| Podosphaera leucotricha | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Leotiomycetes |
| Order: | Erysiphales |
| Family: | Erysiphaceae |
| Genus: | Podosphaera |
| Species: | P. leucotricha |
| Binomial name | |
| Podosphaera leucotricha (Ellis & Everh.) E.S. Salmon, (1900) | |
| Synonyms | |
Albugo leucotricha(Ellis & Everh.) Kuntze, (1892) Contents | |
Podosphaera leucotricha is a plant pathogen that can cause powdery mildew of apples and pears.
A net-like russeting can cut the value of fruit in half and with some orchards spraying up to 15 times per growing season the economic losses from P. leucotricha are high. [1]
Powdery mildew, caused by the obligate biotrophic ascomycete Podosphaera leucotricha, is one of the major diseases of cultivated apple throughout the world. The primary host is apple, but other fruit like peaches and quince provide a host for Podosphaera leucotricha. [2] A list of host plants/species affected includes Cydonia oblonga (quince), Malus (apple), Prunus persica (peach), Prunus domestica (plum), Pyrus (pears), and Mespilus germanica (medlar). [3] On apples, the fungus affects twigs, foliage, blossoms, and fruits of current season growth. [2] Infected plants are characterized by reduced photosynthesis and transpiration, resulting suboptimal carbohydrate assimilation and reduced growth. [2]
Podosphaera leucotricha causes a range of symptoms. On stems, symptoms include wilting and discoloration. Wilting and leaf curling occur on leaves. Symptoms of the inflorescence include discoloration (non-graminous plants), dwarfing, stunting, and twisting. On fruit symptoms include net-like russeting and deformed fruit. [1] [3] Depending on the stage in the disease cycle, symptoms vary. The primary blossom mildew emerges at pink bud stage. Flowers are deformed with pale green or yellow petal and are covered in white mycelium and spores. [4] The secondary mildew may have lesions that appear as chlorotic spots on the upper leaf surface. Symptoms of the secondary mildew also included distorted leaves and premature falling of leaves. [4]
Podosphaera leucotricha has a polycyclic disease cycle. Mycelium overwintering in dormant buds typically produces primary infection on young leaves, which produce inoculum in the form of conidia for the secondary cycles. [5] In spring, the overwintered fungus is evident as 'primary' mildew on leaves emerged from buds infected during the previous growing season. [6] Conidia that are (12 X 20-38 um) and are ellipsoidal, truncate and hyaline [1] are released from the primary mildew during the colonies disperse in air and initiate an epidemic of 'secondary' mildew on growing shoots. Young developing fruitlets may also be infected. [4] Secondary mildew epidemics are effectively continuous from day to day. The infection process does not require surface wetness. [6] Daily infection intensity on leaves is mainly determined by the dose of landed conidia, which is dependent on the concentration of airborne conidia and wind speed. [7] Apple shoots have a long growing season causing the tree to stay susceptible for several months. [4] The pathogen is supposed to spread almost exclusively asexually, although ascospores might be an underrated additional source of infection. [5] Occasionally the sexual state of P. leucotricha occurs as pin-head sized brown/black fruiting bodies (ascocarps) among mycelium on infected shoots or leaves. [4] Although the mycelium can overwinter in dormant buds, overwintering potential is limited primarily by temperature. In severe winters, infected buds are killed as they are more susceptible to the cold than healthy buds. [4]
Intensive applications of fungicides are usually used to control apple powdery mildew. [6] In the UK, most commercial apple orchards receive routine sprays. [4] This is because mildew is always present in the orchard and therefore routine chemical control measures are usually needed. Spraying occurs from green cluster until vegetative growth ceases, and occasionally post-harvest if terminal buds regrow. [4] Once primary mildew levels are high, effective control becomes difficult. Therefore, control strategies depend on maintaining primary mildew at a low level. When levels are high, prompt physical removal of blossoms or shoots may be the only effective way to reduce inoculum levels. [4] In organic orchards, control is based on a combination of cultural levels and fungicide use where possible, but sulphur is the only fungicide active against powdery mildew permitted for use in organic production. [4] Cultural levels are based on removal of primary inoculum by pruning. In winter, prune out silvered shoots. At pink bud and petal fall stages, prune out primary blossom and primary blossom and primary vegetative mildew. [6] There are times when controlling mildew is most important. June is a critical time for monitoring and mildew control as this is the period for rapid extension growth and also when fruit buds are forming and sealing for next spring. [4] Fungicides and cultural controls are the main ways to manage P. leucotricha, however the development of apple varieties displaying durable resistance to the fungi is one of the major aims of apple breeding programs worldwide. [5]
Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of ascomycete 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 spores are formed, and the mildew may spread up and down the length of the plant.
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 most commonly associated with the infection of Malus trees, including species of flowering crabapple, as well as cultivated apple. The first symptoms of this disease are found in the foliage, blossoms, and developing fruits of affected trees, which develop dark, irregularly-shaped lesions upon infection. Although apple scab rarely kills its host, infection typically leads to fruit deformation and premature leaf and fruit drop, which enhance the susceptibility of the host plant to abiotic stress and secondary infection. The reduction of fruit quality and yield may result in crop losses of up to 70%, posing a significant threat to the profitability of apple producers. To reduce scab-related yield losses, growers often combine preventive practices, including sanitation and resistance breeding, with reactive measures, such as targeted fungicide or biocontrol treatments, to prevent the incidence and spread of apple scab in their crops.
Uncinula 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 America. European varieties of Vitis vinifera are more or less susceptible to this fungus. Uncinula necator infects all green tissue on the grapevine, including leaves and young berries. It can cause crop loss and poor wine quality if untreated. The sexual stage of this pathogen requires free moisture to release ascospores from its cleistothecia in the spring. However, free moisture is not needed for secondary spread via conidia; high atmospheric humidity is sufficient. Its anamorph is called Oidium tuckeri.
Grape black rot is a fungal disease caused by an ascomycetous fungus, Guignardia bidwellii, that attacks grape vines during hot and humid weather. “Grape black rot originated in eastern North America, but now occurs in portions of Europe, South America, and Asia. It can cause complete crop loss in warm, humid climates, but is virtually unknown in regions with arid summers.” The name comes from the black fringe that borders growing brown patches on the leaves. The disease also attacks other parts of the plant, “all green parts of the vine: the shoots, leaf and fruit stems, tendrils, and fruit. The most damaging effect is to the fruit”.
Venturia inaequalis is an ascomycete fungus that causes the apple scab disease.
Blumeria graminis 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 Oidium monilioides or Oidium tritici.
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 barley and other Hordeum species.
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 states. Globally, it is also a minor problem with limited occurrences in the Middle East, Europe, and South America. L. taurica causes powdery mildew of onions, but is also known to infect other allium, solanaceous, and cucurbit species. The disease has appeared in parts of the Middle East, the Mediterranean, and South and North America. Currently, it is not a cause for major concern in the U.S. and throughout the world, as its geographic extent is sparse. In addition, it is relatively easy to control through basic sanitation and reducing water stress.
Podosphaera macularis is a plant pathogen infecting several hosts including chamomile, caneberrie, strawberries, hop, hemp and Cineraria. It causes powdery mildew of hops.
Peronospora manshurica is a plant pathogen. It is a widespread disease on the leaves of soybeans and other crop plants. The fungi is commonly referred to as downy mildew, "leafspot", or "leaf-spot".
Erysiphe heraclei is a plant pathogen that causes powdery mildew on several species including dill, carrot and parsley.
Oidium mangiferae is a plant pathogen that infects mango trees causing powdery mildew. Powdery mildew of mango is an Ascomycete pathogen of the Erysiphales family that was initially described by Berthet in 1914, using samples collected from Brazil. O. mangiferae is found in all areas where mangoes have been raised long term, but is particularly widespread in India where both the host and the pathogen are native. Currently no teleomorph stage has been identified, but due to certain morphological characteristics it has been suggested that O. mangiferae belongs in the Erysiphe polygony group. Mango is the only known host for this pathogen, though O. mangiferae appears to be identical to fungi responsible for powdery mildew diseases on various other plant species, particularly oak, though some differences may be observed. In particular, the number of cells in conidiophores varies from 2 on mango to 3-5 on oak. O. mangiferae has been known to infect oak leaves in the laboratory, however due to the lack of a known teleomorph stage O. mangiferae is still considered to only be a pathogen of mango. Recent analysis of its ribosomal DNA suggests it is conspecific with Erysiphe alphitoides, the causative agent of powdery mildew in European oaks.
Podosphaera fuliginea is a plant pathogen that causes powdery mildew on cucurbits. Podosphaera fuliginea and Erysiphe cichoracearum are the two most commonly recorded fungi causing cucurbit powdery mildew. In the past, Erysiphe cichoracearum was considered to be the primary causal organism throughout most of the world. Today, Podosphaera fuliginea is more commonly reported.
Peronosclerospora sorghi is a plant pathogen. It is the causal agent of sorghum downy mildew. The pathogen is a fungal-like protist in the oomycota, or water mold, class. Peronosclerospora sorghi infects susceptible plants though sexual oospores, which survive in the soil, and asexual sporangia which are disseminated by wind. Symptoms of sorghum downy mildew include chlorosis, shredding of leaves, and death. Peronosclerospora sorghi infects maize and sorghum around the world, but causes the most severe yield reductions in Africa. The disease is controlled mainly through genetic resistance, chemical control, crop rotation, and strategic timing of planting.
Elsinoë ampelina is a plant pathogen, which is the causal agent of anthracnose on grape.
This article summarizes different crops, what common fungal problems they have, and how fungicide should be used in order to mitigate damage and crop loss. This page also covers how specific fungal infections affect crops present in the United States.
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, attacking powdery mildew structures as soon as they appear. A. quisqualis is used as the active ingredient in a commercial fungicide.
Peach scab, also known as peach freckles, is a disease of stone fruits caused by the fungi Cladosporium carpophilum. The disease is most prevalent in wet and warm areas especially southern part of the U.S. as the fungi require rain and wind for dispersal. The fungus causes scabbing, lesions, and defoliating on twig, fruit, and leaf resulting in downgrade of peach quality or loss of fruits due to rotting in severe cases.
Cladosporium fulvum is an Ascomycete called Passalora fulva, a non-obligate pathogen that causes the disease on tomatoes known as the tomato leaf mold. P. fulva only attacks tomato plants, especially the foliage, and it is a common disease in greenhouses, but can also occur in the field. The pathogen is likely to grow in humid and cool conditions. In greenhouses, this disease causes big problems during the fall, in the early winter and spring, due to the high relative humidity of air and the temperature, that are propitious for the leaf mold development. This disease was first described in the North Carolina, by Mordecai Cubitt Cooke (1883), on cultivated tomato, although it is originally from South and Central America. The causal fungus of tomato leaf mold may also be referred to as Cladosporium fulvum, a former name.
Golovinomyces orontii is a species of fungus that causes powdery mildew disease and it is in the family Erysiphaceae. It is an obligate biotroph that infects plants in several families including Acanthaceae, Asteraceae, Brassicaceae, Cucurbitaceae, and Lamiaceae.
