Submitted to: Journal of Electrostatics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2017
Publication Date: 9/20/2017
Citation: Martin, D.E., Latheef, M.A. 2017. Efficacy of electrostatically-charged glyphosate on ryegrass. Journal of Electrostatics. 90:45-53.
Interpretive Summary: Herbicides are commonly used to control numerous weed species throughout the United States. In this work, electrical charges were applied to herbicide sprays to increase the rate of spray deposition on plants; the effectiveness of the herbicide treatments were then measured using a remote sensing imaging system. Electrostatically charging glyphosate sprays was shown to improve herbicidal efficacy. The multispectral imaging system used in lieu of visual damage ratings is an effective and time-saving evaluation tool for evaluating herbicide efficacy in greenhouse environments as compared to making visual ratings. These results will help researchers and farmers make more effective spray applications of herbicides.
Technical Abstract: Glyphosate, (N-(phosphonomethyl)glycine, a broad spectrum, systemic, post-emergence herbicide, is used extensively for weed control in production agriculture throughout the world. The objective of this research was to determine whether or not it is beneficial to electrostatically charge herbicidal spray solutions in order to optimize application technique. Cool season annual ryegrass, Lolium multiflorum L., susceptible to glyphosate, was grown and maintained in window boxes in the greenhouse. There were four treatments comprised of combinations of water and glyphosate. Using a TXVK-3 spray tip attached to a battery-powered electrostatic sprayer and operating at 483 kPa pressure, the plants were sprayed with glyphosate at 0.0348 kg/ha. Charge-to-mass ratio (Q/M) for electrostatically-charged glyphosate was 1.686 mC/kg at 10.0 kV charging voltage. Spectral reflectance values from an active multispectral optical sensor were used to calculate the Normalized Difference Vegetation Index (NDVI) to quantitatively describe the surface spectral reflectance characteristics of ryegrass foliage consequent to the damage caused by glyphosate particulates. The intent was to assess whether or not remote sensing technology could be used in lieu of subjective damage ratings to analyze variance between treatments. Reduction in NDVI values between electrostatically charged glyphosate and uncharged glyphosate deviated significantly on the 8th day post-treatment and remained significantly so until the 29th day. Data demonstrated that electrostatically charged glyphosate at 40% of the lowest label rate reduced the foliage health of ryegrass significantly more than uncharged glyphosate. Charging glyphosate reduced foliage vigor 80% faster compared to uncharged glyphosate. Results reported here indicated that electrostatically charging glyphosate improved herbicidal efficacy. Data also demonstrated that the active multispectral optical sensor used in lieu of visual damage ratings is a promising tool for evaluating herbicide efficacy in greenhouse environments.