ABSTRACT

Spray equipment investigations indicated that several high-volume air-assisted sprayers provided the greatest spray coverage on the underside of cotton leaves. Use of a trip- type metal support for drop nozzles either with or without air-assistance provided a high degree of nozzle-orientation control and spray-targeting to the leaf underside. Experiments were conducted on mature cotton to examine the following factors: (1) type of sprayer, (2) level of air assistance, (3) air-assistance angle, (4) application spray rate (gpa), (5) canopy level, and (6) side of leaf. All factors were determined to be statistically important. Generally, increased spray rate and level of air assistance increased canopy penetration and spray deposition. It should be noted that the experiments discovered varying optimum sprayer settings that depended on the exact shape, position, and orientation of the targeted plant surface. Range of mean bifenthrin deposits due to type of sprayer were: (1) leaf upperside, 230 - 580 ng/cm², (2) leaf underside, 130 - 460 ng/cm². Bifenthrin (0.08 lb/ac) uniformly applied to all upper- and under-side leaf surfaces of mature, lapped cotton should result in a deposit of about 75 ng/cm².