| A qualitative technique has been developed to evaluate spray pattern and spray penetration in the canopy of fruit trees. This technique is based on the WRK string technology developed to analyze aerial spraying. The technique produced basically the same deposition pattern as the copper tracing technique but reduced the time and labor required to perform the analysis, thus enabling several passes and tests to be done within a short time and providing almost immediate results.This technique provides fast evaluation of spray deposition in the field site and so greatly assists Extension and educational work. The printout of the spray deposition pattern in the plant canopy provides an excellent guide to assist growers, sprayer operators and sprayer manufacturers in achieving better sprayer performance.In operation, the modified WRK technique uses a cotton string placed vertically in the tree. Three 15-foot support poles hold the string, one at the front tree edge, one at the center and one at the back tree edge. The string comes from the supply string dispenser, goes up and down each support pole, and goes to the motorized take-up spool. A fluorescent dye, Rhodamine WT, was mixed with the spray water in the sprayer tank and sprayed toward the tree canopy under study. The sprayed string was then retrieved by winding it onto the take-up spool. The string was delivered to the computer and fluorometer operator, who analyzed the amount of dye deposited on the string. The relative fluorescence values read by the fluorometer were immediately displayed on the monitor and plotted on the plotter paper, and results were saved on the floppy diskette for later use. The graphical simulation of the spray pattern made it possible to identify faulty spray nozzles, improper nozzle arrangement and other factors so they could be changed to improve the spray deposition. |
