You’re excited that you can finally enjoy fresh, homegrown zucchini. Then you go out to the garden and notice that your normally green and bright zucchini leaves are losing their luster and there are white spots all over the leaves. Unfortunately, your zucchini has probably just fallen victim to powdery mildew. Here’s how to recognize, treat and prevent powdery mildew on zucchini.
Table of Contents
- Zucchini diseases: What is powdery mildew?
- Zucchini leaves turn white: prevention and control.
- What helps against powdery mildew on zucchini?
- Air circulation is particularly important
- Cut off infected leaves with white spots
- Fertilize zucchini correctly
- Home remedy against powdery mildew on zucchini – buttermilk spray
- Fight powdery mildew naturally with baking soda
- Neem oil as a natural remedy against powdery mildew on zucchini
- Zucchini leaves have white spots – treatment with vinegar
Zucchini diseases: What is powdery mildew?
Powdery mildew is caused by various fungal spores that get onto plants through the air and by splashing up from the soil when it rains. The fungus alone is not harmful, but once it gets on your plants, it germinates and starts sucking nutrients from the surface of the plant leaves. In the final stages of powdery mildew infection, zucchini leaves turn yellow and crisp, causing them to shrivel and die.
Powdery mildew (see pictures) is one of the most common plant diseases, and because its appearance is so distinct, it is relatively easy to spot. This plant disease makes the leaves look like they have been dusted with talcum powder. They are white to gray and the disease likes to appear in the summer. Most of the white dust consists of spores that are easily transferred by the wind to other leaves nearby.
Powdery mildew likes low light and temperatures of 20 °C – 30 °C with high humidity (above 95%). However, when the temperature rises above 32 °C, some of the spores die. You can learn more about downy mildew here .
Zucchini leaves turn white: prevention and control.
What helps against powdery mildew on zucchini?
A simple way to control powdery mildew is to keep the foliage of the plants as dry as possible. This means you should always water from the base of the plant rather than wildly spraying the garden with a hose.
Air circulation is especially important
Good air circulation is also important, so make sure you design the space for your plants in the garden appropriately. Every plant needs enough room to grow, and if you give it some space, the stems and leaves will dry faster after a downpour. Also, make sure your plants get plenty of sunlight.
Adequate spacing will also prevent powdery mildew from spreading to a neighboring plant.
Cut off infected leaves with white spots.
Cut off leaves that show the first signs of infection as soon as possible. Throw them in the trash and do not leave them in the compost pile. Remove and destroy all infected plants at the end of the growing season to get rid of as many spores as possible.
Cut half the leaves off each plant early in the season to reduce humidity around the plant and reduce the likelihood of infection.
Fertilize zucchini properly
Do not give nitrogen fertilizer in the middle of the growing season. This will trigger a new growth spurt that will increase susceptibility to the disease.
Home remedy for powdery mildew on zucchini – buttermilk spray.
The use of a diluted milk solution in organic horticulture has long been known and used to treat a variety of plant problems. Why do milk and buttermilk work in the treatment of fungal diseases of plants? The exact reason is not known. There are different opinions about how much to dilute milk solutions. There is much less information about the correct ratio for diluting buttermilk.
The most effective dilution that has been tried is to use 1 part buttermilk to 3 parts water. Simply add 60 ml of buttermilk and 180 ml of water to a spray bottle and shake the solution well. Spray the top and bottom of all zucchini leaves every 2-3 days until the powdery mildew is gone.
Fight powdery mildew naturally with baking soda.
Another common remedy for powdery mildew is baking soda. Add 1 teaspoon to 1 liter of water and spray the plant thoroughly.
Neem oil as a natural remedy for powdery mildew on zucchini.
Neem oil is also a common organic remedy for treating fungal diseases on plants . Extracted from the seeds and fruits of the tropical neem tree, neem oil is commonly used as a pesticide. It is best used preventively, before powdery mildew becomes too severe. Use caution when applying neem-based products, as they are mildly toxic to fish and other aquatic life. Do not spray when bees are active.
Zucchini leaves have white spots – treatment with vinegar.
It is a fairly simple remedy : you need 1 l of water and 1/2 tablespoon of vinegar. Fill a spray bottle with the water-vinegar solution and leave it in your garden so that it is always ready to do its job. Spray the top and bottom of the leaves once a week. The reason this spray is effective is pretty simple. Powdery mildew can’t grow in a moist environment and the vinegar changes the pH of the water and spores it encounters, which the mildew also hates.