Recently while picking raspberries I noticed tiny white worms inside many of...

Asked August 4, 2014, 3:13 PM EDT

Recently while picking raspberries I noticed tiny white worms inside many of the berries,the worms are white and less than 1/8" long, there were several in some of the berries. There were also black bugs on some of the berries that had 4 spots on there back. What are the worms and bugs and should jam and sauce made before they were discovered be discarded.

Sherburne County Minnesota raspberry pest

1 Response

Thank you for the question. If you are finding little white worms in the berry itself it may be Spotted wing drosophila [SWD] larvae; SWD are fruit flies that cut a slit in the fruit and lay their eggs and when the eggs hatch the larvae eat the fruit from the inside.

The insect you see with the 4 spots may be a sap or picnic beetle. The most common picnic beetle (family Nitidulidae) is a small (ΒΌ inch long), black insect with four yellowish-orange spots on the back. Adult beetles are attracted to all types of overripe and decaying fruit. Although not attracted to ripe, undamaged raspberries, these can be damaged once picnic beetles are in the garden

There are cultural steps to take to minimize SWD and sap beetle problems. Note that most of these steps are the very same steps recommended for minimizing most problems with raspberries.

a) Pick fruit as soon as possible. With raspberries, this means harvesting as soon as you can pull the fruit from the plant. If you notice any raspberry fruit with juice inside the caps, discard these berries, preferably after checking for larvae.
b) Harvest thoroughly. Even if you need to pay someone to pull off old fruit, keeping the planting clean will be worthwhile for a number of reasons in addition to this one.
c) Dispose of unwanted fruit in a way that will keep fruit flies from using it as a food source or from hatching from it.
d) What insecticides work if they become necessary? Effective insecticides for which are label specific for spotted wing drosophila have been issued. These are registered on raspberries and blackberries: Danitol (fenpropathrin); Delegate (spinetoram); Entrust and Success (spinosad); Mustang Max (zeta-cypermethrin); and Pyganic (pyrethrins). Other materials registered on caneberries for other pests are also effective on SWD. One big concern is development of SWD populations that are resistant to certain insecticides. This pest has a very short life cycle, so please be sure to use materials from different activity groups for subsequent sprays. It should be noted that the residual activity has sometimes been reported to be shorter than what is listed here, so close watch for return of adults will be needed. And if you choose chemicals: read and follow the directions implicitly for your health and the health of the environment.

If you decide to use an insecticide, please use it when pollinators are less active such as early morning hours on quiet windless days to minimize drift.

Raspberries infested with SWD larva, typically rot from inside within a few days. It's your choice whether or not to keep your jams or sauces but I would think that the cooking process killed any larva that were inside berries that appeared healthy. Information taken from the third publication below reads as follows:

"During minor infestations, infested fruit can be processed into wine or jelly. During severe infestations, the berries are difficult to harvest and should not be processed".

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