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The application of antifeedants, often in combination with other methods within integrated pest management (IPM) strategies, has proven to be a good way to control insect pests. Little is known about compounds that have antifeedant activity against the lesser mealworm, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae). The antifeedant properties of optically pure isomers of pulegone and isopulegol and some enantiomeric pairs of bicyclic terpenoid lactones with the p‐menthane system, derived from these isomeric starting compounds, were studied in choice and no‐choice tests with the lesser mealworm. The original monoterpenes and γ‐spirolactones were weak feeding deterrents to larvae and adults of A. diaperinus. The δ‐hydroxy‐γ‐spirolactones showed significant activity against adults, but substituting the hydroxy group with a ketone group considerably reduced the deterrent activity of the resulting δ‐keto‐γ‐spirolactones. The bicyclic γ‐hydroxy‐δ‐lactones with condensed rings and with the (1S,6R,8R)‐(+) and (1R,6S,8S)‐(–) configuration of the chiral centres, and δ‐hydroxy‐γ‐lactone (1S,4S,6S)‐(+) were very strong antifeedants to both larvae and adults. The hydroxy groups and the configuration of the chiral centres of the molecules were very important features for determining the antifeedant activity of the lactones tested. Generally, the compounds studied were better antifeedants to adults than to larvae.

The chemical composition of the essential oils (EOs) of Thuja occidentalis L. (Cupressaceae) and Tanacetum vulgare L. (Asteraceae), obtained by steam distillation, and their insecticidal activity against larvae (10 and 20 days old) of the lesser mealworm, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae), were studied. The activity of the oils was compared with the activity of their major components, aand b-thujone. Isolation, identification, and quantification of the volatile compounds were performed using a gas chromatograph (GC) coupled to a mass spectrometer (MS). The major components of T. occidentalis EO were the monoterpenoid ketones a-thujone (69.8%), b-thujone (9.5%), and fenchone (7.8%). The monoterpenoid alcohols terpinene-4-ol and p-cymene-8-ol, and the diterpenoid beyerene were only present in low amounts (<3.0%). All other compounds occurred in traces. In contrast to the thuja oil, the main compounds found in the EO of T. vulgare were b-thujone (61.0%), camphor (13.0%), and trans-chrysanthenyl acetate (6.5%). The insecticidal activity of both EOs and pure monoterpenes incorporated into a diet as acetone solutions at a concentration of 10 mg ml À1 depended on the age of A. diaperinus larvae. Young larvae displayed a higher sensitivity toward the tested chemicals than older ones. The survival of 10-day-old larvae, their body mass gain, and pupation rate were affected. The growth and development of the older larvae were similar to those of the control. In all tests, there were no significant differences between the activities of the EOs and their major components.

Starting from precocenes I and II, four of their derivatives with a lactone moiety were obtained. The compounds have been assessed as antifeedants against several diverse insect species including the storage pests the confused flour beetle (Tribolium confusum Duv., larvae and adults), the granary weevil beetle (Sitophilus granarius L., adults), and the khapra beetle (Trogoderma granarium Ev., larvae) and against the herbivorous pest insects Colorado potato beetle (Leptinotarsa decemlineata Say, adults and larvae) and aphids (Myzus persicae Sulz.). Precocenes, especially precocene II, showed a very strong antifeedant effect against all storage pests and aphids. The introduction of a lactone moiety caused a decrease in antifeedant activity against these species. Both precocenes were moderately active against L. decemlineata adults. The best antifeedants to this species were precocene derivatives, especially iodolactones. The introduction of iodine into a molecule had a great effect on the antifeedant activity of those compounds.