Optimization And Effect Verification Of Mist Application Technology For Controlling Cucumber Pests And Diseases In Facilities

In northern China,facility cultivation is the most important cultivation method of cucumber,and the occurrence of cucumber diseases and insect pests is one of the important factors affecting the production of facility cucumber.Because the facility environment is relatively closed and the air humidity is high,this condition is very conducive to the occurrence of pests and diseases.The survey found that most of the small pests such as Bemisia tabaci and thrips were concentrated on the back of the leaves,and only a few were on the front of the leaves.Cucumber downy mildew is also the first to form a watery light green spot on the back of the leaves.At present,the use of chemical pesticides is an important means to control cucumber pests and diseases in facilities,and conventional backpack spray application is the most important mode of operation.It has been found that the deposition of conventional backpack spray pesticides at the target interface is about 35% of the application mass,while less than 0.1% of them reach the target body.Pests and diseases mainly occur on the back of the leaves.It is difficult to spray the liquid evenly on the back of the leaves by conventional spray application,which causes waste of pesticides and brings certain difficulties to prevention and control.The rapid development of the sprayer provides a new choice for the prevention and control of cucumber diseases and insect pests in facilities.However,there are still many problems in the use of the sprayer,resulting in poor application quality.The factors affecting the application quality of the mister mainly include the characteristics of the pesticide itself,additives,nozzle orientation,walking speed,and target interface structure characteristics.Therefore,in this study,by comparing the effects of adding additives and not adding additives on the quality of sprayer application,the effect of additives on the improvement of sprayer was clarified.At the same time,combined with the problems found in the test process,the field application conditions of sprayer were further optimized,and a set of field application technology system of sprayer was established,so as to promote the efficient targeting of pesticides and further reduce the dosage of pesticides on the premise of obtaining ideal field control effect.The main results are as follows:1.The effects of adding hot fog additives and not adding hot fog additives on the quality of sprayer application were clarified.(1)The control effect of sprayer with hot fog adjuvant was better than that without hot fog adjuvant and conventional spray application.The control effect of Bemisia tabaci adults on the back of leaves after adding hot fog adjuvant was higher in the middle layer than in the upper layer and lower layer.At a distance of 3 m from the nozzle,the control effect of the upper and middle layers of the plant on the adults of B.tabaci could reach more than 80%,while the control effect of the lower layer of the plant was not ideal.At a distance of 1 m from the nozzle,due to the small spraying range at this time,the droplet coverage rate of the upper and lower layers of the plant was low,and the control effect was far less than that of the middle layer of the plant.When the distance from the nozzle is 5 m,the droplet coverage on the back of the blade is lower,only about 40% of the control effect.(2)The droplet coverage of the mist machine without adding hot fog additives is generally low,and the diffusion uniformity of droplets in space is not ideal.However,at a distance of 5 m from the nozzle,the front of the lower leaves of the plant has a higher droplet coverage rate,indicating that the sprayer can take the liquid to a distance of 5 m or even farther;when the hot fog adjuvant is added for spraying,the droplet uniformity is further improved,and the droplet coverage rate in the middle layer of the plant is much higher than that in the upper and lower layers of the plant.When the distance from the nozzle is 3 m,the droplet coverage is the best.(3)The field control effect increased with the increase of droplet coverage,but not always improved.When the droplet coverage is about 3%,the control effect can reach more than 50%.When the droplet coverage rate is about 9%,the control effect can reach more than80%,but when the droplet coverage rate is increased to 12% or 15%,the field control effect is not significantly improved.It shows that 9% droplet coverage can be used as the critical value for the control of cucumber B.tabaci in the facility environment.Under this droplet coverage,the field control effect on B.tabaci adults can reach more than 80%.2.The field application conditions of mist machine were optimized.(1)After safety test,deodorized kerosene had no phytotoxicity risk to cucumber and tomato at seedling stage.(2)The droplet coverage at a walking speed of 0.32 m/s can meet the prevention and control needs,which will further save operating time and improve operating efficiency.(3)When the sprayer nozzle was sprayed at a horizontal angle of 0° and an oblique downward angle of 45°,the airflow of the sprayer accelerated the spread of pathogenic spores,and the field downy mildew was more serious.However,when the nozzle is sprayed at an oblique angle of 45°,the influence of airflow on the spread of the disease is relatively small,and the disease is lighter,and the spray at an oblique angle of 45° will not have a significant impact on the droplet coverage.3.The feasibility of multi-prevention and pesticide reduction application of mist machine was evaluated.(1)In the field experiment of spraying spirotetramat and dimethomorph on cucumber Bemisia tabaci,thrips and downy mildew by mist sprayer,the highest recommended dose in the field and the highest recommended dose in 1/2 field had no significant difference in control effect,while the control effect of conventional spray application showed great difference.Therefore,the use of sprayer combined with hot fog adjuvant for spraying,after reducing the dosage by 50%,can still obtain ideal field control effect.(2)The mixture of spirotetramat and dimethomorph at the recommended dose in the field had no negative effect on the efficacy.The control effect of 1 day and 7 days after treatment on B.tabaci adults could reach more than 90%,which was about 20-30% higher than that of conventional spraying.For the more difficult to control in the field of Thrips cucurbitae,it also showed ideal control effect in terms of quick effect and late effect,90.04% and 95.37%,which was about 40% higher than the control effect of conventional spray application.In terms of disease control,the field control effect of cucumber downy mildew can reach more than 80% after 7 days and 14 days after treatment,which is about 20% higher than that of conventional spray application.Therefore,the mist machine can be used in a facility environment to achieve one application,multiple prevention and reduction of pesticides.