What are these worms on my raspberries?
How disappointing to find these larvae on your raspberries! From your description of them, you may have spotted wing drosophila [SWD] larvae or raspberry fruitworm. SWD are fruit flies that cut a slit in the fruit and lay their eggs. When the eggs hatch, the larvae, which are white and about 1/8 inch long, eat the fruit from the inside. I don't know if SWD has been found in St. Louis County or not. If you think this is the pest you have, it is reportable to the Minnesota Department of Agriculture at this site: Arrest-the-Pest program. I'm assuming you didn't see any larvae when you were harvesting and freezing your berries, so the culprit could be SWD.
Raspberry beetles eat raspberry plant leaves, lay eggs on the flower buds or blooms, and larvae (or fruitworm) emerge from the eggs on the flower or immature fruit and begin feeding. The larvae are between 0.1” and 0.25” in length depending on the time of season. They are a light cream color with darker bands across the body. Here is a good photo of the larvae: Raspberry Fruitworm Larvae Byturus spp.
Freezing will kill whichever larvae may be inside the raspberry. If the raspberries are to be used in cooked products, there should be no problem consuming them. It's up to you if you plan to defrost them and eat them whole.
Read about these pests and control options here:
- Raspberry Insect Pests of the Home Garden
- Spotted Wing Drosophila Management Recommendations for Minnesota Berry Growers
- Spotted Wing Drosophila in Home Gardens
Thank you for contacting Extension.