Raymond Mahob

Field evaluation of synthetic sex pheromone traps for the cocoa mirid Sahlbergella singularis (Hemiptera: Miridae)

BACKGROUND Field trapping experiments were conducted to evaluate the attractiveness of five different pheromone blends as well as the impact of trap design on attractiveness towards cocoa mirids, Sahlbergella singularis Hagl. and Distantiella theobroma (Dist.), in Cameroon. RESULTS A total of 361 adults of S. singularis (359 males and two females) were caught. The highest numbers of mirids were found in traps with pheromone blends that combined a monoester and a diester, compared with traps with the diester or the monoester individually and control traps with no pheromone. Rectangular traps caught significantly more mirids compared with delta traps. The mean number of 5.1 mirids trap⁻¹ year⁻¹ caught in rectangular traps was significantly higher compared with the 1.8 mirids trap⁻¹ year⁻¹ for the delta traps. CONCLUSION The data revealed that rectangular traps containing pheromone blends combining both the monoester and the diester have a good potential to lure and trap adult males of S. singularis on cocoa farms. The pheromone blends used were specific for S. singularis, and the use of pheromone traps appears to be a promising strategy for incorporation into integrated pest management strategies for the monitoring or even the control of S. singularis in cocoa plantations.

True Bug (Heteroptera) Impact on Cocoa Fruit Mortality and Productivity

ABSTRACT The real impact of true bug damage on cocoa pods has never been assessed precisely. We conducted a 2-yr study on 1,080 cocoa trees on 36 farms in Cameroon to assess the contribution of true bugs to fruit mortality and production loss. The cocoa fruiting cycle, fruit mortality, and damage caused by true bugs as well as other pests and diseases were monitored on a weekly basis. True bug damage also was described on 2,500 ripe pods per year. Pod weight, bean number, and bean weight were measured and compared for different degrees and types of damage on the ripe pods. Our results showed that true bugs were the main external cause of young fruit abortion. They reduced the abundance of young fruit by up to 10%. In contrast, although one-third of the ripe pods sampled had true bug lesions, only 4% were moderately to heavily damaged. The mean weight of ripe pods was reduced by 12% when there was medium to heavy damage. While the mean weight of wet beans was reduced significantly (by 3–10%), the number of beans per pod was not changed by damage. Despite the reduction in mean weight, the overall weight of beans for the pods sampled was reduced by <2%. Therefore, our study confirmed the common assumption that the economic impact of true bug damage on mature pods is negligible on cocoa farms in Cameroon. However, true bugs have a significant impact on young fruit mortality.