Plan the perfect garden with our interactive tool →

How to Identify Disease in My Raspberry Plants

growing raspberry
dianazh/iStock/Getty Images

Members of the Fragaria genus, black and red raspberry species grow on canes in U.S. Department of Agriculture plant hardiness zones 2 through 7. Typical fungal diseases include anthracnose, blight, rusts, wilts and rots. Common viral diseases include raspberry leaf curl, raspberry mosaic, raspberry ring spot and bushy dwarf virus. These diseases almost all develop in cool, wet spring weather.

Identifying Fungal Anthracnose and Blights

Anthracnose typically strikes in wet spring weather, infecting black or purple raspberries more than red raspberries. The fungus causes small purple spots up to about 1/8-inch wide on young canes. The spots sink in the center, turning gray with purple edges that often join together. The canes may crack and small, pitted raspberries ripen slowly.

  • Members of the Fragaria genus, black and red raspberry species grow on canes in U.S. Department of Agriculture plant hardiness zones 2 through 7.
  • Anthracnose typically strikes in wet spring weather, infecting black or purple raspberries more than red raspberries.

Spur blight strikes strikes in wet, early-spring weather, affecting red raspberries more than black raspberries. However, the symptoms do not occur until mid- to late summer on overgrown, excessively vigorous canes. Chocolate-brown to purple blotches grow around buds, stunting them or causing them to produce weak canes the next year.

Cane blight also appears in early spring, causing purple to dark-brown cankers below wilted leaves on the main branches or canes. Spur blight strikes around buds, but cane blight infects whole stems, turning them purplish-black and causing them to crack. Cane blight typically strikes areas wounded by pruning and can cause failure of buds to develop, wilting of lateral shoots, and the death of canes.

Identifying Fungal Rusts, Wilts and Rots

Infected orange rust leaves turn yellow with rust-colored spores on the bottoms of leaves. The fungus moves to other parts of the plant, including the roots. The plants become spindly and lacking thorns. They will not recover and the plants will die the following spring.

  • Spur blight strikes strikes in wet, early-spring weather, affecting red raspberries more than black raspberries.
  • Cane blight typically strikes areas wounded by pruning and can cause failure of buds to develop, wilting of lateral shoots, and the death of canes.

The popular Heritage red raspberry cultivar ( Fragaria × ananassa "Heritage") is particularly hard hit by late leaf rust in which powdery masses of fine, light-yellow fungal spores appear on leaf stems and berry caps. There is no known way to control this disease.

Soil-borne vermicillium root moves up from the roots, causing leaves to turn yellow and drop beginning at the bottom of the canes. As the disease progresses upward, the canes turn blue and die.

Warm, wet weather also encourages fuzzy botrytis or penicilium mold to develop on ripening raspberries.

Identifying Viral Raspberry Leaf Curl

Raspberry leaf curl can cause a 20- to 70-percent drop in yield and black raspberries to die in two to three years. The tips of yellow and red raspberry leaves may curl downward the first year of infection or there may be no symptoms. The next spring, crinkled, stunted, rounded leaves near the tips curl tightly, turning downward. Pale, yellowish-green shoots of newly infected plants typically do not branch, becoming stiff and brittle and turning dark green. Infected plants grow small dry, seedy, crumbly berries. The plants grow more poorly each year. Black and purple raspberry plants show similar symptoms. Dwarf, stiff leaves arch upward, turning dark, greasy green. As the years pass, severely dwarfed, bushy young canes turn rigid, unable bend to the ground to grow roots at the tips.

  • The popular Heritage red raspberry cultivar ( Fragaria × ananassa "Heritage") is particularly hard hit by late leaf rust in which powdery masses of fine, light-yellow fungal spores appear on leaf stems and berry caps.
  • The tips of yellow and red raspberry leaves may curl downward the first year of infection or there may be no symptoms.

Identifying Viral Common Raspberry Mosiac

Black raspberries typically suffer most by the common raspberry mosaic, a viral disease that can cause raspberry yield to drop by half. Infected red and yellow raspberry canes grow poorly in cool weather, developing mottled, puckered leaves with large, green blisters. The leaves droop as the blisters turn yellowish-green or yellow. Leaves that grow in hot weather show pale yellow spots or show no symptoms at all. Each year the plants get worse, growing dwarf, often-deformed leaves mottled with yellow, yielding fewer raspberries. Black raspberry leaves turn black and rotten and the plants yield fewer berries.

Identifying Ring Spot and Bushy Dwarf Viruses

Soil nematodes spread red raspberry ringspot, caused by the tomato ringspot virus. After one year of infection with no symptoms, diseased plants show yellowing veins and yellow rings on new canes. These symptoms disappear in the second year, but leaves grow slowly in spring, turning yellow. Diseased canes yield crumbly, deformed berries. The raspberry bushy dwarf virus infects both red and black raspberries, resulting in declining vigor and plant yield. The symptoms vary with the season and the cultivar. Some cultivars grow leaves with yellowing between the veins on the leaves, while others develop irregular patterns resembling oak leaves.

  • Black raspberries typically suffer most by the common raspberry mosaic, a viral disease that can cause raspberry yield to drop by half.
  • The raspberry bushy dwarf virus infects both red and black raspberries, resulting in declining vigor and plant yield.

Controlling Raspberry Diseases

Plant raspberries certified by the U.S. Department of Agriculture as being virus- and nematode-free and resistant to fungal disease. Plant them in a fertile, sunny site with good drainage and destroy all neglected or wild raspberry or blackberry canes within 600 to 1,000 feet. Separate red and black raspberries by 150 feet to prevent them from infecting one another. Check for viral diseases in cool, cloudy weather and spray infected plants with 2 tablespoons of powdered Malathion per gallon of water and remove and destroy the plants one or two days later. To prevent infestations of disease-bearing nematodes, anchor a sheet of clear plastic on the ground in late spring and leave in place for at least two months to kill the nematodes by heat. Spray lime sulfur, useful for controlling fungal disease, when new leaves are 1/4- to 3/4-inch long in the spring or when the temperature is above 75 degrees Fahrenheit. To kill aphids, spray the foliage with a 1 to 2 percent of horticultural oil.

  • Plant raspberries certified by the U.S. Department of Agriculture as being virus- and nematode-free and resistant to fungal disease.
  • To prevent infestations of disease-bearing nematodes, anchor a sheet of clear plastic on the ground in late spring and leave in place for at least two months to kill the nematodes by heat.

Related Articles

Pest & Disease Identification on Blackberry Plants
Pest & Disease Identification on Blackberry Plants
Do Raspberry Bushes Have Thorns?
Do Raspberry Bushes Have Thorns?
How to Diagnose Blueberry Plant Problems
How to Diagnose Blueberry Plant Problems
A Blueberry Bush With Brown Leaves
A Blueberry Bush With Brown Leaves
Most Disease-Resistant Tomato Plants
Most Disease-Resistant Tomato Plants
Black Stuff on Raspberries
Black Stuff on Raspberries
Diseases of Grape Vines
Diseases of Grape Vines
How to Grow Raspberries in Wisconsin
How to Grow Raspberries in Wisconsin
Diseases of Walnut Trees
Diseases of Walnut Trees
How to Treat Blueberry Bushes With Spots on Them
How to Treat Blueberry Bushes With Spots on Them
Why Are My Eggplant Leaves Shriveling Up?
Why Are My Eggplant Leaves Shriveling Up?
Why Are My Begonias Dying?
Why Are My Begonias Dying?
Why Do the Leaves on My Jalapeno Pepper Plants Turn Yellow & Curl?
Why Do the Leaves on My Jalapeno Pepper Plants Turn...
How to Prune a Marionberry
How to Prune a Marionberry
Yellowing Leaves on a Grapevine
Yellowing Leaves on a Grapevine
Common Diseases of the Wichita Blue Juniper
Common Diseases of the Wichita Blue Juniper
Garden Guides
×