Prevent and Control Powdery Mildew

Powdery mildew is a fungal disease that is one of the more common plant diseases that many home vegetable gardeners will experience. Powdery mildew is in the order of Erysiphales which contains one family named Erysiphaceae of which many cause powdery mildew.

Powdery mildew begins on a host plant, in this case one of your vegetable plants, when the sexual ascospores, or the asexual conidia germinating on the surface of the plants leaf or stem, resulting in septate mycelium of uninucleate cells.

Powdery mildew is one of the easier plant diseases to spot. If your plants are affected, what you will see are white powdery spots on the leaves and stems. Powdery mildew is most prominent on the lower leaves although powdery mildew will appear on the upper leaves as it progresses. If left untreated, the spots will get larger and more dense as more spores form.

Do you live in an area or environment where you will experience high humidity and moderate temperatures? If so, then you are more likely to experience Powdery mildew.

So what will powdery mildew do to your plants if not addressed? Chances are it won’t kill your plants, but will contribute to the reduction of fruit and vegetable yields.

While many home vegetable gardeners are looking for a cure for powdery mildew, one simply does not exist. So what you need to do is take steps to preventing and controlling powdery mildew. Two good things to make sure your plants are receiving in helping with prevention is air circulation and direct sunlight. Both have shown to inhibit powdery mildew formation.

But, let's say that powdery mildew already exists on your plants. What you have to do now is move into "control" mode. According to Organic Gardening, "Research studies in 1999 and 2003 on infected zucchini and winter wheat (respectively) indicated that spraying cow's milk slowed the spread of the disease."

By mixing 1 part milk and 9 parts water (by volume), you will create a spray that can then be applied to your affected plants. Also you can try a mix of 1 teaspoon of baking soda with 1 quart of water as a spray. This helps raise the pH, which is not a suitable environment for powdery mildew.

At the end of the season, remove all plants that were affected with powdery mildew, bag them up and throw them away. While some sources say they are ok to add to your compost pile, I take a more cautious stand and do not do so.