Notes on Raspberry Diseases
Purple spots with grey-white centres form on new canes, leaves and petioles.
Spots enlarge on canes to form sunken pits. On second-year canes, these
lesions can coalesce into cankers that girdle the cane and cause it to
dry out and crack. Infected canes are more susceptible to winter injury
and produce weak growth in the spring. Fruit infections occur when there
is abundant inoculum and wet weather in the green fruit stage. Fruit symptoms
include shrunken brown druplets or withered, dry seedy fruit.
Anthracnose disease on raspbery
Anthracnose infection on leaves
Period of activity
Ascospores are rain-splashed and air-borne from infected canes in early
spring. Conidia are rain-splashed from overwintering infected canes in
the spring and throughout the summer to new growth. Infection requires
three to twelve hours of wetness; only very young green tissue is infected.
Anthracnose on overwintering
In early spring, look for lesions on overwintering canes which indicate
the potential for problems. From spring through to bloom, check primocanes
and developing laterals for purplish spots with grey-white centres.
Early infection is worst, late infections cause less damage. Early fungicide
applications are important. See the Raspberry Calendar. Boyne, Kilarney
and black and purple varieties of raspberry are very susceptible. Keep
rows narrow and control weeds to improve drying in the row. Dispose of
pruned canes. Destroy wild brambles in the vicinity to eliminate other
sources of infection.