Screening And Primary Field Evaluation Of Infochemicals Manipulating Behavioral Responses Of Rice Brown Planthopper Nilaparvata Lugens (Stal) And Its Egg Parasitoid Anagrus Nilaparvatae Pang Et Wang

In response to herbivory, plants will emit specific blends of volatiles, which may not only attract the natural enemies of the herbivores, but also influence the behavior and/or performance of herbivores, microbes and the nearby plants. It will be important for finding new methods for pest control to identify active chemicals that manipulate behavioral responses of the herbivores and their natural enemies in herbivore-induced plant volatiles (HIPVs). Based on our previous identified volatiles from rice plants infested by rice brown planthopper (BPH) Nilaparvata lugens (Stal), we screened the bioactive chemicals that modulate behavioral response of BPH and its egg parasitoid Anagrus nilaparvatae. Moreover, the efficiency of the active chemicals in enhancing effect of the parasitoid in the field was tested. The main results are as follows:Responses of N. lugens to synthetic HIPVs were determined under laboratory conditions. The results showed that 6 chemicals have significant influence on the behavioral response of BPH. Among the 6 chemicals, farnesene, MeSA and 2-heptanone significantly repelled BPH, while linalool, E-3-ocimene and 2-heptanol significantly attracted BPH. Farnesene and MeSA were more active in repelling BPH than 2-heptanone, and linalool, on the other hand, was the most active among the 3 chemicals that were attractive to BPH.Attractiveness of 18 single synthetic HIPVs and 32 blends to A. nilaparvatae were tested in a Y-tube olfactometer. Five single chemicals, including three green leafy volatiles (E-3-hexenyl acetate, 1-penten-3-ol, E-3-hexenal)(50ppm), one terpenoid (linalool,50ppm) and methyl salicylate (MeSA,5ppm and 50ppm), were found to be strongly attractive to A. nilaparvatae. On the other hand, the parasitoid was also attracted by 3 blends. Interestingly, we also found that the parasitoid was repelled by 2 single chemicals, (+)-limonene and 2-heptanol.Primary field experiments were conducted to evaluate the effectiveness of these bioactive compounds or blends in attracting A. nilaparvatae and predators of BPH. The results showed that parasitism rates of BPH eggs by the parasitoid in the field were significantly increased when plants were hang up a seprum containing linalool, E-3-hexenal, E-3-hexenyl acetate or the mixture; the parasitism rates, compared with those in the control field, were increased by 31.67%,17.47%,7.76% and 34.93%, respectively. Application of other 2 single compounds, MeSA and 1-penten-3-ol, also increased the parasitism rates of BPH eggs, though this difference was not significant compared to the control. Application of all of the single chemicals or the blend did not cause significant increases in predation rates of BPH eggs.The results indicate that some chemicals from HIPVs did have influences on behavioral responses of rice brown planthopper N. lugens and its egg parasitoid A. nilaparvatae. Further elucidation of these active chemicals will exploit new methods and strategies for pest management.