Grape black rot

What you see

Small tan leaf spots with a dark border and a ring of black pinhead dots. On the fruit, a pale spot spreads until the whole berry turns hard, black, shrivelled and mummified while still attached to the bunch.

Conditions

Warm and wet - it needs several hours of rain at 25C or so. Overwinters in mummified berries left on the vine and on the ground.

Treatment

Remove every mummified berry and infected tendril from the vine and the ground during winter pruning. Copper protects from bud burst through to bunch closure.

Prevention

Open the canopy so bunches dry fast. Clear all mummies and prunings. Copper timed from just before flowering is the key protective window.

Months: May, June, July, August

Plants

Grape

Remedies

Bordeaux mixture (copper), Bacillus subtilis biofungicide

The thing people get wrong

The mummies are the disease. Every shrivelled black berry left hanging on the vine or lying underneath is a spore package aimed at next spring's young bunches, and unlike downy or powdery mildew this fungus has nowhere else to overwinter. Clearing them in January is worth more than any spray in June.