Stop Mildew in an Organic Garden

Use Natural Controls to Prevent and Treat Fungal Diseases

Sep 8, 2008

Powdery mildew and downy mildew damage plants with white or gray patches on leaves, stems, and flowers. Use cultural methods or organic sprays to control these diseases.

Powdery mildew and downy mildew are cruel diseases in the organic garden. After the gardener has ushered his tender seedling babies into adulthood, fought off aphid attacks with the blast of a hose, and suffered through late frosts that threatened early blooming lilacs, stealthy fungal diseases can catch one off guard.

Identifying Garden Mildew

Mildew diseases thrive in conditions of high heat and humidity, so they most often appear in the peak of summer. In the earliest stages, the garden fungus that causes mildew may look like a bit of benign white dust, perhaps a circular spot or patch where some water dried and left a bit of residue. As the disease spreads, the leaves of affected plants may curl, wither, or drop off altogether.

Many plants can experience mildew, but some are notoriously susceptible. Roses top the list, especially hybrid tea roses. Lilacs, phlox, zinnias, and bee balm commonly show signs of mildew around the summer solstice. As if the insult to the flower garden wasn’t enough, mildew affects several vegetable garden favorites, including melons, spinach, lettuce, and cucumbers.

Cultural Control

The first tool in the organic gardener’s mildew arsenal is a strategy that denies the fungus an environment that promotes the growth and spread of the spores. Cultural control of garden mildew starts with planting, as gardeners must observe proper spacing requirements to promote air circulation. In bushy shrubs like roses and lilacs, you must use your pruning tools judiciously to thin weak or crossing branches that do little to contribute to the beauty of the plant, but prevent drying breezes from reaching its interior.

If you have a severe mildew outbreak in the garden, remove and destroy the plants. You may manage minor outbreaks by pruning away the infected foliage. Clean up all dropped leaves at the end of the growing season, as the spores spend their winter dormancy in your garden debris, waiting to shoot into the air and reproduce anew in the spring.

Observe smart irrigation practices in the garden. Drip irrigation not only saves water by delivering it directly to the root zone where it’s needed, but it also keeps the leaves dry. Water your gardens in the early morning, so the sun can hasten foliage drying.

Organic Fungicides

No spray can increase the appeal of a lettuce crop sporting fuzzy gray patches, but you can use organic fungicides on your fruit trees and flowers. Fortunately, for organic gardeners, compost can act as natural fungicide when made into compost tea. Place a shovelful of compost into a 5-gallon bucket of water overnight, strain, and spray the resulting tea onto grape vines, apple trees, or strawberry plants.

Baking soda is an old-fashioned natural remedy for garden mildew, with varying rates of efficacy. Researchers have improved on the simple sodium bicarbonate found in our pantries by combining it with surfactants and horticultural oils. You can look for these products under the brand names of Remedy or Kaligreen to fight a number of garden molds and mildews.

The copyright of the article Stop Mildew in an Organic Garden in Organic Gardens is owned by Jamie McIntosh. Permission to republish Stop Mildew in an Organic Garden in print or online must be granted by the author in writing.