Compatibility of Proteus®, matrine, and pyridalyl pesticides with Amblyseius swirskii Athias-Henriot: Sublethal studies and persistence effect

Abstract

The predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) is an effective biological control agent that suppresses populations of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) under greenhouse conditions. Our study assessed the lethal and sublethal effects of three novel pesticides on this predator. Results showed that pyridalyl presented the highest toxicity against A. swirskii adults based on LC50 (41.7 mg L-1). Also, sublethal concentrations (LC25) of Proteus® and pyridalyl not only significantly prolonged the duration of A. swirskii immature stages but alsoreduced the fecundity of the predator female adults by 21.4 and 41.5%, respectively. Similarly, the LC25 of both pesticides significantly reduced life table parameters of the F1 generation, which are important in the effective control of F. occidentalis, particularly in conservation biological control. In contrast, the LC25 of matrine stimulated reproduction in A. swirskii populations by significantly increasingR0 and r. Within a 24-h period, the number of F. occidentalis consumed by A. swirskii adults exposed to fresh Proteus® and pyridalyl residues was reduced by 35.6% and 15.8%, respectively. Proteus® caused the highest mortality in persistence assessments up to 96h. Our results indicated that only matrine is marginally compatible with the use of A. swirskii.