Yesterday, I harvested the very first, sun-warmed, tangy-sweet raspberry of the season.
To me, raspberries rank right up there with tomatoes for good reasons to grow your own. Store bought raspberries rarely have the flavor or plump texture that fresh, homegrown raspberries provide. That being said, cane blight can take all the fun out of growing raspberries at home. If you know what to look for, you can prevent this disease from spreading.
Cane blight is a fungal disease. The fungus responsible for cane blight goes by the name Leptosphaeria coniothyrium. It is also known as Paraconiothyrium fuckelii. [Apparently, someone hates this disease even more than I do!] Cane blight is most commonly seen on raspberries, but it can also attack blackberries. The same fungus also causes a rose canker and a root rot on strawberries. Other host plants include bamboo, juniper, stone fruits, blueberries, and currants.
Symptoms of cane blight
This disease starts out looking similar to fireblight, spur blight, and anthracnose, but it progresses differently. Canes infected with Leptosphaeria coniothyrium will develop purplish-black lesions at wound sites. These lesions will develop into black or brown cankers that encircle the cane, causing wilt and twig dieback. Infected canes may also twist around other stems, rather than growing normally. Bark may split and the wood becomes very brittle. Leaves and fruit on those canes will wither and die, but stay attached to the cane. If you look closely, you can actually see tiny, black fungal bodies on the wood.
Preventing cane blight
Fungal spores can blow in on the wind and be splashed up onto plants by rain, sprinklers, and overhead watering. Spores enter healthy canes through injury sites. Jagged pruning cuts, growth cracks, and damaged roots can all provide points of entry, so keeping plants healthy and protected is the best way to prevent this disease. Use these tips to help prevent cane blight on your raspberries:
How to control cane blight
The only control is removal of infected canes. The cane blight fungus overwinters on the canes, so infected canes should be removed and destroyed. Be sure to dip your pruners in a solution of one part bleach and nine parts water, or bathroom disinfectant can be used. Severely infected plants should be removed completely. Fungicides are not effective against cane blight.
Keep your raspberry plants healthy for many years of summer deliciousness!
You can grow a surprising amount of food in your own yard. Ask me how!