Adult Western Cherry Fruit Fly

Adult Western Cherry Fruit Fly.

Cherry Fruit Fly models developed by Oregon State University indicated that the cherry fruit fly would emerge in The Dalles May 29.

According to Ashley Thompson, Oregon State University Extension horticulturist, the emergence of the fly signals the beginning of the control program against this insect, which is the sweet cherry industry’s chief insect pest.

The entire cherry growing area — including the cities of The Dalles, Mosier and Dufur — are within a cherry fruit fly control district and all homeowners with a backyard cherry tree, as well as commercial orchardists, are required by law to begin a control program within 10 days of emergence.

The control program means an application of an insecticide beginning 10 days after emergence and approximately every seven days through cherry harvest.

For homeowners, the recommended materials would include any product with Spinosad or Malathion as an ingredient that is labeled for fruit trees.

The cherry fruit fly overwinters in a cocoon as a dormant pupa and emerges in response to the rise in temperatures in the spring.

The adult fly mates and begins egg laying within five to seven days after emergence. Eggs are laid beneath the skin of the cherry and the eggs hatch into a worm in approximately three days. The worm feeds within the cherry fruit, maturing in approximately two weeks. The worm then eats its way out of the cherry, falls to the ground, and goes into the resting stage until the next year.

There is only one generation of cherry fruit fly per year. Fly emergence occurs over several weeks, however, which requires a season-long control program, Thompson pointed out.

To obtain a free pesticide spray guide for this and other tree fruit pests, contact the OSU Wasco County Extension Office at 541-296-5494 and leave a message as staff is still working remotely.