Powdery mildew

Powdery mildew: life cycle & resistance management advice

Powdery Mildew - Main


The symptoms appear on leaves, shoots, buds, thorns, peduncles and flowers as a powdery, whitish growth (mycelium, conidiophores and spores) of the mildew fungus. Severe mildew damage reduces leaf growth, aesthetic value of plants, photosynthetic efficiency and thereby plant growth. Plants can be severely stunted if they are heavily infected early in the growing season. When the environmental conditions are favourable, the affected leaves may fall prematurely.


Pruning infected shoots, greenhouse sanitation, adequate ventilation and fungicide applications.

Powdery Mildew Life Cycle

Understanding a disease's life cycle is vital to maintaining control in your crops. Below is the powdery mildew life cycle:

Powdery Mildew

Managing resistance

The mycelium of powdery mildew on the leaf looks like a dry white powder. The name “powdery mildew” is a very descriptive and sums up the fungus’s appearance on the leaf surface very well. The fungus does not like moving water such as rain or irrigation. It is a fungus that can infect many species in almost any floriculture crop. Powdery mildew doesn’t 'destroy' the plant, but is more of a parasite, which could ultimately result in the death of heavily infected plant material. For the germination of the spores, moisture is not essential, which is why the fungus is also difficult to manage by controlling the environment.

To prevent a crop developing resistance it is important that you alternate between the different active ingredients. It is important to pay attention to the mode of action the product has. Rotation of products is a key strategy but it’s important those products have different FRAC codes, as this can reduce further resistance development. Ensure your program takes this into account. If you are in a situation where products with the same mode of action are applied twice in a row, moving to another product with a different FRAC group becomes more even more important.

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