Journal of Pest Science最新文献

This study investigated the infestation of tomato plants by the plant-parasitic nematode, M. incognita, and its accurate detection by plant electrophysiology (PE). Dedicated tests were done on whole plants to record electrophysiological signals from nematode infested and uninfested plants and to establish a trained model indicating nematode-induced stress. Monitoring nematode-induced stress by PE confirmed the results obtained by assessing root galls and quantifying xylem sap 3 to 4 weeks after infestation. The machine learning model captured the stress intensities and the time course of plant damage caused by nematodes. Stress caused by second-stage juveniles (J2) infestation appeared 3 to 5 days after infestation (DAI), whereas stress caused by egg infestation was detected 5 to 7 days later (10–13 DAI). For the first time, the real-time effectiveness of nematicides was recorded in further tests. Nematode infested plants treated preventatively with cyclobutrifluram (TYMIRIUM® technology) showed a delayed and short (about 3 days) period of low stress intensity, whereas infested but untreated plants showed a period of maximum stress for about 12 days. In addition, depending on the type of application (preventative or curative), different modes of biological activity of IRAC group N-2 and N-3 nematicides (fluopyram, abamectin) could be captured by PE signalling. PE offers a new way of monitoring plant health in real time, which is particularly valuable for accessing ‘invisible’ pests, such as plant-parasitic nematodes in the soil.

Climate change leads to more frequent droughts that may alter multitrophic networks in agroecosystems by changing bottom-up and top-down effects on herbivorous insects. Yet, how bottom-up effects of drought alter tritrophic interactions remains poorly understood. This study investigated two intensities of drought stress in the tritrophic system consisting of sugar beet (Beta vulgaris), an aphid (Aphis fabae), and its parasitoid (Aphidius colemani). We thoroughly investigated each trophic level, examining the performance of plants, pest insects, and parasitoids, as well as the attraction of parasitoids to herbivore-induced plant volatiles (HIPVs). Drought stress negatively affected plant growth but benefited A. fabae, leading to faster development and a higher reproduction rate. Drought-stressed plants also emitted less plant volatiles, which resulted in reduced attraction of A. colemani to aphid-infested plants. Drought indirectly affected parasitoid performance, as evidenced by lower emergence rates and production of fewer females, although mummification rates were higher on drought-stressed plants. Reduced parasitoid attraction and performance on drought-stressed plants may exert lower top-down pressure on aphid populations. Combined with increased aphid performance, this may facilitate aphid outbreaks, which could further weaken drought-stressed plants. Our findings highlight the need to study multiple trophic levels and emphasize the importance of incorporating HIPVs and parasitoid attraction when assessing combined abiotic and biotic stresses in crops.

The ecotoxicological consequences of synthetic pesticides have encouraged stakeholders to search for eco-friendly pest control tools, like essential oils (EOs). Nano-delivery systems (nanoparticles and nano-emulsions) seem ideal for developing EO-based biopesticides, although production processes should be standardized and implemented. In this study, nano-emulsions loaded with a high amount of Allium sativum L. EO (15%) were developed using different mixed bottom-up/top-down processes. Garlic EO was chemically analyzed by gas chromatography-mass spectrometry (GC-MS) and formulations were physically characterized using Dynamic Light Scattering (DLS) apparatus. The insecticidal activity against Planococcus citri Risso (Hemiptera: Pseudococcidae) and selectivity toward Apis mellifera L. (Hymenoptera: Apidae) worker bees was evaluated. Garlic EO was mainly composed of sulphur components (96.3%), with diallyl disulphide and diallyl trisulphide as the most abundant compounds (37.26% and 28.15%, respectively). Top-down processes could produce stable nano-emulsions with droplet size in the nanometric range (< 200nm) and good polydispersity index (PDI < 0.2). In contrast, the bottom-up emulsion was unstable, and its droplet size was around 500nm after 24 hours. High-energy emulsification processes significantly increased the residual toxicity of garlic EO against 3rd instar P. citri nymphs, whereas the developed formulations were harmless to A. mellifera workers in topical application. This study confirmed that the production process significantly affected the physical properties and efficacy against target pests. The lack of adverse impact on honeybees denotated the potential of these formulations as bioinsecticides in organic and/or IPM programs, although further extended ecotoxicological studies are necessary.

Lygus lineolaris Palisot de Beauvois (Hemiptera: Miridae) is the primary insect pest of strawberry in eastern and central North America. Strategies to minimize L. lineolaris colonization of strawberry at bloom and peak fruit susceptibility without impacting pollinator health must be developed. To this end, we examined the potential of alfalfa perimeter strips to reduce L. lineolaris populations in June-bearing strawberry fields. Over a three-year experiment, L. lineolaris densities and beneficial arthropod abundance were monitored in commercial strawberry fields with and without alfalfa perimeter strips. Alfalfa perimeter strips were found to concentrate L. lineolaris populations and led to a 36% reduction in L. lineolaris densities in adjacent strawberry plots compared to controls. When a protein immunomark-capture experiment was conducted to examine the extent of movement between the alfalfa strips and adjacent strawberry plots, it was determined that approximately three times as many L. lineolaris migrated from strawberry to alfalfa than vice versa. Moreover, adult females were overrepresented among immigrants to alfalfa, suggesting that alfalfa may be a preferred oviposition site for L. lineolaris. While the presence of alfalfa perimeter strips increased beneficial arthropod abundance and diversity in experimental plots overall, these increases were limited to the alfalfa itself, with little spillover into adjacent strawberry plots. These data suggest that preferential utilization of alfalfa by L. lineolaris underlies the observed population reductions and that alfalfa acts as a trap crop in June-bearing strawberries.

Endosymbiosis is very common between bacteria and insects, and it has been deeply studied for over a century on model insects such as Bactrocera oleae, the key pest of the olives. It was demonstrated that “Candidatus Erwinia dacicola” is the main component of its midgut bacterial communities, acting a fundamental role in the fly’s nutrition process and thus on its fitness. In this study, Trichoderma secondary metabolites have been used to treat olive fruit fly in order to alter the “Ca. Erwinia dacicola” titer and to assess the subsequent effects on its host. The selected metabolites, 6-pentyl-α-pyrone and harzianic acid, directly affect the insect’s fitness also on the subsequent generation, but not always in a concentration-dependent manner. Aside from the direct effects, the treatments also showed a modification of the bacterial titer. Therefore, real-time qPCRs were carried out on wild individual flies highlighting natural variations of the symbiont presence and activity during the seasons. The data obtained suggest that bioactive fungal metabolites can be formulated for direct or indirect control strategies of B. oleae in integrated pest management programs.

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.