Journal of economic entomology最新文献

"Candidatus" Liberibacter spp. infect crop plants and the psyllid vector, and at least 2 species have been shown to be susceptible to RNAi. Here, the knockdown efficacy was analyzed of 4 genes essential for insect physiological processes, vacuolar ATPase (V-ATPase) subunit genes A, B, D, and E, for potential biopesticide activity against the potato psyllid, Bactericera cockerelli Šulc (Hemiptera: Triozidae). Adults and third instar psyllids were given a 48-h ingestion-access period (IAP) on either single or stacked dsRNAs to compare knockdown effects. While adults showed no significant mortality, 10-d post IAP on the individual dsRNAs, mortality was significantly greater post-IAP on the stacked dsRNAs compared to negative controls. Oviposition of dsRNA-treated females was reduced by 50% to 70%, however, there was no significant difference between the single and stacked dsRNA treatments. Adult and third instar psyllids exhibited 58% and 45% mortality, respectively, post-IAP on the 4 stacked dsRNAs. In contrast, only third instar nymphs showed significant mortality after individual dsRNAs targeting V-ATPase subunits, at 42% for subunit A and 35% for subunits D and E. In general, gene silencing was more robust in potato psyllid nymphs compared to the adults. Although gene knockdown was moderately lower following an IAP on dsRNAs delivered singly, IAP on stacked dsRNAs resulted in equal or greater mortality in both psyllid life stages. These findings highlight the potential for delivering multiple dsRNAs to suppress genes involved in essential cellular processes and enhance RNAi efficacy in insects.

Effective control strategies are needed against Phytonemus pallidus Banks (Acari: Tarsonemidae), a major pest in strawberry worldwide. A total of 25 strawberry (Fragaria × Ananassa Duch.) fields in Québec were surveyed for the presence of P. pallidus naturally mycosed by entomopathogenic fungi (EPF) of the genus Hirsutella (Ascomycota: Sordariomycetes). Parameters such as management type (conventional versus organic), growing system (plastic mulch versus matted rows), and meteorological variables (temperature, precipitation, and relative humidity) were monitored to determine their possible impact on the presence of naturally mycosed P. pallidus. Naturally mycosed P. pallidus were observed on 17 of the sites sampled. The number and the proportion of naturally mycosed P. pallidus relative to their total number were influenced by meteorological variables, but not by management type or growing system. Two species, Hirsutella nodulosa and Hirsutella subulata, were identified on mycosed mites. H. nodulosa was previously reported in the province of Québec while H. subulata is reported in the literature for the first time in Canada. This also represents the first report of H. subulata on a mite. Evaluation of the distribution of these EPF combined with a better understanding of the factors contributing to the spread of mycosis among P. pallidus would enable the development of a conservation biological control strategy against this pest in strawberry fields.

Sesame is a valuable oilseed crop grown for culinary uses of whole seed, paste, and oil. Increasing demand, along with breeding of non-shattering (indehiscent) varieties allowing machine harvesting, has promoted interest in growing sesame in developed countries. When establishing new mechanised sesame industries, effective pest management will be essential. The most severe pest of sesame globally is Antigastra catalaunalis, however research on its management, including currently available economic thresholds, is very largely from less developed countries and traditional shattering varieties. We aimed to develop economic thresholds for non-shattering sesame infested with A. catalaunalis. We performed controlled inoculations with fixed numbers of pest larvae, using randomly assigned individual Sesamum indicum "S32" plants at 3 age stages: juvenile, pre-reproductive and early bloom. Damage caused by larval feeding was assessed using a novel damage assessment scale ranging from 0 (no damage) to 9 (complete defoliation). Juvenile plants (8 to 10 leaves) often exhibited severe damage and sometimes death from just 1 or 2 larvae. Pre-reproductive plants could survive and regenerate from damage of 1 to 3 larvae per plant, however seed yield declined with a linear slope of 28% yield loss per larva. Growth cabinet experiments with early bloom stage plants showed a substantial drop in dry weight with increased numbers of larvae. We suggest economic injury levels of one A. catalaunalis larva per 27.9 plants for juvenile plants, one larva per 14.3 plants at pre-flowering stage and one per 8.85 plants at early bloom stage.

The insecticidal activity of microbial volatile organic compounds (mVOCs) remains underexplored, especially that of mVOCs produced by members of the Streptomyces genus (actinobacteria). mVOCs emitted by actinobacteria could represent a promising alternative for the biocontrol of insect pests, including the common bean weevil Acanthoscelides obtectus. mVOCs from five Streptomyces species, cultured axenically on wheat grains, were tested in vitro for their toxic effects on A. obtectus at the adult stage. The bioinsecticidal efficacy of mVOCs from Streptomyces species was further validated using pure VOCs at different concentrations. All Streptomyces species produced mVOCs with insecticidal activity, which was observed within 24 h to 96 h. The mVOCs from three strains (CIAD-IA69, CIAD-CA07, and CIAD-CA27) caused 100% mortality within 24 h of exposure. These mVOCs also impaired female reproductive performance, reducing both oviposition and egg viability. 3-penten-2-one, eucalyptol, and 2-pentanone caused 100% mortality within 4 h at concentrations of 25, 35, and 43 ppmv, respectively. The LD50 obtained with pure VOCs declined with exposure time, confirming their time-dependent toxicity. The LT50 values decreased as the concentration increased. The selected Streptomyces species produced mVOC that efficiently controlled A. obtectus.

Spray adjuvants are typically considered "inert" ingredients that play a crucial role in enhancing the efficacy of chemical pest control by improving pesticide absorption, spread, penetration, and longevity. This study evaluates the toxicity of organosilicone-based spray adjuvants on Drosophila suzukii Matsumura (Diptera: Drosophilidae), an invasive fruit fly species that poses a significant threat to the soft skin and stone fruit. Experiments were conducted under controlled conditions using 2 primary application methods of dipping and spraying egg-infested blueberries to assess toxicity to D. suzukii eggs and adults. Egg viability was assessed by adults that emerged, while adult mortality was evaluated following exposure to spray adjuvants alone and adjuvants combined with phagostimulants, applied on fresh blueberries. No significant reduction in egg viability was observed for either the dipping or spraying method. However, adult mortality increased significantly when adjuvants were combined with phagostimulants. After 72 h of exposure, D. suzukii populations were reduced by up to 83.0% with Syl-Coat (Wilbur-Ellis; wilburellisagribusiness.com) combined with a phagostimulant and 75.6% with Dyne-Amic (Helena Agri-Enterprises, LLC, Tennessee, United States) combined with a phagostimulant. No significant toxicity was recorded in adults exposed to adjuvants alone, although a numerical reduction in D. suzukii survival was noted with increasing exposure time. These findings demonstrate that combining a phagostimulant with an appropriate adjuvant provides a promising, reduced-risk approach to suppress Drosophila suzukii populations while reducing dependence on conventional insecticides. The results also highlight the importance of using spray adjuvants in combination with phagostimulants to enhance feeding-based management strategies and improve overall control efficacy.

The immigration and catastrophic damage caused by brown planthopper, Nilaparvata lugens (Stål) (N. lugens), have posed serious threats to rice production in China since the 1970s because of the influence of El Niño events and La Niña events, as well as anomalies in the spatiotemporal distributions of planthopper immigration and damage. However, the mechanisms through which El Niño events and La Niña events affect N. lugens dynamics remain understudied, especially with the emergence of new El Niño events and new La Niña event types. We analyzed the effects of 4 ENSO event types on the occurrence degree and immigration period of N. lugens in South China via N. lugens light-trap catches and meteorological data from 1979 to 2020. The results revealed that central Pacific (CP) El Niño events imposed significantly different effects on N. lugens occurrence than did eastern Pacific (EP) El Niño events. There was no significant difference between CP and EP La Niña events, more of an interdecadal variation. The atmospheric circulation during El Niño events was more suitable for N. lugens immigration. The differences between the different El Niño event types were due to differences in the locations of sea surface temperature anomalies on the Pacific Ocean, vertical motion in the atmosphere, and differential dynamics of the Western Pacific subtropical high. These results indicate the importance of predicting 2 types of El Niño events and La Niña events before or during N. lugens immigration to South China and reflect the complex relationship between N. lugens occurrence and atmospheric motion.

Global climate warming is characterized by an escalation in extreme high temperatures (EHTs). While the frequency of EHTs is predicted to increase under climate change, there remains a limited understanding of whether maternal exposure to altered EHT frequencies affects maternal provisioning and next-generation phenotypic traits in insects. In this study, we investigated the influence of exposure to varying frequencies (either 1 or 5 peak-temperature days every 10 d, with a peak temperature of 34 °C) of EHTs on reproductive decisions and offspring traits in Menochilus sexmaculatus (Fabricius) (Coleoptera: Coccinellidae). Our results revealed that M. sexmaculatus females exposed to a high frequency of EHTs exhibited a decrease in fecundity, alongside an increase in the proportion of non-viable eggs. Furthermore, maternal ladybirds experiencing a high frequency of EHTs could increase their offspring's body size. Offspring reared under a high-frequency EHT treatment displayed an extended larval development period, decreased egg laying, and a higher proportion of non-viable eggs. However, egg weight, egg clutch number, and egg clutch size in both maternal and offspring generations were unaffected by the increased frequency of EHTs. Our findings indicate that increased frequency of EHTs can generate modification in both maternal and offspring phenotypic traits, suggesting that adaptation to such conditions may occur through maternal effects. This research represents an essential step toward understanding the impact of maternal effects on the phenotypic traits of M. sexmaculatus in response to varying frequencies of EHTs and may further enhance our understanding of M. sexmaculatus population dynamics under future climate scenarios.

Within the past 4 decades, the 2 invasive and destructive subterranean termites, Coptotermes formosanus Shiraki and Coptotermes gestroi (Wasmann), have established in and spread throughout Florida. Monitoring efforts, initiated in the early 1990s, have substantially expanded in the past decade, providing improved resolution of where the 2 species have increased their distribution, allowing for the determination of which communities are most at risk of infestation by either species. This study provides insights on the outcome of the "Florida Termite ID Services" program, which has involved a growing number of participating pest control companies across the state over the years. Thanks to this enhanced monitoring effort, there is now concrete evidence that the Formosan subterranean termite (C. formosanus) has established in most Florida coastal counties and within most large urban areas across the state. Contrary to initial expectations, the Asian subterranean termite (C. gestroi) has established in new localities beyond South Florida, where it was initially restricted, now impacts a growing number of communities. In South Florida specifically, the initial projection that 50% of the metropolitan area will likely be at risk of infestation by either termite species by ∼2040, remains valid. This study highlights the importance of monitoring the spread of these 2 invasive species in partnership with pest control providers, so as to continue to bring awareness of the growing termite risks to exposed communities.

The cowpea aphid, Aphis craccivora (Koch), is a significant agricultural pest that globally affects numerous crops, leading to substantial yield losses through both feeding and the transmission of viral diseases. Flupyradifurone has an excellent safety profile and a unique mode of action; resistance to flupyradifurone has been reported in certain aphid species. In the current study, the cross-resistance and resistance mechanisms of A. craccivora to flupyradifurone were investigated. The results revealed that A. craccivora developed a resistance ratio (RR) of 46.6-fold as a result of laboratory selection for 28 consecutive generations. In the flupyradifurone-resistant strain (R-strain), metabolic enzyme determinations indicated significant increases in cytochrome P450 monooxygenase, esterase, and glutathione S-transferase activities. Moreover, quantitative real-time PCR (RT-qPCR) revealed the differential expression of CYP6DA2 and CYP380C6, with CYP6DA2 being upregulated, suggesting its pivotal role in flupyradifurone resistance. Molecular docking studies demonstrated a stronger binding affinity of flupyradifurone to CYP6DA2 than to CYP380C6, further supporting its involvement in detoxification processes. The findings also highlighted moderate cross-resistance to malathion, underscoring the need for insecticide management to mitigate the evolution of resistance. This study provides critical insights into the biochemical mechanisms underlying flupyradifurone resistance in A. craccivora and emphasizes the importance of developing effective resistance management strategies for pest control.

Spotted-wing Drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), is a damaging insect pest of sweet cherry fruit worldwide including in the central valley of California where it was first reported as an economic pest in spring 2009. The aim of this field-based study was to assess the relationship of Brix level and skin firmness on D. suzukii oviposition and infestation in 4 commercially important sweet cherry cultivars: Bing, Black Tartarian, Brooks, and Rainier. Results of this field study found that both higher Brix values and lower skin firmness resulted in increased fruit infestation in all varieties, highlighting the importance of these factors in host susceptibility. Other potential factors are also discussed as they relate to D. suzukii fruit infestation. Implications of these findings are discussed as well as how they might be used in future D. suzukii management in sweet cherries.