raspberry insect infestation

Asked May 2, 2018, 8:20 PM EDT

What is causing the infestation in our raspberry canes that is causing them to die and how can it be stopped? It looks like an insect is putting eggs in the cane and then the larva are eating the inside of cane.

Washington County Oregon

2 Responses

Damage to tips of newly growing raspberry is likely Rose (Rosa)-Raspberry cane maggot (Pegomya rubivora). The treatment is to cut and destroy these canes. There is no approved home-use insecticide treatment.
I'm not 100% sure this is the correct insect, but there are not chemical controls for others, so the recommendation is the same. I will refer this question to other experts, and if more information is available, you will be contacted. Your photos are very helpful, thank you.
https://pnwhandbooks.org/insect/hort/nursery/hosts-nursery/rose-rosa-raspberry-cane-maggot-0 Link from the PNW Handbook.
http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/PESTS/raspberrycanemag.html Information from UC IPM pest management.

I referred your inquiry and images to the university entomologist for comment. He believes the uniform white objects in the stem are eggs,not plant-damaging larvae (youngsters). He also said this does not appear to be the Raspberry Cane Maggot.

You are obviously a very attentive gardener to have located the small puncture wounds in the cane. The entomologist asked if you also might have seen any insects you suspect may have laid the eggs.
If so, well focused images would definitely be helpful, but so might images which suggest body shape and color.

I believe you have a 2nd issue with the raspberries, probably from using weed killer for clean-up this past fall. A sub-lethal dose of glyphosate in the fall typically results in new spring growth which appears in clumps of short, stringy growth at a single node, just as in your closeup view.
The bleached leaves in the 2nd image also suggest herbicide damage, probably applied this year.

The plants may grow out of the damage this year but the result will depend upon the amount absorbed by the plant. Only time will tell.

Please respond to this email if you discover hatched larvae in the canes or see any of the adult insects.

We look forward to any additional information and/or images you can add, so that we may help you resolve this issue with your raspberries.