Diagnosing viral infections in a raspberry can be particularly challenging, as raspberries tend to display less obvious symptoms than other berry crops. New developments in research suggest that a symptomatic raspberry plant is most likely infected with multiple viruses. For this reason, laboratory diagnosis is the only reliable way to identify a virus infection.
“Most virus diseases of Rubus are caused by virus complexes rather than by infection with a single virus. Tomato ringspot virus is the exception. ” – Bob Martin, Research Plant Pathologist, USDA-ARS Corvalis, OR
Bearing this in mind, the following symptoms can be associated with mosaic virus infection in raspberry. Take caution in pruning and propagating plants with these symptoms, and treat them as if they are infectious until a diagnosis is confirmed.
Tomato ringspot virus is common in older red raspberry plantings and also causes fruit to crumble when harvested.
Raspberry Bushy Dwarf Virus also causes crumbly berries. A lab test is required to determine if this virus is present in a planting. Once infected, a planting will always be infected.
The early symptom of mosaic virus infection is light green mottling on leaves in early spring.
Later, plants decline in vigor and leaves become yellow. Black raspberries are particularly susceptible. Red raspberries may be infected but not show symptoms.
Do not confuse true mottling with leaf discoloration caused by late leaf yellow rust. More on late leaf rust
Mosaic virus is a common cause of leaf yellowing and stunting in black raspberries, although it can affect blackberries and red raspberries, too.
More information:
- Virus Diseases of Raspberries – (Ohio State)
Use these resources if you need additional help with diagnosis and to find solutions to your problem.