Extension > Garden > Yard and Garden > Fruit > Integrated pest management for home raspberry growers > Virus diseases
There are 15 known viruses that infect raspberry plants in North America. Tomato Ring Spot Virus (TomRSV) is common in Minnesota and Raspberry Leaf Curl Virus (RLCV) occurs rarely. Once a plant is infected with a virus, it will never recover. Virus infected raspberry plants suffer from reduce growth, low fruit production and poor fruit quality.
Raspberries infected with viral pathogens exhibit a wide range of symptoms, depending on the variety of raspberry, the virus, weather conditions and the stage of infection. Virus infection can result in yellow rings, lines or blotches on leaves (Figure 1), leaf distortion, crumbly underdeveloped fruit or severely stunted plants. In other cases, raspberry plants with viruses may show few or no symptoms. The only way to determine exactly which virus is causing the symptoms is to send a sample to the UMN Plant Diagnostic Clinic, where laboratory tests will be conducted to identify the virus.
Raspberries infected with tomato ring spot virus produce small, crumbly raspberries. Leaves in infected plants show fine yellow lines and yellow rings. Leaves may or may not show the symptoms, depending on the age of the plant and the variety.
Plants with raspberry leaf curl virus have slightly yellow, small leaves which curl downward and inward. The disease becomes worse each year, and by year 4, the plants are stunted and produce no fruit. The symptoms can be confused with injury by the herbicide glyphosate. Raspberry leaf curl is often found on only one plant in a row, while glyphosate injury will usually affect several plants with different degrees of severity.
Tomato ring spot virus infects a wide range of woody and herbaceous plants, including many common landscape ornamentals and weeds. Red raspberries can be severely affected by the disease, whereas black raspberries are unaffected. Tomato Ring Spot Virus is spread by the dagger nematode, a microscopic roundworm which lives in the soil and feeds on plant roots. Dagger nematode is common in many areas of Minnesota.
Raspberry leaf curl virus infects red and black raspberries and less commonly, black berries. It is spread from plant to plant by aphids. In Minnesota, Raspberry Leaf Curl Virus spreads very slowly and it is not uncommon to see only one to a few plants infected in a patch.
Once a raspberry plant is infected by either virus, the virus spreads throughout the whole plant from the roots to the canes. Viruses also spread from mother plants to daughter plants, and new canes that sprout from an infected mother plant always have the same viruses.
Before establishing a new raspberry patch, remove or kill any wild brambles, old raspberry plants, or weeds at the site.
Obtain new raspberry plants only from a reputable wholesale or a retail nursery, preferably one that sells certified virus-free planting stock. Never transplant daughter plants from an existing patch with virus infected plants. These new plants will already be infected even if they are not yet showing symptoms of the disease.
Plants infected with a virus should either be dug up or killed with an herbicide. Infected plants will never recover and will only continue to decline and produce poor fruit. If plants were infected with raspberry leaf curl virus new plants can be replanted at the same site. Unfortunately, the site should not be replanted to red raspberries if tomato ring spot virus was causing disease. The nematodes that carry tomato ring spot virus remain in the soil and it is likely that replacement plants put in the same site will also become infected. If tomato ring spot virus occurs, it is best to plant new plants in a new location or replant with black raspberries.