Efficacy of Common Carp and Nile Tilapia as biocontrol agents of rice insect pests in the Philippines.

Replicated field plot trials were carried out to evaluate the role of fish as biocontrol agents of insect pests of rice in the Philippines. Evidence from suction sampling, examination of fish gut contents, and rice plant damage assessment strongly suggest that Common Carp Cyprinus carpio (L.) and Nile Tilapia Oreochromis niloticus (L.) do significantly reduce the densities of stemboring moths and chironomid midges, while the abundance levels of other arthropods are not significantly affected. This impact by fish often was more important in the wet season when heavy rains and wind likely caused the arthropods to become dislodged from the plant and fall onto the water. Predation by fish was particularly evident during the first 45 days of the crop during the wet season when adult chironomid midge abundance was high. The fish gut content analysis revealed that all insect guilds are represented in the diet of both of the fish species regardless of whether the life-cycle of the arthropod prey is aquatic, semi-terrestrial, or terrestrial. Thus, fish in rice fields are part of the assemblage of natural enemies of rice pests. While fish alone cannot completely suppress rice pest populations below the economic threshold, their significant contribution should not be overlooked. [ABSTRACT FROM AUTHOR]