The effect of fish on the abundance of the rice caseworm Nymphula depunctalis (Guenee) (Lepidoptera : Pyralidae) in direct seeded, concurrent rice-fish fields

In rite 1996-97 dry season, a rice caseworm (Nymphula depunctalis (Guenee)) outbreak occur red at the Co Do lice-fish experimental station, Can Tho pr ovince, Mekong Delta, Vietnam. A polyculture of Thai silver barb, common ca rp and Nile tilapia was able to I educe the number of rice caseworm larvae (P < 0.001) by at least 93%. As a result, the number of rice caseworm adult s (P < 0.001) and the percentage of damaged lice leaves (P < 0.001) were al so reduced compared with lice fields without introduced fish. As the pest r eduction did not differ infields with high and low seeding densities, it wa s concluded that the access of fish into the ricefield was not severely ham pered by high rice seeding densities. The presence of fish or rice caseworm s had no effect on the rice yield. The broader acceptance of rice-fish cult ure could lead to a reduction of the number of pesticide sprays used agains t highly visible defoliators like rite rice caseworm. This would enforce th e concept that rice-fish culture and integrated pest management are complem entary.