American gooseberry mildew
Problem commonly affects Gooseberries, also Blackcurrants. Whitish-grey powdery fungal growth appears on the upper surface of plants foliage, especially on young growth towards the shoot tips. Shoot tips may become distorted and die off; Powdery mildew which can also been seen on the skin of affected berries/currants turns pale brown and buff with age. Infected fruit, although unsightly, are edible and infection can be rubbed off the fruit with your thumb.
Spray with Systhane Fungus Fighter at, or before, first signs of disease and repeat at fortnightly intervals.
Cultural measures: Ensure that plants are adequately spaced and pruned to remove affected branches and to encourage air circulation within the crown of the bush. Avoid excessive use of high nitrogen fertilisers. A general fertiliser is preferable.