Manejo de inseticidas para controle de pragas do algodoeiro e interação com artrópodes benéficos

Abstract

Beneficial arthropods provide significant services for crop production, such as natural biological control of pest species. Despite that, there is a lack of data on the response of beneficial epigeal arthropod community to the insecticides used on the plant canopy, especially, in the cotton ecosystem, where pest control relies highly on the use of synthetic insecticides. For example, the epigeal predator earwig, Euborellia annulipes (Lucas), can contribute to the control of different cotton pest species, mainly preying upon larvae and pupae of boll weevil inside flower buds fallen to the ground. This work aimed to assess the impact of insecticide use on the beneficial arthropods from the plant canopy and epigeal community (i), and to study the impact of 12 selected insecticides, recommended for the control of cotton pest species, for the epigeal predator, E. annulipes (ii), through insecticide dried-residues, ingestion of contaminated prey, and predation rate under insecticides-treated prey and plant. Response of beneficial arthropod communities to the insecticides was assessed through principal response curves (PRC), abundance, richness, and dominance indices. The impact of non-selective insecticides was detected in 2018, through lower predator abundance, and change in the predator community from plant canopy with significant contribution of ants and spiders for the outcome. There was a lack of impact on the plant canopy predator community, in 2020, and on the epigeal community for both seasons, 2018 and 2020. Across the 12 tested insecticides under laboratory conditions, pymetrozine, chlorantraniliprole, and spinetoram were of low impact to the predator regardless the population, developmental stage, and exposition routes. Cyantraniliprole exhibited impact depending on the predator age and exposition route; while, pyriproxyfen was harmless to the adults, but did not allow nymphs to molt to the adult stage. Chlorfenapyr, indoxacarb, lambda-cyhalothrin, chlorpyrifos, dimethoate, and malathion were harmful to the predator. The field data revealed the importance of insecticide application when the pest populations reach the economic threshold resulting in variable numbers and time of insecticide applications and, hence, showing a variable impact on communities of predator and beneficial arthropods from plant canopy and epigeal. The results from laboratory assays explain that the selectivity outcome varies as a function of predator contact with the insecticides, stage, and behavior of the predator and with the insecticide tested.