The 2012 ASHS Annual Conference

Two intelligent sprayer prototypes were developed to increase pesticide application efficiency in nursery production. The first prototype was a hydraulic vertical boom system using ultrasonic sensors to detect tree size and volume for liner-sized trees and the second prototype was an air-assisted spraying system using a laser scanning sensor to measure tree structure and foliage density for shade trees. Both sprayers had automatic controllers (computer program, a signal generation and amplification unit, and pulse width modulated solenoid valves, but different algorithms and circuit designs). The controllers manipulated nozzles to produce variable-rate spray outputs based on tree characteristics and plant occurrence in real time. Within the spray range, the sprayers had the capability to adjust spray outputs to provide the quantity of spray deposition and coverage as required by specific applications. Application qualities were field tested against industry standard application rates using multiple plant species. Spray deposition and coverage of the hydraulic boom sprayer were determined for five tree species with heights ranging from 2.8 to 8.1 ft, and were compared with 60 and 100 gpa constant-rate applications. Air-assisted sprayer performance was tested at three different plant phenological stages, and was compared with two conventional air-assisted spray systems at a 50 gpa application rate.  Compared to the variable-rate boom sprayer, constant-rate applications of 60 and 100 gpa generally produced excessive spray deposition and coverage with unnecessary runoff. Conventional spray application rates estimated with the tree-row volume method were 131, 60, 40, 36, and 28 gpa, compared with variable rates of 38, 32, 25, 16, and 16, respectively. The variable-rate sprayer reduced spray volume up to 86.4% and 70.8% compared to a constant 100 gpa and tree-row volume estimated rate applications, respectively. Pest control for select insects and diseases was not different from conventional sprayers. Air-assisted intelligent sprayer coverage and deposition inside canopies were more stable over different growth stages at approximately 40% coverage compared to approximately 45–90% saturated coverage for the same air-assisted sprayer (non-intelligent control) and a conventional air-assisted sprayer. Compared to the constant application rate of 50 gpa (considered a half-rate), the intelligent sprayer reduced the application rate by 70, 66, and 52% in April, May, and June, respectively. Laboratory and field tests demonstrated that both variable-rate sprayers controlled spray outputs by continually matching canopy characteristics, which reduced off-target losses, and has potential to drastically decrease pesticide use and associated economic inputs, increase environmental quality, and enhance worker safety.