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 ...
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 d ...
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 spec ...
. 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 consis ...
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 ger ...
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.
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 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 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
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 critica ...
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 s ...
. It is also possible with
hexaconazole
Hexaconazole is a broad-spectrum systemic triazole fungicide used for the control of many fungi particularly ''ascomycetes'' and ''basidiomycetes''. Major consumption is in Asian countries and it is used mainly for the control of rice sheath bligh ...
,
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 (S
8),
potassium bicarbonate, metal salts, and oils.
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 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-modulati ...
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
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 us ...
,
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 b ...
s. The exact mechanism of action is unknown, but one known effect is that
ferroglobulin
Ferroglobulin is a protein in whey.
The presence of ferroglobulin in milk is perhaps the explanation for the ability of this product to treat powdery mildew
Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew ...
, 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
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 (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 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 ...
.
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 th ...
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 archaeolog ...
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 bac ...
and
TALENS 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''
f. sp.
''Forma specialis'' (plural: ''formae speciales''), abbreviated f. sp. (plural ff. spp.) without italics, is an informal taxonomic grouping allowed by the International Code of Nomenclature for algae, fungi, and plants, that is applied to a par ...
''tritici'', causes powdery mildew 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 archaeolog ...
, 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
''Microsphaera diffusa'' is a plant pathogen. ''M. diffusa'' infections on soybeans are referred to as powdery mildew.
Importance:
Powdery mildew of soybeans is an important pathogen and tends to cause epidemics about every 10–15 years in Wi ...
''.
Grape
''
Erysiphe necator
''Uncinula necator'' (syn. ''Erysiphe necator'') is a fungus that causes powdery mildew of grape. It is a common pathogen of Vitis species, including the wine grape, ''Vitis vinifera''. The fungus is believed to have originated in North Americ ...
'' (or ''Uncinula necator'') causes powdery mildew of
grape
A grape is a fruit, botanically a berry (botany), berry, of the deciduous woody vines of the flowering plant genus ''Vitis''. Grapes are a non-Climacteric (botany), climacteric type of fruit, generally occurring in clusters.
The cultivation of ...
s.
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 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 trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ances ...
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 ...
s.
Gourds and melons
Multiple species of
fungus
A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...
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
*'' La ...
:
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 u ...
s),
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 ...
s,
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 var ...
s.
''
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 ma ...
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 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
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 has c ...
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
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 ger ...
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
''Podosphaera fusca'' is a fungus that parasitically infects plants (a phytopathogen). It is one cause of powdery mildew
Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many diff ...
'' 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
Powdery mildew of lilac, or ''Erysiphe syringae'' (formerly ''Microsphaera syringae'') is a fungal pathogen of lilacs.
Importance
The host of the fungal pathogen, ''Syringa vulgaris'' or the common lilac, is an ancient plant with significance ...
'' is a fungus that can cause powdery mildew in
lilac
''Syringa'' is a genus of 12 currently recognized species of flowering plant, 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 wid ...
.
Strawberries
''
Podosphaera aphanis'' is the cause of powdery mildew in
strawberries
The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown Hybrid (biology), hybrid species of the genus ''Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The f ...
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,
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
''Erysiphe'' is a genus of fungi in the family Erysiphaceae. Many of the species in this genus are plant pathogens which cause powdery mildew.
Species
This genus includes, but is not limited to the following species:
* ''Erysiphe alphitoides''
* ...
'' 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 org ...
'' (rockcress) leaves.
''Cannabis''
Caused by several fungi including ''
Golovinomyces ambrosiae
''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 ...
'' (syn. ''
G. spadiceus'') and ''
Podosphaera macularis''.
See also .
Hyperparasites of powdery mildew
In the family
Sphaeropsidaceae of the
Sphaeropsidales fungi, species of the genus ''
Cicinnobolus'' are
hyperparasites of powdery mildew.
[faculty.ucr.edu](_blank)
retrieved December 2015.
''
Ampelomyces quisqualis'' is an
anamorph
In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the Biological life cycle, life cycles of fungi in the Phylum, phyla Ascomycota and Basidiomycota:
*Teleomorph: the sexual reproductive stage (morph), typically a Asc ...
ic fungus that is a
hyperparasite 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 als ...
of powdery mildews (especially in high-value crops such as
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, ...
) has been ongoing since the 1970s, resulting in the development of fungicides which contain ''A. quisqualis'' as the active ingredient.
See also
*
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 spec ...
*
Oidium (genus)
''Oidium'' is a genus of Deuteromycetes, where traditionally most anamorphs of the order Erysiphales are included. Most of them are plant pathogens causing different forms of powdery mildew, for example:
*''Oidium alphitoides'' (= ''O. quercinum ...
References
External links
{{Authority control
Fungal plant pathogens and diseases
Erysiphales