Emergence Profile of Overwintered Boll Weevils 1 and Entry into Cotton 2

Abstract

Small plots of cotton and pheromone traps were used to study the emergence profile of overwintered boll weevils, Anthonomus grandis Boheman, and their entry into cotton. Boll weevil movement into cotton was closely related to the phenology of the plant. Very few overwintered weevils entered presquaring cotton but immigration increased with increasing size and number of squares. Results of this study indicate that overwintered weevil colonization is not a result of random entry into cotton followed by pheromone production. Rather, overwintered weevil immigration into cotton appears to be a positive response to squaring cotton, with attraction greatly intensified by pheromone production after weevils feed on squares. Overwintered weevil response to pheromone traps appeared to provide a relatively accurate index of population size and activity. In the study area pheromone traps indicated that the major portion of the overwintered population was active several weeks before weevil colonization occurred in cotton. These data indicated that ca. the last 10% of boll weevils emerging from overwintering habitat contributed the major portion of the population that entered cotton. The relationship between the number of weevils responding to pheromone traps and the number entering the cotton plots indicates that pheromone traps can be used to predict the degree of overwintered boll weevil infestation which will occur in cotton.