Weather conditions for petal sticking

Petals are a vital part of the infection cycle and disease risk increases if petals stick firmly to the foliage. In recent years, there have been few occasions during flowering when large numbers of petals have stuck to the plant. Laboratory and field observations indicate that the combination of lightly wetted leaves and lightly wetted petals produces the best petal stick. Light showery rain favours petal sticking. Heavy or prolonged rain soaks the petals, which lose their structure and are then readily washed off the foliage.

It is difficult to predict petal sticking events - showery conditions are more likely to favour sclerotinia infection than prolonged heavy rain . These factors are part of the Decision guide.