Essential oils from three Cupressaceae species as stored wheat protectants: will they kill different developmental stages of nine noxious arthropods?

Several plant species belonging to the Cupressaceae family are used in the industry for the production of various pharmaceuticals, food additives, and paint materials. Various essential oils (EOs) derived from these species have been examined for their insecticidal and acaricidal actions. In this study, we examined the efficacy of Hesperocyparis arizonica, x Hesperotropsis leylandii, and Juniperus x pfitzeriana EOs as wheat protectants to control different stages of development of nine stored-product pest species (1 dermestid, 1 curculionid, 1 bostrychid, 1 silvanid, 1 mite, and 4 tenebrionids). The EOs of the above plants were characterized by high percentages of monoterpenoids among which alpha-pinene (16.7-41.0%), sabinene (5.4-10.4%), delta-3-carene (20.5%), limonene (6.9-15.4%), bornyl acetate (36.3%), and trans-sabinyl acetate (18.2%) were the most representative ones depending on the species. Mortality caused by the three EOs at 1000 ppm to Trogoderma granarium adults ranged between 88.9 and 100.0%, after 7 days (d). The EO of H. arizonica, at the highest concentration (1000 ppm), killed 94.4% of exposed Oryzaephilus surinamensis adults, after one week. Complete mortality (100%) of Alphitobius diaperinus larvae occurred after exposure for 5 d to x H. leylandii EO at 1000 ppm. High mortality rates were also reported for Tribolium castaneum (93.3%) and Tribolium confusum (91.1%) larvae, and Tenebrio molitor adults (87.9%) at 1000 ppm of x H. leylandii EO, 7 d after exposure. This investigation shows that x H. leylandii EO provided elevated mortality levels to the majority of the tested pests exhibiting high potential to be considered as an effective grain protectant.