Black bugs in raspberries

Asked August 1, 2019, 11:03 PM EDT

I have noticed I have a lot of black bugs boring through the bottom of my raspberries this year year also when I look inside some of the berries there are little white maggots or tiny larva worms, How can I get rid of these do I need to destroy the whole patch and start over

Todd County Minnesota raspberries raspberry insects spotted wing drosophila

1 Response

Thanks for the question.

In the absence of pictures, it is difficult to make a good assessment of your situation. I am trying to decide if the black bugs you are seeing are related to the maggots in the fruit. In short, I don’t know if you are dealing with one pest or two. I suspect two.

As to the black bugs, there are two common ones that feed upon ripe fruit: Sap beetles (Glischrochilus quadrisignatus) and multi-colored Asian lady beetles. Since you indicated that these are black, I assume they are sap beetles, which are also called picnic beetles. They are found statewide and will eat both summer-bearing and fall-bearing raspberries. The lady beetles have coloration. For a discussion on sap beetles, their biology, and their control, take a look at pages 19 – 21 of the following:

https://conservancy.umn.edu/bitstream/handle/11299/198100/Raspberry%20Home%20IPM.pdf?sequence=1&isAllowed=y

As to the white maggots, I suspect that they are due to a different pest. They are the larvae of the Spotted Wing Drosophila. We have been receiving many reports of their presence throughout the state. Once a raspberry is so infected, there is no control and the berries should be discarded. See pages 22 – 24 in the above site. Also take a look at:

https://extension.umn.edu/yard-and-garden-insects/spotted-wing-drosophila

https://blog-yard-garden-news.extension.umn.edu/2019/07/spotted-wing-drosophila-update-and.html

There is no need to dig up your plants and start over. Just do your customary fall preparation for them. Especially be sure not to leave any berries on the ground. Both of these pests can fly into your patch, often from great distances. In 2020 consider placing netting over the canes to prevent infection of the berries. The above two sites discuss this preventative measure as well as other control procedures.

Good Luck!!