Powdery Mildew

dealing with a powdery mildew problemThe term “Powdery Mildew” is used to refer to a group of several species of fungus that are spread from plant to plant via spores that travel in the wind. What separates this type of fungus from other types is its tendency to thrive in dry conditions. Powdery mildew begins as small white spores that slowly begin to take over an individual plant. In cooler, wetter conditions the fungus will not spread as well. Eventually, it does tend to affect nearby plants. The type of plant affected is dependent upon the specific species of mildew. Over time, powdery mildew will cause the plant’s growth to slow, and an overabundance can prove deadly.

Need to know…

  • “Powdery Mildew” refers to several different species of fungus.
    • The type of plant affected depends upon the specific fungus.
    • The fungus thrives in dry, warm conditions.
    • Will slow growth of the plant and can cause death.

Dealing with a Powdery Mildew Problem

As with other types of fungus or plant infection, you will first want to take a close look at your plants to ensure proper identification of the problem. Plants suffering from powdery mildew will appear to have a coating of flour wherever the spores are present. You may find the mildew spores on leaves, fruit, or stems. Typically, they appear first as small, white, circular spots. Usually, the first afflicted area is the tops and undersides of the leaves, so be sure to pay close attention to these areas.

Additionally, younger plants are more susceptible to damage from powdery mildew than more established plants. You may notice leaves turning yellow or beginning to appear dry. Over time, leaves may also become disfigured, twisted, or broken. While this can become a problem at any time, symptoms are most common late in the growing season.

Though powdery mildew thrives in dry conditions, it does require somewhat high humidity. This means that powdery mildew can tend to be a problem anywhere where you have a high number of plants with poor air circulation, such as indoors. Therefore, allowing drainage trays to remain full, failing to prune overgrown or overcrowded plants, or watering plants from above are other factors that can add to the relative humidity in an enclosed space and increase a plant’s likelihood of developing powdery mildew.

Types of Problems Caused:

  • Powdery mildew slows plant growth
  • Younger plants are most sensitive
  • Look for yellow, misshapen or broken leaves.
  • Reduce relative moisture – moisture in the air – to reduce susceptibility to mildew.
  • Prune overgrown and crowded plants to encourage air flow.
  • Empty drainage trays often.

Getting Rid of Powdery Mildew

Fungicides are a common recommendation for those struggling to eradicate an overgrowth of powdery mildew. However, we strongly encourage anyone committed to growing organic greens and produce to avoid chemical fungicides and insecticides regardless of the appeal for a “quick fix.” In the long run, the damage done by adding toxic chemicals to your precious soil cannot be understated. We have developed this site to help others grow safe, healthy food that will make your bodies feel good, inside and out! With a little patience and creativity, we can avoid using poisons and keep your gardens and farms safe and pest-free too.

In order to get rid of powdery mildew once it has already begun to affect a plant, you will need to do a bit of damage control. Using clean, sharp shears, remove all of the parts of the plant that appear to be infected. Make sure to throw these infected plant parts into the trash or otherwise dispose of them far away from any other plants.

Remember the wind helps spread fungus spores, so it’s not recommended to burn your plants.

After removing any infected parts, treat the remaining plant(s) with organic fungicides such as neem oil (affiliate link), sulfur (affiliate link), lime-sulfur or potassium bicarbonate.

Methods for Removal:

  • Trim all infected plant parts.
  • Dispose of infected parts safely – spores can travel.
  • Treat plants with organic fungicides
  • Neem Oil (affiliate link)
  • Sulfur (affiliate link)
  • Lime-Sulfur
  • Potassium Bicarbonate

For prevention of powdery mildew, always keep your plants pruned and drainage trays emptied. Additionally, you may mix one teaspoon of baking soda into one quart of water and spray plants with this solution to kill growing fungus. Since the solution will only kill fungus if it comes directly into contact with it, be sure to spray your plants thoroughly.

Finally, an option we prefer is to plant mildew-resistant crops such as cucumbers, squash, and melons, which are least likely to develop the fungus in the first place. Of course, always ensure you are purchasing seeds from a quality source. Finally, ensuring that you maintain the cleanliness of your grow space with an effective enzyme cleaner (affiliate link) is our last recommended step for defeating the dreaded powdery mildew.
Happy Gardening!