Powdery Mildew Of Laurel

Disease Information


Powdery Mildew

Powdery mildew is a fungus that can infect the new young leaves on Prunuslaurocerasus under humid conditions and between the temperatures of 6 to 30oC. Rainfall or drier conditions can interrupt the spread of the disease.

Powdery Mildew will not threaten the life of the plant but may look unslightly.

SYMPTOMS

A white powdery coating on the leaf, particularly the underside of the leaf.

Shrivelling of the new leaves.

Once the powdery coating dies off, the leaf will have brown patches or be completely brown and withered.

Management

There is normally no need for chemical control as the plants will grow through the disease once the growing conditions change to become less humid.

If the leaves look particularly unsightly, you can prune them off with a pair of secateurs or a hedgetrimmer. Disinfect the tools before using them on other plants.  Clear up any diseased leaves to prevent re-infection and burn or dispose of them. Do not compost them.

Food-grade Potassium bicarbonate at a rate of 5 grams per litre of water sprayed until run-off has been shown to control powdery mildew on many plants and is now used commercially. A number of applications may be necessary.

Products such as Bayer Fungus Fighter should result in control of powdery mildew.

Examples of Fungicides (Myclobutanil - Neem Oil – Propiconazole - Thiophanate-methyl )

 

 



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