Evaluation of hydraulic spraying parameters for applying foliar fungicides in snap beans

A medium-volume, two-row hydraulic sprayer was used in the application of various treatments of a foliar fungicide solution and fluorescent particle suspension to snap bean foliage. The treatments consisted of 20, 40, or 60 gallons of solution per acre applied at either 50 or 100 psi using 1, 2, or 3 nozzles per row. Trifoliate bean leaves were randomly selected from the treated rows and evaluated for rust control efficiency and completeness of bean leaf surface coverage. Data evaluation in these two areas was based upon visual subjective observation. Rust rating data indicated that fungicide applications of 20 gallons per acre applied using 1 nozzle at 50 psi were just as effective in controlling bean rust as higher application rates applied with 2 or 3 nozzles per row at 50 or 100 psi. Also, pod curvature and yield were not appreciably affected by the various fungicide parameters. Evaluation of coverage data showed that as the application rate increased, increases in the percentage of both top and bottom leaf surface coverage occurred. However, even at the highest application rate, only about 60 percent of the total leaf surface received spray coverage. Increasing sprayer pressure from 50 to 100 psi was found to slightly increase coverage of both top and bottom leaf surfaces. As the number of nozzles per row was increased, leaf coverage was found to also increase. Data indicated that bottom leaf surface coverage was more markedly Influenced by increasing the number of nozzles than top leaf surface coverage.