Journal of economic entomology最新文献

Beet armyworm, Spodoptera exigua Hübner, is a sporadic pest of cotton (Gossypium hirsutum L.) that was once widespread in the crop across much of the US Cotton Belt. During 2021, we collected beet armyworm larvae from a field in North Carolina of transgenic cotton producing the Cry1Ac + Cry2Ab2 + Vip3Aa19 insecticidal proteins with unexpected injury to the plants. In diet-based bioassays with Vip3Aa39 protein, the colony collected from cotton in North Carolina displayed 813-fold resistance to Vip3Aa compared to a field-collected colony from Florida. We then performed reciprocal crosses and bioassays, which determined that the resistance was autosomal, recessive, and monogenic. Furthermore, the resistance likely had fitness costs, supported by the loss of resistance through rearing in the laboratory, requiring re-selection to restore it. Although beet armyworm is not currently a threat to Bt cotton in the United States, our finding of Vip3Aa resistance demonstrates that this pest has the capacity to evolve resistance under field conditions. This finding highlights the potential for beet armyworm to re-emerge as a significant pest if agronomic or climatic conditions shift to favor its establishment and spread. Moreover, the emergence of resistance in this historically sporadic pest should serve as a broader warning that Bt resistance can evolve and persist in non-target or secondary pests.

The cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae), has emerged as a key pest of ornamental plants, yet effective monitoring tools for its management remain limited. This study investigated the spatial distribution and developed fixed-precision sequential sampling plans for P. solenopsis populations on Chinese hibiscus (Hibiscus rosa-sinensis L.) under urban landscape conditions in Khuzestan province, southwest Iran. Spatial distribution analyses using Taylor's power law and Iwao's patchiness regression revealed significant aggregation across developmental stages, with nymphs exhibiting the highest degree of clumping and adults showing weaker aggregation due to greater dispersal ability. Based on these aggregation parameters, sequential sampling plans were generated for nymphs, adults, and combined populations at 3 precision levels (D = 0.25, 0.15, and 0.10). Optimum sample size requirements were density-dependent and consistently higher for nymphs than for adults. Validation through resampling confirmed that achieved precision closely matched target levels, with mean sample sizes for combined stages (nymphs and adults) ranging from 47 (D = 0.25) to 294 (D = 0.10). The D = 0.25 plan provided robust accuracy while substantially reducing sampling effort, making it most suitable for practical pest management. By contrast, the D = 0.10 plan is recommended for research requiring high precision. These findings provide the first validated sequential sampling framework for P. solenopsis on hibiscus, offering an efficient and reliable basis for integrated pest management in urban green spaces.

The striped flea beetle Phyllotreta striolata (Fabricius) (Coleoptera: Chrysomelidea) and the crucifer flea beetle P. cruciferae (Goeze) are significant insect pests of Brassica crops. We investigated the relationship between the presence of adult beetles and subsequent root damage caused by larvae. Additionally, we tested various alternative methods to control flea beetle damage, including net covers, fences, and mass trapping with plastic jugs. Our findings showed a correlation between the accumulation of adult striped flea beetles on foliage and the number of roots damaged. Approximately 96% of the larvae collected in 2023 were identified as striped flea beetles. Net covers helped increase marketable yield and reduce losses due to flea beetle damage to Chinese radish roots while insecticide treatments did not reduce root damage compared to untreated control. Mass trapping with jugs did not reduce root damage; instead, it attracted more adults to the plants, leading to increased foliage damage compared to control. A better understanding of the relative contribution to root damage by both flea beetle species would lead to an increase in monitoring efficiency and make its implementation easier. The use of net covers against flea beetle damage is recommended to increase yield and reduce damage to rooted crucifer crops.

The DBN9936 event (expressing Cry1Ab) and the Ruifeng 125 event (expressing Cry1Ab/Cry2Aj) are the first genetically modified maize varieties granted biosafety certificates in China, primarily targeting Ostrinia furnacalis (Guenée). However, their lethal and sublethal effects on Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), an invasive pest first detected in China in 2018, remain insufficiently understood. This study evaluated the life table parameters of first- to third- instar S. frugiperda larvae fed on V6-V8 stage leaves of DBN9936 and Ruifeng 125 maize under controlled laboratory conditions. Corrected mortality after 7 d was 90.46%, 56.13%, and 6.52% for first to third instars on DBN9936 and 51.85%, 15.79%, and 12.45% on Ruifeng 125, respectively. Both Bt events significantly reduced pupation rate, pupal weight, and fecundity compared to non-transgenic controls. Additionally, larval development was prolonged by 10 to 16 d. Life table analyses revealed reductions in net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), and population growth trend index (I) for larvae fed on either Bt maize. Simulated migration scenarios further indicated that brief access to non-Bt maize before transitioning to Bt maize could allow larvae survival, potentially undermining Bt efficacy. These findings demonstrate that both DBN9936 and Ruifeng 125 exert significant lethal and sublethal effects on S. frugiperda, yet intermittent feeding and larval mobility between Bt and non-Bt plants may accelerate resistance evolution.

The fall armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), is a major global pest that threatens cereal crops. Insecticides remain one of the key strategies for its management. This study assessed the toxicity, developmental effects, detoxification enzyme activity, and molecular docking interactions of 2 chemical insecticides profenophos (organophosphates group) and cypermethrin (pyrethroids group) and 2 bio-insecticides (spinosad and Bacillus thuringiensis) on S. frugiperda. Bioassay results revealed that spinosad exhibited the highest toxicity, followed by cypermethrin, profenophos, and B. thuringiensis against second-instar larvae. Exposure to cypermethrin at the estimated LC50 value significantly prolonged larval duration, while all treatments increased pupal duration. However, none of the treatments affected other biological parameters, including pupal weight, pupation rate, and adult emergence. Enzymatic analysis demonstrated significant alterations in the activities of acetylcholinesterase (AChE) and detoxification enzymes (α-esterase, cytochrome P450, and glutathione S-transferase [GST]) following exposure to lethal concentrations of the insecticides. Molecular docking analysis further indicated that spinosad exhibited the strongest binding affinity to α-esterase and cytochrome P450, whereas cypermethrin displayed the highest affinity for AChE. In contrast, profenophos showed the weakest binding interactions across all enzyme targets. These findings provide insights into the efficacy and biochemical interactions of chemical and bio-insecticides, offering valuable information for the targeted management of S. frugiperda.

The nutritional status of the parasitic wasp Aphidius gifuensis Ashmead (Hymenoptera: Aphididae) is a critical factor affecting its physiological activities, which are key to mass reproduction and field application. In this study, we constructed an age-stage, two-sex life table under a group-rearing conditions by feeding adult A. gifuensis with 5% (w/v) solutions of honey, fructose, glucose, or sucrose. The results showed that fructose, sucrose, and glucose significantly extended the longevity of male A. gifuensis compared to the water control. However, fructose, sucrose, and glucose had no significant impact on the longevity of female A. gifuensis. Sugar-fed parasitoid wasps had significantly shorter mean generation time compared with control, with parasitoids fed with glucose having the shortest mean generation time. The order of intrinsic rate of increase (rm) by treatment was Sucrose (0.4140), Glucose (0.4039), Honey (0.3911), Fructose (0.3903), and Water (0.3679). The rm were significantly higher in the glucose and sucrose treatments than in the water control. Additionally, the peaks of age-stage-specific reproductive value (vxj) by treatment were: Sucrose (190.15), Glucose (154.56), Honey (147.64), Fructose (139.41), and Water (104.05). Fructose, glucose, and sucrose treatments significantly increased female fecundity compared to the control, with sucrose-fed females showing the highest fecundity among the sugar treatments. These results demonstrate that sugar supplementation positively affects the reproduction of A. gifuensis. Both sucrose and glucose resulted in significantly higher rm values in adult, highlighting their effectiveness as nutritional supplements. Considering the lower cost of sucrose compared to glucose, sucrose is recommended as a dietary supplement for adults in mass production and field applications.

The pecan weevil, Curculio caryae (Horn) (Coleoptera: Curculionidae), is a direct pest of pecan nuts often causing economic injury. Larvae feed and develop within the pecan nut, mature fourth instars emerge from nuts during autumn, drop to the orchard floor and complete development underground. However, a proportion of pecan weevil larvae remain in nuts at harvest. We tested electron beam irradiation of pecan weevil larvae as a potential phytosanitary treatment against infested nuts being shipped to production regions free of pecan weevil. Irradiation doses of 0, 150, 400, 750, and 1,000 Gy were assayed against pecan weevil using different larval exposure methods (bare larvae [bare], larvae in microfuge tubes [tube], and larvae in microfuge tubes placed into empty pecan shells [nut]). After treatment application, larvae were held singly in Petri dishes at 15 °C and examined for 60 d to determine mortality. Results revealed that larval mortality increased with days after treatment for each irradiation dose, including 0 Gy, for the 3 exposure methods. Mortality was generally lower for larvae in the tube and nut at 400, 750, and 1,000 Gy than for bare larvae. Overall mortality was lower for lower irradiation doses but higher for higher doses, and over time no larvae survived 1,000 Gy. These results strongly suggest that irradiation is an effective method to control in-shell pecan weevil larvae.

Insect quiescence and diapause are characterized by suspension of development, often accompanied by obvious signs of inactivity such as loss of mobility and reduced respiration. However, in some stored product insects such as the khapra beetle (Trogoderma granarium Everts, Coleoptera: Dermestidae), larvae may fail to develop with few obvious behavioral indicators. A series of experiments were performed to test whether temperature acclimation or crowding that delays development can also affect subsequent adult reproduction, larval orientation toward food-associated kairomones in a wind tunnel, and outcomes of trapping assays. Results indicate that both mechanisms for delaying reproduction led to greater offspring production compared to normal colonies. It was also found that normal larvae were more likely to approach or enter baited traps than cold-acclimated or crowded larvae. Normal larvae were more likely to recognize and walk upwind to wheat odors when they were present, unlike the cold-acclimated or crowded larvae, whose behavior was not affected by the food odor. However, the 2 types of developmental delay treatments differed in that cold-acclimated larvae were more likely to make no movements at all in the wind tunnel compared to the crowded larvae. The results indicate that both triggers for developmental delay may affect the ability of larvae to orient toward kairomone-baited traps, potentially reducing overall population estimates.

The invasive fall armyworm, Spodoptera frugiperda (Smith JE) (Lepidoptera: Noctuidae) is a major invasive agricultural pest worldwide, requiring effective monitoring tools for timely integrated pest management (IPM). The efficacy of pheromone lures can vary geographically, necessitating regional validation and optimisation. To develop a regionally optimised trapping system for monitoring S. frugiperda populations in Zhejiang Province, China, we conducted sequential two-year field trials to evaluate the effects of seven sex pheromone blends, five lure dosages, four trap designs, and the potential synergist nonanal on trapping efficiency. Our results demonstrated that a two-component blend of (Z)-9-tetradecenyl acetate and (Z)-7-dodecenyl acetate in a 99.4:0.6 ratio was the most attractive and specific lure. Trap captures were highest with a high dosage (3,000 µg) deployed in a bucket trap, which significantly outperformed delta, wing, and vertical traps. The addition of 120 µg nonanal to the two-component blend acted as a synergist, significantly increasing S. frugiperda captures. The optimised system was then applied to monitor the local seasonal population dynamics of S. frugiperda, revealing a main flight peak in late September. This study provides the first optimised trapping system for S. frugiperda in this key agricultural region, offering a validated tool for precise, data-driven monitoring and defining a clear 'action window' for improving the sustainable management of this invasive pest.

Sugar transporters play a crucial role in insect life activities, especially in energy metabolism and carbohydrate management. Sugar transporter 1 (St1) is a facilitative glucose transporter highly expressed in the midgut of Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), however its physiological function remains unclear. To explore its pest control potential, we used RNA interference (RNAi) to investigate St1's effects on sugar metabolism and female reproduction. Silencing St1 lowered membrane-bound trehalase (TRE2) activity and inhibited the hydrolysis of trehalose into glucose, impeding glycogen accumulation and glucose availability. Our findings show St1 regulates female reproduction by modulating trehalase activity. This study reveals St1's crucial role in insect physiology and highlights it as a potential target for new, eco-friendly insecticides.