Efeitos letais e subletais de inseticidas utilizados na cultura do pessegueiro sobre o predador Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae) em condições de laboratório e semi-campo

Abstract

Among the main fruits cultivate in the southern region of Brazil, they stand out as having a temperate climate such as peach, plum, and apple trees. In these crops, one of the main problems faced has been the management of pest arthropods, especially Anastrepha faterculus (Wiedemann, 1830) (Diptera: Tephritidae) and Grapholita molesta (Busck, 1916), and the main form of control is the application of pesticides. However, the use of insecticides as the only measure to control, this measure has disagreed with Integrated Pest Management (MIP), which provides for the combination of chemical and biological controls. These studies on the toxicity of pesticides to natural enemies generate important information so that the association of these methods is made possible. Thus, the objective of this work was to evaluate the toxicity of the pesticides acetamiprid + etofenprox, spinetoram, indoxacarb and methoxyfenozide on Chrysoperla externa, using a methodology proposed by the International Organization for Biological and Integrated Control (IOBC), through laboratory bioassays on eggs, larvae, pupae and adults, in addition to biological persistence tests in the greenhouse. Eggs and pupae were conducted direct spraying of pesticides, and larvae and adults consisted of exposing the insects to waste sprayed on glass plates. The bioassays of biological persistence (duration of harmful activity) of the pesticides on larvae and adults, were through the exposure of insects to pesticides residues sprayed on leaf extract and evaluated at different time intervals. In the laboratory conditions, all pesticides tested were harmless (class 1) to predator eggs, and only acetamiprid + etofenprox was considered to be slightly harmful (class 2) to the pupa stage. The effects of the pesticides caused results similar to the larval and adult stage of C. externa in the laboratory, in which the insecticides acetamiprid + etofenprox, espinetoram, indoxacarb were harmful (class 4) to both stages. Concerning the biological persistence of pesticides, spinetoram and indoxacarb were moderately persistent (class 3) to larvae, and the only spinetoram was slightly persistent (class 2) for adults, the other insecticides, acetamiprid + etofenprox, indoxacarb and methoxyfenozide were classified as short-lived insecticides (class 1) in this evaluation. According to the results of the bioassays in the laboratory and the greenhouse, the difference in susceptibility between the larvae and adult stages of C. externa is evident, and the use of the insecticides acetamiprid + etofenprox and methoxyfenozide should be prioritized, because these insecticides no deleterious effects caused in the larval stage of C. externa, which is more sensitive to insecticides than the adult stage, thus favoring the viability of biological control.