KENNEWICK, Wash. -- Several weeks ago, a cherry tree owner brought some cherries in to me to see if they were infested with cherry fruit fly.
Because of an out-of-town emergency, she had missed one or more of the sprays recommended to control cherry fruit fly.
This cherry tree owner knows the importance of regular insecticide sprays to keep her cherries worm-free. However, not everyone with a cherry tree knows that regular sprays are needed to keep their cherries from becoming infested with cherry fruit fly maggots, or "worms."
Also, not everyone knows the law in Benton, Franklin, Yakima and Walla Walla counties requires that if your tree produces cherries, you MUST control the cherry fruit fly or remove your tree. These laws are intended to help protect the region's commercial cherry industry.
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Infested cherry trees in local neighborhoods serve as sources of infestation for commercial cherry orchards, requiring nearby growers to apply more pesticides to avoid the risk of their crop being rejected because of infested fruit.
(The same is true of fruit-bearing apple, pear, crab apple and ornamental pear trees. They're all codling moth hosts. The law also requires the control of codling moth in these trees to protect local commercial apple and pear growers.)
What about flowering cherry trees? Do they need to be sprayed?
No, most ornamental flowering cherry trees, such as the weeping cherries or the Japanese flowering cherries, don't produce fruit and don't require spraying. However, ornamental flowering cherries trees are usually grafted trees. The top of the tree (called the scion) is the desirable flowering variety, but the bottom part of the tree (called the rootstock) is usually a type of cherry capable of flowering and producing fruit. If the scion dies for some reason, the rootstock often grows, flowers and produces fruit. Sometimes the rootstock grows and produces fruit even if the scion is still alive.
The bottom line is that if your tree produces fruit, it must be sprayed regularly to control cherry fruit fly. If your "ornamental" cherry is bearing fruit, your best bet is to remove it and start over again with a new tree. You might want to try planting something other than a cherry!
Home gardeners have two materials available to them for cherry fruit fly control. One is malathion, an organophosphate insecticide. The other is spinosad, which is considered an organic material. Either of these materials must be applied to the entire tree beginning when the fruit starts to soften a bit, typically around Mother's Day weekend in May. Sprays are re-applied every 10 days until close to harvest, stopping when specified on the label as the "pre-harvest interval" before picking.
So if you do miss a spray application or two, how can you determine if your cherries are wormy? Some backyard cherry growers find out when the worms or maggots float to the tops of canning jars after processing, but there are ways to test for them.
In lieu of actually canning the cherries, you can make the maggots separate from the fruit by crushing some cherries and then submerging the mashed mess in a jar or other container with hot (140 to 180 degrees) water. Shake the container for about a minute to kill the maggots, then strain off the pulp with 1/4 inch mesh and look for the maggots to settle out. If you've done a good job of protecting the fruit, then there should be no maggots at the bottom. Yummy.
* Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.