Montana State University's Western Agricultural Research Center (MSU-WARC) invites you to participate in a project to test a simple strategy for preventing codling moth damage in apples.
Codling moths are the major insect pest of apple fruit in western Montana. Many people don’t think about them until they notice wormy fruit at the end of the summer during harvest, but the codling moth adults will be active soon and will begin flying and laying eggs in May. These eggs hatch a couple of weeks later and the new larvae burrow into the newly developing fruit, causing the damage we see later in the season. Early season intervention and control are critical to reduce damage to apples caused by the codling moth.
The project initiated by Rachel Leisso, researcher at the Montana State University- Western Agricultural Research Station, in Corvallis, involves putting nylon bags over apple fruit when they are small, approximately thumbnail size.
The bags are meant to be a preventative shield layer over the fruit, interrupting the codling moth from laying eggs on or near the fruit. This type of preventative control has not been widely tested in apple production.
Leisso hopes to collect some initial information on efficacy to support further testing in the future. If this strategy is successful, it can give backyard orchardists another tool in the toolbox to use in the control of codling moth.
“It is essential to get the bags on the fruit when they are small,” she explains. “We will put the bag over the fruit before the larvae can drill into it, and leave the bags on the fruit all summer long, covering and protecting the apples.”
Bagging fruit is labor-intensive, but only takes a minute or two per fruit, which could make this method attractive for people with just a tree or two. If successful, it would eliminate the need to deal with repeated spray treatments. The protocol for slipping a bag over the fruit is easy and fairly straight forward.
“It’s the perfect opportunity for interested apple growers to participate in citizen science,” Leisso said. “All it takes is a little pruning to select down to one apple per cluster, and to tie off the bag after we slip it over the fruit.”
Codling moths overwinter in the soil around the trees and in crevices in the bark of the tree in a pupae stage. As spring temperatures begin heating up, the pupae transform into adult form, and emerge as a flying adult, ready to mate and lay eggs. The development of the eggs is governed by the ambient air temperature, and the first wave of larvae will typically emerge in late spring.
The Western Agriculture Research Center monitors codling moth activity and regional temperatures, using a computer model to predict the larvae hatch.
Codling moths are active throughout the summer and will need effective control for several weeks after the hatch begins. Whatever control options a backyard orchardist employs, keeping up with that regiment through the first hatch cycle is important to the overall success.
“Getting the upper hand through the first wave of codling moth larvae is critical to the success for control,” she said. “Our control efforts have to extend all the way through the first hatch, and into the second hatch cycle. That means multiple applications of the insecticide used for control.”
“We hope the nylon bags will be a good option for those who cannot keep up with the repeated applications of control sprays. Backyard orchardists can put the bags on once in the spring and get the benefit of codling moth control all summer long.”
Citizen scientists and backyard orchardists can help collect an initial season of field observations on their trees this summer. The only caveat is that the test trees should not have other codling moth control options employed on them, only the fruit bags.
Rachel Leisso has compiled fruit bagging test kits for distribution to interested public. Those interested will be asked to sign up with their contact information, and will be contacted later in the summer and fall to report the results of the bagged fruit. Kits of ten fruit bags are available at the MSU-Ravalli County Extension Office, 215 S. 4th St, Suite G, Hamilton, MT.
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