Ecological fitness of brown planthopper, Nilaparvata lugens (Stål), to rice nutrient management

INTRODUCTION: The brown planthopper (BPH), Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), is a notorious insect pest of rice. Nutrient supplementation can alter plant biochemical compositions which may indirectly affect on ecological fitness parameters of its insect pest. However, few findings are available on nutrient-induced ecological fitness of BPH and relationship of BPH fitness parameters with its host rice plant biochemical contents. METHODS: We studied the main and interaction effects of nitrogen (N), phosphorus (P), and potassium (K) inputs on BPH fitness, as measured by the following variables: nymph survival, nymphal duration, adult body weight, and its survival. Brown planthopper fitness parameters were regressed as function of rice plant (Oryza sativa) biochemical composition. A completely randomized design with four replications in a factorial scheme was used considering N, P, and K levels as factors. RESULTS: Nitrogen application to the host rice plants provided greater survival and enhanced body weight of BPH. The nymphal duration was found to decrease with N subsidy that caused shorter generation time of BPH. Nitrogenous compounds N and soluble protein (SP), total free sugar (TFS), and silicon (Si) content in rice plant tissue correlated strongly with all fitness traits of BPH. Nitrogen, SP, and TFS associated positively with BPH survival and body weight, while negatively with nymphal duration. In contrast, Si had negative correlation with BPH survival and body weight, but positive with nymphal duration. Phosphorus supplementation to host plant contributed to increase BPH body weight. Relationships of P with all parameters of BPH were weak except body weight which was highly significant and positive. Interaction between N and P inputs demonstrated significant effect on BPH body weight. Application of K had no significant effect on BPH survival and development. Regression analysis did not detect significant relationship of BPH fitness parameters with plant tissue content of K. CONCLUSIONS: The results suggest that BPH ecological fitness characters were improved after N and P fertilization to rice plants which are associated with biochemical content of rice plant. Therefore, N and P inputs should be used judiciously in rice cultivation to keep BPH ecological fitness potential at minimum level.