| In recent years,the plant protection by unmanned aerial vehicles(UAVs)has been developing rapidly.However,the application of UAVs in the control of pests in cotton fields,the appropriate pesticides and dosages,and the comparative advantages of plant protection and mechanical efficiency are lagging behind.The performancesof UAV and its application technologies in cotton field were studied with P20 and P20 V2 UAV,the main results are as follows:1.The results of droplet coverage test showed that the deposition of UAV was mainly on the top and middle canopy of cotton,and the coverage rate on the frontal fog face was the highest at 4.81%.Coverage rates were all high in upper,middle and bottom part of canopy at 25.83%,20.17%and 14.35%respectively for ground machine with lance boom sprayer,and the coverage rate of the face side of leaf was 34.60%,which was significantly higher than that of the back side of leaf.The coverage rate of the upper and lower canopy was 30.38%and 16.15%,respectively for the ground machine with suspender boom sprayer,and the coverage rate of the front and the back of the blade was 13.41%and 18.74%respectively.UAV coverage is significantly lower than the ground mechanical spray.2.The spatial distribution of P20 V2 droplets shows that the average coverage of the dominant area of the droplet deposition is 9.86%under the breeze condition,and the displacement of the droplet deposition center with the center of the spray is about 1 m-2 m.The penetration of the unmanned aerial vehicle was insufficient,and the coverage of the upper canopy at 400 mL/m~2 and 500 mL/m~2 was 7.34%and 8.11%,respectively,while the middle and lower parts were below0.5%.In the comparison of three flight speeds of 3 m/s,5 m/s and 7 m/s,the droplet coverage rate of up to 7.35%at 3 m/s,but when the flight speed is 5 m/s,the deposition amount per unit area up to 0.44μL/cm2.3.Control effect of acetamiprid+thiamethoxam on cotton aphid was higher than that of chlorpyrifos+thiamethoxam in the efficacy test of cotton aphid.The optimal doses of acetamiprid and thiamethoxam were 6 g+20 g/667m~2 and 8 g+25 g/667m~2,respectively.Synergist studies have shown that Jijian,urea and Jiexiaoli exhibited significant effect in reducing 30%-50%of the pesticide dosage but increasing control effect on the control of cotton aphids by using sulfoxaflor treated with the unmanned aerial vehicles.The efficacy reached to more than 95%in field。4.The best dose of both acaricides 40%butyl ether urea·pyridaben leachate and 22%Avi spironolate suspension are 50mL/667m~2 in the control experiment of cotton leaf mite.Increasing the amount of application is an effective way to improve the control effect of UAV.The synergist study showed that the control effect of adding Aiket,Maitu A200,Urea and Yiou Synergist was 67.44%-81.21%,71.76%-73.98,74.15%-82.45%and 73.84%-82.00%,respectively,under 25%,50%and75%of the recommended dosage,these synergists showed significant effects in reducing 25%-50%of the acaricide dosage but increasing control effect on the control of cotton mites.5.Effect of different methods applied by UAV to cotton leaf defoliation showed that,the best effect was observed in the treatment of 14 g/667m~2,and the defoliation effect reached to 84.47%.It is even better than that of the ground machine sprayer.There were no significant differences of corrected defoliation rates among 5 different spray volums of 200mL/667m~2-3200 mL/667m~2.The efficacy of UAV treatment is slower than that of ground machinery.Synergist studies have shown that the addition of Jijian,Maitu A910,Knooprex activator,Eckert,Maitu A200,efficacy of the dosages reduced 25%-50%in 5 synergist treatments are similar with 100%recommended dosage and even better. |
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