Issue link: http://read.dmtmag.com/i/283151
24 APRIL 1, 2014 GOOD FRUIT GROWER www.goodfruit.com T he goal of any orchard or vineyard sprayer should be to hit the canopy target. But many sprayers fail to hit their mark and often apply anywhere from less than half to one and a half times the material needed, according to a Washington State University survey. "Your goal should be that your entire spray stays within the canopy row," said Gwen Hoheisel, WSU extension specialist. "You want every drop that comes from your sprayer to end up in the canopy." Hoheisel says there are simple things that can be done to improve hitting and covering the target and the quality of the spray material. Research has shown that only about half the spray from an average orchard or vineyard sprayer reaches target. Of the half that misses, most hits the ground and the rest goes airborne as spray drift. "Half of a $60 per acre spray on the ground is a lot of wasted money," she said during winter tree fruit and grape talks in Washington. When WSU checked spray patterns and nozzles of 20 orchard sprayers throughout Washington's tree fruit industry with a patternator, a device that shows where spray has gone, none of the sprayers were working as the growers intended and only one had 100 percent of the nozzles working properly. "One grower had 60 percent of the spray going to the lower 48 inches of the tree," said Hoheisel. "That's not an effective spray." Another sprayer was leaving gaps at around seven to eight feet high. Improve hitting target To better hit the target, growers fi rst need to know where their spray is going. Vertical patter- nators are commercially available, but they are designed for research and are expensive. However, growers can build one for around $500 in materi- als, following instructions available on the Inter- net, according to Hoheisel. Food-grade dye or clay material like kaolin can be easily used to visually show air direction and deposition. Even stapling a paper to a board affi xed in the row and using dye in the sprayer can give an idea of where sprays are hitting. If there are gaps in the spray pattern, air direction can be changed by using a wrench to adjust nozzle positions, she added. "You have a very powerful tool when holding a wrench." "The problem is in matching airfl ow from older sprayers designed for larger canopies to these mod- ern orchard systems," she said. Even with new sprayers, there is a mismatch early in the season and in spraying young trees because canopies are not fully developed. But Hoheisel says there are easy ways to reduce airfl ow when necessary. One way is to adjust the gearbox to reduce fan speed. Another is to use ply- wood donuts, technology developed by Cornell University to reduce airfl ow. Improving coverage In the near future, some sprayers will allow the applicator to adjust spray louvers from the tractor cab, opening and closing them as desired. Even more precise will be sprayers currently being devel- oped in the United States and Europe that use laser technology to detect location and density of the plant and foliage, and adjust spray outputs automatically. Such technology promises to dra- matically reduce the use of spray materials while reducing spray drift. Nozzles (droplet size), pressure, and speed are factors involved with improving how the sprayer covers the target. "You want a lot of small drops that stick to the leaf surface," she said, recommending that growers aim for 60 to 90 drops per square centimeter, which equates to about 395 to 580 drops per square inch. Generally, droplet size greater than 300 microns will bounce off the canopy, while smaller than 150 microns will drift off the target. High air pressure results in fi ne droplets, low pressure in coarse, large drops. "So many of us never change the pressure gauge on the sprayer," she said, noting that manufacturers generally guarantee pressure gauges for a year and Simple changes made with inexpensive tools can greatly improve spray applications. by Melissa Hansen PHOTO COURTESY OF WASHINGTON STATE UNIVERSITY "You want every drop that comes from your sprayer to end up in the canopy." — Gwen Hoheisel PLAY goodfruit.com/media scan to watch tips for growers PHOTO BY TJ MULLINAX T o make your own patternator, visit: patternator. com. There are lots of calibration videos on YouTube. Three videos recommended by Hoheisel can be watched in this story at goodfruit.com. Make every DROP COUNT A patternator on the right measures the spray output and location from the tower sprayer.