White, powdery fungal growth which develops on the upper leaf surface, along the canes and sometimes over the entire plant. Commonly affects greenhouse plants, perennials and shrubs. The affected leaves can become distorted and brittle especially if the foliage is young. Raspberries are often affected with this type of mildew as are gooseberries, grapes and members of the cucurbit family (cucumber, courgette, squash, pumpkin).
Improve air circulation within plants, allow the correct spacing between plants as over planting can encourage those conditions suitable for powdery mildew. Avoid feeding with high nitrogen plant food.
There is currently no chemical registered for the control of this disease on raspberries.