Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of

ascomycete Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The defi ...

fungi in the order Erysiphales. Powdery mildew is one of the easier plant diseases to identify, as its symptoms are quite distinctive. Infected plants display white powdery spots on the leaves and stems. The lower leaves are the most affected, but the mildew can appear on any above-ground part of the plant. As the disease progresses, the spots get larger and denser as large numbers of asexual

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

s are formed, and the mildew may spread up and down the length of the plant. Powdery mildew grows well in environments with high

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

and moderate temperatures. Greenhouses provide an ideal moist, temperate environment for the spread of the disease. This causes harm to agricultural and horticultural practices where powdery mildew may thrive in a greenhouse setting. In an agricultural or horticultural setting, the

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a g ...

can be controlled using chemical methods, bio organic methods, and genetic resistance. It is important to be aware of powdery mildew and its management as the resulting disease can significantly reduce important crop yields. Oidio Plantas

Reproduction

Powdery mildew fungi can only reproduce on their living cell host and reproduce both sexually and asexually. Sexual reproduction is via chasmothecia (formerly cleistothecium), a type of

ascocarp An ascocarp, or ascoma (), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. Ascocarps are mos ...

where the genetic material recombines. Powdery mildew fungi must be adapted to their hosts to be able to infect them. Within each ascocarp are several

asci ASCI or Asci may refer to: * Advertising Standards Council of India * Asci, the plural of ascus, in fungal anatomy * Accelerated Strategic Computing Initiative * American Society for Clinical Investigation * Argus Sour Crude Index * Association of ...

. Under optimal conditions,

ascospores An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or ...

mature and are released to initiate new infections. Conditions necessary for spore maturation differ among species. Asexual reproduction is where the mother fungi and offspring are genetically identical. Powder mildew fungi offspring of wheat and barley species are more successful from asexual reproduction compared to sexual reproduction counterparts. The overwintering survival structure produced by the powdery mildew fungi is called the chasmothecia. This is a round, dark, hard resting structure. Because of these characteristics, spores are able to survive throughout the winter and be released in the spring for new infection.

Vectors of transmission

Powdery mildew does not need a vector to spread. Spores are usually carried by air currents from a proliferation site to a new infection site.

Management

In an agricultural setting, the pathogen can be controlled using chemical methods, genetic resistance, and careful farming methods.

Prevention

You can look for powdery mildew resistant varieties in seed catalogs and alternate between resistance varieties and not. This rotation of sunflower varieties prevents pathogen resistance. Reduce humidity by allowing space between plants for airflow and pruning to thin foliage

Conventional chemical control

Standard fungicides are an effective way to manage powdery mildew disease on plants. Spray programs of conventional fungicides are advised to begin when powdery mildew symptoms and signs are first noticed. Conventional fungicides should be applied on a regular basis for best results against the disease. Control is possible with triadimefon and propiconazole. It is also possible with hexaconazole, myclobutanil, and penconazole.

Non-conventional chemical control

There are some unconventional chemical control methods that offer alternative modes of action. The most effective non-conventional methods of chemical control against powdery mildew are milk, natural sulfur (S₈), potassium bicarbonate, metal salts, and oils. Maple-leafmildew

Metal salt fungicides should be applied on a regular basis up until harvest of the host. Sulfur must be applied before the disease has emerged since it prevents fungi spores from germinating. Copper sulfate is an effective fungicide allowed in organic farming, but can cause harm to the host plant. Addition of lime hampers this effect.

Neem oil Neem oil, also known as margosa oil, is a vegetable oil pressed from the fruits and seeds of the neem (''Azadirachta indica''), a tree which is indigenous to the Indian subcontinent and has been introduced to many other areas in the tropics. It ...

effectively manages powdery mildew on many plants by interfering with the fungus' metabolism and terminating spore production. Sulfur and Fish Oil + Sesame Oil is a mixture effective against powdery mildew.

Milk Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modulat ...

has long been popular with home gardeners and small-scale organic growers as a treatment for powdery mildew. Milk is diluted with water (typically 1:10) and sprayed on susceptible plants at the first sign of infection, or as a preventative measure, with repeated weekly application often controlling or eliminating the disease. Studies have shown milk's effectiveness as comparable to some conventional fungicides, and better than benomyl and fenarimol at higher concentrations. Milk has proven effective in treating powdery mildew of summer squash, pumpkins, grapes, and

rose A rose is either a woody perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred species and tens of thousands of cultivars. They form a group of plants that can be ...

s. The exact mechanism of action is unknown, but one known effect is that ferroglobulin, a protein in

whey Whey is the liquid remaining after milk has been curdled and strained. It is a byproduct of the manufacturing of cheese or casein and has several commercial uses. Sweet whey is a byproduct resulting from the manufacture of rennet types of har ...

, produces oxygen

radicals Radical may refer to: Politics and ideology Politics *Radical politics, the political intent of fundamental societal change *Radicalism (historical), the Radical Movement that began in late 18th century Britain and spread to continental Europe and ...

when exposed to sunlight, and contact with these radicals is damaging to the fungus. Dilute sprays containing

sodium bicarbonate Sodium bicarbonate ( IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3− ...

(baking soda) and vegetable or mineral oils in water are often recommended for controlling powdery mildew, but such mixtures have limited and inconsistent efficacy. While sodium bicarbonate has been shown to reduce to growth of mildews in lab tests, sprays containing only baking soda and water are not effective in controlling fungal diseases on infected plants, and high concentrations of sodium are harmful to plants. Potassium bicarbonate is an effective low-toxicity

fungicide Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. A fungistatic inhibits their growth. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality ...

against powdery mildew and apple scab. Another non-conventional chemical treatment involves treating with a solution of

calcium silicate Calcium silicate is the chemical compound Ca2SiO4, also known as calcium orthosilicate and is sometimes formulated as 2CaO·SiO2. It is also referred to by the shortened trade name Cal-Sil or Calsil. It occurs naturally as the mineral larnite. ...

. Silicon helps the plant cells defend against fungal attack by degrading haustoria and by producing callose and papilla. With silicon treatment, epidermal cells of

wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

are less susceptible to powdery mildew.

Genetic resistance

The Pm3 allele is an effective genetic resistance strategy that protects host species against powdery mildew fungus.

Gene editing

In 2014, researchers Yanpeng Wang et al. have reported that they were able to induce resistance in hexaploid bread wheat to powdery mildew via targeted mutations with the use of

CRISPR CRISPR () (an acronym for clustered regularly interspaced short palindromic repeats) is a family of DNA sequences found in the genomes of prokaryotic organisms such as bacteria and archaea. These sequences are derived from DNA fragments of bact ...

and

TALENS Transcription activator-like effector nucleases (TALEN) are restriction enzymes that can be engineered to cut specific sequences of DNA. They are made by fusing a TAL effector DNA-binding domain to a DNA cleavage domain (a nuclease which cuts ...

gene-editing technology.

Powdery mildews of various plants

Sunflowers

Sunflower powdery mildew is a disease caused by the pathogens ''Golovinomyces cichoracearum'', ''Podosphaera xanthii'', and ''Leviellula taurica''. The symptoms caused by ''L. taurica'' differ from the other pathogen symptoms. Green-yellow spots appear on upper leaf surface.

Wheat, barley and other cereals

Blumeria graminis ''Blumeria graminis'' (commonly called barley powdery mildew or corn mildew) is a fungus that causes powdery mildew on grasses, including cereals. It is the only species in the genus ''Blumeria''. It has also been called ''Erysiphe graminis'' and ...

'' f. sp. ''tritici'', causes powdery mildew of

, whereas f. sp. ''hordei'' causes powdery mildew of barley.

Legumes

Legumes, such as

soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu ...

s, are affected by '' Microsphaera diffusa''. Powdery Mildew in Soyabean leaves

Grape

'' Erysiphe necator'' (or ''Uncinula necator'') causes powdery mildew of

grape A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus '' Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters. The cultivation of grapes began perhaps 8,000 years a ...

Onions

The fungus causing powdery mildew of onions is '' Leveillula taurica'' (also known by its anamorph name, ''Oidiopsis taurica''). It also infects the

artichoke The globe artichoke (''Cynara cardunculus'' var. ''scolymus'' ),Rottenberg, A., and D. Zohary, 1996: "The wild ancestry of the cultivated artichoke." Genet. Res. Crop Evol. 43, 53–58. also known by the names French artichoke and green articho ...

Apples and pears

Podosphaera leucotricha ''Podosphaera leucotricha'' is a plant pathogen that can cause powdery mildew of apples and pear Pears are fruits produced and consumed around the world, growing on a tree and harvested in the Northern Hemisphere in late summer into Octob ...

'' is a fungus that can cause powdery mildew of

apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ancest ...

s and

pear Pears are fruits produced and consumed around the world, growing on a tree and harvested in the Northern Hemisphere in late summer into October. The pear tree and shrub are a species of genus ''Pyrus'' , in the Family (biology), family Rosacea ...

Gourds and melons

Multiple species of

fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...

can cause powdery mildew of

cucurbits The Cucurbitaceae, also called cucurbits or the gourd family, are a plant family consisting of about 965 species in around 95 genera, of which the most important to humans are: *''Cucurbita'' – squash, pumpkin, zucchini, some gourds *'' Lagena ...

cucumber Cucumber (''Cucumis sativus'') is a widely-cultivated creeping vine plant in the Cucurbitaceae family that bears usually cylindrical fruits, which are used as culinary vegetables.squashes Squash may refer to: Sports * Squash (sport), the high-speed racquet sport also known as squash racquets * Squash (professional wrestling), an extremely one-sided match in professional wrestling * Squash tennis, a game similar to squash but pla ...

(including

pumpkin A pumpkin is a vernacular term for mature winter squash of species and varieties in the genus ''Cucurbita'' that has culinary and cultural significance but no agreed upon botanical or scientific meaning. The term ''pumpkin'' is sometimes use ...

s), luffas,

melon A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. The word "melon" can refer to either the plant or specifically to the fruit. Botanically, a melon is a kind of berry, specifically a "pepo". T ...

s, and watermelons.

'' Podosphaera xanthii'' (a.k.a. ''Sphaerotheca fuliginea'') is the most commonly reported cause on cucurbits. '' Erysiphe cichoracearum'' was formerly reported to be the primary causal organism throughout most of the world. Since 1925, commercial '' Cucumis melo'' (cantaloup and muskmelon) production has been engaged in a biological "arms race" against cucurbit powdery mildew (CPM) caused by the fungus '' Podosphaera xanthii'', with new

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture ...

s of melons being developed for resistance to successively arising races of the fungus, identified simply as race 1, race 2, etc. (seven in total by 2004), for races found around the world, and race N1 through N4 for some divergent races native to Japan. Various subraces have been identified, and given names such as race 2U.S., race 3.5, and race 4.5. A new race S was discovered in 2003, and a specific melon cultivar (''C. melo'' var. ''acidulus'' 'PI 313970') found resistant to it, then used for

backcrossing Backcrossing is a crossing of a hybrid with one of its parents or an individual genetically similar to its parent, to achieve offspring with a genetic identity closer to that of the parent. It is used in horticulture, animal breeding, and produ ...

to increase resistance in other cultivars. Such modern

selective breeding Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant ...

of plants for phytopathological resistance to particular fungal races involves a great deal of genetic research; this PI 313970 versus race S case involved multi-stage

hybridization Hybridization (or hybridisation) may refer to: *Hybridization (biology), the process of combining different varieties of organisms to create a hybrid *Orbital hybridization, in chemistry, the mixing of atomic orbitals into new hybrid orbitals *Nu ...

to propagate a recessive gene, ''pm-S'' in successive generations, and how this may affect other recessive and codominant genes for resistance to other races of ''P. xanthii'' "remains to be determined". A 2004 literature review regarding powdery mildew races that

parasitize Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

various cucurbit plants concluded that "race identification is important for basic research and is especially important for the commercial seed industry, which requires accuracy in declaring the type and level of resistance ... in its products". However, identifying specific races was seen as having little utility in

horticulture Horticulture is the branch of agriculture that deals with the art, science, technology, and business of plant cultivation. It includes the cultivation of fruits, vegetables, nuts, seeds, herbs, sprouts, mushrooms, algae, flowers, seaweeds and no ...

for choosing specific cultivars, because of the rapidity with which the local

population can change geographically, seasonally, and by host plant. At least three other Erysiphaceae fungi can cause powdery mildew in cucurbits: The most frequent, after ''P. xanthii'', is '' Erysiphe cichoracearum'', the former primary causal organism throughout most of the world. '' Podosphaera fusca'' is another, sometimes considered synonymous with ''P. xanthii''. Cucumbers in greenhouse environments have also been reported to be susceptible to '' Leveillula taurica''.

Lilacs

'' Microsphaera syringae'' is a fungus that can cause powdery mildew in

lilac ''Syringa'' is a genus of 12 currently recognized species of flowering woody plants in the olive family or Oleaceae called lilacs. These lilacs are native to woodland and scrub from southeastern Europe to eastern Asia, and widely and commonl ...

Strawberries

'' Podosphaera aphanis'' is the cause of powdery mildew in

strawberries The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid species of the genus '' Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The fruit is widely ap ...

and other Rosaceae like '' Geum rivale'' (the water avens)

Tree leaves

Sawadaea tulasnei ''Sawadaea tulasnei'' is a form of powdery mildew is a species of fungus in the family Erysiphaceae. This fungus attacks the leaves of the ''Acer platanoides'' (Norway maple) in North America, and in Great Britain and/or Ireland, ''Acer palma ...

'' is a fungus that causes powdery mildew on tree leaves. This fungus attacks the leaves of the ''

Acer platanoides ''Acer platanoides'', commonly known as the Norway maple, is a species of maple native to eastern and central Europe and western Asia, from Spain east to Russia, north to southern Scandinavia and southeast to northern Iran. It was introduced to ...

'' (Norway maple) in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

Great Britain Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It ...

, and

Ireland Ireland ( ; ga, Éire ; Ulster-Scots: ) is an island in the North Atlantic Ocean, in north-western Europe. It is separated from Great Britain to its east by the North Channel, the Irish Sea, and St George's Channel. Ireland is the s ...

, ''

Acer palmatum ''Acer palmatum'', commonly known as Japanese maple, palmate maple, or smooth Japanese maple (Japanese: ''irohamomiji'', , or ''momiji'', (栴), is a species of woody plant native to Japan, Korea, China, eastern Mongolia, and southeast Russia. ...

'' (also known as the Japanese maple or smooth Japanese maple).

Oregon grape

'' Erysiphe berberidis'' is a fungus that causes powdery mildew on Oregon grape leaves.

Arabidopsis

'' Golovinomyces orontii'' causes powdery mildew on ''

Arabidopsis ''Arabidopsis'' (rockcress) is a genus in the family Brassicaceae. They are small flowering plants related to cabbage and mustard. This genus is of great interest since it contains thale cress (''Arabidopsis thaliana''), one of the model organ ...

'' (rockcress) leaves.

''Cannabis''

Caused by several fungi including '' Golovinomyces ambrosiae'' (syn. '' G. spadiceus'') and '' Podosphaera macularis''. See also .

Hyperparasites of powdery mildew

In the family Sphaeropsidaceae of the

Sphaeropsidales Sphaeropsidales is an order of Coelomycetes fungi. These are conidial fungi where the conidia form in a growing cavity in the host's tissue. The fruiting structures are spherical with an opening at the apex (pycnidia). Four form-families can b ...

fungi, species of the genus ''

Cicinnobolus ''Cicinnobolus'' is a genus of fungi, either classified as imperfect fungi or as Ascomycota. Species in this genus are hyperparasites of powdery mildew Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew dis ...

'' are hyperparasites of powdery mildew.faculty.ucr.edu
retrieved December 2015. ''

Ampelomyces quisqualis ''Ampelomyces quisqualis'' is an anamorphic fungus that is a hyperparasite of powdery mildews. This parasitism reduces growth and may eventually kill the mildew. These mycoparasites can live up to 21 days on mildew-free host plant surfaces, att ...

'' is an

anamorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a fruiting body. *Anamorph: an a ...

ic fungus that is a hyperparasite of powdery mildews. This parasitism reduces growth and may eventually kill the mildew. Research on biological control of powdery mildews (especially in high-value crops such as grapes) has been ongoing since the 1970s, resulting in the development of fungicides which contain ''A. quisqualis'' as the active ingredient.

References

External links

{{Authority control Fungal plant pathogens and diseases Erysiphales