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American Gooseberry Mildew (Latin name – Podosphaera (syn. Sphaerotheca) mors-uvae) is a common fungal disease of gooseberries and blackcurrants. Red and white currants may also be attacked.
Signs of American Gooseberry Mildew in Gooseberries: A powdery, white coating appears on new shoots, spreading to young leaves and, eventually, the berries. Later these patches form a felt-like mat and turn brown. Leaves curl up and fall off. The gooseberries are small and may be covered with brown felt.
American Gooseberry Mildew occurs:
- in crowded plants
- humid conditions
- areas of coastal fog
- when the soil around the roots is dry
- where irrigation is by overhead sprinkling
- in crowded plants
Life cycle of American Gooseberry Mildew The fungus overwinters in dormant buds. These produce infected shoots in spring which spread the disease by releasing wind-blown spores.
Prevention and control:
- select a suitable planting site which is sunny and not humid
- allow plenty of space between bushes
- prune to keep bushes open and airy
- avoid too much nitrogen-rich fertilizer which will produce soft shoots, more susceptible to infection
- cut out and burn infected shoots in July & September
- water to keep the soil around the roots moist
- use a mulch
- grow mildew resistant varieties such as Invicta
- chemical control – spray with a sulphur fungicide – but check that the chemical is safe on the variety by spraying a small area and waiting for 24 hours to see if the leaves start to curl. Spray just before flowers open, after fruit set and again 2-3 weeks later. Spray flowering crops at dusk when bees are not active. Do not use in full sun. Read the label and follow the instructions.
American Gooseberry Mildew is a common pest in the UK and it is well worth taking steps to control it.