Seletividade fisiológica de inseticidas para o parasitóide Telenomus remus (Hymenoptera: Scelionidae)

Abstract

Spodoptera frugiperda (Lepidoptera: Noctuidae) is one of the main agricultural pests in the world, especially in corn, soybean crops and cotton crops. Its control is carried out through insecticide applications; however, indiscriminate use has selected resistant populations of this pest and caused biological imbalances with a reduction in the population of natural enemies. Therefore, it is very important to evaluate the selectivity of new insecticides for use in integrated pest management programs for these crops. One of the natural enemy species most associated with this noctuid in these crops is Telenomus remus (Hymenoptera: Scelionidae). Given the importance of this parasitoid in controlling S. frugiperda, the aim of this study was to assess the physiological selectivity of the insecticides chlorantraniliprole, indoxacarb, spinetoram and chlorpyrifos, at the highest dosages recommended by the manufacturers, for T. remus. The insecticides were applied to T. remus during the egg-larvae and pupal stages inside S. frugiperda eggs, and also to adults of the parasitoid, using a Potter tower calibrated at 15lb.pol -2 with a deposit of 2.0 ± 0,5 μL.cm -2 . The numbers of surviving insects, parasitized eggs and emerged parasitoids were evaluated, as well as the number of males and females to calculate the sex ratio. The insecticide chlorpyrifos, when applied to S. frugiperda eggs containing T. remus in the egg-larvae and pupal stages, reduced parasitism and the emergence of adult parasitoids of the F1 generation by 100%, and was therefore classified as harmful according to the International Organization of Biological Control (IOBC) classification. The other insecticides evaluated were selective for the immature stage of the parasitoid. Spinetoram and chlorpyrifos were toxic to adult females (F0) of the parasitoid that were exposed to residues of the insecticides on contaminated surfaces. Due to the low toxicity of chlorantraniliprole, spinetoram and indoxacarb to T. remus in its immature stage, and indoxacarb and chlorantraniliprole to the adult stage, these insecticides should be prioritized in integrated pest management programs aimed at preserving this parasitoid species in soybean and corn cotton crops.