扇形喷头结构和压力对微生物农药雾滴分布及活性的影响

扇形喷头是各种喷杆式喷雾机最常用的喷头类型。从减少微生物机体损伤、提高活性的角度，为筛选出扇形喷头中适合喷施微生物农药的喷头型号、喷施压力，该文以常用的延长范围扇形喷头XR11002、广角扇形喷头TT11002、气吸扇形喷头AI11003开展了生物农药活性损伤对比试验。利用喷头雾化测试系统测试不同喷雾样本的雾滴分布，以细菌芽孢萌发率及小菜蛾死亡率量化分析喷头结构、压力对细菌、病毒类生物农药活性损伤影响。研究结果表明：喷头型号、压力及喷雾介质对生物农药雾滴粒径分布的影响程度为喷头型号>压力>介质，其中介质对雾滴粒径分布无显著性影响；压力对细菌与病毒类生物农药活性损伤的影响区别明显，压力对细菌类活性损伤的影响呈显著负相关，对病毒类活性损伤无显著影响，主要跟细菌、病毒不同机体结构相关；喷头型号对细菌与病毒类生物农药活性损伤无显著影响，其中流向单一的XR系列扇形喷头对生物活性损伤影响要小于流向多重突变的TT系列和同时受外界气流混入干扰的AI系列扇形喷头。综合各因素，在利用扇形喷头喷施微生物农药时，从雾滴分布及活性角度，优先选用XR系列扇形喷头中的XR11001，喷施压力为0.15 MPa。在喷施病毒类农药时，可忽略喷头型号、压力对病毒活性损伤的影响。

Effect of fan nozzle structure and pressure on distribution and activity of microbial pesticide droplets

Abstract: The flat fan nozzle is the most common type of nozzle for various boom sprayers. From the perspective of reducing damage and improving activity, in order to screen the nozzle pattern and spray pressure suitable for spraying microbial pesticide in flat fan nozzles, the comparative experiments of bioactivity damage were carried out for extended range fan nozzle XR, wide-angle fan nozzle TT and air suction fan nozzle AI. The nozzle atomization test system was used to test the droplet distribution of three different spray samples of Bacillus thuringiensis, Brassica californica polyhedrosis virus and water. The influence of nozzle structure and spray pressure on the activity damage of bacteria and virus biological pesticide was quantified by spore germination rate of Bacillus thuringiensis and mortality of Plutella xylostella. The experimental results showed that the XR series fan nozzles with a single direction of flow had less impact on the biological activity than the TT series with multiple flow mutations and the AI series fan nozzles with interference from external air flow. When the XR11002 nozzle sprayed microbial pesticide, the fluid flew through the 2 channels of the same flow direction to the nozzle hole, and there was no sudden change of the fluid direction and no external airflow interference during the spraying process. However, the TT11002 nozzle forcibly changed the direction of the liquid, forcing the fluid to entered the horizontal mixing chamber from the vertical direction, and then changing from the horizontal flow channel to the almost vertical orifice channel, resulting in microbial damage caused by shear stress and normal stress. The AI11003 nozzle was provided with a front hole, and in the hole, the air was sucked into the nozzle due to the Venturi effect. The gas and liquid mixed flow structure caused the microorganism to be subjected to multiple interferences and force, causing damage to biological structures. At 0.5 MPa, after 16 hours culture, the spore germination rate of Bacillus thuringiensis sprayed with XR11002 sprinkler was 83.76%, while that of TT11002 and AI11003 were 65% and 68.33% respectively. Pressure on the bacterial and viral biological pesticide activity difference was obvious. The pressure had a negative correlation to the activity damage of bacteria, and had no obvious effect on the damage of the virus activity, it was mainly related to the structure of bacteria and virus. The bacteria had the cell structure, the increase of pressure caused the increase of damage degree to cell wall and cell membrane, resulting in the decrease of the living bacteria and subalgebra. The virus had no cell structure, its genetic material was wrapped in the protein shell, and the destruction of the shell did not affect the virus activity. The damage degree of nozzle to virus biologic pesticides was less than that of bacteria, which was caused by the different structure of the 2 organisms. Therefore, when using the flat fan nozzle to spray the microbiological pesticide, the XR series fan nozzle was preferred. Therefore, when using the flat fan nozzle to spray the microbiological pesticide, the XR series fan nozzle was preferred. From the angle of reducing the activity damage, it was suggested that the spray pressure of XR11002 and TT11001 were not greater than 0.15MPa, and the spray pressure of AI11003 was not greater than 0.3MPa. In combination with various factors, when spraying microbial pesticides with fan nozzles, XR11001 in XR series fan nozzles was preferred from the viewpoint of droplet distribution and activity, and the spraying pressure was 0.15 MPa. In the spraying of virus pesticides, the impact of the type of nozzle and pressure on the viral activity damage can be ignored. This paper provides a reference for screening the optimal nozzle type and spraying pressure suitable for bio-pesticide spraying.