Colonization and Spatial Distribution of Boll Weevil in Commercial Cotton Fields.

Abstract

The departure and arrival of boll weevil in cotton fields have fostered major control decisions against this pest over time. Field colonization and distribution of boll weevil were evaluated using cotton fields from 93.7 to 154ha each, located in Serra da Petrovina and Campo Verde, both in the Cerrado biome of Mato Grosso State, Brazil, as a function of cotton field bordering vegetation and crop phenology. The monitoring of adult weevils was carried out using traps containing sex and aggregation pheromone. The traps were set up considering the four coordinates of the field, bordering vegetation, and distances from the field margin. Six traps were set in each direction with three representing the field margin (0m, 60m, and 120m from the borderline) and the other three set up equidistant from the center of the field (> 200m). Traps were evaluated weekly beginning 10days after plant emergence (DAE) throughout the cotton phenology until harvesting. Boll weevils were caught in the first evaluation 10 DAE, irrespective of the vegetation bordering the cotton field and distance of trap from field margin. The average weevils per trap was relatively low throughout the crop development but increased significantly through the maturation and harvesting periods. Furthermore, the bordering vegetation was not the only determinant factor for boll weevil colonization and distribution throughout the cotton field. Based on these data, boll weevil exhibited early colonization, already occurring beyond the border of the field.