The Q&A Archives: Raspberry canes swelling, stem dies

Question: Each year some of my raspberry canes develop an oblong swelling on the stem and the top half of that stem dies. Is it a fungus? John Angehrn Englewood, NJ

Answer: It's an insect that red neck cane borer, says Herbert Stiles, raspberry specialist at the Southern Piedmont Agriculture Experiment Station in Blackstone, Virginia. Adult beetles spend the winter inside the soft pith in the center of the cane. In May, just before bloom, they emerge to lay eggs on young bramble canes. The eggs hatch and larvae burrow into the stem, causing the characteristic spiraling pattern beneath the bark and the one to three inch long cane swelling. The simplest control isto watch for the swelling after blooming. Cut the affected cane off six inches below the swelling point and destroy it, says Stiles. Removing any wild brambles may also lessen the number of infections in your patch.

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