Powdery mildew in indoor hydroponics

Indoor hydroponics is great because it is contained indoors and is in a controlled environment. This means that pests and diseases will not come in to harm your harvest. Or does it?

No matter how well we try to seal off indoor hydroponics from the outside world, in a typical home, there are gaps and holes, and some pests are actually too small to even be able to keep out. Powdery mildew fungus spores, for example, can travel through even the smallest holes and attach itself to your plants. From there, they will start colonies that eventually cover the stems and leaves of your plant, and reduce your overall yield.

What does powdery mildew look like?

Powdery mildew is a fungus that grows on the surface of a wide variety of plants. Its presence is made quite obvious by a smooth, white layer of growth and a distinct smell.


Generally, less healthy plants are more likely to be affected, but it can affect healthy plants, too. An immediate effect of the fungus apart from being unsightly is that it blocks light, and prevents the leaf from completing photosynthesis. As a result, infected leaves will eventually die and fall off.

How can I treat powdery mildew?

In an indoor hydroponics setup, it isn't as easy or practical to spray leaves with common solutions such as milk, potassium bicarbonate, or neem oil, as the sprayed liquid can contaminate areas such as the deep water culture nutrient solution (you don't want rotten milk sitting in deep water culture!)

The best way would be to temporarily remove the plants from the deep water culture setup and treat them in a separate location. This can be a tedious process, but in severe cases may be your only option.

How can I prevent powdery mildew in indoor hydroponics?

The best way to avoid this problem is to try to prevent it from happening in the first place. Powdery mildew spores are impossible to spot, but they are generally brought indoors via the wind or on contaminated objects brought indoors. On windy days, try not to let the wind carry dust and other particles into the house, and always change your clothes before handling your plants after returning home.

If possible, choose a location that is farther away from the exterior environment. That means placing your grow area as far as possible from windows and vents. Don't forget that you still need sufficient ventilation to keep humidity levels in check, but this can be accomplished without placing the plants so close to a potential contamination source.

Be on the lookout for powdery mildew on your plants as well, as early detection is key to suppressing the colony and preventing it from spreading. In many cases, it can grow near the base of the plant and on the underside. If you do identify powdery mildew growth, very carefully remove the plant from the grow area, as any vibrations or ruffling of the leaves can release and spread more spores to other plants. Once isolated, either dispose of, harvest, or treat the infected leaves or the whole plant. Be aware that powdery mildew spores can lurk on dead leaves as well, so be sure to dispose of them completely.

Is powdery mildew harmful to humans?

There is no known evidence that powdery mildew is harmful to humans. It can typically be rinsed off pretty quickly under lukewarm water. Therefore, as soon as you see powdery mildew, simply eating the infected leaves can be a useful and non-wasteful containment strategy.

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