Environmental Entomology最新文献

This study evaluated the efficacy and shelf life of a locally developed viral prototype product based on Hyphantria cunea granulovirus (HycuGV-Hc1) for the control of the fall webworm (Hyphantria cunea Drury; Lepidoptera: Arctiidae), a polyphagous pest commonly observed in the Black Sea and Marmara regions of Turkey, under field conditions. The field trials were conducted in Trabzon, in the Eastern Black Sea Province, during 2022 and 2023. The viral formulation was tested on mulberry, hazelnut, and walnut host plants against Hyphantria cunea larvae at 2 × 108, 2 × 107, and 2 × 106 occlusion body (OB)/ml concentrations. AGREE 50 WG (Commercial Product), which contains 50% Bacillus thuringiensis as the active ingredient used in Turkey against H. cunea was used as a comparison. At the highest concentration, the mortality rates were recorded at 85.42%, 80.85%, and 79.59% for mulberry, hazelnut, and walnut plants, respectively. When comparing the control groups across different plants, the most damage was observed on the mulberry plant. Comparable efficacy was observed with the commercial B. thuringiensis pesticide. In the shelf-life study, formulations prepared for different periods (0, 6, and 12 mo) were found to have similar mortality effects. The local viral prototype product displayed significant potential for controlling Hyphantria cunea in the field condition at 7 d after application.

Emerald ash borer (Agrilus planipennis Fairmaire) is an invasive wood-boring beetle that has killed millions of ash trees (Fraxinus spp.) across North America. In 2014, emerald ash borer was discovered attacking white fringetrees (Chionanthus virginicus L.) in Ohio, indicating a host range expansion. Since then, emerald ash borer activity in white fringetree has been confirmed in additional states, posing a potential threat to this native tree in natural and managed ecosystems. Though emerald ash borer can complete a full life cycle in white fringetree, there has been little research into the comparative success with which emerald ash borer develops in this novel host versus ash, or how introduced biocontrol agents will respond. We conducted laboratory and field infestations of white fringetree and ash in Delaware to compare the timing of emerald ash borer larval development and the associated response of larval parasitoids. In lab-infested white fringetree bolts, emerald ash borer developed slowly, with no larvae reaching the mature J-shaped larval stage (JL) during the 14-wk lab study, compared with all surviving larvae developing to the J-shaped larval stage in ash. Field results showed delayed emerald ash borer development and reduced survival in white fringetree, with just 1 larva out of 158 reaching the JL stage over 2 growing seasons. There was no parasitism of emerald ash borer larvae in lab- or field-infested white fringetree, likely because few larvae in this host reached instars suitable for larval parasitism. Overall, this study suggests that emerald ash borer populations in white fringetree are not self-sustaining, though further studies should be conducted using larger fringetree material, as small sizes may negatively impact larval survival.

In western North America, 3 pest wireworms in the genus Limonius co-occur on farmland, and the click beetle adult males respond to the same single-component sex attractant, limoniic acid. While divergence in seasonal occurrence may provide a means of separating sexual communication for Limonius canus (LeConte) and Limonius californicus (Mann.), both species overlap temporally with Limonius infuscatus (Mots.), suggesting the existence of additional reproductive isolating mechanisms. To determine the effect of trap height on the relative captures of these species, we deployed ground-based Vernon Pitfall Traps and aerially suspended Japanese Beetle traps baited with limoniic acid dispensed from rubber septa or plastic capsules, in British Columbia, Alberta, Washington state, and Montana. The proportion collected of each species differed among study locations, but our data indicate species differ in trap preference, with L. infuscatus and L. californicus preferring ground traps, and L. canus preferring aerial traps. This possibly reflects preferences in where species locate mates, and therefore another separation mechanism. Lure type also had a significant effect on captures in most studies, with generally more L. californicus and/or L. infuscatus collected if capsule dispensers, and more L. canus if septa dispensers were used. Implications for monitoring these species with these trap and dispenser combinations are discussed.

Embiopterans are reliant on silk for protection and produce the finest silk fibers known in nature. This report compares silk-water interactions for four species representing two different lifestyles: two tropical arboreal species that feed on lichens on bark and two detritivores from arid regions that typically live in leaf litter and underground. Water droplets placed on spun silk transformed the fibrous top layer to a film. Arboreal embiopterans spun a denser silk covering than did the detritivores. The films that formed after exposure to water were also denser for the arboreal species. A possible underlying cause for the difference between the two lifestyles is because detritivores stitch together dried leaves and other detritus to create cover, they may rely more on substrate than on silk alone for protection. In contrast, arboreal embiopterans exposed on the surface of bark rely on thick silk coverings. Contact angles of water droplets on silk revealed that the silks tended to be more hydrophilic than a hydrophobic control, perhaps explaining why silks exposed to water become transformed by water-protein interactions. Results suggest that interesting variability in silk-water interactions exists for this little-known group insects, that also produce silk proteins of high crystallinity and with variable amino acids, one species to the next.

Climate change is reshaping insect population dynamics in North America, notably impacting the migratory pest Empoasca fabae (Harris) (Hemiptera: Cicadellidae). While its phenology is well studied in the United States, knowledge gaps exist regarding its dynamics in Eastern Canada, one of its northernmost migration areas. Our study integrates degree-day models, CLIMEX ecological niche modeling, and field-collected data from Québec to assess E. fabae seasonal phenology and monthly climatic suitability. Our results indicate that E. fabae completes one to two generations in Québec, with earlier emergence and higher generational potential in warmer southeastern regions compared to cooler northeastern regions. CLIMEX modeling showed that suitable climatic conditions for E. fabae growth begin in April, peak from May to September, and decline by November. First adult captures occurred from late May to early June, with population peaks in June-July and a decrease by September. Observed adult peaks occurred earlier than predicted by degree-day models, suggesting that additional environmental factors, such as wind patterns and host plant availability, influence early-season population dynamics. This study provides a comprehensive understanding of E. fabae phenology in Québec and highlights the importance of incorporating regional climate to predict population trends. Further research on diapause onset, late-season persistence, and migration patterns is needed to refine predictive models and inform pest management strategies in Québec. Understanding these factors will be essential in mitigating potential economic impacts amid ongoing climate change.

Different generalist herbivore species within a lineage can differ in their responses to a single plant defensive trait. Herbivore responses to plant defensive traits can also influence their interactions with their own natural enemies. Here, we rear 2 generalist herbivores, Trichoplusia ni Hübner (Lepidoptera: Noctuidae) and Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae), on artificial diets containing 0%, 0.01%, 0.05%, and 0.10% xanthotoxin. We measured and compared growth rate, body size, and mortality among these 4 dietary xanthotoxin concentrations. C. includens grew more slowly and was more likely to die before adulthood as dietary xanthotoxin increased and also varied in body size. Trichoplusia ni had a higher mortality rate overall, which increased as dietary xanthotoxin increased; however, there were no effects on growth rate and body size for this species. In a second experiment, the same 4 diets were given to larvae of both species parasitized by the polyembryonic parasitoid Copidosoma floridanum Ashmead (Hymenoptera: Encyrtidae), and growth rate, mummy size, and mortality were measured and compared. There were no sublethal effects on growth rate or mummy size, and mortality increased in both herbivore species but was higher in C. includens. These results show that different generalist herbivore species can respond differently to plant defensive traits, possibly due to different levels of adaptations to a specific trait, and these responses can affect higher trophic levels. Further research can compare the multitrophic impacts of variation in responses to plant defensive traits among more generalist herbivores.

The scarab beetle Holotrichia oblita Faldermann (Coleoptera: Scarabaeidae) is an economically significant subterranean pest in northern China. Studying the cold tolerance of this pest can elucidate its overwintering survival strategies, thereby providing a scientific basis for predicting its populations and developing precise overwintering control measures. In this study, we evaluated the supercooling capacity of H. oblita at various developmental stages, including larval instars, egg, pupa, and adult stages for males and females. We also examined survival rates and changes in supercooling ability under low-temperature stress. Our research found that SCPs varied significantly across developmental stages, and the lowest SCPs occurred in larvae, followed by pupae, eggs, and adults. However, no significant differences were found between the SCPs of H. oblita pupae or between male and female adults. For larvae of different day-ages, the mean supercooling points (SCPs) ranged from -3.74 to -5.37 °C. After exposure to low temperatures, the SCPs of third instar larvae ranged from -8.0 to -1.6 °C. The median lethal temperature of third instar larvae was -1.27 °C. The results of our study show that H. oblita is a cold-intolerant insect. While this species has limited cold tolerance, it burrows deep into the soil in the winter and therefore is unlikely to be exposed to lethal temperatures. This study offers insights into the overwintering strategies of H. oblita and provides a foundation for predicting larvae overwintering populations.

Insect population dynamics profoundly affect the potential for a species to serve as a pest, highlighting the importance of proper quantification and monitoring of insect reproduction. Important measurements of reproduction include individual female egg load and realized fecundity, which can be affected by insect longevity and host quality. Aster leafhoppers (Macrosteles quadrilineatus Forbes) are an important pest in Western Canada and the upper Midwest of the United States, yet little is known about factors influencing their fecundity, and thus, population dynamics. To evaluate age-specific changes in fecundity, newly emerged pairs of aster leafhoppers were caged onto plants, and egg and nymph numbers were determined on a weekly basis until females died. Moreover, water deficit can affect amino acid concentrations in phloem sap, and in turn, affect plant attractiveness and suitability for insect herbivores. To examine the relationship between water deficit and reproductive potential, aster leafhoppers were reared on unstressed and water-stressed barley plants until adult emergence. Pairs with all possible combinations of leafhoppers from each water stress condition were made and allowed to reproduce. Amino acid concentrations were quantified in unstressed and water-stressed barley plants. Aster leafhoppers produced eggs throughout their adult stage, with numbers decreasing as individuals got older. Females reared on water-stressed plants had fewer eggs following adult emergence. Following mating, females that had been reared on unstressed plants had a similar egg load to those that had been reared on water-stressed plants. Unstressed plants had a higher concentration of aspartic acid and a lower concentration of tryptophan.

The sex pheromone of the oriental armyworm, Mythimna separata (Walker), in China has always been confusing. It was initially considered as cis-11-hexadecenal (Z11-16:Ald) or cis-11-hexadecenyl acetate (Z11-16:Ac) and cis-11-hexadecenol (Z11-16:OH), as well as a mixture of these compounds. However, inconsistent results have frequently occurred using these compounds or mixtures in field trapping. Through gland analysis from individual females and nationwide field experiments, we identified two distinct types: Z11-16:Ald (aldehyde type or A type) and a mixture of Z11-16:Ac and Z11-16:OH (ester type or E type). Electroantennography (EAG) results indicated that both strains of males co-existed in the field. A strain of males had a strong EAG response to Z11-16:Ald but weak responses to Z11-16:Ac and Z11-16:OH, whereas E strain males had strong responses to Z11-16:Ac and Z11-16:OH but a weak response to Z11-16:Ald. Z11-16:OH identified in female E strain inhibited the attraction of A strain males to A type pheromones. Both A and E types of sex pheromone were respectively formulated and field evaluation (2014-2021) across > 20 provinces from southern to northern China showed geographic and generational variations. During overwintering, E strain males were predominantly caught in Hainan, Fujian, and Guangdong provinces, while A strain males were mainly trapped in Guangxi, Anhui, Sichuan, Jiangsu, and Jiangxi provinces. Subsequent generations exhibited mixed populations in most regions. These findings suggest regional adaptation and migration-driven hybridization. The study highlights the necessity of strain-specific pheromone blends for effective monitoring and control. This work resolves long-standing ambiguities in M. separata sex pheromone ecology.

Strategus aloeus (Coleoptera: Scarabaeidae: Dynastinae) represents a significant pest of young oil palm crops in Latin America. Although a pheromone had already been identified, its use as a tool for integrated management remained limited. Thus, to elucidate the fuller characterization of the chemical signaling associated with this beetle and its host, the volatile organic compounds (VOCs) released by S. aloeus and the oil palm bulb (Elaeis guineensis) were isolated, identified, and evaluated. The analysis was conducted using gas chromatography coupled with mass spectrometry (GC-MS), and the attractant potential of the compounds was validated by testing their effects on insects' behavior under laboratory and field conditions. From solvent-assisted extraction (SAE) samples, the compounds 2,4,7,9-tetramethyl-5-decyne-4,7-diol, sec-butyl acetate, and ethyl 4-methyloctanoate in a ratio of 58:34:8 were identified as part of a possible male-specific pheromone. Furthermore, 2-butanone and 3-pentanone were identified as components of the oil palm kairomone using static headspace with solid phase microextraction (HS-SPME) sampling. The laboratory behavioral response of S. aloeus to the 3 male-specific compounds, alone or combined, demonstrated a significant attraction (P < 0.01) of both sexes, indicating their potential involvement in intraspecific interactions, specifically as an aggregation sex pheromone. In field trials, mixtures of 3 to 5 semiochemicals demonstrated high capture rates with a female-biased proportion (80:20). The treatment containing 2-butanone, 3-pentanone, and sec-butyl acetate exhibited the highest efficacy (P < 0.0001).