Toxicity and risk assessment of acaricides on the predatory mite, Euseius scutalis (Athias-Henriot) (Acari: Phytoseiidae) under laboratory conditions

Abstract

Predatory mites belonging to family Phytoseiidae (Acari: Mesostigmata) have long been considered as the most promising candidates for biological control of some economically important plant feeding mites and insects. Among them, Euseius scutalis (Athias-Henriot) is one of the most abundant predators and can be considered as an important component for integrated pest management (IPM) programs in Mediterranean citrus orchards. Evaluation of non-target and toxic effects of pesticides is crucial to measure their threats to E. scutalis. In this study, the effects of some selected acaricides (abamectin, etoxazole, spirodiclofen, spirotetramat and pyridaben), that were widely used in citrus orchards, on eggs, larvae, and adult females of E. scutalis were determined under laboratory conditions. In order to observe some possible results at “worst-case scenario”, the test units were sprayed at maximum recommended doses. According to the results, abamectin and pyridaben respectively caused 18.00% and 33.50% mortality on eggs, 57.33% and 65.33% on larvae, 23.33% and 44.00% on adult females. While etoxazole was only toxic to the larvae with mortality rates reaching 55.33%, spirodiclofen and spirotetramat were harmless to all developmental stages of the predatory mite. In addition, abamectin, etoxazole and pyridaben caused a significant reduction in the egg production of E. scutalis when compared to the control. Accordingly, spirodiclofen and spirotetramat may be compatible with E. scutalis in IPM programs where it is implemented as a predator. However, further semi-field and/or field experiments are essential in order to draw a final conclusion on compatibility of the other three acaricides.