What is the worm boring into my raspberry canes causing them to break off?

June 3, 2022 Ask the Expert, Managing Insect, Diseases, and Animal Pests

Question:

Some of my raspberry canes are breaking off, this is happening to the flourocanes. When I cut into the cane, I find a white segmented worm 1/4 – 1/2 inches long. I’ve had cane borers in the past, but the row around the cane is very obvious. I don’t have that here. What may this be?

Answer:

Rebecca Long, Sustainable Agriculture and Horticulture Professional

I conferred with our insect and raspberry experts and it sounds like it could be a few different things: crown borer, red-necked cane borer or cane maggot.

It would be good to know at what height the canes are breaking off, to help with the diagnosis. Red-neck cane borer usually shows a distinct swelling near the base of the cane. Crown borers usually cause wilting and marginal necrosis of the leaves, due to damage to the vascular system. It may also be raspberry cane maggot; the damage is similar to cane borer without the girdling bands, but the cane tips usually wilt and turn black.

Please review the factsheets below to see if it matches what you are seeing.

Raspberry Crown Borer (Univ. of New Hampshire Cooperative Extension)
Red-necked Cane Borer (Penn State Extension)
Raspberry Cane Maggot (UNH)