Effective treatment depth in soil of clothianidin granules for the brown gourdshaped weevil, <i>Scepticus uniformis</i> Kôno （Coleoptera: Curculionidae） on burdock.

In burdock, root feeding damage caused by Scepticus uniformis Kôno larvae which inhabit the soil significantly reduces the commercial value. However, there is no registered insecticide in the seed furrow treatment for the control of the weevil larvae. Therefore, the registration of clothianidin granules in the seed furrow treatment is expected. Accordingly, we examined the control effects by application depth in soil treatment of clothianidin granule of 6kg per 10 ares for S. uniformis on burdock for two years. As a result, the application of the insecticide at 2cm in depth and that at 5cm respectively reduced the root damage, compared with the application at 10 cm in depth in the first year and plant foot application in the second year. Consequently, it is considered that the application at 2-5cm in depth is effective in the soil treatment of the insecticide for the control of the weevils on burdock.