Role of rice volatiles in the foraging behaviour of the predator Cyrtorhinus lividipennis for the rice brown planthopper Nilaparvata lugens

Abstract

Experiments were conducted inlaboratory to study the impacts of ricegenotypes and rice plants treated withdifferent levels of nitrogen on the predationrates of the predator, Cyrtorhinuslividipennis Reuter, for eggs of the rice brownplanthopper (BPH), Nilaparvata lugens(Stal), and their relation to the ricevolatiles. In two-choice test, the predatorfemales showed different predation rates forBPH eggs on different rice genotypes, but notfor BPH eggs on rice plants treated withdifferent levels of nitrogen. The olfactoryresponse test revealed that more femalepredators oriented to the odours from healthyrice plants compared with the plain air(control); the predator preferred plant-BPHnymph complex over healthy plants, andplant-BPH gravid female complex over plant-BPHnymph complex. Additional experimentsdemostrated that there were obvious differencesin attractiveness of the healthy plants andplant-BPH gravid female complex of various ricegenotypes, while no significant differenceswere found between rice plants treated withdifferent levels of nitrogen. The results ofpredation rates of the predator on variousvarieties and plants treated with differentlevels of nitrogen were consistent with that ofits olfactory response in 5 of the 6 casesevaluated, which showed that rice volatilesplayed an important role in the foragingbehaviour of C. lividipennis.Implications for augmenting the effectivenessof natural enemies by adjusting rice attributesand cultural practices are discussed.