Powdery mildew is a

fungal 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 from th ...

disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of ascomycete fungi in the order

Erysiphales Erysiphales are an order of ascomycete fungi. The order contains one family, Erysiphaceae. Many of them cause plant diseases called powdery mildew. Systematics The order contains one family (Erysiphaceae), 28 genera and approximately 100 speci ...

. 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 Mildew is a form of fungus. It is distinguished from its closely related counterpart, mould, largely by its colour: moulds appear in shades of black, blue, red, and green, whereas mildew is white. It appears as a thin, superficial growth consi ...

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, f ...

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 depe ...

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 germ ...

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 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 ...

), a type of ascocarp 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. Under optimal conditions, ascospores 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 Triadimefon is a fungicide used in agriculture to control various fungal diseases. As a seed treatment, it is used on barley, corn, cotton, oats, rye, sorghum, and wheat. In fruit it is used on pineapple and banana. Non-food uses include pine ...

and

propiconazole Propiconazole is a triazole fungicide, also known as a DMI, or demethylation inhibiting fungicide due to its binding with and inhibiting the 14-alpha demethylase enzyme from demethylating a precursor to ergosterol. Without this demethylation ste ...

. It is also possible with hexaconazole,

myclobutanil Myclobutanil is a triazole chemical used as a fungicide. It is a steroid demethylation inhibitor, specifically inhibiting ergosterol biosynthesis. Ergosterol is a critical component of fungal cell membranes. Stereoisomerism Safety The Safet ...

, 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 Potassium bicarbonate (IUPAC name: potassium hydrogencarbonate, also known as potassium acid carbonate) is the inorganic compound with the chemical formula KHCO3. It is a white solid. Production and reactivity It is manufactured by treating an ...

, 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 i ...

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 digestion, digest solid food. Immune factors and immune ...

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 Benomyl (also marketed as Benlate) is a fungicide introduced in 1968 by DuPont. It is a systemic benzimidazole fungicide that is selectively toxic to microorganisms and invertebrates, especially earthworms, but nontoxic toward mammals. Due to th ...

and

fenarimol Fenarimol, sold under the tradenames Bloc, Rimidin and Rubigan, is a fungicide which acts against rusts, blackspot and mildew fungi. It is used on ornamental plants, trees, lawns, tomatoes, peppers, eggplants, cucumbers and melons. It is mainly ...

at higher concentrations. Milk has proven effective in treating powdery mildew of

summer squash Summer squash are squashes that are harvested when immature, while the rind is still tender and edible. Nearly all summer squashes are varieties of ''Cucurbita pepo'', although not all ''Cucurbita pepo'' are considered summer squashes. Most summ ...

pumpkins 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 ...

grapes 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 ago ...

, 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 hard ...

, produces oxygen radicals when exposed to sunlight, and contact with these radicals is damaging to the fungus. Dilute sprays containing sodium bicarbonate (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 Potassium bicarbonate (IUPAC name: potassium hydrogencarbonate, also known as potassium acid carbonate) is the inorganic compound with the chemical formula KHCO3. It is a white solid. Production and reactivity It is manufactured by treating an ...

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 Apple scab is a common disease of plants in the rose family (Rosaceae) that is caused by the ascomycete fungus ''Venturia inaequalis''. While this disease affects several plant genera, including ''Sorbus, Cotoneaster,'' and ''Pyrus'', it is mos ...

. 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 In botany and mycology, a haustorium (plural haustoria) is a rootlike structure that grows into or around another structure to absorb water or nutrients. For example, in mistletoe or members of the broomrape family, the structure penetrates t ...

and by producing

callose Callose is a plant polysaccharide. Its production is due to the glucan synthase-like gene (GLS) in various places within a plant. It is produced to act as a temporary cell wall in response to stimuli such as stress or damage. Callose is composed ...

and

papilla Papilla (Latin, 'nipple') or papillae may refer to: In animals * Papilla (fish anatomy), in the mouth of fish * Basilar papilla, a sensory organ of lizards, amphibians and fish * Dental papilla, in a developing tooth * Dermal papillae, part of ...

. 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 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 DN ...

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 Powdery mildew is a fungal disease of barley caused by ''Blumeria graminis'' f. sp. ''hordei''. The disease has a worldwide distribution and is most damaging in cool, wet climates. The host range of the form species ''hordei'' is restricted to ba ...

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 an ...

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 ago, ...

Onions

The fungus causing powdery mildew of onions is ''

Leveillula taurica ''Leveillula taurica'' is an obligate fungal pathogen, from the phylum ''Ascomycota'', which causes powdery mildew on onion. This disease prefers warm, dry environments. It is rare in the United States, and is currently restricted to western sta ...

'' (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 artich ...

Apples and pears

'' Podosphaera leucotricha'' is a fungus that can cause powdery mildew of

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

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 Rosaceae, bearing the p ...

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 from th ...

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 Vine#Horticultural climbing plants, creeping vine plant in the Cucurbitaceae family that bears usually cylindrical Fruit, fruits, which are used as culinary vegetables.

s, squashes (including pumpkins),

luffa ''Luffa'' is a genus of tropical and subtropical vines in the cucumber family (Cucurbitaceae). In everyday non-technical usage, the luffa, also spelled loofah, usually refers to the fruits of the species '' Luffa aegyptiaca'' and '' Luffa acuta ...

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". The ...

s, and

watermelon Watermelon (''Citrullus lanatus'') is a flowering plant species of the Cucurbitaceae family and the name of its edible fruit. A scrambling and trailing vine-like plant, it is a highly cultivated fruit worldwide, with more than 1,000 varieti ...

Podosphaera xanthii ''Podosphaera fuliginea'' (also known as ''Podosphaera xanthii'') is a plant pathogen that causes powdery mildew on cucurbits. ''Podosphaera fuliginea'' and ''Erysiphe cichoracearum'' are the two most commonly recorded fungi causing cucurbit powd ...

'' (a.k.a. ''Sphaerotheca fuliginea'') is the most commonly reported cause on cucurbits. ''

Erysiphe cichoracearum ''Erysiphe cichoracearum'' is a fungal plant pathogen that causes powdery mildew disease of cucurbits, including melon, cucumber, pumpkin, and squash. The primary symptoms are white, powder-like spots on the leaves and stems. ''Sphaerotheca fu ...

'' was formerly reported to be the primary causal organism throughout most of the world. Since 1925, commercial ''

Cucumis melo ''Cucumis melo'', also known as melon, is a species of '' Cucumis'' that has been developed into many cultivated varieties. The fruit is a pepo. The flesh is either sweet or bland, with or without a musky aroma, and the rind can be smooth (such a ...

'' (cantaloup and muskmelon) production has been engaged in a biological "arms race" against cucurbit powdery mildew (CPM) caused by the fungus ''

'', 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 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 mal ...

of plants for phytopathological resistance to particular fungal races involves a great deal of

genetic research Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wo ...

; this PI 313970 versus race S case involved multi-stage hybridization 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 A literature review is an overview of the previously published works on a topic. The term can refer to a full scholarly paper or a section of a scholarly work such as a book, or an article. Either way, a literature review is supposed to provid ...

regarding powdery mildew races that parasitize 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 Erysiphales are an order of ascomycete fungi. The order contains one family, Erysiphaceae. Many of them cause plant diseases called powdery mildew. Systematics The order contains one family (Erysiphaceae), 28 genera and approximately 100 speci ...

fungi can cause powdery mildew in cucurbits: The most frequent, after ''P. xanthii'', is ''

'', 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 ''

''.

Lilacs

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

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 ''Geum rivale'', the water avens, is a flowering plant in the genus ''Geum'' within the family Rosaceae. Other names for the plant are nodding avens, drooping avens, cure-all, water flower and Indian chocolate. It is native to the temperate regi ...

'' (the water avens)

Tree leaves

'' Sawadaea tulasnei'' 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 the Car ...

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 is ...

, and

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

, ''

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 Russi ...

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

Oregon grape

'' Erysiphe berberidis'' is a fungus that causes powdery mildew on

Oregon grape ''Mahonia aquifolium'', the Oregon grape or holly-leaved barberry, is a species of flowering plant in the family Berberidaceae, native to western North America. It is an evergreen shrub growing tall and wide, with pinnate leaves consisting of sp ...

leaves.

Arabidopsis

Golovinomyces orontii ''Golovinomyces'' is a genus of fungi in the family Erysiphaceae. It has 66 species. Many of the species cause powdery mildew. ''Golovinomyces'' was originally circumscribed in 1978 by Uwe Braun as a section of genus ''Erysiphe''. It was promoted ...

'' 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 organi ...

'' (rockcress) leaves.

''Cannabis''

Caused by several fungi including '' Golovinomyces ambrosiae'' (syn. '' G. spadiceus'') and ''

Podosphaera macularis ''Podosphaera macularis'' (formerly ''Sphaerotheca macularis'') is a plant pathogen infecting several hosts including chamomile, caneberrie, strawberries, hop, hemp and ''Cineraria''. It causes powdery mildew of hops. Host range and symptoms ...

''. 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 ...

fungi, species of the genus '' Cicinnobolus'' are

hyperparasite A hyperparasite, also known as a metaparasite, is a parasite whose host, often an insect, is also a parasite, often specifically a parasitoid. Hyperparasites are found mainly among the wasp-waisted Apocrita within the Hymenoptera, and in two oth ...

s 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, at ...

'' is an anamorphic fungus that is a

of powdery mildews. This parasitism reduces growth and may eventually kill the mildew. Research on

biological control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also i ...

of powdery mildews (especially in high-value crops such as

) 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