Cures for Powdery Mildew

Problem

• According to Princeton University powdery mildew is defined as "any of various fungi of the genus Erysiphe producing powdery conidia on the host surface." While this is rather technical and may not be easily interpreted by the home gardener, it can also be described as a fungal disease that impacts a vast array of plants but rarely kills them.

  Plants that tend to be highly susceptible to powdery mildew are vegetable plant, ornamentals, shrubs, many varieties of weeds, several different fruit trees and other types of trees and plants. This is a common disease but easy to spot and typically cured quickly.

  If you suspect you may have an outbreak in your backyard, look for common symptoms, since all powdery mildew fungi produce symptoms that are quite similar. Inspect your plants for areas of growth that are white or grey in patchy areas. You also may see very small dots that start out white, turn a yellow-brown color and eventually turn black. These dots are clusters of the fungus. These areas of fungi are typically found on the top of the leaf.

Cure

• You have three options when curing powdery mildew, chemical (pesticides) or cultural (organic). The cultural methods, as recommended by the University of Colorado Extension Program, suggests you should not use nitrogen fertilizer in the late-summer, as this limits the plants' ability to produce succulent tissue making them more prone to infection. Also, since powdery mildew thrives in humid environments, avoid using overhead watering systems that promote increased humidity levels. Ensure your plants are properly ventilated by pruning the plants to allow for better circulation of air.

  Removing as many infected plants as possible can significantly increase your chances of beating this fungus, but do not rely on your compost pile to get rid of your clippings--the temperature does not increase enough to kill the bacteria.

  If you are unable to achieve success curing powdery mildew through natural methods, a fungicide will probably be necessary. Appropriate fungicides include sulfur, Neem oil, potassium bicarbonate and triforine, all found in commercial products.

  In most circumstances, a combination of cultural and chemical treatment will be your best solution for curing powdery mildew. The fungicide should be applied to the infected plants weekly or bi-weekly throughout the growing season for optimal protection. Remember to always follow manufacturer's directions when using these products.