Chemical Characterization of Clove, Basil and Peppermint Essential Oils; Evaluating Their Toxicity on the Development Stages of Two-Spotted Spider Mites Grown on Cucumber Leaves

SIMPLE SUMMARY: Essential oils show considerable acaricidal activity against pests. This study investigated the effects of three essential oils on T. urticae, one of the most serious pests in the world. The quality of the host plant and growth conditions affect the reproduction of Tetranychus urticae Koch, reducing their population levels very quickly. Research is ongoing to find eco-friendly insecticides or natural bioactive compounds against spider mites under greenhouse and field conditions. Clove EO was found to be the most toxic, while basil and peppermint EOs were the least effective, and immature stages were more sensitive to EOs than mature stages. It can be concluded that cucumber cultivars are effective in regard to the biological aspects and reproduction of two spot spider mites (TSSM), and the tested oils are good alternatives to control T. urticae in the protected cultivation of cucumbers. ABSTRACT: The two spotted spider mite (TSSM), Tetranychus urticae Koch, is a cosmopolitan mite. It rapidly reproduces and can develop resistance to chemical pesticides. This study aims to evaluate the toxicity and acaricidal activity of three essential oils from basil, clove, and peppermint against T. urticae reproduction, which is grown on three cucumber cultivars, Chief (SC 4145), Raian (CB898), and Toshka (SC 349), under laboratory conditions at 27 + 3 °C and 70 + 5% RH. GC-MS characterized the volatile oils of basil, clove, and peppermint. Methyl cinnamate, eugenol, and menthol were the main essential oils in basil, clove, and peppermint, respectively. The results indicated significant differences in the duration of development between T. urticae feeding on the three cucumber cultivars (p ≤ 0.05), including eggs, protonymph, and deutonymph time. The Toshka (SC 349) cultivar recorded the lowest developmental time. The longevity period exhibited the same trend with non-significant differences between Raian (CB898) and Toshka (SC 349). Moreover, the lethal concentration (LC50) and LC90 values in tested essential oils (EOs) showed that clove EOs were the most toxic. In contrast, basil and peppermint EOs were the least effective, and immature stages were more sensitive to EOs than adult stages. The infected Toshka (SC 349) discs treated with essential oils and abamectin under in vitro conditions indicated that clove oil is comparable to abamectin regarding its effect on the egg numbers (18.7 and 17.6 egg), immature development time, longevity, life span, and life cycle (20.6 and 20.8 days) of T. urticae. We conclude that the resistant cultivation of cucumber plants can be recommended in integrated pest management programs. The most effective of the tested oils, clove EOs, should be used as alternatives to pesticides to control T. urticae in the protected cultivation of cucumbers.