Natural Plant Mildew Control

Garden plants can fall prey to a variety of fungal diseases, but powdery mildew is one of the more common culprits. White or gray powdery growth on leaves, stems, fruits and flowers weakens the plants and can stunt their growth or kill them. Combating mildew naturally without chemicals requires a combination of the right cultural care and the proper use of organic fungicides. It's easier to eradicate the mildew if you catch the problem early, before it has a chance to spread or weaken the plants.

Air Circulation

Powdery mildew and other plant fungal diseases thrive where air circulation is poor. Spacing plants properly for their expected mature size minimizes mildew problems because fresh air reaches the interior of plants. Thinning overgrown plants also helps eradicate mildew because it opens up the interior of the plant to sunlight and air circulation. Keep areas around the plants or garden bed well weeded so the weeds don't overcrowd otherwise healthy plants and encourage the spread of mildew.

Water Management

Foliage left wet becomes prone to mildew and other diseases. Watering plants at the base, such as with a drip irrigation hose, keeps the leaves dry and helps prevent mildew. Because spores settle and begin growing first on dry foliage, rinsing the leaves with water occasionally can keep them free of mildew spores. If you do rinse, do so in the morning on a dry day so the leaves have time to dry before nightfall. Rinsing primarily helps prevent mildew, although it can also stop the spread of the disease from infected plants to healthy ones.

Sanitation Practices

Proper garden sanitation can prevent mildew spread and help eradicate existing mildew. Keeping beds well-weeded prevents mildew from spreading from weeds to garden plants and also ensures proper air circulation. For small infections, removal and disposal of afflicted leaves can control the powdery mildew. Rinse pruning shears in a dilute solution consisting of 1 part bleach to 9 parts water after each cut where you remove mildewed material. Only prune infected plants when they are dry.

Organic Fungicides

Badly infected plants may require more than cultural care and pruning to eradicate the mildew. An organic oil, such as neem oil, coats the leaves so mildew can't grow. It works best when you apply it at the first signs of mildew and reapply every seven to 10 days. Sulfur dust products and biological fungicides that contain mildew-eating bacteria can also eradicate mildew. Apply these as indicated on the package, usually at two-week intervals. Check labels carefully to ensure the products are certified organic and only contain natural ingredients.

About the Author


Photo Credits

  • Tom Brakefield/Stockbyte/Getty Images
bibliography-icon icon for annotation tool Cite this Article