Research On Spraying Technology Of Thrips In Cotton Field During Anthesis By Multi-rotor Plant Protection Unmanned Aerial Vehicle

Xinjiang is the main cotton producing area in China.In recent years,the damage of thrips has gradually increased.It has evolved from a minor pest to a major pest next to aphids,seriously affecting the yield and quality of cotton.Compared with traditional spraying equipment,plant protection unmanned aerial vehicle(UAV)can avoid mechanical damage to crops during operation,reduce the impact on people and the environment,and can also increase the deposition of pesticides on target crops,reduce the amount of pesticides,and improve the utilization of pesticides.It is widely used in cotton fields for aphid control and cotton defoliation.Here,the research on the regularity of thrips activity in cotton field during anthesis,parameter optimization of UAV and screening for insecticides and application timing were carried out,in order to establish and improve the pesticide application system of UAV to control thrips in cotton fields during anthesis,and provide scientific basis and technical support for effective control of thrips in cotton fields during anthesis.1.Investigation on the activity of thrips in Xinjiang cotton fields during anthesisThrough the investigation of thrips population dynamics and diurnal activities in cotton fields in Xinjiang,the results show that thrips grow slowly at the initial flowering stage of cotton,and reach the peak on July 29,and there were about 2977 adult thrips per 50 cotton flowers.The population distribution of thrips gradually shifted from the lower canopy to the upper canopy as the cotton flowers opened layer by layer from bottom to top;and flowering thrips in cotton fields had frequent flying activities during 9:00-11:00 in the morning and 19:00-21:00 in the evening,mainly inhabiting flowers during 17:00-19:00 in the afternoon.2.Parameter optimization of plant protection UAV for the control of thrips in cotton field during anthesisTest research was carried out on the spraying performance of plant protection UAV under different operating parameters,and the droplet deposition characteristics of different canopy layers of cotton plants and the overall droplet distribution uniformity and penetration were compared,in order to screen out the combination of application parameters suitable for the control of thrips in cotton field.The effects of spray volume and adjuvants,flying speed and height on the spray deposition effect,droplet distribution uniformity and penetration were explored respectively.The results showed that the increase of the amount of spraying liquid significantly improved the droplet density,droplet coverage,droplet deposition and droplet penetration of each cotton canopy.The addition of adjuvants has a certain effect on improving the deposition effect of liquid mist droplets on cotton plants,and BDT has a better improvement effect than the other three adjuvants.The flight speed has a great influence on the penetration of droplet distribution,and the faster the flight speed,the worse the droplet deposition effect in the middle and lower canopy.The flying height affects the uniformity of droplet distribution.If the flying height is too high or too low,the overall droplet deposition effect will be deteriorated.Therefore,when using plant protection UAV to control thrips in cotton fields during anthesis,the recommended application volume is 30 L/hm~2,the flying height is 2 m,the flying speed is 2 m/s,and the parameter combination of adding the flying control additive BDT is recommended.3.Screening of insecticides and application timing for controlling thrips in cotton fields during anthesisFive different types of insecticides in the market were selected as the test agents,and the control effects of various insecticides on thrips in cotton field were explored through spraying by plant protection UAV.The results showed that 10%spinosad suspension concentrate and 10%cyantraniliprole dispersible oil suspension concentrate had better control effects,and the control effects were 80.51%and 79.22%respectively after 7days of application;19:00 in the evening was the best time for plant protection UAV,which control effects of 1 day,3 days and 7 days after treatment were 61.27%,73.14%and 81.51%respectively.In conclusion,it is recommended to use the parameter combination of spray volume 30 L/hm~2,flying height 2 m and flying speed 2 m/s for controlling thrips in the cotton field during flowering period by plant protection UAV.In addition,the insecticides 10%spinosad suspension concentrate and 10%cyantraniliprole dispersible oil suspension concentrate should be used in rotation,the adjuvant BDT should be added,and should be applied around 19:00 in the evening.In this way,the efficacy of pesticides can be improved to the greatest extent,thereby realizing the efficient prevention and control of thrips.