The impact of the variable flow rate application system on pesticide dose-transfer processes and development of resistance to insecticides in fall armyworm Spodoptera frugiperda (J. E Smith)
This study investigated the impact of the variable flow rate system (VFRS) on some of the parameters of the dose transfer process. We utilized 2 standard flat fan nozzles (XR8008vs and XR8001vs) combined with the VFRS at 100 % duty cycle and 40 % duty cycle. The atomization results indicate that (1) the volume median diameters were increased at the 40% duty cycle and (2) the number median diameter significantly increased at 40% duty cycle in XR8008vs but decreased for XR8001vs. Distribution studies showed that the highest vertical deposits were found on the top, middle, and bottom plant sections respectively of all 3 canopies (tomato, soybean, and corn) On corn, the middle leaf sections retained spray deposits more than on the basal and terminal sections in all treatments and was more uniform than on soybean. The lowest CV values were obtained in the middle leaves in all treatments and increased with 40 % duty cycle for both flat fan nozzles. On soybean, the deposits in all treatments were higher on the top leaves than the middle and bottom leaves. The mortality of fall armyworm (FAW) Spodoptera frugiperda (J. E. Smith) and two insecticides indicated that larval mortality in the small droplet patterns was higher than in the large droplet patterns. Total larval feeding and feeding behavior under small droplet patterns was significantly different and less than under the large droplet patterns. These results indicated that small deposit structure was the most effective scenario controlling FAW populations and reducing foliage consumption. The development of resistance to an insecticide under various types of application methods and chemicals has yet to be reported in the literature. FAW larvae from several generations were fed for 72 hours on corn plant sprayed at a minimum recommended rate of cypermethrin and spinosad with small and large droplet nozzles. The results indicated that spinosad demonstrated an insecticidal activity less than cypermethrin. Larvae from all generations (F1-F7) under the XR8008vs treatments were less susceptible to cypermethrin and developed resistance faster than XR8001vs larvae.
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:variable flow rate pesticide application system dose transfer processes spray deposit distribution on canopies biological efficacy development of resistance to insecticides fall armyworm
Date of Publication:01/01/2003