Abstract
Aldicarb is a soil-applied pesticide in Florida that has been found to be very effective for managing certain citrus insects, mites, and nematodes. However, due to its high mammalian toxicity and concerns about leaching into ground water, its application requires a 91 or 305 m (300 or 1,000 ft) buffer zone around all drinking water wells depending on soil permeability. To assess the feasibility of using control/monitoring systems in aldicarb applications, a prototype machine was fabricated that featured both ground- and motor-driven mechanisms. It was equipped with different controllers and electronic circuits to investigate three GPS-based control approaches. The first system consisted of a DGPS antenna and a low-cost data logger. It could record the time of day, latitude, longitude, and quot;On/Offquot; status of the discharge mechanisms for monitoring purposes. The second system used a hand-held computer with variable rate (VRA) software. With this system, it was possible to implement quot;On/Offquot; control of both discharge drives based on a prescription map. The third system utilized a more sophisticated VRA controller, which allowed detailed operator-machine interface. It could generate variable rate maps and information on application rate, acreage, and total material usage. Each system showed certain merits and limitations but all were capable of generating spatial information on aldicarb application. Field tests revealed some response errors in the zone transition areas, which were mostly due to the DGPS signal error. Overall, it appeared that increasing the buffer zone by about 5 m (16.5 ft) could ensure compliance with the quot;aldicarb rulequot; for most citrus applications.
