Journal of Pest Science最新文献

Entomovectoring relies on the dissemination of biocides by insects to control plant pests and diseases. Current research aims at coupling entomovectoring with the Sterile Insect Technique (SIT). Such boosted-SIT is a promising technique to control the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera, Tephritidae), an invasive pest that dooms African and Asian fruit-producers and is invading Europe. Here, we investigated empirically the potential of boosting the SIT using spores of the entomopathogenic fungus, Metarhizium anisopliae. Laboratory bioassay confirmed the transmission potential of the fungus from inoculated males to males and females, with subsequent reductions in survival and fecundity. Inoculation, like sterility, nonetheless reduced male mating success. Semi-field tests (i.e., large outdoor cages) revealed greater costs of fungal inoculation on male competitivity than observed in the laboratory. Combined with effects of inoculation on male survival, these costs led to a lower reduction in female reproduction in the presence of inoculated sterile males compared to plain sterile males. As tested here, boosting the SIT with M. anisoplae spores to control B. dorsalis could reduce its efficacy. The encouraging transmission patterns, however, suggest that technical improvements may render the boosted-SIT effective in some, if not all, ecological contexts.

Plant essential oil (EO)-based insecticides represent a promising tool for Integrated Pest Management (IPM), though their formulation is limited by poor physicochemical properties. EO encapsulation into stable formulations, like nanoemulsions (NEs), could boost EO efficacy and stability. Carlina acaulis L. roots contain an EO recently studied for its excellent insecticidal activities, and chiefly composed of carlina oxide (> 97%). Herein, we developed two carlina oxide NEs (0.25% and 0.5% w/w) through ultrasounds exposure and characterized them by dynamic light scattering (DLS). The NE insecticidal and repellent activities were tested on Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) eggs, larvae, and adults. Nanoemulsions tested showed a monomodal size ditribution and the polydispersity index (PDI) indicaticating a low grade of polydispersity. The 0.25% (w/w) NE showed significant contact toxicity on T. absoluta eggs with high hatching inhibition. 11 days post-treatment. The highest larvicidal effect was observed in translaminar toxicity tests, with complete mortality after 24 h. The NE did not achieve significant oviposition deterrence. Overall, the tested green NE showed promising effectiveness as ovicide and larvicide on T. absoluta, highlighting the need of further research to shed light on its modes of action, as well as to evaluate lethal and sublethal effects on tomato biological control agents and pollinators.

The tobacco cutworm, Spodoptera litura, is one of the most important agricultural insect pests. Plant essential oils can be considered potential candidates for eco-friendly control agents, as they exhibit insecticidal and feeding deterrent activity. The present study investigated the antifeedant and insecticidal activity of 29 essential oils. Their potential for habituation and association with the gustatory sensilla were also examined. In no-choice tests and contact-fumigation bioassays on third instar larvae, clove bud, fennel sweet, and lemongrass oils exhibited notable activities. Still, no direct correlation between insecticidal activity and feeding deterrence was observed. Second instar larvae were pre-exposed to those active oils to test the habituation effect. Larvae reared with lemongrass and clove bud oils showed gustatory habituation, whereas those with fennel sweet oil did not show any desensitization compared to the control. Comparable outcomes were observed in individuals exposed to the main constituents of the three oils. Additionally, the mixture of fennel sweet and clove bud oils showed a synergistic feeding deterrent effect. However, although statistically insignificant, potential habituation for the mixture was observed, and only robust inhibition of habituation was expected at physiologically high concentrations (FDI₉₀ + FDI₉₀). Electrophysiological studies showed that the response of the maxillary palp to citral decreased in the experienced group, while to trans-anethole, it was maintained at levels similar to the naive group. The reduction in feeding deterrence corresponded to the repeated exposure and desensitization of the maxillary palp, varying with the types of essential oils.

Plasma-activated water (PAW) is receiving increased attention as a booster of seed germination and seedling vigor, and some studies have described use of PAW to manage crop pathogens. Here, we examined physicochemical properties of two PAWs (referred to as PAW 6.0 and 9.4 min with atmospheric plasma jet) and assessed “their indirect effects” (applied as supplementary irrigation) on host suitability of tomato plants (Solanum lycopersicum L.) to two-spotted spider mites (Tetranychus urticae Koch). Exposure of water to cold plasma significantly lowered pH and increased concentrations of H₂O_2, NO₂⁻, and NO₃⁻. Supplementary PAW irrigations elicited significant increases in leaf composition of several elements (N, P, K S, Ca, and Mg), leaf reflectance, plant size, and trichome densities (except non-glandular trichomes on the adaxial surface). Preference bioassays revealed significant avoidance of settling and reduced oviposition by two-spotted spider mites on leaf discs from PAW-irrigated plants compared to those from untreated control plants. Performance bioassays showed a significant decrease in two-spotted spider mite populations on PAW-irrigated plants. Results presented in this study provide comprehensive support to the hypothesis that indirect effects of supplementary PAW irrigation significantly reduce host plant suitability to two-spotted spider mites. PAW 6.0 may be slightly better than PAW 9.4, and this difference in performance is discussed in this study. Applications of PAW as supplementary irrigation are likely highly compatible with other IPM tactics and should be considered an innovative and sustainable component in twenty-first-century pest management.

Although the use of chemical insecticides to control Frankliniella occidentalis is widespread, it may also affect its dominant predators such as Orius similis. To understand the consequences of imidacloprid on the growth, development, and reproduction of O. similis, we investigated its toxicity and selected the concentrations of LC₁₀ and LC₂₀ for both contact and stomach toxicity tests. Using the age-stage two-sex life table theory, we evaluated the impact of imidacloprid on the life table of the O. similis population. The results showed that the LC₁₀ and LC₂₀ values for each developmental stage of O. similis were lower under contact treatment than those under stomach toxicity treatment. After treatment with imidacloprid, the average oviposition by O. similis decreased compared to the control, and the net reproductive rate, gross reproduction rate, intrinsic rate of increase, and finite rate of increase were also lower than the control. The results also indicated that the peak value of age-stage-specific fecundity of O. similis was delayed by 1–2 days after imidacloprid treatment. Predictions for population growth of O. similis under unrestricted conditions showed that at 60 days, the population size of the control treatment was 2.06 times and 3.20 times that of LC₁₀ contact and stomach toxicity treatment, respectively. For LC₂₀ concentration, the control treatment's population size was 2.75 times and 3.87 times, respectively. Exposure to imidacloprid at different concentrations and treatment with contact and stomach toxicity had adverse effects on the growth and population growth of O. similis. Under imidacloprid stomach toxicity treatment, O. similis showed longer growth time and a slower population growth rate, indicating strong adaptability to the contact environment.

Crapemyrtle bark scale (CMBS), Acanthococcus lagerstroemiae (Kuwana) (Hemiptera: Eriococcidae), is a non-native scale insect that has spread throughout many urban areas of the Southeast and Middle Atlantic regions of the United States following its initial detection near Dallas, Texas in 2004, severely reducing the aesthetic value and health of the popular ornamental crapemyrtle tree (Lagerstroemia spp.). We infested crapemyrtles with known numbers of CMBS to determine the minimum number of individuals required for establishment after initial arrival on plants. We also investigated how netting—implemented to understand differences in establishment when scale dispersal and predation are inhibited—influenced population growth. We determined that one female CMBS egg sac can successfully establish a new population ~ 92% of the time and that netting had negligible effects on establishment. Our results underscore the importance of surveying and managing CMBS and scale insects with similar biology when attempting to prevent infestation of nursery stock, which is widely implicated as a vector for long-distance dispersal of scale insects.

The southern US has a large presence of mosquito vector species for dengue virus (DENV) and experiences thousands of DENV importations every year, which have led to several local outbreaks. Adulticide spraying targeting active mosquitoes is one of the most common insecticide strategies used as a response to an outbreak. The aim of this study is to evaluate the effectiveness of adulticide spraying conducted at different times of the day to curb DENV transmission. Based on unique dataset of Aedes aegypti diel activity patterns in Miami-Dade County, Florida, and Brownsville, Texas, we developed a mechanistic model of DENV transmission, which simulates adulticide spraying interventions. We estimated that spraying adulticide for 14 consecutive days at 7am or 8 pm was highly effective in reducing DENV outbreak probability from 10% in the absence of interventions to 0.1% for Miami-Dade County, and from 7.8 to 0.1% for Brownsville. Moreover, in case of a local outbreak in Miami-Dade County, we estimated the median number of symptomatic infections after the identification of a local outbreak to be reduced from 67.0 (IQR: 25.5–103.0) in the absence of interventions to 1.0 (IQR: 0.0–2.0) when spraying adulticide for 14 consecutive days at 8 pm. In Brownsville, the same intervention is estimated to lead to a decrease from 15.0 (IQR: 7.0–33.0) cases to 1.0 (IQR: 0.0–2.0). Our study highlights the importance of considering diel activity patterns of vector mosquito species in arbovirus preparedness and response planning and provide quantitative evidence to guide the decision-making of mosquito control authorities.

The obscure mealybug, Pseudococcus viburni, is a serious agricultural pest worldwide. The biological control in commercial fields of P. viburni relies on predators and parasitoids, in particular the generalist coccidophagous ladybird Cryptolaemus montrouzieri and the specific parasitoid Acerophagus flavidulus. However, these two natural enemies can establish an intraguild predation interaction, reducing the efficiency of biological control. Cryptolaemus montrouzieri may negatively impact the population dynamics of A. flavidulus if it feeds indifferently on healthy and parasitized mealybugs. With the aim of improving the biological control of P. viburni, in this work, we studied the feeding behavior of C. montrouzieri in the absence or presence of A. flavidulus larvae of different age within mealybugs, in laboratory conditions. Subsequently, with the data obtained, we mathematically modeled the dynamics of P. viburni to study the impact on P. viburni control of different field implementation schedules for the release of ladybird and parasitoid populations. The ladybird fed on parasitized P. viburni but reduced its consumption when they were infested by parasitoids aged of 4 days or more. Modeling results suggest that these feeding preferences of predators may have a positive impact on pest control, that releasing predators and parasitoids together is in general more effective than releasing them independently, and that releasing highly effective predators alone could be the best choice. Modeling results also provide information on different release schedules.

Climatic conditions are key determining factors of whether plant pests flourish. Models of pest response to temperature are integral to pest risk assessment and management, helping to inform surveillance and control measures. The widespread use of meteorological data as predictors in these models compromises their reliability as these measurements are not thermally coupled to the conditions experienced by pest organisms or their body temperatures. Here, we present how mechanistic microclimate models can be used to estimate the conditions experienced by pest organisms to provide significant benefits to pest risk modelling. These well-established physical models capture how landscape, vegetation and climate interact to determine the conditions to which pests are exposed. Assessments of pest risk derived from microclimate conditions are likely to significantly diverge from those derived from weather station measurements. The magnitude of this divergence will vary across a landscape, over time and according to pest habitats and behaviour due to the complex mechanisms that determine microclimate conditions and their effect on pest biology. Whereas the application of microclimate models was once restricted to relatively homogeneous habitats, these models can now be applied readily to generate hourly time series across extensive and varied landscapes. We outline the benefits and challenges of more routine application of microclimate models to pest risk modelling. Mechanistic microclimate models provide a heuristic tool that helps discriminate between physical, mathematical and biological causes of model failure. Their use can also help understand how pest ecology, behaviour and physiology mediate the relationship between climate and pest response.

Bactrocera dorsalis is a highly invasive fruit pest of economic and quarantine significance. The males are strongly attracted to methyl eugenol (ME). After consumption, ME is converted to metabolites that act as sex pheromones, which increase mating success. ME lure is instrumental in male annihilation technique (MAT) and sterile insect technique (SIT) applications to suppress or eradicate fruit fly populations. A simultaneous MAT-SIT concept is proposed to reduce operational costs and time-to-eradication. However, sterile males released to the field may respond to MAT’s ME-baited traps, reducing the efficacy of SIT. Here, we developed a ME-supplemented diet that reduces males’ response to ME without compromising mating efficiency and survivorship. We offered sugar-yeast diet supplemented with ME (0–5%) to 5-day-old males for 48 h and evaluated their response to ME, mating performance and pheromone production at 3-, 7-, 11- and 15-days post-treatment (DPT), while observing mortality for 60-DPT. Our results indicate that consuming a ME-supplemented diet reduces response to ME lures and enhances mating success, with the 5% ME diet showing the most promising results. The trend of pheromone production at different DPT after consuming various ME-supplemented diets corroborated with those of reduced lure response and mating enhancement. Although diet containing 3 and 5% ME affected males’ survival probability over 60-DPT, the treatment does not impact the survival of all treated males for at least 25-DPT. This finding suggests that pre-release feeding on a 5% ME-supplemented diet by 5-day-old B. dorsalis males is a feasible solution for implementing simultaneous MAT-SIT.