Efeito de inseticidas aplicados nas sementes de soja sobre o controle da lagarta-elasmo e na mortalidade e consumo foliar de lagartas desfolhadoras da cultura

Abstract

Mato Grosso is the main Brazilian state that grows soybeans, producing about 26.0 million tons in the season of 2015/2017. Among the great difficulties of cultivation of this crop, we highlight the high incidence of pests in the crop, especially the soil pests and the defoliating caterpillars. The objective of this work was to evaluate the effect of different insecticides when applied on the seed treatment of the soybean on the control the lesser cornstalk borer, the consumption of defoliators caterpillars and developmentof this crop. Two essays were carried out in areas with a historic of occurrence of Elasmopalpus lignosellus, being one in the municipality of Juscimeira/MT and another in Itiquira/MT. The soybean seeds were treated with different insecticides constituting the following treatments (g a.i./ha): chlorantraniliprole (62.5), imidacloprid + thiodicarb (75.0 + 2.5.0), fipronil (50.0), thiamethoxam 70.0) and cyanthraniliprole + thiamethoxam (60.0 + 70.0), besides a control treatment in which the seeds were not treated with insecticide, totaling six treatments with 4 replication, conducted in the randomized block design. It were evaluated the stand and the attack of lesser cornstalk borer on soybeans plants, the height of plants and the grain yield. Soybean leaflets were also collected at different times after the plants emergence in the experimental area to analysis of the foliar consumption of the caterpillars of Anticarsia gemmatalis and Chrysodeixis includens in the lab. It was verified a significant effect of the different insecticides applied on the soybean seeds to the foliar consumption and the mortality of caterpillars, as well as on the yield. The results evidenced that all the chemical treatments applied in the soybean seeds reduced the number of plants attacked by lesser borer cornstalk, as well as the treatments cyanthraniliprole + tiametoxam and chlorantraniliprole reduced the leaf consumption and caused higher mortality of the caterpillars of A. gemmatalis and C. includens. The treatment of the soybean seeds with the mixture cyanthraniliprole + thiamethoxam also guaranteed highest grain yield of the culture in relation to the control (without treatment).