Study On Drip Application Of Pesticide For Controlling Aphis Gossypii Glover Of Gussypium Hirsutum L.

Drip irrigation under mulch is a new method in integrated pest management system.It transports pesticides to the root area of crops through drip irrigation pipelines under plastic film to control pests,insects and weeds.In this thesis,in order to increase the efficiency and reduce the usage of insecticides,a systematic study on how to control Aphis gossypii Glover by drip irrigation system in Xinjiang was carried out,and a new concept on pest control through efficient,precise,reduced and safe application method was put forward.Firstly,the most effective insecticides for controlling Aphis gossypii G.were selected by continuous immersion tests in lab,root-drenching method in greenhouse,and drip irrigation under mulch in cotton field.Secondly,the relationship between application position,application time,water consumption,flow rate,soil p H,height of cotton,and efficacy,distribution of insecticides applied via drip irrigation under plastic film have been determined in cotton fields in Xinjiang.Thirdly,the efficacy,distribution,safety,and costs of insecticides applied via drip irrigation or foliar spray in the control of Aphis gossypii G.were evaluated systematically.Finally,in order to further reduce the dosage of insecticides applied via drip irrigation under mulch,the relationship between arbuscular mycorrhizal fungi(AMF)and absorptive capacity of cotton plant on insecticides was studied in lab and field,and the preliminary mechanism of AMF in increasing insecticide concentration was also studied in lab by three compartment systems.The main results were as follows:1.Drip application of flonicamid or sulfoxaflor showed high efficacy against Aphis gossypii G.Drip application of 750 g a.i./ha flonicamid and sulfoxaflor both provided≥85%control effects,and the effective periods were longer than 30 days.Moreover,they were both safe to ladybird(Coccinella septempunctata L.)and lacewing(Chrysoperla sinica T.).2.Optimal conditions of pesticides applied via drip irrigation under film in the control of Aphis gossypii G.were defined in open field.The cotton root of seedling stage was mainly distributed in the range of 0-30 cm in horizontal and vertical distances,and the optimum application position of drip application was consistent with distribution range of cotton root.In order to make the distribution of insecticides applied via drip irrigation in soil coincide with the distribution of cotton roots and achieve the best control effect,the optimal water consumptions in silt loam and medium loam were both 175 m~3/ha and the optimal flow rate of dripper in silt loam and medium loam were 2.6 L/h and 2 L/h,respectively.In a day,the optimum time of applying pesticides was before 9-10 a.m.The optimal soil p H was around6.0-7.0.Moreover,the lower the height of cotton plants,the higher the efficacy of insecticide against Aphis gossypii G.According to the calculation,by optimizing application position,application time,water consumption,and flow rate of dripper,the dosage of flonicamid and sulfoxaflor for controlling Aphis gossypii G could be reduced by around 6-13%.3.The control effects of flonicamid and sulfoxaflor applied via drip irrigation and foliar spray against Aphis gossypii G.were compared.The results showed that 700 g a.i./ha flonicamid and sulfoxaflor applied via drip irrigation could effectively control Aphis gossypii G.,and showed higher control effect and longer effective period than that of 75 g a.i./ha flonicamid and sulfoxaflor applied via foliar spray.Both flonicamid and sulfoxaflor applied via drip irrigation mainly concentrated in cotton leaves,especially in top leaves,and the half-lives of flonicamid and sulfoxaflor in cotton root,stem,and leaf were all longer than treatments with foliar spray.Meanwhile,flonicamid and sulfoxaflor concentrations in soil around the dripper were higher than the other areas.With the increment of horizontal distance and vertical distance from dripper,the concentration of insecticide in soil decreased.Compared to foliar spray,drip application significantly reduced the concentrations of flonicamid or sulfoxaflor in aphids,pollen,nectar,and their toxicity on honeybees,ladybird,lacewing,and could save the cost of control.Additionally,drip application of 700 g a.i./ha flonicamid was safe to eisenia foetida,while 700 g a.i./ha sulfoxaflor had moderate risk on eisenia foetida.4.The relationship between AMF and absorptive capacity of cotton plant on insecticides was clarified.Results showed that two types of AMF could effectively infect the cotton root and increase the root growth after soil application in lab.Compared to uninoculated control group,the fresh weight and dry weight of cotton root inoculated with 3 g AMF were increased by 42%and 43%,respectively.Meanwhile,AMF colonization significantly increased the flonicamid concentrations in leaves by 44.49%-165.82%after drip irrigation,consequently3.69%-34.84%increment in control effect of cotton aphid,and shortened the half-lives of flonicamid in soil.Moreover,the mechanism of the enhanced uptake of flonicamid by mycorrhizal root from soil was studied by three-compartment systems.The results showed that the mycorrhizal hyphae could absorb flonicamid from soil and transport it into cotton plants.Finally,it was verified that drip application of 600 g a.i./ha flonicamid could effectively control cotton aphids when cotton plants were inoculated with AMF,and the dosage could be reduced by around 25%compared to that of uninoculated control group.In conclusion,this study has proved the effectiveness of flonicamid and sulfoxaflor applied via drip application under mulch in control of Aphis gossypii G and its superiority compared with foliar spray.This precise,efficient,and dosage-saving application technique of insecticides was established in Xinjiang.The promotional effect of AMF on the uptake of flonicamid by cotton was confirmed and its mechanism was preliminarily explained.Furthermore,the validity of AMF on promoting cotton root to absorb flonicamid from soil,improving the utilization rate and reduce the dosage of flonicamid was demonstrated.This study showed that drip application of insecticides was an efficient,precise,reduced and safe application method in control of Aphis gossypii G,and it contributes to achieve the goal of increased efficiency and reduced application rate of pesticides.This study also provided theoretical basis and guidance for the integration of water into fertilizer and insecticides.