Good Fruit Grower

April 15

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Hidden costs of rodent control R odents—particularly voles, ground squirrels, and gophers—can have a big economic impact on orchard and vineyard production costs. Rodents cause obvious damage to orchards and vineyards, especially to young trees that have yet to establish a large root mass. They also can girdle adult trees when they chew on the trunk. Examples of girdled trees and young trees that can be easily pulled out the ground are the obvious costs to orchard management, says Mike Omeg, a cherry grower from The Dalles, Oregon. But then there are the hidden costs. That's when the gopher or squirrel eats some—but not all—of the root system. "The tree lives, but it's never healthy and never produces normal yields," Omeg said. He believes growers spend more on annual rodent control than they think they do. Oregon State University Extension estimated that growers spend an average of $95 per acre for rodent control, according to the 2012 Enterprise Budget for high-density, sweet cherry production. The budget is based on actual orchard management costs of a cross-section of by Melissa Hansen commercial growers. "Ninety-five dollars per acre is a lot of money, and that doesn't even reflect the damage done to the trees," said Omeg. Based on figures contained in the enterprise budget, Omeg calculates that if 0.5 percent of new trees are lost to rodent damage in a 20-acre high-density planting with 340 trees per acre (at a planting cost of $17 per tree), a grower will lose about $580 per year in lost trees (34 dead trees). Three years of losing 0.5 percent of the planted trees results in a loss of nearly $1,750, and that's not counting the replanting costs and lost time. Rodent control can cost $100 or more per acre. Barn owl economics Mike Omeg displays drain tubing he uses for bait stations in the orchard. He brings the ends together, tied with twine, and places the tubing under a pallet to keep coyotes from getting to the tubing. He keeps the tubing filled with half of a coffee can of bait from spring through fall when voles and gophers are most active. 28 April 15, 2013 GOOD FRUIT GROWER photo by melissa hansen For a 20-acre block, two barn owl nesting boxes for rodent control could be commercially built and installed for around $250 each—even less if the boxes are homemade. "Young orchards are perfect for barn owls because the tree canopy is not too big," he said, though young orchards also provide perfect conditions for voles and gophers. "Raptors, including hawks, owls, and kestrels, were designed by Mother Nature to be rodent killing machines," Omeg said. "Barn owls live to eat voles and gophers." Studies have shown that a family of barn owls will eat 10 to 12 gophers per night during the brood period from April through July, according to Omeg. In a year, that equates to more than 3,000 gophers. For voles, a barn owl

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