Powdery Mildew Management Guide

Caring for your garden means protecting your plants from harmful diseases. Several fungal diseases can affect your indoor and outdoor plants, including powdery mildew. This disease can damage and weaken plants once it gets established. We’ve gathered information to help you control and prevent powdery mildew. 

Powdery mildew is a disease that is caused by fungi spores. The spores are spread via the wind, infecting plants they come in contact with. Early signs of powdery mildew include white spots on plant leaves. These spots will begin to connect, forming large white patches. The presence of powdery mildew can result in leaves yellowing or turning brown and crumbling. It can also cause leaf drop. This disease thrives in dry soil and areas with high humidity. It most often develops during mid to late summer, especially in dry, warm climates. Powdery mildew can affect many types of plants including flowers, fruit trees, shrubs, and grasses. 

Inspect Plants Regularly: Before purchasing a new plant, examine it for signs of powdery mildew. Look for discoloration or damage to leaves. You’ll also want to inspect the plants you already have. Catching a problem early will make it easier to stop it and prevent it from spreading to other plants.

Set Your Plants Up for Success: To help minimize your plant’s susceptibility to powdery mildew, you want to make sure it receives the nutrients, water, and sunlight it needs. Know the needs of your plants and place them in areas where they will receive the correct amount of sunlight. Water your plants as needed.

Create Space Between Plants: To prevent powdery mildew, you’ll want to make sure there is good air circulation. Provide adequate spacing between plants to improve airflow. Pruning your plants can also help to create space for your plants.

Remove Infested Plants: If you notice powdery mildew developing on your plant, you’ll want to prune the infected leaves. Be careful to not shake the leaves to prevent the spores from spreading. After pruning, disinfect your garden shears to ensure you don’t spread the disease to other plants.

Use Mulch in Your Garden: Powdery mildew thrives in dry soil. Adding mulch to your garden will help to preserve the moisture, helping to prevent powdery mildew.

If your plants are dealing with powdery mildew, you’ll want to treat them with a spray labeled for fungal diseases. Maggie’s Farm offers two products that can help to prevent and control powdery mildew.

Plant-Based Insecticide Sprays

Our 3-in-1 Garden Spray and our Vegetable Garden Insect & Disease Control spray are labeled to prevent and control powdery mildew and other common diseases. Our 3-in-1 Garden Spray is formulated using plant oils as the active ingredients. It is a triple defense fungicide, insecticide, and miticide. It can be used for home gardening and applied to flowers, shrubs, vegetables, herbs and other edible plants, and ornamental plants. Our Vegetable Garden Insect & Disease Control spray is formulated with pyrethrins. It can be used in home gardens, home greenhouses, and on indoor plants. This product can be applied to vegetables, flowers, ornamental trees and shrubs, and fruit or nut trees.

Application Tips

When treating your plants, it’s best to spray early in the morning or in the evening. Avoid spraying in the heat of the day. For best results, apply as a protective spray early in the season before diseases are noticed. Thoroughly spray all parts of the plant, including the underside of leaves. Our 3-in-1 Garden Spray should be applied so that the solution runs off the tips of the leaves. It can be applied every 7–10 days and can be used up to the day of harvest. Our Vegetable Garden Insect & Disease Control shouldn’t be used if temperatures are expected to be over 90° F. Don’t wet plants with this product to point of runoff or drip. It can be applied every 7–10 days and can be used up to the day before harvest.

It is always best to test treat a small inconspicuous area of the plant first before applying to the entire plant.

It's important to take steps to protect your plants from powdery mildew. Implementing preventative measures and using the right products can help to control this fungal disease.