mean total lifetime production of 635.6 eggs. The gross reproductive rate was 317.8 daughter eggs per female and the net reproductive rate was 240.4 daughter eggs per female. The intrinsic rate of natural increase was 0.179. The stable age distribution (cx) was comprised of 51% larvae, 25% eggs, 16% pupae, and 8% adults. The sex ratio over time was≈1:1.Weconclude with a comparison of our data with previous work on D. suzukii and other Drosophila, and discuss the implications for control and monitoring of this pest.
During the past decade, Apolygus lucorum (Meyer-Dür) has become a key pest on cotton in northern China. Whether or not this species is a migrant, and if so, what pattern of seasonal migration this species exhibits remains unknown. The combination of searchlight trapping and radar observation on an isolated island in the center of Bohai Gulf during the past 11 yr provided direct evidence that both male and female A. lucorum adults migrate at least 40–60 km (and probably much greater distances) across the Bohai Gulf waters. There were considerable yearly and monthly variation in the number of A. lucorum trapped on BH, and the migration period during 2009–2013 ranged from 102 to 154 d. A. lucorum adults had downwind displacement rather than randomly by heading toward their seasonally favorable directions, which toward the east—northeast in summer, but south—southwest (SSW) in early autumn. The vast majority of adults flying at airspeeds 0.5–2.5 m/s and at altitudes <150 m above ground level. Most of trapped females were virgins with little or no ovarian development, as suggests that the onset of migration is initiated mainly by sexually immature individuals, which is termed the “oogenesis-flight syndrome.” Such findings reveal a new route for A. lucorum movements northward to and southward from the northeastern agricultural region of China, which will help us develop more effective management strategies against this pest species.
Biological characteristics of corn leaf aphid, Rhopalosiphum maidis (Fitch), on barley, Hordeum vulgare L., were examined for two generations under four different elevated temperature and CO2 combinations. The developmental duration for each life stage was significantly reduced under the elevated temperature ( 4°C). The elevated CO2 (700–750 µl/liter) reduced only the development time of fourth-instar nymph. The overall duration of nymphal stage was reduced in the second generation. Thus, the temperature was the dominant factor to development duration of corn leaf aphid. The fecundity of corn leaf aphid was significantly increased under the elevated temperature and CO2, as well as in the later generation. Elevated temperature and CO2 increased the number of alate production, which may enhance the aphid migration or dispersal and the spread of plant viruses. Corn leaf aphid had the highest intrinsic rate of increase under the elevated temperature and CO2 combination in the second generation. These results indicate that the combined effects of both elevated temperature and CO2 on aphid biology may exacerbate aphid damage on barley under the climate change in accompany with elevated temperature and CO2 level.
Quantitative feeding behaviors were analyzed by electronic penetration graph technique to evaluate the resources utilization efficiency of the solenopsis mealybug, Phenacoccus solenopsis (Tinsley) (Hemiptera: Pseudococcidae), transferred to a novel host. Both nonphloem and phloem factors were contributed to the host availability during host shift; while only “prephloem” factor was involved with their offspring’s fitness to the transferred host, on which they fed as effectively as their mothers did on the origin host. Different performances on different hosts were supposed to have relations with the diverse phloem components, rather than feeding behaviors. P. solenopsis could try and exploit an efficient stylet pathway to reach the phloem, which would be an importance factor to account for the expansion of the host range and adaptations to different hosts. High efficient feeding behaviors of P. solenopsis in the current study manifested its capability of resource utilization to the novel host, which was suggested to be advantageous for its host shift, and to be the explanation for rapid host shifts associated with its broad host range and quick settlement.
Temperature is known to play a crucial role in the population dynamics of insects. Insects have evolved different mechanisms to resist unfavorable extreme temperatures. In recent years, western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), and onion thrips, Thrips tabaci (Lindeman) (Thysanoptera: Thripidae), have caused significant damage to vegetable crops. Because of global warming and expanding areas of vegetable cultivation, a study of the effects of heat stress on these thrips species is warranted. We exposed the various developmental stages of western flower thrips and onion thrips to temperatures of 41, 43, or 45°C for 2, 6, 12, 24, or 36 h to determine the effects of heat stress on survival. Our results showed that the heat resistance of nonadult western flower thrips was greater than that of the nonadult onion thrips, and that the natural heat resistant ability was the primary factor in heat resistance in western flower thrips. In contrast, the heat resistance of adult onion thrips was greater than that of the adult western flower thrips, which was primarily the result of the ability of searching suitable microenvironment that enabled the onion thrips to mitigate the effects of high temperatures more efficiently than the western flower thrips. Our analysis of the differences in heat resistance between western flower thrips and onion thrips provides important information for the development of thermal treatments for controlling western flower thrips and onion thrips.
The success of mating disruption using synthetic sex pheromones depends not only on preventing mating, but also on delayed mating in the target insect. Using the rice leaffolder moth, Cnaphalocrocis medinalis (Guenée), we determined the effect of increased age at mating imposed on males only (male treatment), females only (female treatment), or on both sexes simultaneously (both sexes treatment). These increased age treatments had a negative effect on the percentage of mating, the total number of eggs, and the hatchability. The female reproductive performance in C. medinalis was decreased with increased moths' age. The both sexes treatment had the most potent negative effect on reproductive performance. Longevity of mated moths and duration of the preoviposition period in C. medinalis were not significantly different among these increased age treatments. The underlying mechanisms causing a decline in female reproductive performance of C. medinalis when increased age was imposed on males versus females and the potential of using mating disruption strategies to control the populations in paddy fields are discussed.
The toxicity of an emulsifiable formulation of pirimiphos methyl (Actellic 25EC) on Anopheles gambiae s.s. Giles, Culex quinquefasciatus Say (Diptera: Culicidae), and predator fish Poecilia reticulata Peters (Pisces: Poeciliidae) was investigated. Acute toxicity tests were carried out to determine the effect of the larvicide on mosquito larvae and fish species. To investigate the nontarget effects on P. reticulata, fish of similar size (3.5 ± 0.2 cm) were randomly selected and exposed for 28 d, under static renewal bioassay, to sublethal concentrations of the larvicide capable of killing 30 and 70% of Cx. quinquefasciatus. The 24 h LC50 value of pirimiphos methyl on the test organisms ranged between 20.44 and 697.30 µg liter-1. The ultrastructural changes observed in the intestinal cells of P. reticulata were characterized by degenerating cell membranes with gradual loss of gray area in pycnotic nucleus at lower concentration. Marked damage was found at higher concentration including distinct loss of gray areas in cytosol, absence of cristae, numerous ruptures, and several dead cells. Pirimiphos methyl was toxic to a predatory fish species, and for its relevance in vector control and crop protection, warrants cumulative assessment to establish its comprehensive ecological risk, and the dosage required for field larviciding.
We present the results of evaluating the response of three species of bees, Trigona fulviventris (Guérin), Scaptotrigona mexicana (Guérin-Meneville), and Apis mellifera (L.), to food sources baited with the toxic bait GF-120 (NF Naturalyte), a spinosad-based bait exclusively used to manage fruit flies. Groups of foragers were trained to collect honey and water from a feeder located 50 m from the colonies. Once a sufficient number of foragers were observed at the experimental location, the training feeder was changed to two or three feeders that offered either honey and water, GF-120, Captor (hydrolyzed protein), GF-120 and honey (4:6), or Captor and honey (1:19). T. fulviventris and S. mexicana rarely visited GF-120, Captor, or their mixtures with honey, while ∼28.5 and 1.5% of A. mellifera foragers visited the GF-120 and honey and Captor and honey mixtures, respectively. Our results show that GF-120 clearly repels T. fulviventris and S. mexicana, whereas for A. mellifera, repellence is not as marked when GF-120 is combined with highly nutritious substances like honey.
Soybean aphid is an economic pest of soybean in North America. Currently, management of soybean aphid is achieved through the use of foliar- and seed-applied insecticides. However, natural enemies play an important role in regulating soybean aphid populations, and may be adversely affected by insecticides. The effects of imidacloprid and thiamethoxam seed treatments on the soybean aphid parasitoid, Aphelinus certus Yasnosh, were examined using a tritrophic bioassay. A. certus was able to parasitize soybean aphids feeding on imidacloprid- and thiamethoxam-treated plants 5 and 6 wk after planting, respectively. However, up to 10 wk after planting, overall parasitism rates were reduced by 69 – 88% compared with the control. Therefore, neonicotinoid seed treatments may reduce the effectiveness of A. certus as a natural enemy of soybean aphid in seed-treated crops.
Alexandre Specht, Miguel Ferreira Soria, Talita Saiara Mafini Maba, Luana Maria De Rossi Belufi, Bárbara Weschenfelder Godoi, Mônica Josene Barbosa Pereira, Silvana V. Paula-Moraes
This is the first report of Elaphria agrotina (Guenée, 1852) and Elaphria deltoides (Möschler, 1880) (Lepidoptera: Noctuidae) feeding on maize (Zea mays L.). The specimens were collected in maize fields during the crop season of 2012 and 2013 in three municipalities in Mato Grosso State, Brazil. Larvae were collected while feeding at the ear base, which often resulted in ears dropping to the ground. Larvae also were observed feeding on kernels in fallen ears. Ear injury often leads to reduced grain quality, and when the ears fall to the ground, reduced yield. A previous report of Striacosta albicosta (Smith, 1888) feeding on maize in Brazil was probably a misidentification of an E. agrotina male, which has wing pattern and coloration similarities with S. albicosta.
Regions of southern Florida and southern Texas (extending into Mexico) provide the overwintering source populations for virtually all fall armyworm infestations affecting the continental United States. Understanding how these migratory populations annually disperse is important to predict and control infestations by this specific pest and to more generally investigate the environmental factors that influence the long-distance movements of flying insects. The two overwintering locations are associated with differences in the distribution of certain mitochondrial haplotypes that overlap in the region near the border separating the states of Alabama and Georgia. This provided an opportunity to test the resolution of the haplotype method by comparisons between smaller geographical areas and shorter time frames than previously examined. Correspondences were found between trap-capture numbers, fall armyworm strain proportions, and haplotype ratios calculated for individual counties and within season time periods that were generally consistent with expectations, providing confidence that those population movements could be accurately inferred. The comparison of haplotype distributions identified a migratory boundary separating the Texas and Florida populations coincident with the eastern edge of the Apalaehicola—Chattahoochee—Flint River basin. Calculations of strain numbers based on genetic markers revealed similarities and differences in strain population dynamics that can be applied to study the migratory behavior of fall armyworm subpopulations. The use of this methodology for the detailed mapping of migratory pathways and the identification of factors that influence the direction and extent of pest migration are discussed.
The Russian wheat aphid, Diuraphis noxia (Kurdjumov) is a serious pest of small grains, such as wheat and barley. High population growth rates and a broad gramineae host range have allowed this aphid to successfully establish and become pestiferous across much of North America since its invasion in the mid-1980s. Resistant wheat cultivars were developed and provided control of D. noxia until 2003, when a new biotype (designated RWA2, as contrasted with the original biotype’s designation, RWA1) emerged and rapidly spread through dryland winter wheat-growing regions. RWA2 displaced RWA1 more quickly than expected, based on RWA2’s advantage in RWA1-resistant wheat cultivars. Previous research suggested that RWA2 may out-compete RWA1 in cooler temperatures. Thus, we sought to determine if RWA2 had a competitive advantage over RWA1 during the overwintering period. We placed a known distribution of RWA1 and RWA2 aphids in the field for the winter at three sites across a latitudinal gradient (from northern Colorado to Texas) to test for a competitive advantage between these biotypes. We found overwhelming support for an overwintering competitive advantage by RWA2 over RWA1, with evidence suggesting a >10-fold advantage even at our Texas site (i.e., the site with the mildest winter). This substantial overwintering advantage helps explain the quick dispersion and displacement of RWA1 by RWA2.
Economically important species of wireworms (Coleoptera: Elateridae) were successfully associated with adults using cytochrome oxidase I (COI) barcoding, proving the usefulness of this technique to associate life stages in taxonomically difficult pest groups. Previously unrecognized and morphologically difficult, even indistinguishable, pest larvae were shown to be identifiable using this technique. This is a critical step toward discovering effective species-based integrated pest management strategies for this resurgent pest group following the loss of Lindane seed treatments. Three new adult—larval associations were discovered for Hadromorphus callidus (Brown), Hemicrepidius carbonatus (LeConte) and Metanomus insidiosus (LeConte). Hypnoidus bicolor (Eschscholtz) was shown to comprise multiple divergent lineages at a level usually considered different species, indicating that the population structure of some pest species requires more investigation. The status of the prairie grain wireworm, Selatosomus destructor (Brown), as a full species or as a subspecies of Selatosomus aeripennis (Kirby) is called into question.
In southeastern China, the invasion of the nipa palm hispid Octodonta nipae (Maulik) (Coleoptera: Chrysomelidae) results in devastating damage to palms. Host plants play an important role in the population increases and outbreaks of O. nipae. O. nipae could not complete its development on the Majestic palm (Ravenea rivularis Jumelle & Perrier), and females did not lay eggs on Chinese fan palm (Livistona chinensis R. Brown). However, this insect species both completed development and laid eggs on Chinese windmill palm (Trachycarpus fortunei (Hooker) H. Wendland), Canary Island date palm (Phoenix canariensis Chabaud), and pygmy date palm (Phoenix roebelenii O' Brien). The demographic characteristics of O. nipae reared on Chinese windmill palm, Canary Island date palm, and pygmy date palm were compared with an age-stage, two-sex life table. In this study, the developmental periods from egg to adult varied from 42.1 d on Chinese windmill palm to 49.8 d on pygmy date palm. The survivorship from egg to adult on Chinese windmill palm, Canary Island date palm, and pygmy date palm was 77.5, 79.4, and 66.7%, respectively. Although the adult longevity and the mean fecundity for individuals reared on Chinese windmill palm, Canary Island date palm, and pygmy date palm were not significantly different, there were significant differences in the intrinsic rate of increase, the finite rate, and the mean generation time among palm species, and the values of intrinsic rate of increase and finite rate were higher for populations reared on Chinese windmill palm and Canary Island date palm (0.0313 and 1.0318 d-1 and 0.0278 and 1.0282 d-1, respectively) and lower for populations reared on pygmy date palm (0.0192 and 1.0194 d-1). However, mean generation time was shorter on Chinese windmill palm (124.11 d) and Canary Island date palm (129.62 d) and longer on pygmy date palm (166.03 d). Our study indicated that different hosts affected life parameters of O. nipae, with the most preferred hosts being the Chinese windmill palm and Canary Island date palm. These results may be useful for the design of culture management strategies for O. nipae.
The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a serious invasive pest of North American ash (Fraxinus spp.) that has caused devastating mortality since it was first identified in North America in 2002. In 2012, we conducted field trapping assays that tested the efficacy of purple prism and fluon-coated green multifunnel (Lindgren funnel) traps. Traps were baited with combinations of several lures that were previously shown to be attractive to A. planipennis: manuka oil—a sesquiterpene-rich oil, (3Z)-hexenol—a green leaf volatile, or (3Z)-dodecen-12-olide [= (3Z)-lactone], a sex pheromone. Eighty-nine blocks (trap lines) were tested throughout nine states along the outer edges of the currently known A. planipennis infestation in North America. Trap catch was highest on fluon-coated green multifunnel traps, and trap detections at sites with low A. planipennis population density ranged from 72 to 76% for all trap and lure types tested. (3Z)-hexenol and (3Z)-lactone baited traps functioned as well as (3Z)-hexenol and manuka oil-baited traps. Independent of the lure used, detection rates on green fluon-coated multifunnel traps were comparable with glued purple prism traps in areas with low A. planipennis population densities.
The relationship between different release densities of sterile flies and fly trap captures, expressed as flies per trap per day, in the monitoring of Anastrepha ludens (Loew) populations was evaluated in mango orchards. The induction of sterility in fertile females was evaluated using different ratios of sterile: fertile males under field cage conditions. A direct relationship between recaptured flies and densities of release sterile flies was found. However, trap efficiency, expressed as percentage of recaptured flies, decreased as the density of released flies increased. Sterility induction was positively correlated to the ratio of sterile: fertile flies. A significant difference in egg fertility among treatments was observed. The trajectory of sterility induction slowed down after a sterile: wild ratio of 30:1, which suggests that this ratio could be appropriate in an sterile insect technique program with A. ludens. Sterility induction was greater when only sterile males were released than when releasing both sterile males and females, but the differences were not significant. Our findings contribute to a better interpretation of fly captures obtained from the field trapping networks, and to an improvement in the efficiency of sterile insect technique against A. ludens fruit flies, through the implementation of more rational sterile fly release densities.
Field experiments were conducted in commercial southern highbush blueberries and wild blackberries to evaluate the attractiveness of different trap designs, bait types, and bait age on captures of the spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). During the 2012 trap design study, the five treatments evaluated were four 1-liter clear plastic cup traps (with and without a yellow visual stimulus or odorless dish detergent) and the fifth treatment was a Pherocon AM yellow sticky card trap. Cup traps were baited with 150 ml of apple cider vinegar (ACV) and the Pherocon AM trap had a 7.4-ml glass vial containing ACV. In 2013, the Pherocon AM yellow sticky card was omitted because of low spotted wing drosophila captures in 2012. The four treatments evaluated were four 1-liter cup traps with and without a yellow visual stimulus. One cup trap (with a yellow stimulus) was baited with yeast sugar in place of ACV and the other cup traps were baited with ACV. In both years, there were no differences in spotted wing drosophila captures among cup traps baited with ACV with and without yellow visual stimulus. However, the cup trap baited with yeast sugar and yellow visual stimulus captured more spotted wing drosophila than the ACV-baited cup traps irrespective of visual stimulus or detergent. In another study, four baits including 1) ACV, 2) yeast sugar mixture, 3) yeast flour mixture (yeast, sugar, water, whole wheat flour, and ACV), and 4) wine vinegar mixture (rice vinegar and merlot wine) were evaluated in a commercial blueberry planting using 1-liter clear plastic cup traps (as described above). The experiment was repeated in wild blackberries but the yeast flour bait was replaced with ACV merlot wine sugar. Results indicated that the two yeast baits captured significantly more spotted wing drosophila and more nontarget organisms than the vinegar baits. In the final study, although we found that the attraction of ACV and yeast sugar to spotted wing drosophila did not change with bait age, the attraction to other Drosophilidae flies decreased with age. The ease of implementing a trap-and-lure system for spotted wing drosophila is discussed.
The univoltine Bactrocera minax (Enderlein) is a devastating pest of citrus in Nepal, India, Bhutan, and China. To better understand the overwintering pupal diapause, we investigated the juvenile hormone III (JH III) and ecdysteroid 20-hydroxyecdysone (20E) titers across the developmental stages, and the effects of juvenile hormone analog (JHA) and 20E treatments on adult emergence patterns. The results showed that both JH III and 20E levels fluctuated from the late larval stage to the late pupal stage. JHA and 20E treatments at the late larval stage had marginal effect on the adult emergence patterns, with slightly faster adult eclosion and higher eclosion rate. Similarly, JHA treatment at the early pupal stage did not affect the adult emergence. However, 20E treatment at the early pupal stage remarkably shortened the duration of diapause, but lowered the eclosion rate, especially with relatively high dose. These findings demonstrated that 20E treatment at the early pupal stage is a suitable method to hasten the diapause termination of B. minax, which will contribute to the rearing of B. minax in the laboratory as needed for routine experiments.
Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), is an important pest on onion and cabbage. Two reproductive modes—arrhenotoky and thelytoky—are found in this species and co-occur in the field. We compared life table traits between arrhenotokous and thelytokous T. tabaci on cabbage and onion. Experiments were conducted in cages to determine which reproductive mode is more competitive. Additionally, host adaption of the arrhenotokous and thelytokous T. tabaci between onion and cabbage was investigated. On onion, arrhenotokous T. tabaci performed better than thelytokous T. tabaci, while on cabbage the opposite occurred. When comparing life table and demographic growth parameters (net reproductive rates R0, mean generation time T, the intrinsic rate of natural increase rm, finite rate of increase λ, and population doubling time Td) on different host plants, we found that arrhenotokous T. tabaci performed better on onion than on cabbage, whereas thelytokous T. tabaci performed better on cabbage than on onion. Host-related performance differences in this species suggest that the divergence between two reproductive modes might be associated with host adaption. Pest management strategies for this global pest should recognize that the two reproductive modes can impact population dynamics on different crops.
The hunting billbug, Sphenophorus venatus vestitus Chittenden, is a pest that damages stems, rhizomes, and roots of zoysiagrass through a combination of adult and larval feeding. Management of this pest is difficult because it has multiple, overlapping generations in the southern United States, and symptoms of infestations are often misdiagnosed and inappropriately treated as drought stress or disease. Experiments were conducted in a greenhouse where 18 zoysiagrass cultivars were potted and infested with S. v. vestitus adults to examine the response of zoysiagrass genotypes to S. v. vestitus feeding damage. Results showed that zoysiagrass species and cultivars differed in susceptibility to S. v. vestitus, indicating that variable tolerance may exist in these turfgrasses for improvement through breeding. In general, Zoysia japonica Steudel was more susceptible to S. v. vestitus feeding damage and supported more S. v. vestitus than Zoysia matrella (L.) Merrill. Among the Z. japonica cultivars, ‘Belair’ and ‘Zenith’ had less desirable agronomic traits and incurred greater feeding damage than other cultivars more tolerant to billbug damage. With Z. matrella, ‘Diamond’ and ‘Pristine Flora’ displayed superior agronomic traits and had the least feeding damage and lowest infestations of billbug immatures and were therefore considered the most tolerant or resistant Z. matrella cultivars tested. Results indicate that stem diameter may be an important factor for adult feeding and oviposition site selection, which might explain the different responses between Zoysia spp. to S. v. vestitus damage.
Increasing restrictions on chemical pesticide use in orchards have encouraged the use of alternative strategies to control the northern strain of the plum curculio, Conotrachelus nenuphar (Herbst). Some of these strategies target larvae as they emerge from fruit, so existing models for larval emergence from fruit were evaluated for accuracy while examining the effect of multiple larvae and fruit type on emergence timing. Larval head width growth rate was established and used to gauge larval development. Larval emergence timing, quantified as degree—days (base 11.1°C), was recorded in tart cherries on trees, and emergence timing was recorded in multiple apple varieties both in cyclical field conditions and in constant laboratory conditions. Ovipositing females and fruit were isolated, so larvae in a fruit were all siblings. Adult emergences from pupation in soil were recorded in the laboratory and compared with existing model predictions. Model predictions did not accurately reflect the timing of larval or adult emergence, and future incorporation of factors that could improve models are discussed. Colder conditions and changing host fruit type had no significant effect on larval emergence timing but changing host fruit type correlated with a shorter pupation interval. Results suggested that females preferred to oviposit on multiple fruit rather than lay multiple eggs in one fruit. Higher numbers of larvae per fruit did not significantly alter the timing of first larval emergence, although more larvae per fruit resulted in a significantly longer emergence period in apples.
In the Azores archipelago, a significant proportion of buildings are infested with the urban exotic drywood termite Cryptotermes brevis (Walker), causing major economical and patrimonial losses. This work aims to understand the potential spread of this termite species in the Azores and estimate the costs for both treatment and reconstruction of infested buildings in the entire archipelago. A maximum entropy niche modeling process was used to determine the potential occurrence of the species on each island. Different scenarios were built using independent global and regional incidence and environmental data. Both projections reveal the same pattern. Generally, the probability of occurrence is higher near the coast line, where, in Azores, the majority of the towns and villages are located. We also predict that the infestation has potential to spread to yet unaffected towns and islands. It is estimated that the cost of treating all currently infested buildings in the archipelago is 51 million, while reconstruction of the same buildings would rise the costs to 175 million. We predict that the absence of a control strategy will cause a further expansion of the pest to more localities in the Azores. An estimate to future scenarios implies higher costs, with treatment and rebuilding values rising up to eight times the current values.
The donor: recipient ratio and the time of donor exposure to termiticide required for maximal toxicant transfer among termites are crucial information for the development of termite management plans. Most of the available information on termiticide toxicity came from temperate zonal termite species, whereas little is known about tropical Asian species. In this study, mortality patterns of recipient termites, Coptotermes gestroi (Wasmann) subjected to seven formulated insecticide exposures under different donor exposure times and donor: recipient ratios were examined. For fipronil, lethal transfer was not affected by donor exposure time but was affected by the mixing ratio. The moderate-to-less toxic termiticides (imidacloprid, indoxacarb, bifenthrin, chlorfenapyr, and chlorantraniliprole) required long exposure time and a high mixing ratio to ensure maximal uptake by recipient workers compared with fipronil. For chlorantraniliprole and chlorfenapyr, donors must constitute >30% of the donor-recipient mixture to achieve 100% mortality of the recipient workers. Among the termiticides tested, cyantraniliprole was the most fast-killing insecticide against C. gestroi. The potential of lethal transfer among recipient termites does not necessarily require both high donor exposure time and a high mixing ratio, but the toxicity of a given termiticide against termites must be factored in to achieve colony elimination.
laboratory study was conducted to understand the effect of low concentrations of lufenuron on termite physiology and behavior. Survivorship, running speed, body water content, food consumption, tunneling, microbial infection, and two behavioral patterns (carcass-burying behavior and particle transport behavior) were compared among Formosan subterranean termites, Coptotermes formosanus Shiraki, fed lufenuron-treated (250, 500, or 1,000 ppm) or untreated (control) filter paper. In 30–32 d, all lufenuron treatments significantly reduced survivorship, running speed, consumption, and tunneling, but had no substantial effect on body water content. In addition, termites fed the three concentrations of lufenuron became infected by opportunistic pathogens. Carcass-burying and particle transport behaviors also were inhibited by lufenuron. Potential application of lufenuron at low concentrations for the control of C. formosanus is discussed.
The bed bug, Cimex lectularius L. (Hemiptera: Cimicidae), has resurged recently as a domestic pest in North America with very limited options for decisive control. We report efficacy studies with sulfuryl fluoride (SF) toward use as a structural fumigant to control bed bugs. Laboratory studies were conducted in which eggs, adults, and nymphs from a pesticide susceptible laboratory population were fumigated for 24 h using SF at 99.8% purity in airtight, 3.8-liter glass containers under two temperatures, 25°C and 15°C. Bed bugs were placed in separate ventilated glass vials and wrapped in mattress padding before fumigation. The gas concentration within each jar was determined using quantitative gas chromatography-mass spectrometry. Dose-response trials using eggs of known age (48–96 h) were conducted at five or six target concentrations measured as concentration X time accumulated dosages (g-h/m3) and one untreated control at each temperature. Each target dose was replicated in four different fumigation containers (replicates), with at least 32 eggs per replicate. The number of hatched and unhatched eggs postfumigation, and number of live and dead nymphs that resulted from hatched eggs, were evaluated daily for at least 1 wk after egg hatch. The lethal accumulated dosage (LAD99) for bed bug eggs was 69.1 (95% fiducial limits [FLs] of 62.9–79.5) g-h/m3 at 25°C and 149.3 (95% FLs of 134.4–177.9) g-h/m3 at 15°C. Confirmatory trials with dosages of 1.5× the LAD99 were conducted at 25°C and 1,5× the threshold mortality dose at 15°C with at least 15 adults, 13 late-instar nymphs and 79 eggs of known age per replicate. At 25°C, a target dosage of 103.7 g-h / m3 resulted in 100% mortality of adults and late-instar nymphs. Nymphs emerged and survived from two of 439 eggs treated with SF dosages that were 6–7 g-h/m3 less than the target dosage. No nymphs emerged from eggs fumigated with dosages >97.9 g-h/m3 in the validation study. Therefore, the threshold dosage for complete egg mortality (97.9 g-h/m3) was used, rather than the LAD99, to calculate the monitored field dosage rate of 148.2 g-h/m3 (= 1.5 × 97.9 g-h/m3) for control of all life stages of bed bugs at 25°C. Based on these results, at 15°C, 1.5× the threshold dosage for complete egg control (189.7 g-h/m3) was used to calculate a target dosage of 285 g-h/m3 for the confirmatory trial, which resulted in 100% mortality of adults, late-instar nymphs, and eggs.
The effect of spinosad exposure on the susceptibility of pyrethroid- and organophosphate-resistant populations of lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), to insecticides was investigated in broiler house farm and laboratory studies. A field pyrethroid- and organophosphate-resistant population showed a 3.6-fold increase in susceptibility to γ-cyhalothrin following spinosad treatment. Overall, cyfluthrin- and fenitrothion-resistant field populations were more susceptible to these insecticides following spinosad treatments, but populations that were not resistant showed no change in susceptibility following spinosad treatment. In a related study, three broiler farm beetle populations with very similar levels of cyfluthrin and γ-cyhalothrin resistance and similar susceptibilities to spinosad were used to investigate temporal effects of spinosad field treatments on the susceptibility to pyrethroids. Farm insecticide regimes applied at the start of each flock differed: the control broiler house received no insecticide applications, another house was systematically treated with cyfluthrin at the start of each study flock, and the third house was systematically treated with spinosad at the start of five flocks. Afterwards, treatments reverted to cyfluthrin on all farms. At the end of flocks, beetles were tested with cyfluthrin, γ-cyhalothrin, and spinosad. The control and cyfluthrin house beetles did not change susceptibility to pyrethroids over the period of the study. In the spinosad house, spinosad had no effect on spinosad susceptibility but dramatically increased cyfluthrin and γ-cyhalothrin susceptibilities. These new susceptibilities were maintained while spinosad applications continued, but pyrethroid susceptibility declined once spinosad applications ceased. This study provides evidence of a synergistic interaction between spinosad and pyrethroids in pyrethroid-resistant beetles. This evidence has significant implications for management of insecticide-resistant populations through an integrated spinosad-pyrethroid strategy that aims to minimize insecticide use while enhancing control.
Host plant resistant (HPR) crop varieties offer control of many insect pest species. However, the evolution of virulent biotypes capable of overcoming plant resistance poses challenges for the implementation of HPR. Widespread planting of HPR crops further reduces HPR efficacy by increasing selection pressure on pests, favoring the rapid proliferation of virulence. An analogous situation occurs in managing insect resistance to transgenic Bt crops, where planting of susceptible refuges effectively delays the evolution and spread of Bt resistance. We investigated the applicability of susceptible refuges in HPR as a tactic to manage virulent biotypes, using the soybean aphid (Aphis glycines Matsumura) as a model system. The virulent biotype 3 and avirulent biotype 1 were reared in greenhouse microcosms using a variety of refuge size, HPR gene, and biotype mixture treatments, allowing us to discern how the presence of a refuge alters the relative fitness and movement of biotypes both by themselves and in competition. The virulent biotype had greater relative fitness in 10 of 12 tested microcosms, with the greatest advantage observed in refuge-free microcosms. In microcosms with a refuge, avirulent fitness increased significantly as these biotypes moved to and used refuge plants. When the two biotypes were reared in the same microcosm, biotype 3′s fitness increased significantly relative to when reared in isolation, while biotype l’s fitness was slightly, but not significantly, increased. Our findings suggested that while susceptible refuges would be incapable of reversing the proliferation of virulent biotypes, they could slow the spread of virulence by maintaining avirulence.
Considerable attention has been given to delaying the evolution of insect resistance to toxins produced by transgenic crops. The major pests of cotton in Australia are the Lepidoptera Helicoverpa armigera (Hubner, 1805) and Helicoverpa punctigera (Wallengren), and the toxins deployed in current and imminent transgenic cotton varieties are Cry1Ac, Cry2Ab and Vip3A from Bacillus thuringiensis. In this study, lines that carry alleles conferring resistance to Cry2Ab and Vip3A were isolated using F2 tests. Extensive work on the Cry2Ab resistant lines, and preliminary work on the Vip3A resistant lines, suggested a single common resistance to each toxin in both species thereby justifying the use of more efficient F1 tests as the primary means for monitoring changes over time. A potential further efficiency could be gained by developing a single resistant line that carries both types of Bt resistance. Herein we report on work with both H. armigera and H. punctigera that tests whether dual Cry2Ab-Vip3A resistant lines can be developed and, if so, whether they can be used to effectively monitor resistance frequencies. Furthermore, the creation of dual resistant lines allowed linkage between the Cry2Ab and Vip3A resistances to be investigated for H. punctigera. We show that dual resistant lines can be used to increase the efficiency of the Fx screen for recessive alleles, and that in H. punctigera there is no linkage between Cry2Ab and Vip3A resistance.
The brown planthopper, Nilaparvata lugens (Stål), is one of the most important insect pests on paddy rice in tropical and temperate Asia. Overuse and misuse of insecticides have resulted in the development of high resistance to many different insecticides in this pest. Studies were conducted to evaluate the change of resistance level to four insecticides over 15 generations without any exposure to insecticides in brown planthopper. After 15 generations’ rearing without exposure to insecticide, brown planthopper could reverse the resistance to imidacloprid, chlorpyrifos, fipronil, and fenobucarb. The range and style of resistance reversal of brown planthopper differed when treated with four different insecticides. To monitor potential changes in insect physiological responses, we measured the activity of each of the three selected enzymes, including acetylcholinesterases (AChE), general esterases (EST), and glutathione Estratosferas. After multiple generations’ rearing without exposure to insecticide, AChE and EST activities of brown planthopper declined with the increased generations, suggesting that the brown planthopper population adjusted activities of EST and AChE to adapt to the non-insecticide environment. These findings suggest that the reducing, temporary stop, or rotation of insecticide application could be incorporated into the brown planthopper management.
The green peach aphid, Myzus persicae (Sulzer), is a serious pest throughout the world, attacking a broad range of crop plants across numerous agricultural industries. This species has a high propensity to develop chemical resistance, and has the unenviable title of having resistance to more insecticides than any other insect species. An extensive survey of field populations was undertaken across Australia, and showed widespread and high levels of resistance to carbamates and synthetic Pyrethroids in M. persicae. Moderate levels of resistance to organophosphates were also observed in many populations, while there is new evidence of resistance developing to neonicotinoids. Isofemale (clonal) lines of M. persicae were generated and subsequently tested across a range of insecticides; individual genetic clones were found to contain resistance to multiple chemical classes. Resistance genotyping of these aphids were consistent with published literature of known resistant mechanisms. The high and widespread levels of resistance identified within Australia are concerning. Resistance in M. persicae has spread quickly across Australia, and thus farmers are likely to have fewer chemical control options in the future. There is a need to develop resistance management strategies that rotate insecticides, spray insecticides only when economically necessary, and incorporate nonchemical control options.
Indoxacarb gel bait was evaluated for its efficacy in the laboratory and field against American cockroaches, Periplaneta americana (L.), and German cockroaches, Blattella germanica (L.). Advion 0.6% indoxacarb gel bait was toxic to both P. americana and B. germanica. There were no significant differences in the LT50 (h) values for treatment levels of 0.25 g, 0.5 g, and 1.0 g gel applied against P. americana, whereas gel applied at 0.5 g to B. germanica had a significantly greater LT50 (h) in the laboratory than the gel treatments on P. americana. The LT50 for both cockroach species ranged from 40.65 to 145.60 h. There was no control mortality in the laboratory bioassays. In the field, 55 houses were treated with 0.5 g of 6–8 spots of indoxacarb gel bait per kitchen of two or three bedroom bungalows from three Local Government Areas of Lagos State, comprising Sumiere (22), Alimosho (12), and Shomolu (21). Mean reduction in cockroach populations varied from location to location based on the level of infestations. Percentage reductions in the indoxacarb gel-treated units ranged from 3.5% at 1 d after treatment to 99.8% at 14 d at Sumiere, while reductions ranged from 8.9% at 1 d after treatment to 99.7% at 14 d at Shomolu; a similar trend was observed for Alimosho. Indoxacarb gel bait was highly effective in the control of cockroaches.
The genus Spodoptera comprises 31 species, 4 of which are listed as quarantine pests for the European Union: Spodoptera eridania (Cramer), Spodoptera frugiperda (Smith), Spodoptera littoralis (Boisduval), and Spodoptera litura (F.). In international trade, the earlier life stages (eggs and larvae) are being intercepted at point of inspection most frequently, challenging the possibilities of morphological identification. To realize a rapid and reliable identification for all stages, we developed and validated four simplex real-time polymerase chain reaction identification tests based on the mitochondrial cytochrome b gene using dual-labeled hydrolysis probes. Method validation on dilutions of extracted DNA of the target organisms showed that low levels of template (up to 0.2–100 pg) can reliably be identified. No cross-reactivity was observed with 14 nontarget Spodoptera and 5 non-Spodoptera species in the specific Spodoptera tests. The tests showed to be repeatable, reproducible (both 100%), and robust. The new Spodoptera tests have proven to be suitable tools for routine identification of all life stages of S.eridania, S. frugiperda,S. littoralis, and S.litura.
Digestive enzymatic activity and nutritional responses of sixth-instar larvae of the tomato fruit borer, Helicoverpa armigera (Hübner), were studied on eight tomato cultivars commonly cultivated in Iran. Among various tomato cultivars, the larvae fed on ‘Cal JN3’ (4.860 ± 0.092 U/mg) significantly showed the highest level of proteolytic activity. However, proteolytic activity of the larvae reared on ‘Sun 6108 fl’ (2.182 ± 0.161 U/mg) was significantly lower than those reared on Cal JN3, ‘Korral,’ ‘Rio grande UG,’ ‘Super crystal,’ and ‘CH falat’. Also, the larvae fed on Korral (0.170 ± 0.007 mU/mg) significantly had higher amylolytic activity than the other tomato cultivars. The pupal weight of H. armigera was significantly lower on Rio grande UG (0.208 ± 0.014 g), Sun 6108 fl (0.216 ± 0.008 g), and Super strain B (0.229 ± 0.014 g) than Cal JN3 and CH falat. Because the larvae and pupae reared on Rio grande UG were lighter than those fed on the others, this cultivar can be suggested as the least suitable host for feeding of H. armigera. However, because the mean weight gain of the larvae, food consumption, and larval weight during feeding period were significantly highest on CH falat, it can be selected as suitable cultivar for feeding of the pest.
The preferences of the West Indian sweet potato weevil, Euscepes postfasciatus (Fairmaire), to tubers of sweet potato, Ipomoea batatas (L.), for food and for oviposition were evaluated, and correlated to sweet potato's resistance to immatures. Adults (parent) were released in a plastic box containing tubers of sweet potato cultivars and maintained for 5 d, after which the adults on each tuber were counted. All adults were then removed and each tuber was maintained separately. New adults that emerged from the tubers were counted. Cultivars were grouped by cluster analyses using the number of parent adults on the tubers and the number of new adults emerging from the tubers, adjusted for the weight of each tuber. Cultivars were divided into five groups: average level of preference, preferred, preferred for oviposition but not for food, preferred for food but not for oviposition, and not preferred. New adults from the first two groups took less time to eclose than those from the other groups, and their body size was smaller. In a second experiment, one to five cultivars were selected from each group and inoculated each tuber with 10 weevil eggs on each cultivar. Although the proportion of eclosed adults was not significantly different between cultivars, the time to eclosion was shorter and body size was smaller on preferred cultivars. The selection of tubers by parent adults was not linearly related with larval development, and did not reduce the survival of the immatures.
The insecticidal genes from Bacillus thuringiensis Berliner (Bt) have long been successfully used for development of insect-resistant rice. However, commercial planting of Bt rice has been delayed by the concern over food safety, although no scientific evidence is ever found to justify the concern. To address this safety concern, we developed a transgenic insect-resistant rice line using a green tissue promoter to minimize the Bt protein expression in the rice seeds. The Bt protein expressed in the rice was a fusion protein of two different Bt toxins, Cry1Ac and Cry1I-like protein. The fusion of the two toxins may be helpful to delay the development of insect resistance to Bt rice. Laboratory and field bioassays demonstrated that the transgenic rice plants created by this study were highly active against the rice leaf folder Cnaphalocrocis medinalis (Guenée) and the striped stem borer Chilo suppressalis (Walker). Western analysis indicated that the fusion protein was specifically expressed in green tissues but not in seeds. Therefore, the transgenic rice created in this study should be useful to mitigate the food safety concern and to delay the development of insect resistance.
The soybean aphid (Aphis glycines Matsumura) is a threat to soybean production in the Midwestern United States. Varieties containing the Rag1 soybean aphid resistance gene have been released with limited success in reducing aphid populations. Furthermore, virulent biotypes occur within North America and challenge the durability of single-gene resistance. Pyramiding resistance genes has the potential to improve aphid population suppression and increase resistance gene durability. Our goal was to determine if a pyramid could provide improved aphid population suppression across a wide range of environments.Weconducted a small-plot field experiment across seven states and three years. We compared soybean near-isolines for the Rag1 or Rag2 gene, and a pyramid line containing both genes for their ability to decrease aphid pressure and protect yield compared with a susceptible line. These lines were evaluated both with and without a neonicitinoid seed treatment. All aphid-resistant lines significantly decreased aphid pressure at all locations but one. The pyramid line experienced lower aphid pressure than both single-gene lines at eight of 23 location-years. Soybean aphids significantly reduced soybean yield for the susceptible line by 14% and for both single-gene lines by 5%; however, no significant yield decrease was observed for the pyramid line. The neonicitinoid seed treatment reduced plant exposure to aphids across all soybean lines, but did not provide significant yield protection for any of the lines. These results demonstrate that pyramiding resistance genes can provide sufficient and consistent yield protection from soybean aphid in North America.
St. Augustinegrass (Stenotaphrum secundatum (Walter) Kuntze) is an economically important turfgrass in the southeastern United States. However, this turf species is prone to southern chinch bug, Blissus insularis Barber (Heteroptera: Blissidae) outbreaks. This insect is the most destructive pest of St. Augustinegrass wherever this turfgrass is grown. Host plant resistance has historically been an effective management tool for southern chinch bug. Since 1973, the ‘Floratam’ St. Augustinegrass cultivar effectively controlled southern chinch bug in the southeast. However, southern chinch bug populations from Florida and Texas have now circumvented this resistance, through mechanisms still unknown. Therefore, identifying and deployingnewcultivars with resistance to the southern chinch bug is imperative to combat this pest in an economically and environmentally sustainable manner. Currently, the number of cultivars with resistance against southern chinch bug is limited, and their efficacy, climatic adaptability, and aesthetic characters are variable. Hence, the main focus of this study is the identification of alternative sources of resistance to southern chinch bugs in previously uncharacterized St. Augustinegrass plant introductions (PIs) and its closely related, crossbreeding species, Pembagrass (Stenotaphrum dimidiatum (L.) Brongniart). The PIs exhibited a wide range of responses to southern chinch bug feeding, as indicated by damage ratings. Damage ratings for seven PIs grouped with our resistant reference cultivars. Moreover, nine PIs exhibited antibiosis, based on poor development of southern chinch bug neonates, when compared with our susceptible reference cultivars. Altogether our study has produced strong support to indicate these materials are good candidates for future southern chinch bug resistance breeding in St. Augustinegrass.
Alkali bees, Nomia melanderi Cockerell, are solitary, gregarious, soil-nesting bees native to the western United States that are commercially managed in the Walla Walla Valley of Washington State to provide pollination service on alfalfa, Medicago sativa L., produced as a seed crop. In 2010 and 2011, we compared two techniques for estimating N. melanderi abundance in commercially managed bee beds. The first technique involved quantifying the abundance of emergence holes in 24 0.5-m2 quadrats on the surface of 13 bee beds during the peak period of N. melanderi foraging activity in July of both years. When we counted emergence holes, we marked a subset of eight quadrats per bee bed with plastic tabs. Subsequently, in late October of the same year, 0.014-m3 soil cores were collected in close proximity to the plastic tabs. The soil cores were teased apart in the laboratory and the absolute abundance of overwintering prepupae was quantified per core. Simple regression was highly significant between the means of emergence holes within the 0.5-m2 soil surface quadrats and the means of the counts from the 0.014-m3 soil cores. Using mean emergence hole counts, mean prepupae counts from the soil cores, and the surface area of the bee beds, we were able to calculate the estimated abundance of N. melanderi in each bee bed. We conclude that the nondestructive quadrat method of sampling N. melanderi abundance in commercially managed beds is robust compared with the destructive, labor-intensive, absolute soil core method.
The concentration of carminic acid was found to vary based on the size and life cycle stage of the cochineal, Dactylopius coccus Costa. The concentration of carminic acid in cochineal eggs, nymph I, nymph II, fertilized adults, ovipositing adults, and sterile adults female was measured using capillary electrophoresis, and the total fluorescence of the carminic acid globules was measured using flow cytometry. The smallest sterile adult females had a greater percentage of carminic acid relative to their weight (26.27%; P < 0.001) than adult females in the remaining groups. In general, ovipositing females had a greater percentage of carminic acid than the remainder of the females. Nymph II was the phase that had the smallest percentage of carminic acid. Usingflowcytometry, it was demonstrated that ovipositing females had a greater total fluorescence than the other sampled groups (P < 0.05). A positive correlation was found between the percentage of carminic acid and the total fluorescence of the carminic acid globules (r2 = 0.68; P < 0.05). The results of this study, together with others that involve industrial processes, shall allow an improvement of the current classification criteria of the commercial quality of dry cochineal.
The aim of this research was to determine chemical composition and repellent and insecticidal activities of the essential oil of Kaempferia galanga L. rhizomes against the booklouse, Liposcelis bostrychophila Badonnel, and to isolate insecticidal or repellent constituents from the oil. The essential oil was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. Twenty-eight components of the oil were identified. The major compounds in the oil were ethyl-ρ-methoxycinnamate (38.6%), ethyl cinnamate (23.2%), 1,8-cineole (11.5%), transcinnamaldehyde (5.3%), and borneol (5.2%). Based on bioactivity-guided fractionation, four active constituents were isolated from the oil and identified as 1,8-cineole, ethyl cinnamate, ethyl ρ-methoxycinnamate, and trans-cinnamaldehyde. The essential oil exhibited contact toxicity against the booklouse with an LC50 value of 68.6 µg/cm2. Ethyl cinnamate (LC50 = 21.4 µg/cm2) exhibited stronger contact toxicity than ethyl ρ-methoxycinnamate and trans-cinnamaldehyde (LC50 = 44.6 and 43.4 µg/cm2, respectively) while 1,8-cineole showed weak acute toxicity. The essential oil also possessed fumigant toxicity against the booklouse with a LC50 value of 1.5 mg/liter air. 1,8-Cineole and trans-cinnamaldehyde (LC50 = 1.1 and 1.3 mg/liter, respectively) possessed stronger fumigant toxicity against the booklouse than ethyl cinnamate and ethyl ρ-methoxycinnamate (LC50 = 10.2 and 10.2 mg/liter air, respectively). trans-Cinnamaldehyde was strongly repellent to booklice, whereas ethyl cinnamate and ethyl ρ-methoxycinnamate were weakly repellent and 1,8-cineole did not repel booklice. The results indicate that the essential oil and its constituent compounds have potential for development into natural insecticides or fumigants and repellents for control of insects in stored grains.
D. T. Silva, L. L. Silva, L. P. Amaral, C. G. Pinheiro, M. M. Pires, B. Schindler, Q. I. Garlet, S. C. Benovit, B. Baldisserotto, S. J. Longhi, C. B. Kotzian, B. M. Heinzmann
Odonate larvae can be serious pests that attack fish larvae, postlarvae, and fingerlings in fish culture tanks, causing significant loss in the supply and production of juveniles. This study reports a screen of the essential oils (EOs) of Nectandra megapotamica (Sprengel) Mez, Nectandra grandiflora Nees, Hesperozygis ringens (Bentham) Epling, Ocimum gratissimum L., Aloysia gratissima (Gillies & Hooker) Troncoso, and Lippia sidoides Chamisso against Coenagrionidae larvae. In addition, the most effective EO and its 50% lethal concentration (LC50) and chemical analysis are described. The larvae of Acanthagrion Selys, Homeoura Kennedy, Ischnura Charpentier, and Oxyagrion Selys were used to assess the EO effects. EO obtained from H. ringens, O. gratissimum, and L. sidoides showed the highest larvicidal effects at 19 h of treatment.Themajor constituents of theEOofH. ringens include pulegone and limonene, while eugenol and Z-β-ocimene predominate in the EO of O. gratissimum, and carvacrol and π-cymene were the major compounds of the EO of L. sidoides. Leaf EOs from H. ringens, O. gratissimum, and L. sidoides showed activity against Coenagrionidae larvae at similar concentrations with LC50s of 62.92, 75.05, and 51.65 µl liter-1, respectively, and these were considered the most promising treatments.
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