DETERMINATION OF COTTON PLANT INJURY BY AERIAL APPLICATION OF GLYPHOSATE USING REMOTE SENSING AND SPRAY DRIFT SAMPLING.

Off-target drift of aerially applied glyphosate can cause plant injury, which is of great concern to farmers and aerial applicators. To determine the extent of crop injury due to near-field drift, an experiment was conducted from a single aerial application of glyphosate. For a larger-scoped project involving identification of the drift effect on different crops, a field was planted in alternating blocks of cotton, soybeans, and corn. Spray samplers were placed in the spray swath and in several downwind orientations to quantify relative concentration of applied chemical. An Air Tractor 402B spray airplane equipped with fifty-four CP-09 nozzles was flown down the center of the field to apply 22 oz/acre of Roundup Weathermax and Rubidium Chloride (RbCl) tracer at a 5 gal/acre spray rate. Relative concentrations of this tracer were quantified at downwind spray samplers. At one week intervals aerial Color- Infrared (CIR) imagery was obtained over the crop field using a Global Positioning System (GPS)-triggered Geospatial Systems MS-4100 camera system. This study's main focus was to assess glyphosate spray drift injury to cotton using the CIR imagery and spray drift sampling. The processed image data were compared with data from spray drift samplers placed downwind. Results will be helpful for determining the extent of near-field drift sampling, and demonstrated that multispectral imaging can be viable tools for determining the extent of damage relative to derived concentrations of glyphosate. [ABSTRACT FROM AUTHOR]