[compost tea], I buy into big time,” he said. “But when I’m doing 100 acres of Galas for mildew, I need a lot of gallons.”
Dovex’s organic orchards use a mint compost. David Granatstein, with Washington State University, said a major mint farmer in Washington’s Columbia Basin is making compost out of the waste that is produced when mint oil is distilled, as a way to dispose of it. A number of orchardists are using it as a soil amendment and mulch. It has lower salt and nitrogen content than poultry manure, and the waste is already heat-treated during the distillation process.
Because it’s locally produced, hauling should not be too expensive. “It’s a nice product,” Granatstein said. “It breaks down quickly and has a nice carbon-to-nitrogen ratio.” However, when Granatstein tested it as a mulch for weed control, weed seeds grew in it as if it were potting mix. Adkins said weeds in Dovex’s organic orchards and even in some of its conventional blocks are controlled mechanically.
Lime sulfur is applied during bloom for thinning, and this also is being used in conventional orchards, as the sulfur helps control mildew. However, Fuji is difficult to thin with lime sulfur, and in some cases, lime sulfur has caused phytotoxicity. For the past five years or so, Dovex’s orchard managers have been mixing micronized sulfur with a lesser rate of lime sulfur, and found it works well, he said.
Dr. Jay Brunner, director of Washington State University’s Tree Fruit Research and Extension Center in Wenatchee, described how a problem with codling moth in one of Dovex’s organic orchards in the Columbia Basin was brought under control. In 2002, as many as 67 codling moths were trapped weekly in August.
Workers hand culled 158 bins of damaged fruit from the 270-acre block, which took 989 worker hours. Excessive use of oil was affecting the trees and fruit quality. Costs were high, and there was still 5 percent fruit damage at harvest. Dovex was on the verge of reverting to a conventional program.
In 2003, Brunner recommended a new approach to controlling codling moth, using mating disruption, Entrust (the organic formulation of spinosad), codling moth granulovirus, and minimal oil treatments. The cost of controlling codling moth increased from $407 per acre to $487 per acre, but the amount of lost fruit dropped from 368 bins to 38 bins.
There was no hand culling, and damage at harvest was less than 1 percent. In 2004, mating disruption was supplemented with oil (1.4 applications per acre, on average), limited use of the granulovirus (1.3 applications per acre, on average), and spot treatments with Entrust. The cost dropped to $190 per acre.
Only 80 moths were trapped the whole season, and fruit injury was negligible. At harvest, damage was less than half a percent. “We’re hoping that’s a sustainable program, where you have the pest under control,” Brunner said.