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ARS Home » Research » Publications at this Location » Publication #122971


item Kirk, Ivan

Submitted to: Ag Pilot Aviation and AGCIC Worldwide
Publication Type: Trade Journal
Publication Acceptance Date: 6/16/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pesticide applicators should be aware that pesticide product labels often require that sprays of certain crop protection products must be applied in a specific droplet size. The droplet size classifications range from Very Fine to Extremely Coarse. Product labels have the force of law so applicators need to know how to achieve a specified droplet size with their rspray system. Spray nozzle size, angle, pressure, and airspeed are the primary factors that influence spray droplet size from sprays applied from aircraft. Droplet size calculators or models were developed for spray nozzles commonly used on helicopters and airplanes. These computerized models will permit aerial spray applicators to compute spray droplet size from their spray nozzles and application conditions. The models also provide options for applicators to compute adjustments needed for their spray system to achieve the specified spray droplet size for the product they expect to apply. These spray droplet size models provide a useful tool that aerial applicators can use to ensure compliance with crop protection product labels. The models also provide information that can be useful in controlling spray drift.

Technical Abstract: Crop protection product labels are now being written with spray droplet spectra classification terms that have specific definitions relative to range of spray droplet size in which the product must be applied. The directions for use on product labels have the force of law. Consequently it is imperative that pesticide applicators understand the terminology and have means for establishing spray system performance for producing sprays with droplet spectra classifications as specified on product labels. Ground applicators can use charts supplied by nozzle manufacturers for droplet spectra classification, but aerial applicators need additional information to attain label specifications because of the tremendous influence of airspeed on spray droplet size and droplet spectra classification. Spray nozzle atomization models were developed for spray nozzles in predominant use in the agricultural aviation industry in the USA. The models were demonstrated to provide reliable estimates of spray droplet spectra parameters that are useful in controlling spray drift and complying with product label specifications. The models provide information on droplet size, relative span, percentage of spray volume in the highly driftable portion of the spray spectrum, and droplet spectra classification. This information will be useful to aerial applicators in responsible application of crop production and protection products.