Greek oregano EO may be a good alternative to antibiotic growth promoters and coccidiostats whose use in feeding farm animals has been prohibited since January 2006 under European Union directives. The introduction of O. vulgare L. ssp. hirtum EO into the premises of farm and poultry houses may help to improve sanitary conditions and control of the lesser mealworm inhabiting these buildings. © 2017 Society of Chemical Industry.

Chemical transformation of the piperitone molecule by the introduction of a lactone function and a halogen atom strongly changed its antifeedant properties against the lesser mealworm. Optimum activity is dependent on the presence of a chlorine atom at C-5 of the cyclohexane ring. The activity of bromo- and iodolactones depended strongly on the chiral centre configuration and the halogen substituent.

The effects of dietary applied of β-damascone and its synthetic derivatives γ- and δ-halolactones, which show strong antifeedant activity, on the growth and development of larvae of the lesser mealworm, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae), were studied. Bioassays were performed in a dose-dependent manner. In the bioassays, oat flakes treated with 1.0, 0.5, and 0.1 % (w/v) acetone solutions of the tested compound or acetone alone as control were served as food. The experiments were conducted using 2-week-old larvae with an average body weight of 4.35–4.88 mg. High correlations between antifeedant activity and larvicidal and growth-inhibitory effects were observed. Larvae reared on diets containing the compounds (at a concentration of 1 %) with high deterrent activity were characterized by a prolonged period of development, lower body weight gain, and strong tendency for cannibalism as a result of starvation. The control larvae ended their development after 24 days with a mean body weight of 22.9 mg. At the same developmental time, the mean body weights of larvae treated with the δ-halolactones γ-chloro- and γ-bromo-δ-lactone were only 60.3 % and 43.2 % of that of the control larvae. The larval periods for larvae on the diets containing γ-chloro- and γ-bromo-δ-lactone were 33 and 41 days, respectively. The larval developmental time and body weight gain were not significantly influenced by lower doses of the compounds, with the exception of γ-bromo-δ-lactone. This compound, when applied at a concentration of 0.5 %, significantly prolonged larval development as compared to the control larvae, and caused high mortality of larvae and pupae. The adult emergence percentage was 37.51 % when this treatment was applied, as compared to 90.0 % in the control. Thus, β-damascone derivatives with a lactone ring exhibit both dose-dependent behavioral effects and post-ingestion toxicity against A. diaperinus larvae, and may have the potential to control this pest.