Control effects and sublethal effects of four pesticides on Atheloca bondari (Lepidoptera: Pyralidae) caterpillars

Abstract

• The concentration of abamectin used to control A. guerreronis caused 100% mortality of A. bondari caterpillars; • The residues of abamectin, azadirachtin, and fenpyroximate affected the behaviour of A. bondari caterpillars; • Acaricide residues did not interfere with infestation of coconut fruits by A. bondari caterpillars. Atheloca bondari Heinrich is an opportunistic lepidopteran that uses necrosis caused by the mite Aceria guerreronis Keifer, the most important pest of the coconut palm, to access the meristematic region of coconuts. Because of this moth-mite positive association, pesticides used to control A. guerreronis (abamectin, azadirachtin, fenpyroximate, and pyridaben) may impact A. bondari caterpillar behavior and/or survival. Thus, we used three methodologies (toothpick, triangle, and mesocarp fragment) to evaluate mortality caused by abamectin, the most commonly used pesticide to control A. guerreronis . The toothpick method proved to be suitable for toxicity tests of A. bondari caterpillars. Subsequently, the mortality caused by these four pesticides was evaluated, and abamectin caused 100% mortality in A. bondari caterpillars. Abamectin showed higher toxicity than the other pesticides to A. bondari caterpillars, with LC 50 and LC 95 values of 1.35 and 3.64 mg/L, respectively. The preference test showed that A. bondari caterpillars infested pesticide-treated fruits in the same proportion as untreated fruits. In the behavioral test, A. bondari caterpillars showed lower locomotor speed when exposed to surfaces with abamectin, azadirachtin, and fenpyroximate residues. Our study presented that pesticides used to control A. guerreronis affect the behavior and survival of A. bondari caterpillars. We discuss how spraying these pesticides can indirectly control the population of A. bondari , reducing the impact of this moth on coconut production, and modifying the importance of this species as a pest of coconut palm.