[Behavioral responses of Holotrichia oblita larvae to root exudates from three host plants]

The larva of Holotrichia oblita is a serious soil pest that feed with plant roots in north China. To explore the effects of host root exudates on the larva could provide theoretical basis for the development of green prevention and control methods. In order to elucidate the behavioral responses of Holotrichia oblita larva to the roots of peanut, soybean and maize, an experiment was conducted using the Y-olfactometers with the air as control. The constituents of the root exudates from the three host plants were identified by the gas chromatography-mass spectrometer (GC-MS). The olfactory responses of H. oblita larvae to the main components were tested. The results showed that H. oblita larvae had a significant behavioral preference toward the roots of peanut, soybean and maize than the control. The GC-MS analysis showed that the main components of volatile compounds in the three plants had more than twenty compounds, with only three shared ones, which was glycerol, dodecanol, ethyl benzene. The results of the Y-olfactometers showed that at low concentrations (40 to 80 μg·mL^-1), the number of insects attracted by compound 2-butenoic acid, methylsuccinic acid, myristic acid, acetic acid and phthalate was significantly higher than that of control. At the concentrations of 100 μg·mL^-1, 200 μg·mL^-1, compound tetradecane and hexadecane were more attractive to the larvae than the control. The compounds p-xylene, o-xylene, and palmitic acid glycerol were found to significantly induce the larva at the concentration of 300 μg·mL^-1 and 500 μg·mL^-1. In summary, the main components of plant root exudates had a significant luring effect on H. oblita larvae.