But it also opens up the trap to flooding by rain. To protect the traps, hang them below a rain shield, such as the top cover of a commercial codling moth trap, to shed the water.
For cherry growers, Van Steenwyk recommends filling the containers with about 1 inch, or 4 ounces, of a mixture of unflavored apple cider vinegar to which 1 tablespoon per gallon of unscented dish detergent has been added.
Mark Borda, a UC Cooperative Extension farm adviser in Santa Cruz, recommends a bait made from fermented mixture of baker’s yeast and sugar to berry growers along California’s Central Coast.
“We kind of settled on the apple cider vinegar and the yogurt container because everybody can find apple cider vinegar and it’s not expensive,” says Joe Grant, a UC Cooperative Extension farm adviser in San Joaquin County. “Putting yeast in it does improve the attractiveness, but it doesn’t make enough of a difference to justify the added hassle and expense.”
Isaacs, on the other hand, is using a clear 32-ounce deli container into which 10 3/16- inch holes have been drilled near the top. He favors apple cider vinegar also because of its availability and ease of use.
“Yeast has shown in some West Coast trials to catch flies earlier than the apple cider vinegar,” Isaacs says. “But other studies in the East last season found that the type of bait had no significant effect.”
He will be working with MSU colleagues to use the same design across a monitoring network in Michigan, which will consist of traps in blueberries, blackberries, strawberries, cherries and a few tomato fields.
Results will be posted weekly on a central website, http://www.ipm.msu.edu/SWD. htm, so growers can monitor the situation.
Washington State University researchers also will monitor a trap network in its fruit production areas this season. The first trap catch in each region will be posted on its website, http://extension.wsu.edu/swd/.
Growers also can sign up to receive the alerts.
As the website points out, “Until we have a better understanding of what trap catch means, we are NOT recommending that you use the traps as an indicator of the need to spray on a block-by-block basis.
Once trap catch has occurred in a region, it is likely present throughout that region.”