Spatial and temporal distribution of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) and Euxesta spp. (Diptera: Otitidae) in the corn crop

Abstract

The aim of this study was to verify the pattern and the spatial and temporal behavior of the corn earworm and corn-silk fly in the corn crop. Hybrid corn was planted without chemical insect control in one hectare, this area was divided into 100 plots of 100 m². For the occurrence of Euxesta spp. all parts of the plants were visually analyzed, whereas for Helicoverpa zea (Boddie) 10 ears were removed at random from each plot, totaling 1,000 ears per sample. Population fluctuation was related to the phenological stages of corn. For spatial behavior, the dispersion indices, frequency distribution models and geostatistics (Krigagem) were analyzed. The corn earworm (small and large) and corn-silk fly showed aggregate pattern and spatial behavior. The reach of caterpillars <1 cm had an area of influence greater than caterpillars > 1 cm, with spatial dependence being considered moderate. The corn-silk fly had a maximum area of influence of 1.33 ha with moderate and weak spatial dependence. The maps demonstrated that these insects occur dispersed throughout the corn area, but with aggregations influenced by the adjacent areas and edges of the crop. The largest occurrence of corn earworms was at the R3 stage. It was also found that the corn-silk fly followed the occurrence of the corn earworm. It is concluded that the studied pests have an aggregate spatial tendency in the corn crop and with the influence of adjacent areas, in addition to presenting related population peaks in the reproductive period of the corn crop.