Impact of vineyard agrochemicals against Panonychus ulmi (Acari: Tetranychidae) and its natural enemy, Neoseiulus californicus (Acari: Phytoseiidae) in Brazil

Abstract Grapevines are attacked by diseases and pests, and strategies used by wine makers for the control of these involve the use of agrochemicals, causing in balancing of predator-prey ratios. The spider mite Panonychus ulmi causes damage to grapevines in the South of Brazil, whereas Neoseiulus californicus is the most frequently used predatory mite in biological control of tetranychids in Brazil. The effects of 13 agrochemicals used in the wine growing sector and their effect on P. ulmi and N. californicus were evaluated. A residual contact method by air-brush spraying was used. The corrected mortality rate and the effect of products on mite reproduction were evaluated and eggs were monitored until larval hatching to evaluate viability. Products were classified according to the total effect caused, in toxicity classes proposed by the IOBC/WPRS Working Group “Pesticides and beneficial organisms”. Lambda-cyhalothrin was the product that caused the highest mortality rate of P. ulmi : 76% within 24 h after spraying, reaching 100% mortality within 72 h. The other products caused mortality between 50% and 60% at 96 and 120 h. None of the products fitted into the harmless category; however, the fungicides azoxystrobin, metiram + pyraclostrobin, copper hydroxide and mancozeb showed low toxicity to the pest and predator. So, it is probably they can be used for doses management without disrupting the mite biocontrol. The products recommended which were harmful to the predator were cymoxanil + mancozeb, tetraconazole, lambda-cyhalothrin, famoxadone + mancozeb. These results can be used to develop guidelines on the best products to be used in the field, thus creating pest management practices that preserves predatory mite populations in vineyards.