Abstract:

[Objectives] The purpose of this study was to evaluate the effects of three rice farming methods; conventional rice paddies, and those with either shrimp farms or co-planted with Vetiveria zizanioides), on the population dynamics of rice pests and their natural enemies, in order to help prevent and control pest outbreaks and conserve natural enemy populations in paddy fields. [Methods] Visual inspection, net sweeping, pot-patching and stripping, were used to collect and count rice pests (rice planthoppers, rice leafhoppers and rice borers) and their natural enemies (rice spiders, grass midges, Crytorrhinus lividipennis and Paederus fuscipes), during the rice heading stage. [Results] Significantly fewer rice planthoppers were observed in paddy fields co-planted with V. zizanioides than conventional rice paddies, or rice paddies with shrimp farms (P<0.05). Significantly higher numbers of rice leafhoppers and rice borers were found in conventional rice paddies relative to those with V. zizanioides or shrimp farms (P<0.05). The natural enemies of rice pests were spiders, grass midges, C. lividipennis and P. fuscipes. Significantly higher numbers of P. pseudoannulata, Pirata subpiraticus and C. lividipennis were found in paddies co-planted with V. zizanioides, or with shrimp farms, than conventional paddies (P<0.05). [Conclusion] Significantly fewer rice leafhoppers and rice borers were observed in paddies co-planted with V. zizanioides and with shrimp farms than conventional paddies.

Key words: farming technology, rice-shrimp co-cultivating, Vetiveria zizanioides, rice pests, population dynamics of natural enemies