Helopeltis cinchonae (Hemiptera: Miridae) is a major pest of tea plantations in Asia. Conventional control of pests with pesticides is unsustainable. Therefore, safe and eco-friendly alternatives, such as pheromones, are required to manage the pest. In GC-EAD analyses of whole-body extracts of virgin female H. cinchonae, two compounds elicited EAG responses from male antennae. These were identified as hexyl (R)-3-acetoxybutyrate and (R)-1-acetoxy-5-butyroxyhexane using GC-MS analysis compared to synthetic compounds. This is the first study to report 1-acetoxy-5-butyroxyhexane as an insect pheromone component. The synthetic compounds elicited dose-dependent EAG responses from the antennae of male H. cinchonae. In two field trapping experiments, the individual compounds were highly attractive to male H. cinchonae when dispensed from polyethylene vials. However, higher catches were obtained with blends of the two compounds in a 1:10 ratio. The blend of racemic compounds was as attractive as the blend of (R)-enantiomers. We reported that 1-Acetoxy-5-butyroxyhexane and hexyl 3-acetoxybutyrate are components of the female-produced sex pheromone of H. cinchonae, but further work is required on the blend and loading of pheromone and on trap design to provide an optimized system for monitoring and control of this pest. The results may also facilitate the identification of the pheromones of other Helopeltis species, which are major pests in many crops. This article is protected by copyright. All rights reserved.

Transgenic crops producing insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) have been used to manage insect pests for nearly 30 years. Dose of a Bt crop is key to assessing the risk of resistance evolution because it affects the heritability of resistance traits. Western corn rootworm (Diabrotica virgifera virgifera, LeConte), a major pest of maize, has evolved resistance to all commercially available Bt traits targeting it, and threatens resistance to future transgenic traits. Past research shows the dose of Bt maize targeting western corn rootworm can be confounded by larval density-dependent mortality. We conducted a 2-year field study at two locations to quantify larval density-dependent mortality in Bt and non-Bt maize. We used these results to calculate dose for our method and compared it to three previously published methods. Additionally, adult emergence and root injury were analyzed for predicting initial egg density. Increased pest density caused greater proportions of larvae to die in Bt maize than in non-Bt maize. All methods for calculating dose produced values less than high-dose, and stochastic variation had the greatest impact on dose at high and low pest densities. Our method for calculating dose did not produce values positively correlated with pest density while the three other methods did. To achieve the most accurate calculation of dose for transgenic maize targeting western corn rootworm, density-dependent mortality should be taken into account for both transgenic and non-transgenic maize and assessed at moderate pest densities. © 2024 Society of Chemical Industry.

To discover novel fungicide candidates, five series of novel norbornene hydrazide, bishydrazide, oxadiazole, carboxamide and acylthiourea derivatives (2a-2 t, 3a-3 f, 4a-4 f, 5a-5 f and 7a-7 f) were designed, synthesized and assayed for their antifungal activity toward seven representative plant fungal pathogens. In the in vitro antifungal assay, some title norbornene derivatives presented good antifungal activity against Botryosphaeria dothidea, Sclerotinia sclerotiorum and Fusarium graminearum. Especially, compound 2b exhibited the best inhibitory activity toward B. dothidea with the median effective concentration (EC50) of 0.17 mg/L, substantially stronger than those of the reference fungicides boscalid and carbendazim. The in vivo antifungal assay on apples revealed that 2b had significant curative and protective effects, both of which were superior to boscalid. In the preliminary antifungal mechanism study, 2b was able to injure the surface morphology of hyphae, destroy the cell membrane integrity and increase the intracellular reactive oxygen species (ROS) level of B. dothidea. In addition, 2b could considerably inhibit the laccase activity with the median inhibitory concentration (IC50) of 1.02 μM, much stronger than that of positive control cysteine (IC50 = 35.50 μM). The binding affinity and interaction mode of 2b with laccase were also confirmed by molecular docking. This study presented a promising lead compound for the study on novel laccase inhibitors as fungicidal agrochemicals, which demonstrate significant anti-B. dothidea activity and laccase inhibitory activity. This article is protected by copyright. All rights reserved.

Citrus huanglongbing (HLB) is a devastating disease caused by Candidatus Liberibacter asiaticus (CLas) that affects the citrus industry. In nature, CLas relies primarily on Diaphorina citri Kuwayama as its vector for dissemination. After D. citri ingests CLas-infected citrus, the pathogen infiltrates the insect's body, where it thrives, reproduces, and exerts regulatory control over the growth and metabolism of D. citri. Previous studies have shown that CLas alters the composition of proteins in the saliva of D. citri, but the functions of these proteins remain largely unknown. In this study, we detected two proteins (DcitSGP1 and DcitSGP3) with high expression levels in CLas-infected D. citri. Quantitative PCR and Western blotting analysis showed that the two proteins were highly expressed in the salivary glands and delivered into the host plant during feeding. Silencing the two genes significantly decreased the survival rate for D. citri, reduced phloem nutrition sucking and promoted jasmonic acid (JA) defenses in citrus. By contrast, after overexpressing the two genes in citrus, the expression levels of JA pathway-associated genes decreased. Our results suggest that CLas can indirectly suppress the defenses of citrus and support feeding by D. citri via increasing the levels of effectors in the insect's saliva. This discovery facilitates further research into the interaction between insect vectors and pathogens. © 2024 Society of Chemical Industry.

Insects use odor detection to sense their surroundings. Use of volatile compounds, such as essential oils (EOs) of plants, to repel pests and disrupt their olfaction-driven behaviors has great practical potential for use in integrated pest management. Despite the available information on the repellent effects of EOs on herbivorous insects, the olfaction-based mechanisms remain unknown. Y-tube olfactometer tests showed that the EOs of three Lamiaceae plants - Mentha arvensis L., Mentha piperita L. and Lavandula angustifolia Mill. - were significantly repellent to winged cotton aphid, Aphis gossypii Glover. Electropenetrography (EPG) tests indicated the EOs reduced phloem feeding and increased the level of nonproductive probing by the aphids. The EOs also reduced the fecundity of winged A. gossypii. Electrophysiological bioassays and mass spectrometry (GC-MS) identified five physiologically active volatiles, i.e., menthone, isomenthone, neomenthol and menthol from M. piperita; menthone and menthol from M. arvensis; and linalool from L. angustifolia. Behavioral tests confirmed that all five compounds repelled winged A. gossypii. Under field conditions, the growth rate of aphid populations after seven days was significantly lower in fields treated with these compounds than in the control fields. Our findings demonstrated that three EOs not only repelled winged A. gossypii but also interfered with the aphid's feeding behavior and reduced its fecundity. These EOs and their active constituents have great potential as eco-friendly control products for use against A. gossypii. The effects of these EOs also exceed other repellents that only keep pests away from host plants. This article is protected by copyright. All rights reserved.

A major impact of the invasive Myocastor coypus in the introduction range is the collapse of riverbanks and nearby infrastructure, such as railway lines, due to the species' burrowing activities. As the ubiquitous implementation of preventive measures along watercourses is unfeasible, identifying susceptible areas is key to guide targeted management actions. This study used species-habitat models to (i) identify the local environmental features of the railway line/watercourse intersections (RLWIs) that make them particularly susceptible to coypu damage, and (ii) predict species occurrence probability in a wide lowland-hilly area of northern Italy (Lombardy) to identify priority areas for monitoring. The local scale models stressed that the RLWIs most susceptible to burrowing were those surrounded by arable lands with interspersed hedgerows locally characterized by high herbaceous vegetation and clay soil. In urbanized and intensive agricultural areas coypu dens were generally located significantly closer to the railway, increasing the collapse risk. The landscape-scale species distribution model showed that lowland areas located along major rivers and lake shores, but also agricultural areas with a dense minor hydrographic network especially in the southeast of the study area, are more likely occupied by the species. The local scale models shown that specific environmental characteristics increase the risk of burrowing near RLWIs. The landscape scale model allowed predicting which areas require thorough monitoring of RLWIs in search of such local characteristics to implement preventive management measures. The proposed model-based framework can be applied to any geographical context to predict and prevent coypu damages. This article is protected by copyright. All rights reserved.

Due to the non-availability of any clear targets for molluscicides against Pomacea canaliculata (P. canaliculata), target-based screening strategy cannot be employed. In this study, the molluscicidal effects of typical pesticides on P. canaliculata were evaluated to obtain the molluscicide target. A series of arylpyrrole compounds were synthesized based on the discovered target, and the structure-activity relationship was explored. A preliminary strategy for screening molluscicides based on specific targets was also developed. A laboratory colony of P. canaliculata was developed, which showed no difference in sensitivity to niclosamide compared with the wild group, while exhibited a higher stability against pesticide response. Mitochondrial adenosine triphosphate (ATP) synthase inhibitors and mitochondrial membrane potential uncouplers were identified and validated as potential targets for molluscicide screening against P. canaliculata. A series of arylpyrrole compounds were designed and synthesized. The median lethal concentration (LC50) of 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile (Compound 102) was 10 times lower than that of niclosamide. New molluscicide targets were discovered and validated, and preliminary strategies were explored for pesticide screening based on these targets. Compound 102 exhibited a high molluscicidal activity and had a great potential value for exploring a molluscicide to control P. canaliculata. This article is protected by copyright. All rights reserved.

In Thailand, the scaly grain mite, Suidasia pontifica Oudemans, impacts the feed industry by emitting a lemongrass-like odor in contaminated feed, reducing its palatability. This study focused on identifying volatile organic compounds (VOCs) associated with this odor in contaminated chicken feeds and ground maize, as well as individual mites using gas chromatography-mass spectrometry (GC-MS). We explored the relationship between VOC concentration and mite population size in chicken feed cultures, aiming to detect minimal mite presence through regression models. Additionally, we tested the sensitivity of nine electronic odor sensors in detecting these VOCs. Our results showed Z-citral and E-citral present in mite-contaminated ground maize, chicken feeds, but absent in uncontaminated samples. Mite populations in chicken feed followed a normal distribution, increasing rapidly, peaking, and then declining, a pattern mirrored in the concentrations of Z-citral and E-citral. Simple linear regression models confirmed a positive correlation between mite density and citral concentrations. Polynomial regression models indicated Z-citral is detectable at mite densities over 67 individuals per gram and E-citral over 3.89 individuals per gram. Odor sensors showed varying readings across different citral concentrations, uncontaminated, and mite-infested chicken feeds. Our study confirms that S. pontifica are responsible for the lemongrass-like odor in infested samples, due to Z-citral and E-citral. The citral concentrations increase with mite population growth and are detectable at low mite densities, suggesting their effectiveness as biomarkers for early mite infestation detection. Additionally, MQ series odor sensors detected these VOCs, indicating their potential for monitoring mite infestations in storage environments. This article is protected by copyright. All rights reserved.

In the perpetual struggle to manage mosquito populations, there has been increasing demand for the development of biopesticides to supplant/complement current products. The insecticidal potential of Xenorhabdus and Photorhabdus has long been recognized and is of interest for the control of important mosquitoes like Aedes albopictus which vectors over 20 different arboviruses of global public health concern. The larvicidal effects of cell-free supernatants, cell growth cultures and cell mass of an extensive list of Xenorhabdus and Photorhabdus spp. was investigated. They were quite effective against Ae. albopictus causing larval mortality ranging between 52-100%. Three Photorhabdus spp. and 13 Xenorhabdus spp. release larvicidal compounds in cell-free supernatants. Cell growth culture of all tested species exhibited larvicidal activity, except for Xenorhabdus sp. TS4. Twenty-one Xenorhabdus and Photorhabdus bacterial cells (pellet) exhibited oral toxicity (59-91%) against exposed larvae. The effect of bacterial supernatants on the mosquito eggs were also assessed. Bacterial supernatants inhibited the hatching of mosquito eggs; when unhatched eggs were transferred to clean water, they all hatched. Using the easyPACId approach, the larvicidal compounds in bacterial supernatant were identified as fabclavine from X. szentirmaii and xencoumacin from X. nematophila (causing 98 and 70% mortality, respectively, after 48 h). Xenorhabdus cabanillasii and X. hominickii fabclavines were as effective as commercial Bacillus thuringiensis subsp. israelensis and spinosad products within 5 days post-application (dpa). Fabclavine and xenocoumacin can be developed into novel biolarvicides, can be used as a model to synthesize other compounds or/and can be combined with other commercial biolarvicides. This article is protected by copyright. All rights reserved.

Leaf feeders, such as Spodoptera frugiperda and S. litura, and stem borers Ostrinia furnacalis and Chilo suppressalis, occupy two different niches and are well adapted to their particular environments. Borer larvae burrow and inhabit interior of stems, which are relatively dark. By contrast, the larvae of leaf feeders are exposed to sunlight during feeding. We therefore designed series of experiments to evaluate the effect of light intensity (0, 2000, and 10 000 lx) on these pests with different feeding modes. The development of all four pests was significantly delayed at 0 lx. Importantly, light intensity affected the development of both male and female larvae of borers but only significantly affected male larvae of leaf feeders. Furthermore, the proportion of female offspring of leaf feeders increased with increasing light intensity (S. frugiperda: 33.89%, 42.26%, 57.41%; S. litura: 38.90%, 51.75%, 65.08%), but no significant differences were found in stem borers. This research also revealed that the survival rate of female leaf feeders did not vary across light intensities, but that of males decreased with increasing light intensity (S. frugiperda: 97.78%, 85.86%, 61.21%; S. litura: 95.83%, 73.54%, 58.99%). These results improve understanding of how light intensity affects sex differences of important lepidopteran pests occupying different feeding niches and their ecological interactions with abiotic factors in agroecosystems. This article is protected by copyright. All rights reserved.