I’ve learned from this article in the Almanac what is affecting my zucchini – powdery mildew! I pasted a snippet of the article below. I really need to get a handle on this! in my own garden! What I’ve thought was the natural end-of-life for the plants may actually be more due to damage by powdery mildew the entire time…
HOW TO IDENTIFY POWDERY MILDEW DAMAGE
- Plants infected with powdery mildew look as if they have been dusted with flour.
- Powdery mildew usually starts off as circular, powdery white spots, which can appear on leaves, stems, and sometimes fruit.
- Powdery mildew usually covers the upper part of the leaves, but may grow on the undersides as well.
- Young foliage is most susceptible to damage. Leaves turn yellow and dry out.
- The fungus might cause some leaves to twist, break, or become disfigured.
- The white spots of powdery mildew will spread to cover most of the leaves or affected areas.
- The leaves, buds, and growing tips will become disfigured as well. These symptoms usually appear late in the growing season.
Powdery mildew first appears as small white spots on the upper part of the leaves. Photo Credit: The Regents of the University of California, UC Davis.
CONTROL AND PREVENTION
HOW TO CONTROL POWDERY MILDEW
- Remove all the infected plant parts and destroy them. Remember, do not compost any infected plant, as the disease can still be spread by the wind and persist in the composted materials.
- Spray infected plants with fungicides. Effective organic fungicides for treating powdery mildew include sulfur, lime-sulfur, neem oil, and potassium bicarbonate.
PREVENT POWDERY MILDEW
- Choose plants that are resistant or tolerant to powdery mildew. Many mildew-resistant varieties of cucurbits (melons, cucumbers, squash, etc.) have been developed and can be bought from major seed suppliers.
- Avoid watering plants from overhead in order to reduce relative humidity.
- Selectively prune overcrowded areas to increase air circulation; this also helps to reduce humidity around your plants.
- Spray your plants with the fungicides mentioned above according to the directions included with the products.
- If you don’t want to use fungicides, try spraying your plants with a bicarbonate solution:
- Mix 1 teaspoon baking soda in 1 quart of water. Spray plants thoroughly, as the solution will only kill fungus that it comes into contact with.”