LETHAL AND SUBLETHAL EFFECTS OF PESTICIDES USED IN BRAZILIAN COMMERCIAL FLOWER GREENHOUSES ON TETRANYCHUS URTICAE (TETRANYCHIDAE) AND ITS NATURAL ENEMIES

Mortality of Tetranychus urticae and natural enemies by pesticides

Abstract

The aim of this study was to evaluate, under laboratory conditions, the lethal and sublethal effects of eight commonly used pesticides on the phytophagous mite Tetranychus urticae Koch (Tetranychidae) and the predatory mites Neoseiulus californicus (McGregor) and Phytoseiulus macropilis (Banks) (Phytoseiidae), all associated with gerbera (Gerbera jamesonii) and chrysanthemum (Chrysanthemum morifolium) production in southern Brazil. A residual spray contact bioassay was conducted using a handheld sprayer, and mortality, reproductive performance, and egg viability were assessed. Pesticides were classified according to IOBC/WPRS (International Organization for Biological Control / West Palaearctic Regional Section) criteria, considering both lethal and sublethal (reproductive) effects. The results showed that chlorfenapyr was the most effective against T. urticae (98.36% mortality), whereas copper sulfate was the least effective (32.79%). For N. californicus, chlorfenapyr, pyridaben, and abamectin caused the highest mortalities (>97%), while spiromesifen was the least harmful (39.71%). In contrast, reproduction of P. macropilis was stimulated by copper sulfate, hexythiazox, and spiromesifen, although most compounds were classified as harmful to this predator. According to the IOBC/WPRS categories, 50% of the pesticides tested were harmless to N. californicus, while 87% were harmful to P. macropilis. These findings provide valuable insights into the compatibility of chemical and biological control strategies in ornamental crop systems, supporting integrated pest management (IPM) programs that prioritize the conservation of predatory mites in greenhouse production.