Research On Relationship Between Fungicide Biocide Radius And Wheat Powdery Mildew Control Efficiency

At present,chemical control is the main way to prevent and cure wheat powdery mildew,and UAV?unmanned aerial vehicle?plays an important roal in wheat field spraying.To establish the relationship between four kinds of fungicides concentration,droplet size,droplet density and wheat powdery mildew control efficiency,we used a method of bioassay and field test in this research.For indoor test,we use potter spray tower and walking spray tower produce three different sizes of droplets,and set different concentrations and different droplet density,and we studied the relationship between four kinds of fungicide biocide radius and indoor inhibition rate of wheat powdery mildew;For field test,we use UAV and knapsack electric sprayer spraying propiconazole and kresoxim-methyl,using allura red as the spray tracer,studied the droplet distribution of two different spray conditions and the control efficiency on wheat powdery mildew.The followings are the major conclusions:?1?It makes no significant influence on the physicochemical properties?viscosity,surface tension,etc.?and droplets spectrum of the fungicides when adding allura red,and the elution recovery rate is high on the filter paper and the Mylar slice.?2?For the first time put forward the concept of EN₅₀?inhibited medium droplet density?,and the EN₅₀ values of four fungicides under different concentration and droplet size were calculated.When the VMD was 122?m,the concentration of propiconazolee was 0.01g/L,0.05 g/L,0.1 g/L,0.5 g/L and 1.0g/L,the corresponding EN₅₀ was 18.7,22.8,9.8,6.2 and 5.1.cm^-2;When the concentration of kresoxim-methyl was 0.01g/L,0.05 g/L,0.1 g/L and 0.5 g/L,the corresponding EN₅₀ was 227.1,77.8,15.0,6.4.cm^-2.It means when we use Teejet11001 nozzle spray 0.5g/L propiconazole and kresoxim-methyl,6.2 and6.4.cm^-2 droplets can achieve half of the control efficiency.?3?The biocide radius of four kinds of fungicides under different concentrations and droplets size was calculated.Take Teejet11001 nozzle an example,the biocide radius of fluopyram increased from 0.11mm to 0.52mm and propiconazole increased from 0.92mm to 1.77mm when the concentration increased from0.01 g/L to 1.0 g/L;The biocide radius of propanthiazole increased from 0.22mm to 0.50mm and kresoxim-methyl increased from 0.27mm to 1.58mm when the concentration increased from 0.01 g/L to0.5 g/L.?4?Under the same concentration of the same fungicide,fine droplets'killing ability is stronger.For0.01g/L kresoxim-methyl,the 43?m fine droplets r_50/VMD is 7.16,122?m medium droplets'r_50/VMD is 2.17,and 205?m droplets'r_50/VMD is 2.11.The results showed that the control effect of fine droplets was better.From the point of view of fungicide,the propionazole's biological activity was the best,the kresoxim-methyl was the second,and the difference between kresoxim-methyl and propionazole was not obvious,and fluopyram was the worst.?5?The field spraying test of propiconazole and kresoxim-methyl against wheat powdery mildew were conducted by using MG-1S UAV and knapsack sprayer.When tested with the spray volume of 15.0 L/hm²for UAV and the concentration of 5.0 g/L,the droplet density on flag and 2ⁿdd top leaf was 29.7 and 9.5cm^-2,respectively.After 3d,5d,and 7d,the control efficacy was 41.9%,80.7%,90.2%for propiconazole,and 30.8%,67.9%,84.5%for kresoxim-methyl.When tested with the spray volume of 450.0 L/hm² for knapsack sprayer and the concentration of 0.17g/L,the droplet density on flag and 2ⁿdd top leaf was 287.9and 204.2 cm^-2,respectively.After 3d,5d,and 7d,the control efficacy was 42.1%,85.3%,94.3%for propiconazole,and 28.5%,80.1%,90.5%for kresoxim-methyl.As a consequence,a certain concentration droplet density instead of wet all the leaves would insure an efficient spraying of fungicides.Using UAV low volume spraying,10-30?.cm^-22 droplets can achieve the ideal control efficacy.