Toxicity of insecticides used in melon crops to Opius scabriventris (Hymenoptera: braconidae)

Abstract

Melon cultivation is an important agricultural activity in the Northeastern Region of Brazil. During its commercial cultivation, the melon crop is attacked by pests, mainly leafminers Liriomyza sativae Blanchard and Liriomyza trifolii (Burgess) (Diptera: Agromyzidae). To keep leafminer populations below an economic issue level, it is essential to adopt control measures such as spraying insecticides and biological control. However, there is little information on the toxicity of insecticides used in the melon crop against leafminers' natural enemies. Therefore, the aim of this study was to evaluate the toxicity of insecticides used in melon crops against the parasitoid Opius scabriventris, a natural enemy of leafminers from the genus Liriomyza (Diptera: Agromyzidae). The experiment was conducted under controlled laboratory conditions, in a completely randomized design, using two bioassays: I - Contact of parasitoids with a recently sprayed surface; and II - Contact of parasitoids with a surface containing dried residues of the insecticides that were significantly toxic in the bioassay I. In both bioassays, the toxicity of the insecticides was evaluated by observing parasitoid mortality. In bioassay I, from eight insecticides tested, only Cartap hydrochloride and Abamectin + mineral oil were considered harmful (Class 4) and Deltamethrin showed to be slightly harmful (class 2). Only Abamectin + mineral oil was harmful (Class 4) to the parasitoid O. scabriventris in the bioassay II. These are the first results regarding the effect of insecticides used in the management of melon pests on the parasitoid of the leafminer fly O. scabriventris.