It appears that my raspberries may have a disease. I noticed some fruiting canes getting
discolored, then curling leaves, then dying completely. I ripped out ones that were dying or dead, but others seem to be showing beginning symptoms.
There are many potential culprits that could be causing the problems you
are observing with your raspberries. It could be a pest, or it could be a
fungal disease. Remember that summer bearing raspberry canes die after bearing fruit. The canes start to look bedraggled even as fruit is ripening. Once all fruit has been picked these canes should be cut to the ground. Next year’s fruiting canes will look healthy and should not be cut down to the ground.
Have you looked inside any of the affected canes after cutting them? If
you have cane borers, you may find that white grubs have burrowed toward
the base of the cane. Crown borers also cause wilting of new growth in
the spring followed by dieback of the cane. Here are links to
information and images so you can compare what you are seeing with your
plants:
Insects and Diseases of Raspberries from University of Illinois Extension.
Pests and Disorders of Blackberries and Raspberries from University of California.
Washington State University’s Hortsense page on Raspberries (see sidebar on left for diseases and insects)
Raspberry root rot information is available in the Pacific Northwest Disease Management Handbook.
Washington State University Extension’s information for home gardeners says:
“Foliage symptoms of root rots. Root rot is usually noticed when leaves
begin to wilt, turn yellow or brown, and die. Symptoms commonly occur
during warm spring or summer weather and may develop in a few days or
take longer. If longer, leaves are generally yellowish and stunted before
they die.
“Root symptoms of general root rot. Root systems are small, dark brown or
black, and rotted. Since healthy roots may or may not have dark surfaces,
determine root condition by cutting or scraping them. All of the inside
of a healthy root is whitish, but the inside of a rotted root is partly
or entirely brownish or blackish. Wash the cutting tool in soapy water
and swab in rubbing alcohol after cutting.”
You may want to bring samples plus photos of the whole plant to a Master Gardener clinic for diagnosis. There is a link to the current clinic schedule on their website.
Once you have identified the source, you can try to address the problems
and resume growing happy raspberry plants. Oregon State University has a guide to growing raspberries which may be helpful.