Powdery Mildew

Definition - What does Powdery Mildew mean?

Powdery mildew is a common fungal disease that affects many different plants. It is caused by a wide array of fungi of the Erysiphales order. Pososphaera xanthii (aka Sphaerotheca fuliginea) is the most common reported cause.

Powdery mildew is easy to spot by the white, powdery residue that covers leaves and stems on the infected plant.

MaximumYield explains Powdery Mildew

Powdery mildew grows best in high humidity and moderate temperatures, with greenhouses providing the most optimal growing conditions. Powdery mildew can infect everything from common houseplants to field crops such as squash, beans, or cucumber. It also affects many landscape plants and legumes including soybeans.

Chemical methods, genetic resistance, and careful farming are the common methods of controlling powdery mildew in agribusiness and professional horticulture. If not monitored and treated, powdery mildew can lead to low yields or even crop failure.

There are many home remedies for the average gardener, as well. Milk is a common remedy popular with gardeners when it is diluted in water and sprayed on plants at the first signs of the disease. A weekly application is suggested thereafter. Exactly why milk is an effective treatment isn’t known, but it is believed to be the result of the protein in whey that produces free radicals when exposed to sunlight. Contact with these radicals is toxic to the powdery mildew fungi. There are also commercial fungicides available, but most often these are generally used only in an agricultural setting.

Another popular treatment is a careful weekly washing. This works best on plants with glossy or waxed leaves such as a spider plant, but not on textured leaves such as an African violet.

Because powdery mildew is so widespread and can infect so many species of plants, a grower must remain vigilant to the early signs of the fungal disease.

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