Latin name: Elsinoe veneta
Reason for Concern:
1) This pest occasionally affects raspberries.
2) Serious if rains continue late into spring; cane spots may retard sap flow, thus girdling canes.
3) Uneven berry ripening may result from infected canes.
Initial infections typically occur on lower cane portions toward the inside of the plant but can also affect leaves and fruit. The first symptom is small, purplish or reddish circular patches on the cane. As they enlarge, the central portion grays, sinks and cracks. Margins raise and purple. Damaged patches are often so clustered that they merge, forming large, irregular areas. Canes eventually girdle and die. Leaves and leaf stems may show various degrees of purple spotting, depending on plant variety. Berries may ripen unevenly and have abnormally small drupelets.
Cause: a fungus spread by spores produced in the small black bodies that form in gray patches in the fall. In winter, the fungi overwinter on infected canes. In spring, splashing rain carries spores to infect new shoots, leaves or fruit.
- A pest that seriously affects black raspberries, red raspberries are generally not infected.
- Check rootstock of susceptible varieties very carefully when planting for any sign of galls.
- Excluding black raspberries, the disease is not always severe enough to warrant the cost of spraying.
- Becomes particularly serious if rains continue late into spring, when spots on canes may be plentiful enough to retard sap flow, thus girdling the canes.
- Early-season infections are more severe than late-season infections.
- At 4 locations in a 10 acre plot, sample at least 5 plants per location.
- Watch for sunken grey areas with purple raised margins on canes on floricanes in the spring when primocanes are emerging.
- The floricane is most commonly infected from 6 to 24 inches above the ground.
- Record total number of plants with lesions.