Beetle Tenebrio molitor L. (Coleoptera, Tenebrionidae) is a well-known pest of grain and flour in food stores and grocery shops. Recently, commercial cultivation of the insect was started for human food and animal feed. Behaviour control of this insect using natural repellents is promising both for grain protection and commercial cultivation. We analysed if natural products of plant origin, namely essential oils (EOs), could be used for this purpose. Behavioural tests were performed using EOs of six plants: thymus (Thymus vulgaris), eucalyptus (Eucalyptus globulus), spearmint (Mentha spicata), lavandin (Lavandula × hybrida), East-Indian lemongrass (Cymbopogon flexuosus), and clove (Eugenia caryophyllus). The most effective repellent for mealworm larvae was EO of spearmint, moderate activity showed that of clove and the least repellent were EOs of lemongrass thymus and lavandin. EO of eucalyptus caused almost no or very low effect. Six of the most abundant compounds of the EOs were selected for testing. The most effective single compounds were terpinene-4-ol and carvone, low-effective cis-sabinene hydrates and those of no significant activity were limonene, myrcene and γ-terpinene.

European cherry fruit fly, Rhagoletis cerasi (Diptera: Tephritidae), is the most important pest of sweet and sour cherry fruit. This fly is difficult to control by insecticide application since most of the conventional insecticides used have been banned in Europe. Traps are used for both the pest’s mass trapping and the detection of the beginning of the flight period. Data on flies’ reactions to host-plant volatile organic compounds (VOCs) can be used to search for new attractants. VOCs were collected from the headspace of sour cherry, P. cerasus, fruit. Gas chromatography–mass spectrometry (GC–MS) resulted in the identification of 51 compounds. Terpenes and esters predominated in two aspects: in the highest diversity of the compounds, and the amount of the total VOC emissions (62.3%). Among the single VOCs, ethyl octanoate prevails, followed by (E)-4,8-dimethyl-1,3,7-nonatriene. GC–electroantennographic detection (GC–EAD) revealed 14 EAG-active compounds and those were identified. In Y-tube olfactometer tests, EAG-active compounds ((E)-β-ocimene, linalool, and (Z)-3-hexenyl 3-methylbutanoate) attracted R. cerasi females in a similar way to the odour of sour cherry fruit.

Plant–insect interactions mediated by chemical compounds are well documented in roots and above-ground plant parts except seeds. The latter chemoecological interactions remain poorly studied. The chemical composition of seeds, including attractive, repellent, or inhibitory compounds, likely influences oviposition behavior, yet specific studies on this subject are scarce. This study evaluated the oviposition behavior of the yellow mealworm (Tenebrio molitor L. (Coleoptera, Tenebrionidae)) on substrates of common oat (Avena sativa L. (Poales: Poaceae)), common wheat (Triticum aestivum L. (Poales: Poaceae)), rapeseed (Brassica napus L. (Brassicales: Brassicaceae)), and pure sand. Females laid the most eggs on oat and wheat substrates, while oviposition on sand was reduced by 22%. The chemoreceptors located in the antennae of T. molitor were found not to influence oviposition. Hexane extracts of oat flour were found to contain oviposition-inhibiting compounds, identified as fatty acids. Behavioral tests showed that oleic, palmitic, linoleic, and stearic acids inhibited oviposition at concentrations ranging from 5% to 0.5%. A lower concentration (0.05%) did not have this effect. Additionally, linoleic, palmitic, and oleic acids exhibited repellent properties, whereas stearic acid did not. These findings provide valuable insights into optimizing substrate composition to enhance T. molitor reproduction. This has applications for small-scale laboratory research and large-scale industrial production, supporting the use of T. molitor as an alternative protein source for feed and food.

Application of insecticides for pest control must be minimized due to well-known risks to human health. Application of environmentally friendly means is the best option. For stored product pests’ control, new means are needed alongside a deep understanding of the ecology and behavior of the pests. The present study investigated whether the odor released from wheat grain infected by mold fungus Aspergillus flavus (Eurotiales: Aspergillaceae) influences the behavior of the yellow mealworm (Tenebrio molitor L. (Coleoptera: Tenebrionidae)), a stored product pest of economic importance with worldwide distribution. Analysis of video-recorded behavior and computer data analysis revealed a significant difference in reactions depending on the beetle’s sex. Females were more sensitive to fungus contamination as they discriminated between A. flavus-infected and uninfected wheat grains from the onset of infection, while males discriminated only after a 5-day period. Analysis of single volatile organic compounds (VOCs) revealed the presence of both repellents and attractants. Among those, hexanal was repellent for both males and females, 1-octen-3-ol was repellent for males and indifferent to females, 1-hexanol was attractive to females and repellent (at high concentrations only) to males, and 3-methylbutan-1-ol was attractive to females (at high concentrations only) and indifferent to males. Hexanal, as a potential repellent, was suggested for further testing under grain storage conditions.