Environmental Entomology最新文献

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).

Long's Braya, Braya longii Fernald (Brassicales: Brassicaceae), is an endangered plant in the family Brassicaceae found only on the Limestone Barrens of the Great Northern Peninsula of Newfoundland, Canada. Conservation of this species hinges on management of pests, diseases, and disturbances, which threaten their small populations. In particular, a global agricultural pest, diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), causes significant damage to persistence of B. longii and contributes to possible extinction. This study investigates if there are key volatiles that attract P. xylostella to B. longii, thereby contributing to the pest's impact on the plant. Headspace collections, GC-MS, and GC-EAD revealed a unique volatile profile for B. longii, with (E)-2-nonenal as a key volatile that elicited strong antennal responses in P. xylostella. Oviposition assays confirmed female preference for E2-nonenal-baited radishes. This finding has implications for P. xylostella pest management, highlights the importance of chemical ecology in both crop protection and endangered species conservation.

Black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae), larvae convert organic wastes into insect biomass that can be used as livestock feed. Recent evidence also suggests larvae can reduce emissions of greenhouse gases (GHG) and noxious odors. However, these benefits are substrate and scale dependent. The current study examined the impact of black soldier fly larval digestion on resulting moisture level, greenhouse gas (i.e., carbon dioxide), noxious gases (i.e., ammonia, carbon monoxide, and hydrogen sulfide), and volatile organic compound production for coconut, honeydew, orange, and control (Gainesville diet) substrates at an industrial scale. Overall, the moisture content for some substrates digested by larvae was significantly (P < 0.05) lower (>20%) than those without larvae. However, differences were substrate dependent with final moisture content ranging from 35% (coconut) to 52% (oranges). The presence of black soldier fly larvae did not significantly (P > 0.05) impact overall GHG emissions. However, significant differences were detected at select days of the experiment. From an industrial perspective, recycling waste with larvae (7-d process) would potentially result in reduced duration for producing GHG versus placing substrates in a landfill (i.e., weeks to months to compost). The presence of black soldier fly larvae significantly (P < 0.05) impacted overall volatile organic compound profiles of the substrates. Larval impact on volatile abundance, richness, and evenness was substrate dependent. These results demonstrate the need to formulate diets and engineer systems that maximize benefits associated with black soldier fly larvae, while minimizing greenhouse gas and volatile organic compound emissions.

Florida is the second-highest producer of strawberries in the USA. Chilli thrips Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) have become a major pest in Florida strawberries following its establishment in the USA after 2005. Insecticide application is the leading management approach for S. dorsalis. However, this pest demonstrated the tendency to develop resistance to a broad range of active ingredients. Host-plant resistance (HPR) may contribute to the management of this pest, yet mechanisms of HPR, including antixenosis and antibiosis against S. dorsalis in strawberries, are not well studied. Therefore, this study aimed to evaluate the preference of S. dorsalis to select strawberry cultivars as oviposition sites that resulted in a successful egg eclosion. Seven commercial strawberry cultivars namely, "Florida Brilliance," Florida Medallion "FL 16.30-128," Sweet Sensation "Florida 127," Florida Pearl "FL 16.78-109," "Strawberry Festival," "Florida Beauty," and "Florida Radiance" were evaluated as hosts in an oviposition choice test. Greenhouse potted strawberry plants were infested with 1- to 3-d-old adult S. dorsalis females. The cultivars used as treatment were replicated five times, and the study was repeated twice. Among the seven cultivars, Florida Pearl "FL 16.78-109," "Florida Beauty," and "Strawberry Festival" had a higher number of eggs in the leaf tissue compared with other tested cultivars. However, the egg hatching percentage did not demonstrate a specific trend. The results showed that S. dorsalis has a strong oviposition preference for certain strawberry cultivars over others, and this information may be incorporated into HPR for managing S. dorsalis in strawberries.

Interactions between parasitoids and herbivore hosts are complex as parasitism affects multiple components of host behavior and fitness through both consumptive and non-consumptive effects. Understanding how these multiple effects unfold is especially important in applied systems where parasitoids play a role in biological control. In lab-based experiments, we manipulated parasitism in striped cucumber beetles, Acalymma vittatum (Coleoptera: Chrysomelidae), a major pest of cucurbits in North America, using Celatoria setosa (Diptera: Tachinidae) to assess how parasitism affected multiple components of male and female fitness, including survival, herbivory, oviposition, and reproductive signaling through the emission of vittatalactone, a male-specific aggregation pheromone. In follow-up experiments, we investigated the potential non-consumptive effects of parasitoids on these metrics by exposing beetles to arenas with or without parasitoids. Parasitized female beetles experienced a 4-fold increase in mortality, consumed 49.6% less leaf tissue, and were less likely to oviposit eggs compared to non-parasitized control females. In addition, parasitized males in small groups emitted 52.5% less vittatalactone than non-parasitized control males. Lastly, we found some evidence of non-consumptive effects of parasitoids in which individual females and groups of males, exposure to parasitoids resulted in reduced foliar damage. Our findings highlight broad effects of tachinid parasitoids in a common pest and point to multiple mechanisms for reduced pest performance.