Crop producers are well past “the good old days of spraying,” when they applied pesticides using basic equipment and strategies, said Bob Eccles, agronomy risk manager with agricultural products distributor Wilbur-Ellis.
The high-tech equipment and data-driven strategies that materialized since then can make seed growers much more efficient and effective — particularly if they simultaneously manage “spray drift,” an increasingly important issue, he said.
“Where does the spray come down? We are kind of our own worst enemies,” said Eccles, who spoke to the Idaho-Eastern Oregon Seed Association convention Nov. 27 in Boise. Sixty-four percent of problem-level drift occurrences are the fault of the person applying the pesticide, and the result of “mostly poor applications.”
Managing spray drift has become increasingly important in recent years given trends such as urban sprawl and less-tolerant neighbors, increased planting of high-value specialty crops, greater public awareness of and concern about pesticides, and potential impacts on air and water quality, he said.
Crop producers can reduce drift problems and increase pesticide efficiency by paying closer attention to variables such as nozzle and droplet sizes and distance between nozzle tip and plant. They can be controlled fairly easily given the correct approach, he said.
Other variables include wind, temperature, evaporation and the height of booms on which nozzles are mounted. Many effective applications are from beside or over the top of the plant from fairly close range, Eccles said.
Particle drift refers to the chemical leaving the nozzle and failing to hit the target. Vapor drift occurs after it hits the target but subsequently moves due to an intervening factor such as a temperature or humidity change.
Eccles recommends spraying in a steady, gentle wind of at least 4 mph as measured from two to three feet off the ground. Lower wind speeds are generally less predictable and often associated with temperature inversions, he said.
Droplet size is important because it interacts with all other variables, he said. Bigger drops fall faster and drift less. Smaller drops drift more but offer more coverage. Changes in droplet sizes and wind speeds can change drift likelihood and distances exponentially, he said.
Manufacturers state the proper droplet sizes to use. “The label is the law,” said Eccles, who is based in Filer, Idaho.
He recommends adding a drift-reducing substance to the tank mixture to help reduce drift and improve coverage.