More money is spent trying to control pests in pears than in any other tree fruit, and the costs are continuing to escalate according to Tim Smith, a Washington State University Extension educator. Some growers, he estimates, are spending approximately $1,000 per acre on pest control.
Orchardists could reduce their spray costs by improving spray coverage on the trees, he suggested during the Washington State Horticultural Association’s convention. Sometimes, poor coverage can be attributed to the size of the trees. For example, in big, old trees, it’s difficult to get a good covering of oil to control scale. Smith challenged growers to do a spray coverage test using 25 pounds of Surround (kaolin) in 100 gallons of water.
The white areas where the spray was applied will be visible. “This will show you where the spray is going and will show you where it’s not going,” Smith said. “It’s a $25 perfect test for coverage to your trees. I bet you you’ll be disappointed in what you see.” Coverage can be improved by driving the sprayer more slowly.
Driving at 2.0 miles per hour, it takes about 12 minutes to cover an acre. At 1.2 miles per hour, it takes 21 minutes, but the coverage will be much better. For a 20-acre block, the slower speed means an additional three hours of spraying time, or an 11-hour day instead of an 8-hour day.
“It’s boring,” Smith acknowledged. “You’re going to have your tractor and sprayer operating more hours, and time costs money.” He figures that driving at 1.2 mph, rather than 2.0 mph costs an additional $9 per acre, but better coverage might allow the grower to cut one to two sprays—or even more. “I’m confident that if you slow down and spend the extra hours out there, you’ll save money in the long run,” he said.
Some growers try to improve coverage by increasing the gallonage to perhaps 200 gallons per acre instead of 100. Although higher gallonage is helpful, that’s not the whole answer, he said. Using more volume means filling up the spray tank more often. It typically takes between 20 and 25 minutes to refill it.
Growers spend 40 percent of their time actually spraying and the other 60 percent doing other things, such as refilling and would be better off if they could flip that. They could cut the total time they spend spraying if they could find a faster way to fill up the tank, Smith said. “Is your fill site set up properly? What are you doing that you could do ten minutes faster?”
Changing the orchard
One of the best ways to improve coverage is to change the orchard so that the trees are all on one plane. “These orchards are going to be a dream to spray,” he said. “You’ll be able to drive faster again. You could go up to 2 mph or even faster.” New orchard systems will also present opportunities to use new designs of sprayers that aren’t compatible with old-style orchards, he added.