Nitrogen fertilization to recover irrigated rice productivity, in infested areas by the South American rice water weevil, Oryzophagus oryzae

Among the strategies for South American rice water weevil, Oryzophagus oryzae (Costa Lima) (Coleoptera: Curculionidae), integrated pest management is the increment of nitrogen fertilization in infested areas. Nevertheless the extra amount of N to apply is unknown. To address this question, an essay of nitrogen fertilization doses, with and without pest control, was carried out. Plots of 5 x 2m were delimited with PVC sheets in a irrigated rice field, in a factorial design with two pest control levels, five nitrogen fertilization doses (0, 40, 80, 120 e 160kg of N/ha) and four replications. The larval population, rice productivity and yield components were checked according to standard protocols. The productivity was influenced by the levels of pest control and the doses of nitrogen fertilization, but with no interaction between them. The extra amount of 40kg of N/ha replaces the effect of chemical control for the water weevil on the productivity, in an area where the mean dose of 80kg of N/ha were adopted for nitrogen fertilization.