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Two pure natural volatile compounds, carvacrol and menthone were investigated for repellent, insecticidal, ovipositional and egg hatching inhibition activities against pulse beetle, Callosobruchus chinensis (Coleoptera: Bruchidae). Carvacrol and menthone repelled bruchid adults in choice oviposition assay. Both compounds caused toxicity, reduced oviposition potential and viability of eggs significantly when fumigated. In chronic toxicity assay, both carvacrol and menthone reduced F1 progeny production and weight loss in cowpea seeds. Reduced in grain damage was probably occurred due to inhibition of oviposition and egg hatching. Acetylcholine esterase enzyme activity was inhibited in adults when fumigated with carvacrol and menthone showing neurotic mode of action. Findings of the present study suggest that application of carvacrol and menthone can be effective in the management of C. chinensis.

The orange wheat blossom midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), is a significant wheat pest in the Prairie Provinces of Canada and northern regions of the USA. Wheat phenology plays a critical role in wheat midge oviposition. We hypothesized that S. mosellana oviposition behaviour is influenced by volatile organic compounds (VOCs) emitted by wheat at two adjacent wheat growth stages: preanthesis and postanthesis. A higher number of S. mosellana eggs laid on preanthesis than postanthesis spikes in an oviposition choice experiment using the susceptible spring wheat cultivar ‘Roblin’. In preanthesis, wheat emitted higher amounts of Z-3-hexenyl acetate (Z3-06:OAc) than at the postanthesis stage. Higher amounts of methyl ketones such as 2-tridecanone, 2-pentadecanone, and 2-undecanone were emitted by wheat in the postanthesis stage and these VOCs were sensitive to S. mosellana antennae used in the Gas Chromatography-Electroantennographic Detection. Females were attracted to synthetic Z3-06:OAc but were deterred by 2-tridecanone relative to the solvent control in the vertical Y-tube olfactometer. 2-Undecanone and 2-pentadecanone did not show any attractiveness or deterrence. In a no-choice oviposition experiment, fewer eggs were laid in preanthesis wheat exposed to a synthetic VOC blend of Z3-06:OAc, 2-undecanone, 2-tridecanone, and 2-pentadecanone at the concentrations released by postanthesis spikes. This study shows that the reduction of Z3-06:OAc, in the VOC mix, and possibly the increase in 2-tridecanone, are likely responsible for the reduction in oviposition on postanthesis wheat. These results elucidate for the first time the role of specific VOCs mediating S. mosellana oviposition in preanthesis and postanthesis wheat.

Abstract The Queensland fruit fly (Q-fly) Bactrocera tryoni is the most economically destructive tephritid pest in eastern Australia, inflicting substantial damage to diverse fruit and vegetable crops. Broad-spectrum, persistent, synthetic insecticides have been used to manage tephritid fruit flies. However, the adverse effects of these insecticides on human health, the environment, and nontarget organisms, as well as regulatory restrictions, have prompted the search for alternative control methods. This study explores the potential of essential oils as alternatives by evaluating their toxicity and behavior-modifying properties against adult Queensland fruit flies. We evaluated 16 essential oils for contact and fumigation toxicity, oviposition inhibition, and repellence. The chemical profiles of the essential oils were analyzed with Gas Chromatography-Mass Spectrometry and antennal responses were assessed by gas chromatography-electroantennographic detection. Chamomile, lemon-scented tea tree, and citronella exhibited notable contact toxicity (ED50 0.054 to 0.068 mg/µl) after a 24-h exposure, while garlic, aniseed, pennyroyal, basil, and peppermint exhibited high fumigation toxicity (ED50 3.293 to 4.950 µl/liter air) over the same period. Aniseed, cumin, and pennyroyal essential oils repelled both Queensland fruit fly sexes in 4-arm olfactometer assay. Aniseed, basil, chamomile, citronella, cumin, dill, garlic, lemon-scented tea tree, pennyroyal, peppermint, thyme, and yarrow essential oils inhibited oviposition. This study demonstrates essential oils as toxicants, oviposition deterrents and repellents, offering promising alternatives to conventional pest control methods for managing Queensland fruit fly populations.

Aedes aegypti, also known as the yellow fever mosquito, presents a major public health challenge, highlighting the need for effective biorational agents for mosquito control. Here, we investigated the synergistic effects of essential oil mixtures derived from Hypenia irregularis that is a mint-family shrub native to Brazil’s Cerrado biome, known as “alecrim do Cerrado”, in combination with essential oils from noni (Morinda citrifolia), Brazilian mint (“salva-do-Marajó”, Hyptis crenata), and lemongrass (Cymbopogon citratus) against Ae. aegypti. We conducted phytochemical analyses and assessed larvicidal, repellent, and oviposition deterrent activities. Using in silico methods, we predicted molecular interactions between key essential oil components and physiological targets involved in repellent action (odorant-binding protein AeagOBP1 and olfactory receptor Or31) and larvicidal activity (GABA and octopamine receptors, TRP channels, and acetylcholinesterase [AChE]). Major compounds identified included octanoic acid (23%; Hipe. irregularis × M. citrifolia), 2,5-dimethoxy-p-cymene (21.9%; Hipe. irregularis × Hypt. crenata), and citral (23.0%; Hipe. irregularis × C. citratus). Although individual oils showed strong larvicidal activity (Hipe. irregularis LC50 = 2.35 µL/mL; Hypt. crenata = 2.37 µL/mL; M. citrifolia and C. citratus = 2.71 µL/mL), their mixtures did not display synergistic effects. Similarly, repellency and oviposition deterrence were comparable to DEET for individual oils but were not enhanced in mixtures. Notably, the Hipe. irregularis × C. citratus essential oil blend reduced oviposition deterrence. Molecular docking confirmed strong binding of major oil components to AeagOBP1 and Or31, supporting their role in repellency. For larvicidal effects, AChE showed the highest predicted binding affinity. Overall, our findings suggest that H. irregularis, Hypt. crenata, C. citratus, and M. citrifolia (alone or in 1:1 mixture) are promising, sustainable agents for A. aegypti control.

Spotted wing drosophila, Drosophila suzukii (Matsumura), is an important invasive insect pest in the United States. Spotted wing drosophila females have serrated ovipositor that enables them to deposit eggs inside healthy, ripening softskinned fruits. In many berry and fruit crops, spotted wing drosophila is primarily controlled using synthetic insecticides in the organophosphate, pyrethroid, and spinosyn groups. However, alternative, reduced-risk insecticides with short residuals are necessary to minimize the possibilities of insecticide resistance and address other negative effects of synthetic insecticides. Neem-based products as alternative plant-based insecticides have antifeedant, repellent, antiovipository, and molting interference effects on insects and have been shown to affect the oviposition activities of some tephritid flies. We conducted laboratory studies to evaluate the oviposition deterrent activities of selected neem-based insecticides that contain either azadirachtin, or CHENO, or a combination of both, on spotted wing drosophila using sweet cherry in California. The results of the study showed that some of the neem oil products could reduce the degree of spotted wing drosophila oviposition by half compared with the control.

The massive use of synthetic pesticides to manage agricultural pests results in environmental pollution and health hazards. The secondary plant metabolites, which are majorly dominated by terpenoids, have the potential to be developed into novel alternatives to synthetic chemicals. Therefore, in our current investigation, six majorly dominated essential oil constituents were evaluated for their toxicity against adults and immature stages of oriental fruit flies, Bactrocera dorsalis, a worldwide fruit pest. The results indicated that carvacrol was the most toxic essential oil constituent (EOC) to adult flies, with LC50 of 19.48 mg/mL via fumigant assay, followed by thujone 75% mortality via ingestion toxicity test against adult fruit flies. Similarly, when larvae were dipped in different concentrations of EOCs, carvacrol appeared as the most toxic EOC with the lowest LC50 (29.12 mg/mL), followed by (−)-alpha-pinene (26.54 mg/mL) and (R)-(+)-limonene (29.12 mg/mL). In the oviposition deterrence tests, no egg was observed on oranges seedlings treated with 5% of each EOC (100% repellency). Regarding the repellency assay, a significantly higher number of flies (77%) were repelled from the Y-tube olfactometer arm containing (−)-alpha-pinene, followed by carvacrol (76%). Our results showed that the selected essential oil constituent has the potential to be developed as an alternative to synthetic pesticides against B. dorsalis. However, further research is required to assess the activities of these EOCs under open-field conditions.

The essential oils extracted from mandarin (Citrus reticulata Blanco) fruits, and from tea tree (Maleleuca alternifolia (Maiden and Betche) Cheel) leaves have been chemically analyzed and tested for their bioactivity against D. suzukii. Besides, to estimate consumers’ acceptability of the essential oil (EO) treatments, we evaluated their impact on the organoleptic characteristics of the EO-treated fruits. The main chemical constituents of the two EOs were 1,8-cineole and 4-terpineol for M. alternifolia (22.4% and 17.6% of the total components, respectively), and limonene (83.6% of the total components) for C. reticulata. The behavioral tests indicate that the two EOs are able to deter D. suzukii oviposition and that D. suzukii shows positive chemotaxis to low concentrations of the EOs and negative chemotaxis when the EO concentration increases. While no negative effects on the organoleptic profiles were detected for fruits treated with C. reticulata EO, the olfactory profile of fruits treated with M. alternifolia EO was so negative that they were defined as “not suitable for consumption” by panellists. Overall, our findings indicate that the use of EOs for the post-harvest protection of small fruits is feasible, provided that the essential oils are selected not only for their bioactivity against the insect pest but also for their affinity with the consumers’ sensorial system.

The whitefly Bemisia tabaci (Gennadius, 1889) (Hemiptera: Aleyrodidae) is a globally important insect pest, causing extensive damage and losses in horticultural production systems. New natural options are needed to control the whitefly. Ethanol extracts (92) of different organs from 40 plant species of the Yucatan Peninsula were evaluated against B. tabaci in a greenhouse, and an adult repellency index (RI) was determined for leaves and an oviposition deterrence index (ODI) for the extracts. Ethanol extracts at 1% (w/v) after 48 h suppressed the population density of B. tabaci. Leaves of Malpighia glabra L. had the highest repellent activity, causing a decrease in the population density of adults (RI 0.05) and eggs (ODI − 85). Three fractions differing in polarity were obtained by partitioning the ethanol extract of M. glabra, and the hexane fraction had an intermediate RI, but the ODI was not active. LC–UV–HRMS analysis of the fractions showed the presence of syringaresinol, 10-hydroxy-pheophorbide a, pheophorbide a, and lupenone, the first report of these four for this species. Eleven unknown compounds were also detected. This bioprospecting research on botanical extracts from native species of the Yucatan Peninsula enriches our knowledge of potential sources of products for pest management. M. glabra is a promising candidate for further formulation and application studies to control B. tabaci.

Lucilia sericata is a facultative ectoparasite causing fly strike or myiasis in warm-blooded vertebrates. It is controlled by traps or insecticides, but both have drawbacks and alternative ways of control are urgently needed. Essential oils (EOs) of vetiver (Chrysopogon zizanioides), cinnamon (Cinnamomum zeylanicum), and lavender (Lavandula angustifolia) and their blends (OBs); OB1 (2 ml of each EO plus 4 ml of sunflower oil as a carrier) and OB2 (2 ml of each EO) were tested. Oils were tested at 5% for deterrence assays, and a dose response assay 0.01–0.6%, was conducted to determine forced-contact toxicity. We evaluated the efficacy of oils as oviposition deterrents, repellents/attractants, and their effects on mortality and longevity of adult L. sericata. Our data indicated that 0.2% EOs killed all flies by 5 min post-treatment and that vetiver oil greatly deterred flies from the oviposition medium and reduced adult longevity. Sunflower oil repelled all flies from ovipositing and greatly reduced the lifespan of treated adults. The blend of the four oils (OB1) had the greatest repellent effect on the flies. EOs have insecticidal, repellent, and oviposition-deterrent activities against L. sericata that could be used for suppression of blow fly populations.

The food industry is increasingly turning to healthy and eco-friendly alternatives for meat preservation, with recent attention focused on chitosan (CH) and essential oils (EOs). Here, we propose two liquid formulations of CH enriched with Laurus nobilis or Piper nigrum EOs to preserve beef patties stored for 4 days at 4 °C from colour changes, secondary lipid oxidation, and alteration in volatile organic compound emissions while also preventing oviposition by Calliphora vomitoria on beef loaves hung for the same time at around 13 °C in a netted polytunnel. Overall, the L. nobilis EO-enriched CH solution increased the meat colour lightness compared to the control (+7.58%), kept redness and yellowness comparable to the control, maintained the level of thiobarbituric acid-reacting substances below the threshold for rancidity perception for at least 96 h, reduced the release of ethanol, enhanced the perception of fatty and woody notes in the meat along with the fresh, green, and citrusy aromas specific to the EO, and also provided significant protection (88.83%) against blowfly oviposition compared to the control. Therefore, the development of a spray CH formulation containing the L. nobilis EO appears to be a promising tool for stable and prolonged meat protection.