Spur Blight in Home Raspberry Plantings

Red and purple raspberries are more affected by spur blight than black raspberries. Blackberries appear to be immune.
Spur Blight in Home Raspberry Plantings - Articles

Updated: August 8, 2017

Spur Blight in Home Raspberry Plantings

In extremely overgrown and weedy plantings, the disease can cause a loss in yields, especially if excessive nitrogen is applied.

Symptoms and Disease Cycle

Spur blight is caused by the fungus Didymella applanata, which overwinters in infected canes. Symptoms appear in late spring or early summer as chocolate-brown, dark-blue, or purplish spots or bands on new canes and petioles. These lesions enlarge until the cane is girdled. By late summer, canes may crack and split lengthwise, at which time the reproductive, pimple-like, black fruiting structures of the fungus can be seen. These structures overwinter and the following spring discharge spores into the air or may ooze to the surface of the stem during wet periods. Symptoms on leaves appear as chocolate-brown, angular, or wedge-shaped areas. The effects of spur blight are increased plant susceptibility to winter injury and reduced yield as a result of the withering and eventual death of infected laterals. Leaflets also wither and drop prematurely.

Disease Management

Suggested controls are the same as those for cane blight, botrytis blight, and anthracnose. Keeping the plant canopy open to ensure that leaves and canes dry rapidly after rain will help in controlling this disease. Thorough pruning, including the removal of pruned canes from the planting, is helpful. Lime sulfur and sanitation are useful, and keeping row width narrow to increase air movement is particularly effective. Producing only the fall crop on primocane bearers has greatly reduced the incidence of the disease. Several fungicides can be used during the season. Refer to Table 7.5 for pesticide recommendations.

The important insects and diseases to be controlled, except for viruses, are listed in the right-hand column of this spray schedule. Always consult the label before making pesticide applications. Labels vary greatly among commercial products of the same material. It is important to refer to the label for the best timing and application rates when applying pesticides. Also read the text for information on cultural practices to minimize the application of pesticides. Due to a wide array of various products containing the same active ingredient, for insecticide recommendations, when appropriate, the active ingredient is listed instead of the name of the formulated product.

Table 7.5. Pesticide recommendations for brambles. (Follow all instructions and application rates listed on pesticide labels.
Time to Spray
Suggested Materials
Pests to be Controlled
Dormant (blackberries) - before buds open
Lime sulfur
Anthracnose, cane blight, powdery mildew, rust
Delayed Dormant - just as buds begin to open
Lime sulfurAnthracnose; spur blight on raspberries; powdery mildew, rust, and cane blight on blackberries
New shoots 8 inches long
Sulfur; Malathion; Esvenvalerate
Anthracnose; Botrytis, cane blight, and spur blight on raspberries; fruit worms; plant bugs
Petal Fall
Sulfur; Carbaryl plus Rotenone or PyrethrumAnthracnose; Botrytis, cane blight, and spur blight on raspberries; fruit worms; rose chafer; aphids; mites; plant bugs
PreharvestSulfurFruit rots
MidharvestSulfurFruit rots
PostharvestMalathion plus CarbarylAphids, if present; Japanese beetles

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