Downy Mildew

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Related to Downy Mildew: powdery mildew, damping off

downy mildew

[¦dau̇n·ē ′mil·dü]
(plant pathology)
A fungus disease of higher plants caused by members of the family Peronosporaceae and characterized by a white, downy growth on the diseased plant parts.

Downy Mildew


a dangerous plant disease caused by parasitic fungi of the class Phycomycetes of the family Perono-sporaceae. It attacks the green parts of the plant, primarily the leaves. Spots form on the diseased parts of the plant; the lower portions of the spots are covered with a whitish, grayish, or violet film, which is the sporangiosphore of the fungus (zoosporangia with sporangiosphores). Zoosporangia may appear repeatedly during the growing season; disseminated in the air, they are the principal source of infection. High humidity and soil with high moisture content foster the development of downy mildew. In most of the causative agents, the mycelium lives one year, dying along with the affected parts of the plant. However, sometimes it is perennial, surviving in bulbs, roots, and other wintering organs. All species of the family Peronosporaceae are obligate parasites, extremely specialized in their nutrition (requiring a specific host). The most injurious downy mildews are those that infect grapes, cabbages, turnips, onions, alfalfa, cucumbers, sunflowers, beets, tobacco, and several other cultivated plants.

Control measures include the implementation of correct cultivation procedures, the selection of resistant varieties, and dusting or spraying the plants with fungicides.


References in periodicals archive ?
Unfortunately, this summer has been a perfect year for downy mildew and this, of course, is one of the few diseases that can devastate Impatiens.
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ATHE grotty weather at the end of this summer and into early autumn meant that there was a lot of downy mildew fungus about, and I'm fairly sure that this is what attacked your lettuce - it certainly had a field day on some of my varieties.
He also has found that the spores of some species, such as the downy mildew fungus (which causes disease in onions), are propelled in these parallel trajectories even though they are borne in grape-like clusters.
Folpet is a broad-spectrum fungicide with excellent control effect against vegetable diseases, such as downy mildew and leaf spot.
It gets its name from Bordeaux where it was first found to be effective in treating downy mildew on vines, and although no longer available for sale, you are allowed to mix your own, applying once in early July and again four weeks later.
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