Can Air-Carrier Sprayers Be Used to Obtain Effective Pest Control in Shade Trees?
Sprayers that blow the spray into the trees with a blast of air are equipped with powerful fans to generate the required air current. Nozzles dispense the spray droplets into the high velocity air stream. Various combinations of air volume, air velocity, liquid volume, and liquid pressure are used in air sprayers to obtain uniform spray distribution. Research has shown that more spray volume should be directed toward the top of the tree than to the lower portions to obtain uniform coverage, because the larger droplets containing most of the spray volume settle out of the air stream very rapidly. Since air sprayers use both air and water as diluents, they give full coverage with less water than hydraulic sprayers. The use of a lower water-to-pesticide ratio with air sprayers is termed concentrate or low-volume spraying. With this technique, three, five, or even 10 times the amount of pesticide is used per 100 gallons of spray, but only one-third, one-fifth, or one-tenth as many gallons
