Three Most Common Fungi Found on Plants

May 27, 2020
Category: Growing Tips

Fungus is a threat to any greenhouse that holds humidity, but it can be treated.

The three most common fungi found in greenhouses are:

  • Powdery Mildew
  • Botrytis
  • Fusarium Wilt Disease

Powdery Mildew

Powdery Mildew prefers cooler temperatures and thrives in humidity.

Be on the lookout for it anytime you have cool, cloudy weather.

This fungus will spread through the air. If you see one plant with Powdery Mildew, the surrounding plants are likely to soon be infected.

Powdery Mildew starts off as small spots of white powder. This powder can appear fluffy at times.

Infected leaves left untreated will turn brown and die. Nutrients will not reach the plant, and it will suffer.

You can treat Powdery Mildew with a fungicide. For best results, follow the instructions on the label closely. 

If you are looking to keep your crops organic or just looking for a safer alternative, you can find organic fungicides to treat Powdery Mildew.

We do not feel that it is necessary to remove the infected leaves unless you feel that it is absolutely necessary due to a major outbreak.


Botrytis also thrives in humidity and can be spread from plant to plant through the wind, water, and gardening tools.

This fungus feeds on debris such as dropped petals and leaves, and wounded plants leaking nutrients. Once it is fed, it will begin infecting your crops.

Botrytis first takes the appearance of a white growth, but it quickly darkens to a grey color.

Begin by removing the debris from infected plants, as well as those that are not yet infected.

Then remove the debris from the greenhouse. Plant waste left sitting in the greenhouse is a breeding ground for pests and a feeding ground for fungi.

Lastly, spray the infected plants with a fungicide. Follow the instructions on the label for the best results.

If you are looking to keep your crops organic or just looking for a safer alternative, you can find organic fungicides to treat Botrytis.

Fusarium Wilt Disease

Fusarium Fungus, also called “yellows,” is a soil-borne fungus. It enters the roots of young plants and stops the path of the nutrients.

This fungus likes warm soil and feeds on plant debris.

The first sign of Fusarium Fungus is wilting.

If your plants still look wilted after receiving water, you will need to check their roots and see if they are healthy and white or black and rotting.

Black and rotting roots are a sign of root rot, and the plants need to be treated or dumped.

Fusarium Wilt is a soil-borne fungus that will require a drench treatment.

Fully submerge the roots of the infected plants or inject fungicide into your hose if you are treating a large number of infected plants.

How can you prevent fungus on your crops?

  • Sanitize tools after use
  • Clear debris from pots
  • Don’t reuse contaminated soil
  • Reduce the humidity in your greenhouse
  • Allow plants to dry out (appropriately for the variety) between waterings
  • Apply preventative sprays during poor weather (but not in excess)
  • Rotate chemicals to prevent building up resistance

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