Raspberry white veins and holes
I have 20 raspberry bushes in Cass County. They began to show white lines in late July when berries were abundant. After cutting back old canes the remaining canes have from 6 inches to a foot of whiteness and holes from the top down. There are no insects in sight. What is this? What should I do? Cut them all back? Remove them?
Cass County Minnesota
We can't be sure without seeing the plants or sharp photos of the affected stems, but, based on your description, we suspect that cane borers may be causing the damage. If so, the following excerpt from a University of Wisconsin bulletin may be useful.
Raspberry Cane Borer
When this insect lays its eggs, it makes a double row of punctures around the stem tip, causing the cane tips to wilt. The adult female is a slender, black and yellow-striped beetle about 1⁄2-inch long with very long antennae. Grubs bore down the cane a few inches and hibernate for the winter. The following season, grubs bore downward within the cane, killing it.
To control, remove wilted cane tips 5 to 6 inches below the punctured area. Burn the prunings to destroy the insects inside.