Cherry Fruit Fly models developed by Oregon State University indicate that the cherry fruit fly emerged in The Dalles Wednesday, May 15. According to Lynn Long, Oregon State University Extension Agent, the emergence of the fly signals the beginning of the very important 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, is 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. The regulations of the district will be administered by Merle Keys of the Wasco County Weed and Pest Department.
The control program means an application of an insecticide beginning immediately and approximately every seven days through cherry harvest.
For homeowners, the recommended materials would include any product with spinosad as an ingredient that is labeled for fruit trees or Malathion.
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, Long pointed out.
To obtain a free pesticide spray guide for this and other tree fruit pests, contact the OSU Wasco County Extension Office at 296-5494.