The Q&A Archives: Cherry fruits have tiny pinholes and small worms

Question: Every year my cherry tree sets fruit, but the fruits have tiny pinholes and small worms in them. What are these worms and what can I do about them? Sheryl Shedlow Chicago, IL

Answer: The worms in your cherries are cherry fruit fly larvae, says Jim Schmidt, Extension home horticulturist with the University of Illinois, Urbana. The flies overwinter as pupae in the soil near the fruit trees. In our area, the adults emerge in late May or early June and move into the cherry trees, where they lay eggs in the fruit. The eggs hatch and white larvae feed on the fruit, causing much of it to be deformed and to drop prematurely. There is one generation a year in your area, explains Schmidt. If you have just one or two trees and they are small enough, the most effective control is to enclose each tree with floating row cover material before the flies begin laying eggs. In most regions, that's just as the fruit begins to soften and turn color, about three weeks before harvest. Be sure to cover the tree thoroughly, wrapping and tying the fabric to the trunk below the lowest branch. If you can't cover the trees, you'll need to spray to prevent damage. About three weeks before harvest, spray with Sevin (carbaryl) and repeat the application a week to 10 days later. This will kill many adults before they can lay eggs, advises Schmidt. Or use rotenone or pyrethrum, repeating the spray every three or four days and immediately following a rain.

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