Submitted to: Journal of Electrostatics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2017
Publication Date: 9/15/2017
Citation: Martin, D.E., Latheef, M.A. 2017. Aerial electrostatic spray deposition and canopy penetration in cotton. Journal of Electrostatics. 90:38-44.
Interpretive Summary: Many cotton insect pests reside on the underside of cotton leaves where it is difficult for traditional pesticide spray applications to reach. Plant viruses vectored by some of these insect pests have been shown to result in complete and devastating yield losses in commercial cotton fields. Field studies were conducted to determine the effect of applying an electrostatic charge of up to 10,000 Volts to an aerial spray on spray deposition and canopy penetration. Study results indicated a doubling of spray droplets on the top side of cotton leaves and a three times increase on the underside of the leaves compared to an uncharged spray. Aerial applicators will be able to use the findings from this study to improve the efficacy of aerially-applied insecticides for control of cotton pests.
Technical Abstract: Spray deposition on abaxial and adaxial leaf surfaces along with canopy penetration are essential for insect control and foliage defoliation in cotton production agriculture. Researchers have reported that electrostatically charged sprays have increased spray deposit onto these surfaces under widely different plant canopy conditions. Objectives of this study were to determine whether or not an electrostatically charged spray cloud would increase deposition and penetration of the spray in late season cotton. Three different aerial spray treatments were imposed on field cotton; electrostatic nozzles with charge off, electrostatic nozzles with charge on, each at a spray rate of 9.4 L/ha and a rotary atomizer nozzle at a spray rate of 28 L/ha. A daylight visible fluorescent dye (10% v/v) was mixed with water as a marker to quantify deposition on cotton foliage. Cotton leaf samples collected from the top and bottom canopy regions were digitally imaged under ultraviolet light and these images were then analyzed with ImageJ processing software to assess spray droplet distribution on the adaxial and abaxial surfaces of cotton leaves. Water-sensitive paper (WSP) samplers placed on the ground near the field edges described spray droplet characteristics. Electrostatic charging slightly depressed all three spray droplet parameters (Dv0.1, Dv0.5 and Dv0.9) compared to uncharged sprays, but not significantly so. Droplet density (number of droplets per cm2) was comparable between charged and uncharged sprays; however, rotary atomizer nozzle produced significantly more droplets than either the charged or the uncharged treatment. Electrostatically charged spray cloud significantly increased spray deposition as much as 2 to 3-fold on both adaxial and abaxial surface of top canopy leaves compared to uncharged spray system. However, deposition on adaxial and abaxial surface of bottom canopy leaves was comparable, which indicated that electrostatic charging did not increase penetration of spray droplets to the lower layers of cotton canopy. Data reported here indicate that the fluorescent imaging appears to be a useful technique to quantitatively estimate distribution and density of spray droplets on cotton for electrostatically charged spray applications.