Cercosporella leaf spot

Cercosporella leaf spot is caused by the plant-pathogenic fungus Cercosporella rubi. The fungus is responsible for a number of different conditions in cane fruit.

Symptoms
Infected blossoms do not form berries whilst infected plants with symptomless blossoms produce poor quality fruit. Blossoms have distorted petals and enlarged sepals, giving the appearance of a double flower. Unopened flowers are usually elongated and larger, coarser and redder than normal. In addition, shoots may appear abnormal with leafy proliferation (rosette) or witch's broom.

Cultural
Select a site isolated from wild blackberries or other brambles. Use disease-free nursery stock, roots only. If the disease appears and is not already severe, infected rosettes and blossom clusters should be removed and destroyed before they produce spores. Old canes should be removed and destroyed immediately after harvest. Remove and destroy wild blackberries and other brambles near the planting. Some growers control this disease by harvesting blackberries in alternate years and destroying the above ground parts of both the new and old canes in spring every other year.

Chemical
If available, the fungicide Benlate can be used up to 5 times in a season with severe cases, beginning at first bloom and extending through harvest.