Biocontrol Of Batocera Horsfieldi (Coleoptera: Cerambycidae) With Parasitoid Dastarcus Helophoroides (Coleoptera: Bothrideridae)

Batocera horsfieldi (Hope) is a serious forest trunk-borer pest on many kinds of trees, such as poplar, ash and walnut, in Hunan, Hubei, Shanxi, Shaanxi and Shandong Provinces, etc. At present, chemical control effect is poor because of the so hidden damage, inside trunks by B. horsfieldi larvae. For realizing sustainable control of B. horsfieldi, biocontrol techniques by releasing parasitoid Dastarcus helophoroides(Fairmaire)is studied, based on damage survey. Main results showed as follows.It was shown by survey that B. horsfieldi mainly attacked poplars in the Dongting Lake Plain and Jianghan Plain, ashes in the Huanghe Yellow River Delta, and walnuts in the Mt. Taihangshan region. Obvious differences of feeding habit, complementary nutrition, and ecological behavior of B. horsfieldi were found in different regions. It shoud be considered as a niche differentiation phenomenon because of host specalization in different geographic regions. The spatial distribution pattern of frass hole were both aggregated distribution when B. horsfieldi damaged poplars and ashes.By using the parametersαandβin Iwao's m*-m regression equation,the optimal and sequential sampling numbers, which the frass hole was biocontrol survey indexes, were determined at different accuracy when B. horsfieldi damaged the poplars and ashes.Biocontrol of B. horsfieldi was applied by releasing the parasitoid Dastarcus helophoroides eggs and adults, respectively on poplars in the Dongting Lake Plain and Jianghan Plain, ashes in the Huanghe Yellow River Delta, and walnuts in the Mt. Taihangshan region. Control effect was evaluated by three investigation indexes: infested trees, frass holes density and larvae density.Adults and eggs of D. helophoroides were released in the fields for biocontrol Batocera horsfieldi at nine plots in Dongting Lake Plain of Hunan Province and Jianghan Plain of Hubei Province. The control effect was that: Among three egg-releasing plots, corrected mean reducing rate of larvae per tree was 83.27%, corrected mean reducing rate of infested trees was 74.33%. Among six adult-releasing plots, corrected mean reducing rate of larvae per tree was 84.23%, corrected mean reducing rate of infested trees was 75.65%.They were also released in the fields for biocontrol B. horsfieldi at eight plots in Dongying and Binzhou City of Huanghe Yellow River Delta, Shandong Province. The control effect was among five egg-releasing plots, corrected mean reducing rate of larvae per tree was was 73.16%, corrected mean reducing rate of infested trees was 72.36%. Among three adult-releasing plots, corrected mean reducing rate of larvae per tree was 77.20%, corrected mean reducing rate of infested trees was 69.68%.At other three plots in Zuoquan County of Mt. Taihangshan region, Shanxi Province, the control effect was at two egg-releasing plots, corrected mean reducing rate of larvae per tree was 46.66%, corrected mean reducing rate of infested trees was 43.31%. At adult-releasing plot, corrected reducing rate of larvae per tree was 42.86%, corrected reducing rate of infested trees was 49.16%.Above results showed that releasing eggs or adults can effectively control B. horsfieldi,and the control effect was better than netmatode and Scleroderma sichuanensis, closer to stem injection pesticides and inserting poison pick. Releasing adults was a little better than releasing eggs by comparing the control effect in the first and second year, while significance test showed no obvious difference between them. Considering higher cost of releasing adults than eggs, it is suggested to release Dastarcus helophoroides eggs to control Batocera horsfieldi in fields.This is the first attempt to apply parasitoid Dastarcus helophoroides for biocontrol of Batocera horsfieldi. Result showed that this natural enemy can effetively control B. horsfieldi larvae. Control effect is good in the first year after releasing adults or eggs. It is proved that the biocontrol technique has bright prospect in the field of controlling B. horsfieldi and is worthy of further application.