Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2019
Publication Date: 5/15/2019
Citation: Martin, D.E., Latheef, M.A. 2019. Aerial application methods control spider mites on corn in Kansas. Experimental and Applied Acarology. 77:571-582.
Interpretive Summary: Spider mites are noxious pests in US corn that cause loss of foliage, stalk breakage, kernel shrinkage and yield loss. Studies in a commercial corn field in northwest Kansas determined the efficacy of an electrically-charged aerial spray application at one-third the carrier volume of spray solution compared to conventional aerial application. The electrically-charged treatment at lower spray volume provided just as good control of spider mites as did the conventional spray application. Aerial applicators will be able to use this information to increase operational efficiency and productivity while continuing to protect America's food supply.
Technical Abstract: The Banks grass mite, Oligonychus pratensis (Banks) and two-spotted spider mite, Tetranychus urticae Koch are important chelicerae herbivores on irrigated corn in Kansas. They cause loss of foliage, stalk breakage, kernel shrinkage and yield loss. Aerial application methods were evaluated to control spider mites in a commercial corn field in August, 2017 near Hoxie, Kansas. Dimethoate (0.56 kg active ingredient/ha) and Lorsban Advanced (1.05 kg active ingredient/ha) mixed with a nonionic surfactant, Traverse (0.25% v/v), were aerially applied using conventional flat-fan hydraulic nozzles at 28.1 L/ha and aerial electrostatic nozzles at 9.3 L/ha. To assess spray droplet spectra of the aerial application methods, water sensitive paper samplers were deployed at the whorl of husk leaves at the tip of the ear before aerial spray treatments were applied. Spray droplet spectra were quantified using commercial image analysis software. Treatment efficacy was assessed both objectively and subjectively. Objective efficacy evaluation incorporated the use of an active multispectral optical sensor via spectral analysis of the midrib regions of corn leaves on the abaxial surface where spider mites reside. Subjective damage ratings based upon in-field spider mite movement observations were scored by professional crop scouting consultants. Results of objective spectral analysis and subjective damage ratings indicated that both the conventional and electrostatic nozzles with 283 and 210-µm spray droplet volume median diameter at 28.1 and 9.3 L/ha, respectively, controlled spider mites compared to an untreated check.