Deb Babcock: Cherry fruit fly update

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Deb Babcock

Deb Babcock's gardening column appears Thursdays in Steamboat Today.

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— Two years ago, some gardeners reported that they had bugs in their cherry harvest. So master gardeners looked into the problem last year by hanging sticky traps in their trees to gauge the size of the outbreak and spread the word about how you can help prevent the cherry fruit fly from infecting your tree.

The results of last year’s study found pockets of infestations, mainly in Old Town Steamboat Springs. It’s a problem that can spread throughout the county and ruin cherry harvests — once a cherry tree has been infected, the fruit is no good.

You can get a jump on this destructive pest early this season.

There are four primary controls recommended for eliminating this pest. Spinosad is the least toxic to mammals and will last about a week and should be repeatedly sprayed until a week before harvest. It can be found under the Ferti-lome and Natural Guard labels

Carbaryl products such as Sevin also are effective but can cause spider mite problems if used repeatedly. Therefore, you should alternate this product with other ones.

There are several products containing malathion that can be used to control cherry fruit flies but have just a two to three day residual value and need to be repeated often.

Two pyrethroid insecticides called permethrin and esfenvalerate can be used for cherry fly control. These insecticides give a week or more of residual value.

Keep in mind with any of these controls that as your cherries grow larger, the fruit will outgrow the insecticide. As a result, you need to stay on top of spraying as the fruit expands in size. If your cherry trees are quite large, you may need to contract with a professional.

The western cherry fruit fly (Rhagoletis indifferens Curran) first was found in cherries in the western part of Colorado in the late 1990s and now has spread to Routt County. This pest attacks only cherries, and is a problem with all varieties (but not chokecherries). It will not harm the tree, just the produce.

The western cherry fruit fly produces one generation of offspring per year. The pest spends the winter in the soil as a pupa and then comes out as an adult fly during a two month period in the spring when the weather warms up. It lays its eggs (50 to 200 per fly) in the cherry fruit (one egg per cherry) when temperatures reach 75 to 85 degrees. The eggs hatch within a week, and the larvae spends the next two weeks inside the fruit, ruining it, before burrowing out and falling to the ground to push itself into the soil to overwinter as a pupa.

Smaller than a housefly, the western cherry fruit fly has a black body with thin white stripes across its stomach. Once it reaches adult stage, it can be identified by a pattern of distinctive black markings on its wings.

If you have any questions about your cherry trees, contact the Routt County Extension Office.

Deb Babcock is a master gardener through the Routt County CSU Extension Office. None of the products or professionals mentioned in this article are endorsed by the master gardener program but are provided for informational purposes. Call 970-879-0825 with questions

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