Prevent & combat powdery mildew on begonias: How to get rid of the fungal disease

Prevent & combat powdery mildew on begonias: How to get rid of the fungal disease

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If begonias suddenly get stains on the leaves, this is a sure sign of a mildew infestation. Then quick action is important to save the plants.

Begonias can also be affected by powdery mildew Begonias are resistant to most pests and diseases. Nevertheless, powdery mildew can also occur if properly cared for. The fungal disease shows up with spots on the leaves. But be careful: powdery mildew is not the same as powdery mildew. Here you have to distinguish between the wrong and the real one. But no matter what it is: natural and chemical agents are suitable for fighting. Sufficient moisture is important as a preventative measure.

Downy mildew and powdery mildew on begonias

Both the downy mildew and the powdery mildew are fungal diseases. Both damage the plant and cause the leaves to die. The infestation can spread to the shoots and leaves. You can recognize the infestation by:

Wrong mildew:

The downy mildew initially shows up on the underside of the leaves and forms a mosaic-like coating. The color can be brownish, bluish or greenish. Later the covering spreads out on the top of the leaves.

Powdery mildew:

Powdery mildew is visible in the early stages on the leaf margins. It is a whitish-gray covering. The infestation spreads to the entire leaf if you do nothing about it.

Causes of mildew infestation

Begonias need enough moisture to stay healthy and resilient. Usually the leaves of the begonia are fleshy to succulent. A leaf that is too dry therefore forms a good landing site for fungal spores. The humidity in the room also plays a role in indoor begonias. A small infection is sufficient, which can break out with great caution.

Warning, now it gets tricky: powdery mildew can break out if the environment and the earth are too dry. Downy mildew, on the other hand, spreads when the climate is too humid. Too much moisture on the leaves promotes infestation. The right balance is important!

How to prevent an infestation

The best prevention is to monitor your begonias on a regular basis. Healthy begonias have intact leaves. Resistant begonia leaves feel e.g. fleshy and thick, they give way slightly at the touch of a finger. A possible infestation is quickly visible, but fortunately there are effective antidotes.

Fighting mildew: the best methods

Milk-water mixture:

Get rid of mildew with a really simple remedy: milk. It effectively repels the fungal parasites from the leaves! All you have to do is mix milk and water in a ratio of 1: 9. Then spray the diseased plant twice a week with the solution. Recent research has shown that there are microorganisms in milk that fight the mildew fungus. The sodium phosphate contained also strengthens the plant.


It is also helpful if you spray the begonias with field horsetail tea (instructions for making the tea can be found here). In addition, you must also remove heavily infested plant parts and dispose of them in the household waste. Not about the compost! Otherwise the mildew could spread in the garden.


If the natural methods don't help, a chemical antifungal agent has to be found. Fungicides quickly and reliably eradicate the fungi. The sprays are not harmful to the plant. We recommend e.g. Compo Duaxo Universal mushroom-free (e.g. available here). But first try the tip with the milk. It has been found that milk is often said to be even more effective than commercially available fungicides. So before you reach for the chemical club, try the natural method first.