Biocidal radiuses of cycloxaprid, imidacloprid and lambda-cyhalothrin droplets controlling against cotton aphid (Aphis gossypii) using an unmanned aerial vehicle.

BACKGROUND

Unmanned aerial vehicles (UAVs) are a recently advanced aerial spraying technology. However, the median lethal number of droplets (LN ) and biocidal radiuses (r ) of insecticides droplets sprayed by UAVs are still unknown. Therefore, we evaluated the LN and r of cycloxaprid, imidacloprid and lambda-cyhalothrin droplets associated with adjuvant controlling against Aphis gossypii.

RESULTS

A small UAV and Potter spray tower (PST) were used to generate different size of droplets (Dv0.5 = 185 ± 5 and 43 ± 2 μm). The mortality of A. gossypii showed a droplet density-dependent process. At the concentration of 5 g L , the LN of lambda-cyhalothrin, imidacloprid and cycloxaprid droplets sprayed by the UAV were only 49.2, 34.6 and 19.7 droplets cm , respectively, and the r were 0.57, 0.68 and 0.90 mm, respectively. The LN values were negatively correlated with insecticide concentrations, but the r values increased with the increasing concentrations. Although cycloxaprid is less toxic to A. gossypii than lambda-cyhalothrin, cycloxaprid had a larger r than lambda-cyhalothrin due to its translocation ability. Furthermore, cycloxaprid had a relatively larger r than imidacloprid because it is more toxic to A. gossypii. Moreover, adjuvant silwet DRS-60 can significantly increase the r of droplets.

CONCLUSION

Our results revealed that the r of a droplet was higher than its droplet size at tested concentrations. Smaller droplets generated by the PST had relatively higher insecticidal potential. The median lethal dose (LD ) and translocation ability of insecticides and spray adjuvant contributed to their r . Therefore, ultra-low-volume spray with UAVs is feasible to control cotton aphids. © 2020 Society of Chemical Industry.