Influence Of Elevated CO₂on Nilaparvata Lugens （Stal） In Biology And Fitness Costs Of Buprofezin-Resistance

Climate change can influence growth, development, and allocation of plants, which results in distribution, abundance of insects that feed on the plants. So far, most of research on effects climate change on sucking-mouthpart insects targeted on aphids, and relatively few studies on planthoppers. The thesis was designed to investigate potential effects of climate change on biology of the brown planthopper (BPH), Nilaparvata lugens (Stal). The following questions were addressed in this study:(1) whether do elevated CO2and N fertilizer have combined effects on individual development and reproductive of BPH?(2) is there any influence of elevated CO2on fitness costs of pesticide-resistant BPH. The main results and conclusions are summarized as follows.1. Effects of elevated CO2and nitrogen fertilization on development and reproduction of the brown planthopper. According to Newman’s model for influence of elevated CO2and nitrogen fertilization on plant sap-sucking insect abundances, it was predicted that elevated CO2and increasing nitrogen fertilization could have negative influence on the rice planthopper, Nilaparvata lugens in developmental and reproductive parameters. To verify the prediction, experiments were conducted to manipulate CO2(390and780μL/L) and nitrogen fertilization (20,40,80,120and160mg/L) treatments in incubators, where rice plants were cultured and development and fecundity of the planthopper observed. The results showed that CO2and nitrogen fertilization treatments had either independent or combined effects on egg and nymph development time, nymph survival, female fecundity, and female longevity. Compared with ambient CO2, under elevated CO2nymph survival and fecundity were obviously increased, but with increasing nitrogen fertilization were following biological performances adversely influenced as that:(1) egg development time was extended by08%;(2) nymph survival rate was decreased from77.%at low N fertilization level (20mg/L) to49.3%at high N level (160mg/L);(3) fecundity declined from360.9eggs per female at low N level (20mg/L) to195.4eggs per female at high level (160mg/L);(4) female longevity was shortened from26.8days at the low N level to16.3days at the high N level. Out results confirm the prediction based on Newman’s model. The study suggested that increasing nitrogen fertilization would reduce advantages to development and reproduction of BPH accrued by elevated CO2under climate change.2. Fitness costs of the brown planthopper under elevated CO2. In order to examine effects of elevated CO2on development and reproduction of susceptible and resistant strains of brown planthopper, Nilaparvata lugens (Stal), experiments were carried out to observe development, reproduction and survival of buprofezin-susceptible and resistant strains (a400-fold difference in resistance) of BPH under different CO2levels (390and780μL/L). The results indicated a significant interaction between the two factors for developmental parameters and fecundity of BPH. Compared with the susceptible strain, the resistant BPH was lower in nymph survival, fecundity, female longevity, but higher in egg hatching rate and longer in nymph duration, under ambient CO2; but egg and nymph duration and nymph survival were decreased, but egg hatching rate increased under elevated CO2. The results suggested that elevated CO2can partly reduce fitness costs of the buprofezin-resistant strain of Nilaparvata lugens.3. Effects of elevated CO2on feeding behavior of the buprofezin-resistant strain of the brown planthopper Feeding behaviors of buprofezin-susceptible and resistant strains (a400-fold difference in resistance) of the brown planthopper (BPH) were compared by using electronic penetration graph technique (EPG). The results showed that total duration of N3, N4-a and N4-b of both susceptible and resistant strains was shorter when feeding the rice seedling grown under elevated CO2(780μL/L) than that under ambient CO2. Compared to the buprofezin-susceptible strain, the resistant strain had longer total duration of N4-a and N4-b when feeding on rice grown under ambient CO2, but had shorter duration when feeding on the rice seedling grown under elevated CO2. The results suggested that elevated CO2can affect the phloem-sucking behavior of resistant strains of the brown planthopper.