Downy mildew
Downy mildew refers to any of several types of oomycete microbes that are obligate parasites
Obligate parasite
An obligate parasite is a parasitic organism that cannot complete its life cycle without dependence on its host.-See also:*Obligate intracellular parasite*Parasitism*Parasitic plant*Facultative parasite...

 of plants. Downy mildews exclusively belong to Peronosporaceae
Peronosporaceae are a family of water moulds that contains 17 genera, comprising more than 600 species. Most of them are called downy mildews. The closest relative of Peronosporaceae is Phytophthora....

. In commercial
While business refers to the value-creating activities of an organization for profit, commerce means the whole system of an economy that constitutes an environment for business. The system includes legal, economic, political, social, cultural, and technological systems that are in operation in any...

Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

, they are a particular problem for growers of crucifers, grape
A grape is a non-climacteric fruit, specifically a berry, that grows on the perennial and deciduous woody vines of the genus Vitis. Grapes can be eaten raw or they can be used for making jam, juice, jelly, vinegar, wine, grape seed extracts, raisins, molasses and grape seed oil. Grapes are also...

s and vegetable
The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....

s that grow on vines. The prime example is Peronospora farinosa
Peronospora farinosa
Peronospora farinosa is a plant pathogen. It causes downy mildew on leaves of wild and cultivated Amaranthaceae: Amaranthus, Atriplex, Bassia, Beta, Chenopodium, Halimione, Salsola, Spinacia, etc...

featured in NCBI-Taxonomy and HYP3.

Plant specific mildews

Hop Downy Mildew (caused by Pseudoperonospora humuli
Pseudoperonospora humuli
Pseudoperonospora humuli is a plant pathogen that causes downy mildew on hops and hemp.- External links :* *...

) is specific to hops
Hops are the female flower clusters , of a hop species, Humulus lupulus. They are used primarily as a flavoring and stability agent in beer, to which they impart a bitter, tangy flavor, though hops are also used for various purposes in other beverages and herbal medicine...

 (Humulus lupulus). The disease is the single most devastating disease in Western United States hopyards, since the microbe thrives in moist climates. Infected young hop bines
Bine (botany)
A bine is a climbing plant which climbs by its shoots growing in a helix around a support. It is distinct from a vine, which climbs using tendrils or suckers.The stems of many bines are rough or have downward-pointing bristles to aid their grip....

 become stunted with thickened clusters of pale curled leaves. These spikes have a silvery upper surface, while the undersides of leaves become blackened with spores. These dwarfed spikes are called "basal spikes". 'Lateral' or 'terminal' spikes occur further up the vine. An entire hop crop could be devastated in only a few days.

Similarly, cucurbit downy mildew (caused by Pseudoperonospora cubensis
Pseudoperonospora cubensis
Pseudoperonospora cubensis is a species of water mould known for causing downy mildew on cucurbits such as cantaloupe, cucumber, pumpkin, squash and watermelon. This water mould is an important pathogen of all these crops, especially in areas with high humidity and rainfall, such as the eastern...

) is specific to cucurbits (e.g., cantaloupe (Cucumis melo), cucumber (Cucumis sativus), pumpkin
A pumpkin is a gourd-like squash of the genus Cucurbita and the family Cucurbitaceae . It commonly refers to cultivars of any one of the species Cucurbita pepo, Cucurbita mixta, Cucurbita maxima, and Cucurbita moschata, and is native to North America...

, squash, watermelon (Citrullus lanatus) and other members of the Cucurbitaceae
The plant family Cucurbitaceae consists of various squashes, melons, and gourds, including crops such as cucumber, pumpkins, luffas, and watermelons...

/gourd family). The disease is one of the most important diseases of cucurbits worldwide.

See also

  • Blue mold
    Blue mold
    Blue mold is a downy mildew disease of tobacco that is caused by Peronospora tabacina, a fungus-like protist in the family Peronosporaceae. Blue mold can cause severe damage to susceptible tobacco plants in many parts of the world...

     (of tobacco plants)
  • Peronosporaceae
    Peronosporaceae are a family of water moulds that contains 17 genera, comprising more than 600 species. Most of them are called downy mildews. The closest relative of Peronosporaceae is Phytophthora....

    (with a list of the downy mildew genera)
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