A number of measures will help reduce occurrence of the disease;
- Gooseberries are best pruned to an open form to aid picking. This also discourages stagnant air amongst the branches and promotes the circulation of air
- Avoid planting in low-lying or enclosed areas or with poor air flow
- Opening up bushes will also greatly ease picking and control of gooseberry sawfly
- Avoid excessive quantities of nitrogen rich manure, dried poultry manure pellets for example or mulching with manure, because the resulting soft growth is more readily attacked
- A dressing of a balanced fertiliser, such as Growmore, is more suitable – use 50g per sq m (1½oz per sq yd)
- The fungus overwinters within the buds and on the shoots, and (with blackcurrants in particular) on fallen leaves. It is therefore essential to ‘tip’ prune the bushes by removing and disposing of (bonfire or shredding and composting) the ends of affected shoots as soon as they are seen, as well as disposing of all fallen leaves in autumn
Eating affected fruit
The fungal growth on the berries can be rubbed off, and the gooseberries are edible, so there is no need to waste the crop if many of the fruits are affected. However, even after this laborious process the diseased berries will turn brown when cooked.
Organic gardeners, and gardeners who find spraying ineffective, can grow resistant cultivars which can offer a useful level of resistance to this disease:
'Greenfinch' AGM: Resistant
‘Hinnomaki Gold’: Slightly Resistant
‘Hinnomaki Red’: Resistant
‘Hinnomaki Green’: Resistant
'Invincta' AGM: Resistant (Although young plants of this variety show moderate attacks of mildew the shoots of mature plants and fruits are highly resistant)
‘Pax’: Slightly Resistant
‘Ben Alder’: Slightly Resistant
‘Ben Connan’ AGM: Resistant
‘Ben Gairn’: Resistant (Also resistant to reversion virus)
‘Ben Hope’: Resistant (Also resistant to gall mite)
‘Ben Lomond’ AGM: Slightly Resistant
‘Ben More’: Resistant
‘Ben Sarek’ AGM: Resistant
‘Ben Tirran’: Resistant
‘Big Ben’: Resistant
To source plants use: RHS Plant Finder
The fungicides myclobutanil (Systhane Fungus Fighter*) can be used to control this disease and spraying should be carried out according to the manufacturer’s instructions.
A product containing a blend of plant and fish oils (Organic 2 in 1*) is also available and can be used by organic gardeners. It acts by physical, rather than chemical, action.
*NB: The following products are being withdrawn:
Myclobutanil (Bayer Garden Systhane Fungus Fighter concentrate and Bayer Garden Fungus Fighter Disease Control). These products cannot be sold after the 30th November 2015 and remaining stocks must be used or disposed of before the 30th November 2016.
Plant and fish oil blends (Vitax Organic 2 in 1). These products are being withdrawn but as they are not registered fungicides there is no date by which stocks have to be used up before.
Fungicides for gardeners (Adobe Acrobat pdf document outlining fungicides available to gardeners)