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Virus diseases

virus-diseases

Virus disease on raspberry leaves.

Michelle Grabowski, UMN Extension

There are 15 known viruses that infect raspberry plants in North America. 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. Raspberry plants with viruses may show few or no symptoms. In other cases, the virus will result in yellow rings, lines or blotches on leaves, leaf distortion, crumbly underdeveloped fruit or severely stunted plants. Unlike fungal and bacterial diseases, viruses cannot spread through the water or air. Raspberry viruses spread from plant to plant by aphids, nematodes or when two roots graft to each other. Viruses also spread from mother plants to daughter plants, and new canes that sprout from an infected mother plant always have the same viruses. Most viruses are systemic in raspberry plants. Once a plant is infected, the virus spreads throughout the whole plant from the roots to the canes.

Raspberry Leaf Curl Virus (RLCV) is rare, but infected plants become so weak that they cannot produce fruit. Plants with Raspberry leaf curl virus have uniformly small leaves which curl downward and inward. Infected leaves are slightly yellow. The disease becomes worse each year, and by year 4, the plants are stunted and produce no fruit. The symptoms can be confused with glyphosate injury. Raspberry leaf curl usually is found on one plant in a row, while glyphosate injury will usually affect several plants with different degrees of severity. The raspberry leaf curl virus is spread by aphids. In Minnesota raspberry leaf curl spreads very slowly.

Plants with raspberry leaf curl should either be dug up or killed with a herbicide. Never dig up plants for replanting in a section of a field with raspberry leaf curl. Avoid transplanting from old raspberry beds; rather, buy new plants each time you start a raspberry patch.

Tomato Ring Spot Virus (TomRSV), 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. Raspberries infected with TomRSV exhibit symptoms known as crumbly berry. Infected plants 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. The virus is spread by the dagger nematode, which is common in many areas of Minnesota.

Plants known to be infected with crumbly berry should be removed, as they will never recover and only produce poor fruit. Unfortunately, because the nematodes that carry the virus remain in the soil, it is likely that replacement plant put in the same site will also become infected. If crumbly berry occurs, it is best to plant new plants in a new location or replant with black raspberries.


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