Effect of rice husbandry on mosquito breeding at Mwea Rice Irrigation Scheme with reference to biocontrol strategies.

A study was carried out at Mwea Rice Irrigation Scheme, Kenya, to assess the impact of rice husbandry on mosquito breeding and identify indigenous biocontrol agents with potential for controlling mosquito breeding in the scheme. The study established a close relationship between the schedule of the farming practices (particularly the flooding phase) and mosquito breeding. Two groups of agents, entomopathogenic bacteria (Bacillus thuringiensis var. israelensis) and larvivorous fish, were identified. Laboratory evaluation of the agents produced encouraging results. The bacterial isolates showed broad-spectrum larvicidal potency against Anopheles, Culex and Aedes mosquito larvae and 2 of the fish species, Tilapia zilli and Oreochromis niloticus, demonstrated a strong predation for a mosquito larval diet. To facilitate their use in effective biocontrol strategies, the agents would require further evaluation under field conditions.