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My raspberries and red and very sweet and now I have found thread-like worms on the fruit (about 2-4 in a bowl) when washing. What are they and how do I treat the fruits? They are black or grayish and threadlike and about 1/ to 2/3 of an inch long.

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A

It sounds like you might have the western raspberry fruitworm, but it is hard to know for sure without a sample.  This is a beetle. The adults will feed on the leaves in spring and lay eggs on the fruit.  The larvae feed within the developing fruit for 5-6 weeks, and are especially noticed at harvest. The larvae, however, are whitish and only about 1/3-inch long.  The larvae then drop to the ground to overwinter as pupae in the soil.  Treatment is targeted at the period of egg hatch, just at pre-bloom and again post bloom, if necessary.  Spinosad is an excellent, safe product to use, but carbaryl and malathion will also work.

These larvae can be washed out, as you have done, and they are also killed in the canning or freezing process.

If possible, please bring a sample of the damaged fruit as well as the larvae to your local Extension office, and they can send the sample to the Utah Plant Pest Diagnostic Lab.  Or, you can visit the Web site for forms and mailing instructions:  www.utahpests.usu.edu/uppdl. This way, we will be recommending the right treatment for the right pest.

Posted on 9 Jul 2008

Marion Murray
Intergrated Pest Management Project Leader

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