Dinâmica populacional, distribuição espacial e temporal de Chrysodeixis includens (Walker) na cultura da soja

Abstract

Soybean, Glycine max (L.) Merril, are widely cultivated in Brazil and the world, but soybean have faced major problems with several pests that can attack the crop. The soybean looper, Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae), stands out among defoliation caterpillars that attack soybean, because it is difficult to control and has gained key pest status in the crop. In integrated pest management it is important to know the bioecological aspects of pests, to monitor population, to know their biology, behavior and relationships around pest insects. The objective of this work was to obtain information about the population fluctuation, to study the relationships and vertical distribution of C. includens in the soybean crop, aiming to provide subsidies to be used in the integrated management of this pest. The experiments were conducted under field conditions, with the monitoring of the stages of the soybean looper caterpillars carried out with the beat cloth, adult pheromone traps and inspection of the plants for egg sampling. The study of the correlations between the immature forms and the adults of C. includens was carried out. To study the behavior of caterpillars in the soybean canopy during the day, ten plants were collected at different times (6h, 8h, 10h, 12h, 14h, 16h, 18h, and 20h) and sectioned in three strata (upper, middle and lower) ) that were bagged individually, for the subsequent count of eggs and caterpillars in the laboratory. It was not possible to find significant correlation between adults captured in the pheromone traps and the immature densities of C. includens in soybean plants. However, a positive and significant correlation was observed between the density of eggs and of caterpillars of the pest in the soybean crop. The moths preferentially oviposited the lower part of the plants, while the caterpillars prefer to position themselves in the lower and middle parts of the plants. However, at warmer temperatures during the day, the caterpillars migrate to the top of the soybean plants.