Powdery mildew

in : Problems: Flowers

Symptoms

In summer, a white powdery coating covers the leaves and possibly the shoot tips and flowers too. Leaves may then become discoloured and distorted, with poor growth and even dieback.
Find it on shrubs
Time to act summer

Problem categories

Overview

There are many different fungi that cause this problem, each of which usually affects a particular plant or group of plants. In each case they produce similar symptoms. Affected plants will have discoloured leaves, often also distorted when young, while general growth and vigour is poor. Also learn about powdery mildew on roses.
Solution
In summer, a white powdery coating covers the leaves and possibly the shoot tips and flowers too. Leaves may then become discoloured and distorted, with poor growth and even dieback.
Organic
Prune out affected parts of the plant and destroy. Healthy plants are less prone to attack, so make sure you water regularly and mulch around them to conserve moisture in the soil. Space out your plants to avoid over-crowding and thin out congested growth to improve the airflow. Also minimise the use of high-nitrogen fertilisers, as these lead to lots of soft, leafy growth, which is vulnerable to an attack. Get rid of weeds as they can spread the fungus.
Chemical
Spray ornamental plants with myclobutanil or sulphur. Always check the label first if you're using these products on edible crops.

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Talkback: Powdery mildew
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jegpad 24/11/2011 at 15:29

Apparently mildew has been a prolific problem this year according to Mail Order Trees from whom I purchased a 2 year old Amelanchier canadenisis which quickly developed the disease. Have pruned heavily and will spray with fungicide.

Barbara_Smith 24/11/2011 at 15:29

I have powdery mildew on an red acer tree (I think it's a Crimson King Maple) which is over 25 years old. It had been heavily pruned in recent years to allow some more light in the garden. The mildew has also affected some other plants in the garden, ie my trailing begonias, this year. Should I take the tree out altogether?