Dinâmica populacional de Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) em soja na região de Cerrado brasileiro: avaliação da incidência de adultos e lagartas e sua relação com as variações de temperatura e umidade

Abstract

Spodoptera frugiperda (Lepidoptera: Noctuidae), known as the corn fall armyworm, is a pest with widespread polyphagy and notorious as a primary pest in several agricultural crops. In soybean crops, their larvae can cause serious damage in the early stages of plant development, as well as during grain formation. The objective of this study was to investigate the incidence of S. frugiperda caterpillars and adults in relation to some environmental factors, specifically temperature and humidity, in two agricultural years of Intacta soybeans in the region of Ponta Porã and Dourados-MS. The 2021/22 harvest experiment was conducted at the unit of the Federal Institute of Mato Grosso do Sul, Ponta Porã campus, in the municipality of Ponta Porã, state of Mato Grosso do Sul, while the 2022/23 harvest experiment was conducted in the experimental area from Unigran, Mato Grosso do Sul, in the municipality of Dourados. . To capture males, a Delta-type trap was used with attractive commercial bait (Bio Spodoptera, Biocontrole®), while the caterpillar count was done visually, directly on the plants. Both analyzes were carried out weekly, starting before sowing and continuing until the end of the crop cycle. Climatic temperature and humidity data were obtained from INMET for Ponta Porã and EMBRAPA - Agropecuária Oeste for Dourados. To evaluate the influence of these abiotic factors on the population density of adults and caterpillars, linear regression analyzes were performed between population and climatic data. S. frugiperda adults and caterpillars were detected in both harvests, where the number of adults was higher in relation to the number of caterpillars. In the 21/22 harvest, the caterpillars were present both in the initial period of the harvest and at the end, diverging from the 22/23 harvest, in which the caterpillars were only present in the final sampling period. No significant correlation was found between temperature and humidity with the number of adults or caterpillars. The occurrence of caterpillars in the initial stages of soybean can compromise the establishment of the crop, due to the high destructive capacity of these pests on seedlings. Furthermore, the occurrence in the reproductive phases interferes with soybean yield, since the caterpillars prefer to feed on the pods in this phenological phase. Therefore, continuous monitoring of S. frugiperda throughout the soybean cycle is recommended, especially in the initial phases of vegetative and reproductive development, as the presence of caterpillars in these phases represents a substantial risk to crop yield.