These results demonstrated that the proper concentration of MSO, NIS or OSB in spray mixtures improved the homogeneity of spray coverage on both waxy and hairy leaf surfaces and could reduce pesticide use. This article is a US Government work and is in the public domain in the USA.

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Spray drift potential, spray coverage, droplet size, and spray pattern width for various sizes of air induction and conventional flat-fan nozzles with equivalent orifice areas were investigated and compared under laboratory conditions. Droplet sizes were measured with a laser imaging system; spray coverage on water-sensitive paper (WSP) was evaluated with a boom sprayer at a constant travel speed in a greenhouse, and ground and airborne spray deposits were determined in a wind tunnel at two wind velocities (2.5 and 5.0 m/s). Tests were also conducted to evaluate the effect of air-intake holes being sealed or open on spray characteristics of air induction nozzles. With the equivalent nominal flow rate, air induction nozzles had approximately 2.1 to 2.75 times larger exit orifice areas than the conventional nozzles. With the equivalent orifice area and equal liquid flow rate, there was no significant difference in droplet size, spray pattern width, spray coverage, ground spray deposit, and airborne deposit among regular air induction nozzles, air induction nozzles with two sealed air-intake holes, and conventional flat-fan nozzles. Spray characteristics of air induction nozzles could be achieved by conventional nozzles with the equivalent orifice size operated at the reduced operating pressure.

Efficient and effective precision spray equipment and strategies are in high demand to reduce pesticide use in tree crop production. An experimental variable-rate air-assisted sprayer implemented with a high-speed laser scanning sensor was developed to control the spray output of individual nozzles in real time. The sprayer consisted of a laser scanning sensor control system and an air and liquid delivery system. Each nozzle in the delivery system, coupled with a pulse width modulated (PWM) solenoid valve, achieved variable-rate delivery based on occurrence, height, and width of the target tree and its foliage density. Other components of the sensor control system included a unique algorithm for variable-rate control that instantaneously processed measurements of the canopy surfaces. To determine system delay time, a high-speed video camera was used to record the time period between sensor detection of the canopy and nozzle activation. Spray deposition uniformity inside canopies was verified by quantifying spray coverage inside four ornamental nursery trees of different sizes and canopy densities at 3.2 and 6.4 km h-1 travel speeds. Test results demonstrated that differences in spray coverage inside the canopies of these four trees in the spraying direction were not statistically significant, even though these trees had different structures, canopy volumes, and foliage densities. The canopy volume and foliage density measured with the algorithm developed for the laser sensor-controlled detection system exhibited little variation between the two travel speeds. Design criteria for the sensor-controlled system in the experimental sprayer were acceptable for variable-rate application, having great potential for spray volume and drift reduction, and thus reducing environmental impact.