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Spot-checking for successful aerial spray.

Seeing spots isn't so bad anymore--at least, not for the people whose job is to check the accuracy of farm pesticide applications.

That's because ARS agricultural engineer Eric Franz devised a way to take the tedium out of analyzing spray depositions, the pattern of droplets that shows whether aerial applications of pesticides are landing where they're most needed. Franz, who worked in the ARS Aerial Application Research Unit at College Station, Texas, died in February 1994.

In conventional spray deposition analysis, small water-sensitive cards are placed in a field. The aerial applicator--yesteryear's "crop duster"--flies over the field and sprays, depositing spray droplets across the cards. Every little splotch has to be counted and measured, a chore that can take an hour per card.

Frantz's system, called image analysis, uses a computer and a video camera to count and measure the spots. The water-sensitive cards are still used, and the aerial applicator still does the fly-by.

But after the fly-by, the cards are scanned with the video camera, which is attached to the computer. Using Franz's software, the computer translates the spots to digital information. It can calculate the area of spray coverage, the number of spots in a unit area, and the droplet size.

Poor coverage often means poor control of targeted pests--and wasted pesticides. But simply getting the material to the pest isn't necessarily enough.

In earlier studies, Ivan W. Kirk of the College Station lab demonstrated that droplet size is important in effective pest control. Kirk pinpointed the size of droplet needed for control of certain insects and showed that some insecticides are more effective in larger droplets.

Although Franz's image analysis system is only a research tool as yet, the College Station lab has already cooperated with the National Agricultural Aviation Research and Education Foundation (NAAREF) on a project to demonstrate to aerial applicators how wind, aircraft setup, spray boom length, boom location, altitude, and airspeed can affect droplet size and distribution.

At NAAREF's request, the College Station scientists found a way to use a hand-held scanner to take the place of the video camera. NAAREF subsequently demonstrated that system in workshops throughout the South and in Texas, Arizona, and California. Such equipment would allow a consultant to use Franz's system in the field with a portable computer.

For more information, contact Ivan W. Kirk, USDA-ARS Southern Crops Research Laboratory, Room 231, Scoates Hall, Texas A & M University, College Station, TX 77843; Phone (409) 260-9364, fax (409) 260-9367.
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Author:Hays, Sandy Miller
Publication:Agricultural Research
Date:Jun 1, 1994
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