Evaluating host location in three native Sclerodermus species and their ability to cause mortality in the wood borer Aromia bungii (Coleoptera: Cerambycidae) in laboratory

Abstract In China Aromia bungii (Coleoptera: Cerambycidae) is an economically important wood-boring pest of Prunus trees, particularly peach, and it has recently entered Japan and several other countries as an invasive species. Larvae of A. bungii are attacked by parasitoid species in the genus Sclerodermus (Hymenoptera: Bethylidae), which have potential to be released as biological control agents. In this study we evaluated the olfactory responses and parasitism rates of three Sclerodermus species against A. bungii when reared on the substitute host, Tenebrio molitor (Coleoptera: Tenebrionidae). In Y-tube olfactometer studies, the odor of frass from the larvae of A. bungii was highly attractive to S. guani adults, but not to S . sichuanensis or S. pupariae adults. When reared on A. bungii larvae (rather than T. molitor ) for one generation, S. sichuanensis adults were also attracted to the odor of frass from A. bungii larvae. This indicates that learning plays an important and positive role in successful host location by S. sichuanensis . For S. pupariae , it is possible that more extensive learning experience is required to adapt to A. bungii larvae. When we studied mortality of immature A. bungii larvae in infested peach tree logs under semi-field conditions, we found that mortality rates were similar for the three species of Sclerodermus : S. guani 54.81 ± 8.07%, S. sichuanensis 42.59 ± 9.01% and S. pupariae 40 ± 6.76%, respectively. However, there was a significant difference in mortality between S. guani and the control. Parasitism rates caused by S. sichuanensis (35.56 ± 9.48%) were similar to S. guani (42.96 ± 14.20%) and S. pupariae (34.44 ± 10.10%). From these results we suggest that S. guani would be the best candidate for biological control of the immature stages of A. bungii , and that more field trials should be done in the future.