American gooseberry powdery mildew
Sphaerotheca mors-uvae belongs to the order of powdery mildew fungi and is widespread among susceptible gooseberry varieties. The species introduced into Germany, however, has a hard time with modern breeding. Infested berries are not suitable for consumption.
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Damage image
Not only leaves, but also shoot tips and fruits are attacked by this type of fungus. First, a fine white mushroom mycelium appears at the tips of the shoots, which later spreads to the leaves and gooseberries. As the braid thickens, it takes on a brown color, reminiscent of a felt cover. The compression of the young shoots can be clearly seen, as their growth is negatively affected. Instead, replacement shoots develop on them, making the entire shrub appear broom-like.
Effects:
- Loss of fruit yield as it cannot fully mature
- Weakening of plant health due to high energy consumption for alternative shoots
- Impairment of the development of flower systems
prevention
Regular pruning during the winter months is one of the most important measures to curb the fungal disease. Shorten all shoots by a third and dispose of the clippings in the household waste. Remove branches that grow deep on the trunk. If the fruit ripens too close to the ground, the susceptibility to fungal attack is increased. Make sure you have a balanced crown. This should neither appear too dense nor be too exposed. Also avoid one-sided fertilization with nitrogen.
Combat
If the disease occurs more often on a plant, you can spray a remedy with network sulfur. Apply the preparation before the new leaves sprout. Note that the varieties react differently to the active ingredient.
European gooseberry powdery mildew
Microsphaera grossulariae is another type of powdery mildew. It is considered harmless compared to American powdery mildew. This fungal disease occurs from July to August, when the harvest has already been completed. The typical damage pattern includes roundish spots on the leaves that appear grayish and dry in the middle and have dark edges. A whitish fungal mycelium develops on the underside of the leaf, from which yellow fruiting bodies later develop. As the spores ripen, they turn black, while the fungal network on the leaves hardens and appears brown.
Tips
This species rarely affects shoots and does not infect fruits.
Does fighting make sense?
Usually there is no need to fight the condition directly. If the crop is badly affected, you can use pesticides with potassium hydrogen carbonate. Lecithin, which is found in milk, is also found to be effective against this mildew. Sulfur-containing products, which at Gall mites are used have a side effect on powdery mildew fungi.