Deposition and distribution of six insecticides in greenhouse cucumber canopies and the impact on the control efficacy to Aphis gossypii

In this work, the droplet deposition and distribution of different insecticides in cucumber canopies and the impact on the control efficacy against Aphis gossypii were investigated. The droplet coverage of six insecticides was determined by DepositScan software. The insecticide droplets were collected by the relevant collection devices and spray droplet test cards. Meanwhile, the insecticide deposition was determined by the Allura red tracer. Then the relationship between the droplet deposition distribution in the cucumber canopy and the control efficiency against A. gossypii was illustrated. The results showed that the droplet deposition and coverage of abamectin, spirotetramat, pyriproxyfen, thiamethoxam, imidacloprid and acetamiprid on cucumber plants had no significant difference. The droplet deposition and coverage of the six insecticides was manifested with the distribution trend of top > middle > bottom. On the 1^st and 3^rd day after spraying, the corrected control efficacy of the six insecticides against A. gossypii on the same canopy position or the same insecticide to A. gossypii on different canopy positions were all above 65% and no significant different was detected among treatments. The droplets from knapsack manual sprayer mainly deposited on the top canopy of the cucumber. The droplet deposition on the top canopy accounted for above 1/3 of the total deposition amount, while the deposition was relatively lower on the middle and bottom canopies. However, the insecticide deposited in the middle and bottom canopies could still provide good control efficacy against A. gossypii when applied with the recommended dosage in the field. The results have provided a scientific basis for the rational control of A. gossypii.