Influence of plant surface spray adhesion of dinotefuran and thiodicarb on control of apple leafminer

This study was conducted to obtain the correlation between the plant surface spray adhesion amount of pesticides and the pest control effect. The linearity of the standard curves of dinotefuran and thiodicarb was R² = 0.9999, and recovery was between 70% to 120% which was satisfactory for insecticide residue analyses. The pest control effect was evaluated by assessing the number of apple leafminers (Phyllonorycter ringoniella, Gracillariidae, Lepidoptera) captured by sex pheromone traps from late June to late September in 2015. For the adhesion amount, dinotefuran recovered from trap A and B, respectively were 47 μg/50 ㎠ and 23 μg/50 ㎠, which can be characterized as a very low adhesion amount in comparison to the average adhesion amount of 81 μg/50 ㎠ in the field. In case of thiodicarb, 691 μg/50 ㎠ and 71 μg/50 ㎠ were recovered from trap A and B, respectively, and the average amount in the field is 325 μg/50 ㎠. These results showed close correlation with the insect population captured by trap A and B. The numbers of insects captured by trap A and B between the end of July and late August were similar. After spraying thiodicarb on August 28, the number of apple leafminers captured by trap B is bigger than that of trap A. It appears that pest occurrence tended to be high at low adhesion amounts of the active ingredient. Therefore, in order to obtain an optimal control effect, it is suggested that uniform application of insecticides is critical instead of relying on the amount of insecticide applied in the field.