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The navel orangeworm, Amyelois transitella (Walker), is the primary insect pest of pistachios and almonds in California. Four years of research (2002–2006) were conducted in Madera and Kern Counties to elucidate the pattern of adult emergence of the overwintering navel orangeworm population. Springtime emergence from unharvested (mummy) nuts was protracted (600 degree-days or more from 1 January of each year) and in 2004 and 2006 extended to mid-July. The population structure, sex ratio, and timing of emergence differed between pistachio and almond mummies, Pistachio populations had a significantly greater proportion of late stage individuals compared with almond mummies, 85.7 versus 34.1%. The sex ratio of adults emerging from pistachio mummies was significantly skewed with a ratio 57:43 male:female compared with 50:50 in almond mummies. Emergence from mummies held outdoors (variable temperature) began in early March and continued through early June in both pistachio mummies and almond mummies. The adult emergence pattern from pistachio mummies contained a single emergence peak, whereas emergence from almond mummies occurred in multiple peaks. These same patterns occurred when mummies were held at constant temperature, and the emergence peak from pistachio mummies occurred sooner. The impact of these findings on understanding navel orangeworm population dynamics and current control recommendations is discussed.
Overwintering survival of Helicoverpa armigera (Hübner) was studied under field conditions during the winter of 2004–2005 and 2005–2006 to clarify whether a local population of this insect is established in northern Greece. Additionally, the postdiapause eclosion times of the overwintering generation was compared with adult male dynamics using pheromone traps. Our study supplies strong evidence that part, if not all, of the late-season generation of H. armigera overwinters as diapausing pupa in northern Greece, suggesting that a local population exists in this area. Pupae enter diapause during September and October in response to declining temperatures and photoperiod. A limited number of degree-days in autumn prevented part of the population from developing to the diapausing pupal stage. Larvae of H. armigera that were placed in field conditions late in October were not able to pupate and died. The termination of diapause and the eclosion of adults in the following spring were determined by the local soil temperatures. Diapause terminated between mid-April and early May, and adult emergence occurred within a 4- to 6-wk period from late April to early June. Females emerged slightly earlier than the males. The emergence of 10, 25, 50, 75, and 90% of adults required 153, 199, 252, 303, and 347 DD, respectively. Differences in timing and degree of overlap between adult emergence from the experimental population and pheromone trap catches suggests that the spring population of this species also includes immigrants.
Reduced insecticide use in cotton, Gossypium hirsutum L., as a consequence of the Boll Weevil Eradication Program and the broad adoption of Bt cotton, have helped make the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), a consistent pest of cotton each year in the mid-south. Maize, Zea mays L., has been implicated as having a role in the season-long dynamics of tarnished plant bug infestations in cotton. To date, no published information exists describing the quality of maize as a host for tarnished plant bug. No-choice field studies indicated that adult tarnished plant bug females oviposited into maize leaves, tassels, and ears. Laboratory studies showed that first-instar tarnished plant bugs could successfully develop to the adult stage when fed maize silks at the R1 growth stage, tassels before (VT) and during (R1) pollen shed, and milk stage (R3) kernels from the tip and base of the ear. The proportion of nymphs surviving to the adult stage on these tissues was often similar to that of broccoli, Brassica oleracea L. Nymphs did not develop to adults when fed V5 or R1 maize leaves. However, survival of first instars to the adult stage was improved when nymphs fed on tassels with pollen for 6 d and then moved to silks or leaves. Another field study showed that tarnished plant bugs reproduced in maize mainly during the tassel (VE and VT) and the R1–R3 ear growth stages, and a single new generation was produced in maize during these stages. The highest population recorded during the study (24 June 2005) consisted mostly of nymphs and was estimated to be 29,600/ha (12,000/acre). These studies showed that maize is a suitable host for tarnished plant bug reproduction and development, and its production plays a significant role in the population dynamics of the tarnished plant bug in the mid-south.
The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), is an invasive pest of canola (Brassica napus L. and Brassica rapa L.) in western Canada. Under current climatic conditions, C. obstrictus is spreading from established populations in southwestern Alberta at ≈55 km/yr. We studied the influence of climatic conditions on C. obstrictus flight behavior in 2007 and 2008 and eastward dispersal from the western border of Saskatchewan from 2002 to 2007. Positive linear relationships between increases in mean temperature and flight height and between greater mean maximum temperature and expanded dispersal distances were significant. Increases in relative humidity were associated with reduced flight heights and dispersal distances. We developed models that predict the relationships of temperature and relative humidity with flight height and with dispersal distance. We also discuss implications for C. obstrictus dispersal under current climatic conditions and in the context of predicted climate change.
Seven mark-recapture studies were conducted over 3 yr to assess dispersal of newly emerging adult stable flies, Stomoxys calcitrans L., from larval development sites in a mixed agricultural environment in northeastern Nebraska. Infested hay debris piles were marked by dusting their surfaces with fluorescent pigments, adults were captured with surrounding grids of Alsynite sticky traps, and specimens were dissected to determine feeding histories and reproductive age, Distances and directions of 3,889 marked specimens indicated males and females dispersed equally and in all directions. Midguts of males and females were equally likely to contain blood-meal remnants. Percentage with blood remnants and percentage of females with yolk increased with distance from mark origin, indicating survival and spread were positively associated with host finding success. A time-integrated diffusion model fit to results from the seven studies indicated 50% of stable fly adults had dispersed beyond 1.6 km of their natal site, but only 5% had dispersed beyond 5.1 km. These results indicate that stable fly adults on cattle in a given area are most likely to have originated from larval development sites within an ∼5 km radius of the subject cattle.
Commercially produced maturity group (MG) IV soybeans, Glycine max L., were sampled during bloom for tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), during May and June 1999 (3 fields) and 2001 (18 fields). The adults and nymphs were found primarily in single population peaks in both years, indicating a single new generation was produced during each year, The peak mean numbers of nymphs were 0.61 and 0.84 per drop cloth sample in 1999 and 2001. respectively. Adults peaked at 3.96 (1999) and 3.76 (2001) per sweep net sample (25 sweeps). Tests using laboratory-reared and field-collected tarnished plant bugs resulted in very poor survival of nymphs on 16 different soybean varieties (MG III, one; IV, four; V, nine; VI, two). A large cage (0.06 ha) field test found that the number of nymphs produced on eight soybean varieties after mated adults were released into the cages was lower than could be expected on a suitable host. These results indicated that soybean was a marginal host for tarnished plant bugs. However, the numbers of adults and nymphs found in the commercially produced fields sampled in the study may have been high enough to cause feeding damage to the flowering soybeans. The nature of the damage and its possible economic importance were not determined. Reproduction of tarnished plant bugs in the commercially produced early soybean fields showed that the early soybeans provided tarnished plant bugs with a very abundant host at a time when only wild hosts were previously available.
We examined the effect of regional climate warming on the phenology of butterfly species in boreal forest ecosystems in Manitoba, Canada. For the period 1971–2004, the mean monthly temperatures in January, September, and December increased significantly, as did the mean temperatures for several concurrent monthly periods. The mean annual temperature increased ≈ 0.05°C/ yr over the study period. The annual number of frost-free days and degree-day accumulations increased as well. We measured the response of 19 common butterfly species to these temperature changes with the date of first appearance, week of peak abundance, and the length of flight period over the 33-yr period of 1972–2004. Although adult butterfly response was variable for spring and summer months, 13 of 19 species showed a significant (P < 0,.05) increase in flight period extending longer into the autumn. Flight period extensions increased by 31.5 ± 13.9 (SD) d over the study period for 13 butterfly species significantly affected by the warming trend. The early autumn and winter months warmed significantly, and butterflies seem to be responding to this warming trend with a change in the length of certain life stages. Two species, Junonia coenia and Euphydryas phaeton, increased their northerly ranges by ≈150 and 70 km, respectively. Warmer autumns and winters may be providing opportunities for range extensions of more southerly butterfly species held at bay by past climatic conditions.
The changes in the plant community that occur during the process of succession affect the availability of resources for the community of herbivores. In this study, the richness of galling insects was evaluated in restored stands of Amazonian tropical rain forest of several ages (0–21 yr), as well as in areas of primary forest in Brazil. The richness of gallers increased with the age of the restored stands. Fifty-eight percent of the variation in the richness of galling insects was explained by forest stand age, but an increase in richness was observed at intermediate stages of succession. The greatest similarity among groups was found between the initial successional stages and intermediate ones. The results indicate a recovery of both host plants and insect community and that succession directly affects the richness and composition of these herbivores.
Invasive ants are notorious for directly displacing native ant species. Although such impacts are associated with Argentine ant invasions (Linepithema humile) worldwide, impacts within natural habitat are less widely reported, particularly those affecting arboreal ant communities. Argentine ants were detected in North Carolina mixed pine-hardwood forest for the first time but were localized on and around loblolly pines (Pinus taeda), probably because of association with honeydew-producing Hemiptera. We explored the potential impacts of L. humile on arboreal and ground-foraging native ant species by comparing interspersed loblolly pines invaded and uninvaded by Argentine ants. Impacts on native ants were assessed monthly over 1 yr by counting ants in foraging trails on pine trunks and in surrounding plots using a concentric arrangement of pitfall traps at 1, 2, and 3 m from the base of each tree. Of floristics and habitat variables, higher soil moisture in invaded plots was the only difference between plot types, increasing confidence that any ant community differences were caused by Argentine ants. Overall patterns of impact were weak. Composition differed significantly between Argentine ant invaded and uninvaded trunks and pitfalls but was driven only by the presence of Argentine ants rather than any resulting compositional change in native ant species. Native ant abundance and richness were similarly unaffected by L. humile. However, the abundance of individual ant species was more variable. Although numbers of the arboreal Crematogaster ashmeadi (Myrmicinae) declined on and around invaded pines, epigeic Aphaenogaster rudis (Myrmicinae) remained the most abundant species in all plots. Argentine ant densities peaked in late summer and fall, therefore overlapping with most native ants. Unexpected was their continued presence during even the coldest months. We provide evidence that Argentine ants can invade and persist in native North Carolina forests, probably mediated by pine-associated resources. However, their localized distribution and minimal impact on the native ant fauna relative to previously described invasions requires further resolution.
Vertebrate dung and carrion are rich and strongly attractive resources for numerous beetles that are often closely linked to them. The presence and abundance of beetles exploiting such resources are influenced by various ecological factors including climate and forest cover vegetation. We studied selected assemblages of coprophilous and necrophagous beetles in Quebec along a 115-km north-south transect in three balsam fir (Abies balsamea (L.) Miller) forest sites and in a fourth forest site dominated by sugar maple (Acer saccharum Marshall), close to the southern fir site. Beetle abundance was estimated using a sampling design comprising replicated pitfall traps baited with red deer meat or dung in each site. A total of 8,511 beetles were caught and identified to family level, 95.7% of which belonged to families with known coprophilous or necrophagous behavior. Meat-baited pitfall traps caught nearly 15 times as many beetles as dung-baited traps. All Histeridae, Hydrophilidae, Scarabaeidae, and Silphidae were identified to species to examine specific diversity variation among sites. For the beetles caught in the meat-baited traps (majority of captures), decreases in abundance and species richness were observed from south to north along the fir forest transect, with evidence of decreasing specific diversity as measured by the Shannon index of diversity. Strong differences in species assemblages were also observed between the southern maple and fir forest sites. The Silphidae and Histeridae were more abundant in the maple forest, whereas the Hydrophilidae and Ptilidae were more abundant in the fir forest.
Invasive species significantly contribute to biological change and threaten biodiversity, with a growing body of evidence that plant invasions affect higher trophic levels. We explored the relative importance of plant invasion and forest structure on aerial arthropod abundance, diversity, and composition on Robinson Crusoe Island, Chile. We used flight intercept traps to sample aerial arthropods within distinct canopy strata of native and invaded forests over 3-mo periods in 2006 and 2007. Arthropod abundance and diversity were higher in native than invaded forest, and arthropod communities were distinct between forest types. In both forest types, arthropod abundance was highest in the lower canopy, and canopy strata exhibited some differences in arthropod community composition. Several morphospecies were distinctly associated with each forest type. The strong differences in aerial arthropod communities associated with the invasion of native forest by non-native plants may affect other trophic levels, such as insectivorous birds. Steps to stop invasive plant spread and to restore native forest composition and structure are needed to safeguard the integrity of native communities, from plants to higher-level consumers.
At two temperate pasturelands in northern Mexico, we explored possible competition for food and space under pats during the simultaneous nesting periods of the univoltine species Dichotomius colonicus (Say), Phanaeus quadridens (Say), and Copris sierrensis Matthews. To simulate unlimited resources, 50 5-kg cow dung pats were placed at regular distance intervals in each pastureland. After building trenches around the pats, the number and depth of each nest, as well as larval development status, were documented once for a period of 1–8 mo. Analyses of variance and association tests were used to make a between-site comparison of dung pat occupation, nests occupied per species, nests per dung pat, and nest depth below each pat. The proportion of pats occupied by each species differed significantly between sites. C. sierrensis colonizing most pats at one site and D.colonicus at the other. There were no differences between sites in the frequency of pats occupied by more than one species. The association test and Ochiai index showed that each species colonized dung pats independently. The results suggest that pat occupation depended on their location by beetles and the relative abundance of each species. The species tended to dig nests at different depths, possibly reducing interspecific competition for space. It can therefore be concluded that, when food resources seem to be unlimited, they are shared following a “lottery dynamic” model if there is spatial differentiation among species.
Folsomia Candida Willem (Isotomidae: Collembola) is an edaphic parthenogenetic species commonly used in ecotoxicity studies. We exposed F. Candida to a high dose of three antibiotics, tylosin, ampicillin, and Oxytetracycline, that target different bacterial groups. Possible toxic effects were assessed through egg production, hatching, and body size. All three antibiotics caused toxic effects. Treatment with Oxytetracycline proved the most toxic. This group showed the smallest body size and lowest number of eggs laid, likely the result of a combination of antibiotic toxicity and avoidance of the antibiotic spiked food. Active toxin avoidance by F. Candida in toxicological assays may play a role in minimizing their exposure to toxic compounds. Despite the administration of high doses of Oxytetracycline, F. Candida individuals remained infected with the intracellular bacteria Wolbachia indicating that this strain is resistant to this antibiotic or that the host or its gut flora had detoxified the compound. An increase in percent egg hatch with time was seen in the ampicillin and Oxytetracycline treatments, indicating a possible accommodation of the host and/or gut-flora to these antibiotics.
Phylogenetic analyses, from polymerase chain reaction (PCR)-amplified 12S rRNA and 18S rRNAgene sequences from cochineal insects of the genus Dactylopius present in Mexico, showed that D. ceylonicus, D. confusus, and D. opuntiae are closely related. D. coccus constitutes a separate clade, and D. tomentosus is the most distantly related. Bacterial 16S rRNA sequences from all the Dactylopius species sampled showed a common β-proteobacteria, related to Azoarcus, also found in eggs and in bacteriocytes in D. coccus. We propose the name “Candidatus Dactylopiibacterium carminicum” for this endosymbiont. Other bacterial sequences recovered from the samples were close to those from soil or plant associated bacteria, like Massilia, Herbaspirillum, Acinetobacter, Mesorhizobium, and Sphingomonas, suggesting a possible horizontal transmission from Cactaceae plant sap to Dactylopius spp. during feeding. This is the first molecular analysis of Dactylopius species and of their associated bacteria.
Nezara viridula L. and Euschistus servus (Say) are the predominant species of phyto-phagous stink bugs on corn, Zea mays L., in Georgia. Oebalus pugnax pugnax (F.) occurs in relatively low numbers, and the predatory stink bug Podisus maculiventris (Say) is commonly found, Limited information is available on natural biological control of these four stink bug species in Georgia corn fields; therefore, a 6-yr study of parasitism and predation of their eggs was initiated in 2003. Naturally occurring stink bug eggs were parasitized by six scelionid species, Trissolcus basalis (Wollaston), T. thyantae Ashmead, T. brochymenae (Ashmead), T. euschisti (Ashmead), Telenomus podisi Ashmead, Telenomus calvus Johnson, and one encyrtid species, Ooencyrtus sp. T. basalis was the most prevalent parasitoid of N. viridula, parasitizing E. servus and P. maculiventris eggs at low levels. T. podisi, the predominant parasitoid species emerging from eggs of E. servus and P. maculiventris, also parasitized O. p. pugnax eggs exclusively and parasitized N. viridula eggs at low levels. T. euschisti and T. thyantae parasitized E. servus egg masses. T. brochymenae parasitized eggs of both E. servus and P. maculiventris. T. calvus parasitized only P. maculiventris eggs. The same species of egg parasitoids that parasitized naturally occurring eggs of N. viridula and E. servus parasitized sentinel eggs of these bugs, except that no T. calvus and Ooencyrtus sp. were obtained from sentinel eggs, and T. thyantae and T. brochymenae emerged from sentinel eggs of N. viridula. Generally, parasitization of an egg mass was either greater than or equal to predation of sentinel eggs of N. viridula and E. servus. However, on some dates in late June and July, predation of sentinel egg masses was numerically approximately twice as high as parasitism. Results indicate stink bug egg parasitoids and predators are significant factors in the natural biological control of stink bugs in corn fields.
The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), is an alien invasive pest of canola, Brassica napus L., in North America. Field populations of both adults and larvae are known to be aggregated in their distributions, but the causal mechanism for this clustering is not understood. We investigated the hypothesis that spatial distributions of C.obstrictus adults, larvae, and their parasitoids were directly or indirectly related to host plant quality as indicated by leaf tissue nutrient contents. During the years of 2005 and 2007, these insect populations were sampled in a grid pattern in three commercial fields of B. napus located near Lethbridge, Alberta, Canada. Leaf samples were collected from plants in each grid plot and analyzed for nutrient contents. Spatial patterns and associations among the collected variables were analyzed using Spatial Analysis by Distance IndicEs software. We observed significant spatial associations among C.obstrictus adults, larvae, and parasitoids. The distributions of C.obstrictus adults and larvae were correlated with several plant nutrients, most notably nitrogen and sulfur. Evidence was found for a possible nitrogen-sulfur interaction in which ovipositioning C.obstrictus females appeared to prefer plants with high levels of sulfur and low levels of nitrogen. Spatial tracking of C.obstrictus larvae by its parasitoids was evident in only one field, and this appeared related to comparatively low parasitoid populations in two of the three fields. The associations between C.obstrictus and plant nutrients may have possible applications in fertility management, trap cropping, and precision insecticide application technology.
Diuraphis noxia (Kurdjumov) (Russian wheat aphid) has severe economic impacts on wheat and barley production in the United States. The interaction between the Russian wheat aphid and its cereal hosts is poorly understood. However, the recent appearance of new biotypes in the United States showed that specific interactions exist between wheat resistance loci and Russian wheat aphid biotypes. At present, Dn7 is the only known gene in hexaploid wheat that confers resistance against all U.S. Russian wheat aphid biotypes. This study was conducted to investigate the molecular mechanism of Dn7-mediated resistance against two U.S. Russian wheat aphid biotypes (Russian wheat aphid 1 and Russian wheat aphid 2). Using GeneChip Wheat Genome Arrays, we compared transcript profiles of resistant and susceptible lines infested with either Russian wheat aphid 1 or Russian wheat aphid 2 using two time intervals (5 and 48 h after infestation). Russian wheat aphid feeding on hexaploid wheat led to the induction of groups of genes functioning in oxidative and general stress, photosynthesis, cell respiration and energy production, signal transduction, calcium-dependent signaling, pathogenesis related (PR) responses, and defense compound synthesis. The number of differentially expressed genes was higher in plants infested with Russian wheat aphid 1 compared with those infested with Russian wheat aphid 2. Although most genes involved in basic cellular functions were shared, unique genes were also obtained. This finding may indicate subtle differences in genes induced in response to different virulence proteins.
We evaluated the relationships between plant water status and leaf temperature, and between leaf temperature and spider mite (Acari: Tetranychidae) and predatory mite (Acari: Phytoseiidae) populations in eight vineyards in California in 2006 and 2007. Temperature of south-facing leaves increased significantly by 0.8°C for every 1.0°C increase in ambient air temperature, and by 5.3°C for every one MPa drop in leaf water potential. Peak population densities of Pacific spider mite, Tetranychus pacificus McGregor, increased significantly with increasing frequency of leaf temperatures above 31°C. In contrast, peak population densities of Willamette spider mite, Eotetranychus willamettei (McGregor), showed no relationship with the frequency of leaf temperatures above 31°C. This differential relationship between the two mite species and high leaf temperatures is consistent with their upper thresholds for development, which are 40°C for T. pacificus and 31°C for E. willamettei, as identified in a previous study. Predatory mite population densities showed no relationship with peak population densities of either spider mite species during the analysis period, but decreased with the frequency of leaf temperatures above 31°C. In addition, predatory mite population densities were significantly higher on south-facing than interior leaves after adjusting for the effect of leaf temperature. These results help to explain why outbreaks of T. pacificus occur in warmer or water-stressed vineyards, whereas E. willamettei develops higher populations in cooler or well-irrigated vineyards. In addition, these results suggest that regulated deficit irrigation should be implemented with caution, especially in those vineyards with a high risk of T. pacificus outbreaks.
A complex of invasive weevils that consume roots as larvae and foliage as adults have become established in northern hardwood forests in North America. We evaluated adults of the two most prominent species, Phyllobius oblongus and Polydrusus sericeus, for longevity, foliage consumption, and egg production on several putative hosts commonly found in this ecosystem. Adult pairs were monitored in no-choice laboratory assays for the duration of their lifespans on basswood, Tilia americana, ironwood, Ostrya virginiana, sugar maple, Acer saccharum, raspberry, Rubus spp., or leatherwood, Dirca palustris. Overall, P. sericeus lived more than twice as long as P. oblongus and lived longer on all hosts. P. sericeus consumed more total leaf area than P. oblongus on basswood, ironwood, and raspberry, but P. oblongus had a higher leaf consumption rate on sugar maple. Basswood was a very good host for P. sericeus. Leatherwood was not a suitable host for either weevil species. The higher longevity and fecundity of P. sericeus than P. oblongus did not agree with that expected from population data, in that the latter species is substantially more abundant. This likely reflects P. oblongus' superior performance on sugar maple, the dominant flora in the study area. These data provide a basis for estimating the broader impacts of adult weevil feeding.
The oriental army worm, Mythimna separata Walker (Lepidoptera: Noctuidae), was adopted as a host to keep Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae) populations in the laboratory, because it can be mass reared, However, wasp cocoon production in this system via single parasitism was not satisfactory. To improve the rearing efficiency of C. chlorideae on M. separata, we studied the effects of superparasitism on the offspring production of C. chlorideae, as well as the host discrimination ability of the adult wasps in the laboratory. The results showed that, compared with single parasitism, both double and quintuple parasitism significantly increased C. chlorideae cocoon production in M. separata without a significant effect on emergence, weight, or sex ratio of adult wasps at the P < 0.05 level. Host selection experiments suggested that C. chlorideae preferred to lay eggs on unparasitized hosts rather than freshly parasitized hosts but could distinguish neither the 24-h postparasitization hosts from the unparasitized hosts nor the freshly self-parasitized hosts from the conspecifically parasitized hosts. Nochoice behavior tests indicated that C. chlorideae took significantly longer time to accept the freshly parasitized hosts containing more than two eggs compared with the unparasitized hosts. In the end, superparasitism behavior and its application in the mass rearing of this endoparasitoid are discussed.
Remote sensing can be used in combination with ground sampling to detect aphid(Aphis gossypii Glover) infested cotton (Gossypium hirsutum L.). Changes in wavelengths in the near-infrared (NIR) have proven useful for such detection, but these changes can be confused with other factors stressing plants, such as water deficiency and nutrient status. This study was designed to test the utility of this technology to distinguish between two factors stressing plants: nitrogen deficiency and aphids. Field plots were created by applying varying rates of nitrogen to cotton at different dates in the growing season in 2003 and 2004. Subplots were created by applying disruptive insecticides, which increased aphid populations in a portion of the subplots. Airplane and satellite remote sensing data in 2003 and 2004 were supplemented with ground sampling of aphid populations in both years. Insecticide application, nitrogen application rate and date influenced aphid abundance. Cotton with higher aphid populations could be distinguished from cotton with natural aphid infestations independent of plant nitrogen status using a NIR wavelength in 2003 and a proprietary 2004 index. Complex distinctions among varying nitrogen treatments and aphid abundance were not possible using this data. In the future, possible confounding factors should be investigated from the perspective of their change on crop physiology before remote sensing can be used in an integrated pest management (IPM) program.
The glassy-winged sharpshooter, Homalodisca vitripennis (Germar), vectors the bacterium Xylella fastidiosa that induces Pierce's disease of grape. This study determined the effect of temperature on the feeding activity of H. vitripennis adults and the resulting production of excreta. The Logan type I model described a nonlinear pattern that showed excreta production increased up to an optimal temperature (33.1°C), followed by an abrupt decline near an estimated upper threshold (36.4°C). A temperature threshold for feeding, at or below which adults cease feeding, was estimated to be 10°C using a linear regression model based on the percentage of adults producing excreta over a range of constant temperatures. A simulated winter-temperature experiment using fluctuating thermal cycles confirmed that a time period above the temperature threshold for feeding was a critical factor in determining adult survival. Using data from the simulated temperature study, a predictive model was constructed by quantifying the relationship between cumulative mortality and cooling degree-hours. In field validation experiments, the model accurately predicted the temporal pattern of overwintering mortality of H. vitripennis adults held under winter temperatures simulating conditions in Bakersfield and Riverside, California, in 2006–2007. Model prediction using winter temperature data from a Riverside weather station indicated that H. vitripennis adults would experience an average of 92% overwintering mortality before reproduction in the spring, but levels of mortality varied depending on winter temperatures. The potential for temperature-based indices to predict temporal and spatial dynamics of H. vitripennis overwintering is discussed.
The raspberry weevil, Aegorhinus superciliosus (Guérin) (Coleoptera: Curculionidae), is the most important pest in blueberry and raspberry fields in the south of Chile. In this study, we investigated the electroantennographic and behavioral responses of A. superciliosus to semiochemicals released from conspecific individual adults, with particular attention to male attraction to females. Odors released from females significantly attracted males in a Y-tube olfactometer. Gas chromatographic and mass spectral analysis of female volatile extracts revealed the presence of limonene and α-pinene. Electroantennogram recordings from both sexes indicated that males of A. superciliosus possess olfactory sensitivity for the R isomer of limonene and α-pinene, whereas females only perceived R-limonene. Behavioral assays using synthetic compounds showed that only R-limonene elicited an attraction response from male weevils. Field experiments confirmed the laboratory results, showing that R-limonene was attractive to weevils. This is the first report of intraspecific chemical communication in this weevil. We discuss the origin of these compounds, their possible role in the sexual behavior of this species, and their potential use in a pest control strategy.
The performance of clear delta traps baited with 3.0 mg of pear ester, ethyl (E,Z)2,4-decadienoate, and 5.0 ml of acetic acid in separate lures was compared with orange delta traps baited with a single lure containing 3.0 mg of both pear ester and the sex pheromone, (E,E)-8,10dodecadien-1-ol (codlemone) for codling moth, Cydia pomonella (L.), in apple, Malus domestica (Borkhausen). Residual analyses and field tests demonstrated that both the pear ester and acetic acid lures were effective for at least 8 wk. The two trap-lure combinations caught a similar number of total moths in an orchard treated with sex pheromone dispensers during short-term trials in 2008. However, the mean catch of female moths was significantly higher and male moths significantly lower in clear traps baited with pear ester and acetic acid versus orange traps baited with pear ester and codlemone. Season-long studies were conducted with these two trap-lure combinations in orchards treated with (n = 6) and without (n = 7) sex pheromone dispensers during 2009. The two trap-lure combinations caught similar numbers of moths in dispenser-treated orchards. In contrast, total catch was significantly higher (>2-fold) in the orange compared with the clear traps in untreated orchards. The clear caught >6-fold more females than the orange trap in both types of orchards. These studies suggest that deploying clear delta traps baited with pear ester and acetic acid can be an effective monitoring tool for female codling moth and an alternative to codlemone-baited traps in sex pheromone-treated orchards.
Levels of atmospheric CO2 have been increasing steadily over the last century and are projected to increase even more dramatically in the future. Soybeans (Glycine max L.) grown under elevated levels of CO2 have larger herbivore populations than soybeans grown under ambient levels of CO2. Increased abundance could reflect the fact that these herbivores are drawn in by increased amounts of volatiles or changes in the composition of volatiles released by plants grown under elevated CO2 conditions. To determine impacts of elevated CO2 on olfactory preferences, Japanese beetles (Popillia japonica Newman) and soybean aphids (Aphis glycines Matsumura) were placed in Y-tube olfactometers with a choice between ambient levels of CO2 gas versus elevated levels of CO2 gas or damaged and undamaged leaves and plants grown under ambient levels of CO2 versus damaged and undamaged plants grown under elevated levels of CO2. All plants had been grown from seeds under ambient or elevated levels of CO2. Painted lady butterflies (Vanessa cardui L.) were placed in an oviposition chamber with a choice between plants grown under ambient and elevated levels of CO2. A. glycines and V. cardui showed no significant preference for plants in either treatment. P. japonica showed no significant preference between ambient levels and elevated levels of CO2 gas. There was a significant P. japonica preference for damaged plants grown under ambient CO2 versus undamaged plants but no preference for damaged plants grown under elevated CO2 versus undamaged plants. P. japonica also preferred damaged plants grown under elevated levels of CO2 versus damaged plants grown under ambient levels of CO2. This lack of preference for damaged plants grown under elevated CO2 versus undamaged plants could be the result of the identical elevated levels of a green leaf volatile (2-hexenal) present in all foliage grown under elevated CO2 regardless of damage status. Green leaf volatiles are typically released from damaged leaves and are used as kairomones by many herbivorous insects for host plant location. An increase in production of volatiles in soybeans grown under elevated CO2 conditions may lead to larger herbivore outbreaks in the future.
The potato psyllid, Bactericero. (=Paratrioza) cockerelli (Šulc) (Hemiptera: Triozidae), is a major pest of potato. We examined the role of chemical signals in sex attraction, assessing male and female response to male- and female-produced volatile chemicals. In laboratory olfactometer assays, potato psyllid males were attracted to odorants emitted from live females and from solvent extract of females. These results indicate that the female-produced chemicals responsible for attracting males may be isolated by means of insect extractions. Males were also attracted to volatile chemicals from males and extracts of males, providing the first example of male—male attraction in the Psylloidea. Males exposed simultaneously to odorants from conspecific females and males were preferentially attracted to female odorants, suggesting the presence of a female-specific sex attractant for males. Potato psyllid females avoided volatile chemicals emitted by females and extracts of females and by volatile chemicals emitted by males and extracts of males. Possible explanations for avoidance of conspecifics by females are discussed. This study is the first report of male attraction to volatile chemicals emitted by females and female extracts in the Triozidae and more specifically in the potato psyllid.
The cuticular wax structures of Scymnus louisianae J. Chapin larvae were investigated as a defense against ant aggression by Lasius neoniger Emery. The presence of wax structures provided significant defense against ant aggression compared with denuded larvae in that these structures attenuated the aggressive behavior of foraging ants. Furthermore, reapplication of wax dissolved in hexane partially restored defenses associated with intact structures, showing an attenuation of aggression based in part on cuticular wax components rather than solely on physical obstruction to ant mouthparts.
This study aimed to evaluate adult emergence and duration of the pupal stage of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), and emergence of the fruit fly parasitoid, Diachasmimorpha longicaudata (Ashmead), under different moisture conditions in four soil types, using soil water matric potential. Pupal stage duration in C. capitata was influenced differently for males and females. In females, only soil type affected pupal stage duration, which was longer in a clay soil. In males, pupal stage duration was individually influenced by moisture and soil type, with a reduction in pupal stage duration in a heavy clay soil and in a sandy clay, with longer duration in the clay soil. As matric potential decreased, duration of the pupal stage of C. capitata males increased, regardless of soil type. C. capitata emergence was affected by moisture, regardless of soil type, and was higher in drier soils. The emergence of D. longicaudata adults was individually influenced by soil type and moisture factors, and the number of emerged D. longicaudata adults was three times higher in sandy loam and lower in a heavy clay soil. Always, the number of emerged adults was higher at higher moisture conditions. C. capitata and D. longicaudata pupal development was affected by moisture and soil type, which may facilitate pest sampling and allow release areas for the parasitoid to be defined under field conditions.
Developmental thresholds, degree-days for development, larval weights, and head capsule widths for each larval instar and the pupal stage of Anophphora glabripennis (Motschulsky) (Coleoptera: Cerambycidae) were studied at eight constant temperatures (5, 10, 15, 20, 25, 30 ,35, and 40°C) for two source populations (Ravenswood, Chicago, IL [IL], and Bayside, Queens, NY [NY]). The estimated lower threshold temperature for development of instars 1–5 and the pupal stage was near 10°C and was near 12°C for the higher instars. Developmental rate was less temperature sensitive for instars 5–9 compared with instars 1–4. Development for all but the first instar was inhibited at constant temperatures >30°C, and all instars failed to develop at 40°C. Although the two source populations had similar responses to temperature, IL larvae were heavier than those from NY. Temperature and its influence on larval weight had profound impacts on whether a larva proceeded to pupation. Based on the temperature effects detailed here, larval development and pupation should be possible in most of the continental United States where suitable hosts are available. These data can be used to develop a degree-day model to estimate beetle phenology; however, at least 2°C should be added to air temperatures to adjust for the mediation of temperature by the wood. These data provide a basis for predicting the potential geographical range of this species and for developing phenological models to predict the timing of immature stages, both of which are important for management programs.
The molecular phylogeny of the long-horned beetle tribe Lamiini Mulsant (Coleoptera: Cerambycidae) in Japan (12 genera, 25 species, 3 additional subspecies) was determined based on mitochondrial 16S rRNA and cytochrome oxydase subunit I. The monophyly of the tribe Lamiini was supported, whereas that of the genus Acalolepta Pascoe was unclear. Evolution of host plant use in Lamiini was estimated using the molecular phylogeny. For adult and larval host plant kind-and-condition, the most ancestral state was for weakened to dead broad-leaved trees, whereas derived states favored conifers, healthy broad-leaved trees, and herbs. For adult and larval host range, the most ancestral state was polyphagy, whereas oligophagy and monophagy were derived. Evolution of hosts' idiosyncrasy and that of the insects' host range were related in many lineages. Our results partly support the hypothesis that habitation in living trees requires dietary specialization in phytophagous insects.
The pink bollworm Pectinophora gossypiella is an invasive pest insect that has successfully established populations in many cotton growing regions around the world. In this study, the genetic diversity and population structure of Chinese populations of P. gossypiella were evaluated using mitochondrial DNA sequence data (COII and Nad4). For comparison, individuals of Pakistan and America were also sequenced at the same two mtDNA regions. Extremely low genetic variation was observed in the two mitochondrial regions among all populations examined. Most of the populations harbored only one to two haplotypes. Although the Nad4 region showed relatively high haplotype diversity and nucleotide variation, ranging from 0.363 to 0.591 and from 0.00078 to 0.00140, respectively, there were only three haplotypes observed in this region. COII and Nad4 haplotype networks shaved one or two common haplotype (s) forming the center of a star-shaped phylogeny. Pairwise tests showed that most of the populations were not significantly differentiated from each other. The Chinese populations were differentiated from the Pakistani and American populations in the Nad4 region. The low level of population genetic variation of P. gossypiella is attributed to invasion bottlenecks, which may have been subsequently strengthened by its nonmigratory biology and the mosaic pattern of agricultural activities.
The effect of temperature on development and survival of Chilocorus bipustulatus L. (Coleoptera: Coccinellidae), a predator of many scale insects, was studied under laboratory conditions. The duration of development of egg, first, second, third, and fourth larval instars, pupa, and preovioposition period at seven constant temperatures (15, 17.5, 20, 25, 30, 32.5, and 35°C) was measured. Development time decreased significantly with increasing temperature within the range 15–30°C. Survival was higher at medium temperatures (17.5–30°C) in comparison with that at more extreme temperature regimens (15 and >30°C). Egg and first larval instars were the stages where C. bipustulatus suffered the highest mortality levels at all temperatures. The highest survival was recorded when experimental individuals were older than the third larval instar. Thermal requirements of development (developmental thresholds, thermal constant, optimum temperature) of C. bipustulatus were estimated with application of linear and one nonlinear models (Logan I). Upper and lower developmental thresholds ranged between 35.2–37.9 and 11.1–13.0°C, respectively. The optimum temperature for development (where maximum rate of development occurs) was estimated at between 33.6 and 34.7°C. The thermal constant for total development was estimated 474.7 degree-days.
As part of an investigation into the potential unintended ecological impacts of transgenic trees, invertebrates were sampled from a field trial of transgenic Pinus radiata D. Don carrying the expressed antibiotic resistance marker gene neomycin phosphotransferase II (nptII) along with other genes known to affect reproductive development in plants and from nontransformed control trees. Invertebrate species abundance, richness, diversity, and composition were measured and compared among trees of five different transclones and nontransformed isogenic control trees. Invertebrates were sampled at six-monthly intervals over a period of 2 yr. In total, 19,162 individuals were collected comprising 279 invertebrate recognizable taxonomic units. Total invertebrate populations as well as populations of herbivorous lepidopteran larvae and Hemiptera were compared among transgenic and control trees. The results show that the transclones had no significant unintended influence on species abundance, richness, diversity, or composition for all populations investigated.
One major concern regarding the release of Bt rice is its potential impact through tritrophic interactions on nontarget arthropods, especially natural enemies. We studied the effects of two Bt transgenic rice varieties, TT9-3 and KMDl, expressing CrylAb/CrylAc and CrylAb, respectively, on a predatory ground spider [Ummeliata insecticeps (Bösenberg et Strand)] supplied with Bt rice-fed brown planthopper [Nilaparvata lugens (Stål)] nymphs. Although immunoassays confirmed that U. insecticeps ingested Bt insecticidal protein when supplied with Bt rice-fed N. lugens, no negative effects were found on its survival and development. Furthermore, the fecundity of U. insecticeps fed prey reared on Bt rice was not significantly different from that of those fed prey reared on non-Bt rice. A 3-yr field trial indicated that Bt rice did not significantly affect the population density of U. insecticeps in comparison with non-Bt rice. In conclusion, the Bt rice lines tested in this study had no adverse effects on the survival, developmental time, or fecundity of U insecticeps in the laboratory or on population dynamics in the field.
Transgenic cotton has shown great promise for the control of target pest insects; however, frequent outbreaks of nontarget pest mirids has been recorded in recent years in northern China. To test the hypothesis that transgenic cotton contributes to nontarget pest outbreaks, we studied the impact of transgenic Bt cottons (both Bt and BtCpTI) on the fitness of nontarget pest Adelphocoris suturalis Jakovlev. No significant differences were detected between population densities of A. suturalis in unsprayed nontransgenic cottons and in unsprayed transgenic Bt cottons in 2007, 2008, and 2009. No difference in preferred oviposition site or egg production was detected between transgenic and nontransgenic cottons in both free choice and no choice tests. No difference in life table parameters was detected for A. suturalis between Bt cottons and nontransgenic cottons. All these results indicated that transgenic crops did not contribute to the nontarget pest outbreaks when being compared with their parental lines. The possible reasons for intensified pest status of A. suturalis, such as decrease of pesticide application, deficient natural enemies, and area-wide shift of cotton varieties, were discussed.
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