An evaluation of pheromone trapping for banana weevil (Cosmopolites sordidus Germar) management in Costa Rican smallholder plantain farms

The banana weevil (Cosmopolites sordidus Germar) is an important pest of plantain (Musa spp.) in Costa Rica. Pitfall traps using lures containing the aggregation pheromone of the banana weevil have reduced weevil damage in large plantain plantations (>200 ha), but have not been tested in small (0.25-3 ha) farms. We evaluated the effects of pheromone traps on banana weevil damage and plantain yield in smallholder plantain farms within the Bribri-Cabécar Indigenous Territories of Talamanca, Costa Rica. Mass trapping with pheromone lures was conducted in six farms, and five farms were controls without traps. Four traps per hectare were placed in a line at 20 m spacing, and the line was rotated monthly within the hectare. Number of weevils per trap was recorded weekly. The mating status of a sub-sample of female weevils collected from traps was determined by examining the spermatheca for presence of sperm. Each farm was sampled for weevil damage and plantain bunch weight before and after 58 weeks of trapping. Percent damage was estimated in harvested plants from two cross-sections through the corm. Damage was not significantly different after 58 weeks in control farms (P=0.37), but dropped from 5.1% to 3.4% in farms with pheromone traps (P=0.017). Damage was correlated with initial trap catches. Bunch weight increased in farms with traps and decreased in control farms, but differences were not significant. Almost all (99%) of dissected females had mated. The reduction in damage in farms with pheromone traps indicates that traps are effective in smallholder plantain farms.