The majority of the growth of most powdery mildews is found on the plant surface. The fungus sends feeding structures into the surface cells, greatly reducing the vigour of the plant. Because of this surface growth, powdery mildews are even more influenced by the environment than other plant diseases. Choosing the right plant for the right place, along with some simple measures to adjust the environment can go a long way to minimising powdery mildew issues in gardens. Clean up and destroy fallen leaves to reduce the amount of the downy mildew pathogen surviving the winter Galls should be removed promptly before the fungus sporulates (the white stage when the spores are released and the disease can spread) Mulch plants each season to avoid drought stress, which predisposes them to powdery mildew infection, and make sure vines are adequately watered helping to prevent this problem There are no products available to amateur gardeners for the control of either downy mildew or grey mould.

Don’t plant too densely, giving space between plants. Aim for an open environment to increase air circulation and reduce humidityPowdery mildew: the powdery mildew fungus over-winters in the buds and when these start to growin the spring it produces airborne spores which spread the disease. The pathogen originated in north America, but is now present wherever vines are grown. Leaf infection reduces plant vigour. When fruits are infected they split as they expand and this allows secondary infection by grey mould ( Botrytis cinerea). Powdery mildew or leaf spots: leaf removal is not recommended as it would cause severe defoliation. Unless very severe, these infections should be tolerated

Petal blight: the fungus causing petal blight produces wind-dispersed spores on old infected flowers which remain hanging on the plant from the previous season. Asexual spores (conidia) of the g rey mouldfungus are always present in the air. They require leaf wetness or very high humidity to germinate and infect. Damaged or senescent plant parts are a very common way in which the fungus gains entry to the plant. The disease has a huge host range, and is active over a wide temperature range.When to use: At the beginning of an infestation or when the first symp toms become visible. The maximum number of applications is limited for reasons specific to the active substance. For this reason, sufficient control cannot be expected in all cases. If necessary, products that have other active substances can be used subsequently or alternately. Thorndown’s Wood Paint is now available in 72 colours – so you’ll be spoilt for choice! Highly water-repellent and durable, it is also available in UV Clear for a natural timber look.