Volume 6, Issue 5 (May 2009)
The Influence of Tank Mix Additives While Making Low Volume Aerial Fungicide Applications
Multiple experiments using low volume aerial applications with nine different adjuvants in combination with fungicide were conducted to compare coverage, droplet spectra, yield, and disease control. Four locations were scattered over three states: Arkansas, Kansas, and Illinois. Four aircraft with different nozzle and boom setups were used to complete the studies. Volume median size (DV0.5) ranged from 232 μm to 364 μm. Kromekote® papers used as collectors were placed in the center 9 m of each aerial swath/treatment (20 m) at three different plant heights: top corn leaf, ear leaf, and the leaf three collars below ear leaf. In each treatment, sampling consisted of 30 papers; 10 corn plants at the three heights, with all papers at 30 cm from the main stalk. DropletScan™, utilizing a high resolution color scanner to digitize the images on the Kromekote® papers, was used to analyze each paper. Means for percent area coverage and DV0.5 were used to separate differences in treatments. Relative span was calculated as an indicator of the range in the droplet spectrum. Yields were taken from the center of each treatment. Three to five replications per treatment were completed and a SAS GLIMMIX analysis was performed. Significant differences were measured among adjuvant treatments for both droplet spectra and deposition/coverage. Mixed results are reported across all treatments and locations. A mixture of water, Headline, and Crop Oil Concentrate (Treatment 2) was consistently measured with the lowest amount of coverage, and in two of four locations had the largest DV0.5. Overall, droplet spectra were impacted by the addition of adjuvants to the tank mix. The largest droplets were not associated with the best coverage, and the trend was for the lowest coverage to be associated with the smallest droplets. Treatment 5 (NIS+Interlock) had the smallest DV0.5 in three of the test locations. A limited number of significant yield differences were found. This effect could be due to low disease pressure.