Effect of insecticides on generalist predatory mites released in vineyards

Abstract: Generalist predatory mites belonging to the Phytoseiidae family are considered key biocontrol agents of phytophagous mites in European vineyards. In IPM strategies, inoculative releases of predatory mites are effective tools against phytophagous mites. However, the activity of predatory mites can be limited by the use of non-selective pesticides. Here, in three field experiments we evaluated the effect of insecticides applied in vineyards on the releases of Kampimodromus aberrans. The effects of insecticides and K. aberrans releases on naturally occurring predatory mites and phytophagous mites were also considered. In the first experiment the insecticides thiamethoxam, buprofezin, etofenprox and indoxacarb were applied to control grape leafhoppers. In the second experiment the insecticides Bacillus thuringiensis, emamectin benzoate, methoxyfenozide and chlorantraniliprole were applied against grape berry moths. In the third experiment releases were performed on two grapevine varieties characterized by different levels of leaf hairiness. Two insecticides were tested, i.e. B. thuringiensis and chlorantraniliprole, targeted at grape berry moths’ control. In all release treatments K. aberrans was the predominant predatory mite species. K. aberrans abundance was reduced by etofenprox and buprofezin in the first experiment while none of insecticides used in the second were associated to a detrimental effect on predatory mite. In the third experiment K. aberrans abundance differed between grapevine varieties and no effect of insecticides was observed. The implications on interspecific interactions among predatory mites and biological control of phytophagous mites in vineyards are discussed.