| Ovulinia azaleae | |
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| Ovulinia petal blight caused by O. azaleae | |
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| Species: | O. azaleae |
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| Ovulinia azaleae F.A.Weiss (1940) | |
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Ovulinia azaleae is a plant pathogen affecting azaleas and rhododendrons.
Ovulinia petal blight is commonly referred to as Ovulinia flower blight, Azalea flower blight, and Azalea flower spot. [1] First reported in the 1930s on the Belgian-Indica hybrids, petal blight can attack most azaleas under favorable weather conditions. Infected flowers first exhibit small spots, about 1 mm in diameter, which appear water-soaked. [2] The spots enlarge rapidly and become very slimy, causing entire petals to become slimy and limp, usually within 2–3 days after initial infection. Infected areas of flowers soon become tan or light brown, and eventually entire flowers turn prematurely brown. [3] Infected flowers dry and generally cling to the plant longer than uninfected flowers do. One to 20 (commonly two to five) small, black sclerotia (a fungal resting stage) form on an infected flower 6–8 weeks later. They appear first as small white areas on the dried petals and slowly become dark as they mature.
Caused by the Ovulinia azaleae fungus, the disease develops during periods of moist weather at flowering time. Early- and late-flowering cultivars or species tend to escape the disease. The fungus overwinters as sclerotia on diseased petals adhering to plants, on the soil surface, or in leaf mulch under the bushes. [4] Sclerotia are able to survive for up to two years while in soil. [5] At the beginning of the host's blooming period, the sclerotia germinate and in 3–5 days give rise to small stalked, cup-shaped fruiting bodies (apothecia) filled with spore sacs called asci, which discharge ascospores with sufficient force that they strike the lower blooms above the sclerotia or are carried in air currents to nearby blooms on adjacent plants. [6] In addition to ascospores from cup-shaped fruiting bodies initiating the primary infection, after the primary infection cycle has completed, asexual spores called conidia are able to form and incite further infection; these conidia are dispersed via rain-splash, wind currents, and insect vectors. [7]
The rate of infection is higher when periods of frequent precipitation and warm weather coincide with flowering. [8] Heavy dew or extended periods of misty weather are particularly favorable. Low temperatures at the beginning of the flowering period and dry conditions toward the end of it most likely reduce the infection potential.
Spraying the infested soil with fungicides and removal of the leaf litter beneath infected plants have not been reliable methods of disease control. Sprays applied at or just before bud opening have offered the best means of control. [9] In general, sprays of triadimefon or benomyl applied at weekly intervals throughout the flowering period have controlled the blight and inhibited sclerotium formation. Making sure diseased or disease-carrying plants are not introduced into the growing area reduces the disease potential. [10]
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”.
Pyrenophora graminea is the causal agent of barley stripe. Barley stripe is disease of barley that once caused significant crop yield losses in many areas of the world. Its associated anamorph is Drechslera graminea(Rabenhorst ex Schlechtendal) S. Ito 1930.
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.
Glomerella graminicola is an economically important crop parasite affecting both wheat and maize where it causes the plant disease Anthracnose Leaf Blight.
Monilinia laxa is a plant pathogen that is the causal agent of brown rot of stone fruits.
Mycosphaerella coffeicola is a sexually reproducing fungal plant pathogen. It is most commonly referred to as the asexual organism Cercospora coffeicola.
Podosphaera leucotricha is a plant pathogen that can cause powdery mildew of apples and pears.
Diplocarpon earlianum is a species of fungus that causes disease in strawberry plants called strawberry leaf scorch. The disease overwinters in plant debris and infects strawberry plants during the spring season when it is wet. The five main methods to reduce strawberry leaf scorch include: irrigation techniques, crop rotation, planting resistant and disease-free seeds, fungicide use, and sanitation measures. Control of strawberry leaf scorch is important because it is responsible for the majority of disease in strawberries. Diplocarpon earliana affects the fruit quality and yield of the strawberry crop. Losses range from negligible to severe depending on numerous epidemiological factors including cultivar susceptibility, type of cropping system, and weather conditions
Ascochyta is a genus of ascomycete fungi, containing several species that are pathogenic to plants, particularly cereal crops. The taxonomy of this genus is still incomplete. The genus was first described in 1830 by Marie-Anne Libert, who regarded the spores as minute asci and the cell contents as spherical spores. Numerous revisions to the members of the genus and its description were made for the next several years. Species that are plant pathogenic on cereals include, A. hordei, A. graminea, A. sorghi, A. tritici. Symptoms are usually elliptical spots that are initially chlorotic and later become a necrotic brown. Management includes fungicide applications and sanitation of diseased plant tissue debris.
Alternaria solani is a fungal pathogen that produces a disease in tomato and potato plants called early blight. The pathogen produces distinctive "bullseye" patterned leaf spots and can also cause stem lesions and fruit rot on tomato and tuber blight on potato. Despite the name "early," foliar symptoms usually occur on older leaves. If uncontrolled, early blight can cause significant yield reductions. Primary methods of controlling this disease include preventing long periods of wetness on leaf surfaces and applying fungicides. Early blight can also be caused by Alternaria tomatophila, which is more virulent on stems and leaves of tomato plants than Alternaria solani.
Ascochyta pisi is a fungal plant pathogen that causes ascochyta blight on pea, causing lesions of stems, leaves, and pods. These same symptoms can also be caused by Ascochyta pinodes, and the two fungi are not easily distinguishable.
Colletotrichum coccodes is a plant pathogen, which causes anthracnose on tomato and black dot disease of potato. Fungi survive on crop debris and disease emergence is favored by warm temperatures and wet weather.
Elsinoë ampelina is a plant pathogen, which is the causal agent of anthracnose on grape.
Botrytis fabae is a plant pathogen, a fungus that causes chocolate spot disease of broad or fava bean plants, Vicia faba. It was described scientifically by Mexican-born Galician microbiologist Juan Rodríguez Sardiña in 1929.
Monilinia oxycocci (Woronin) Honey,, common names cranberry cottonball, cranberry hard rot, tip blight, is a fungal infection of large cranberry and small cranberry. The tips of young flowering shoots wilt before they flower. Fruit that forms on the plant can then be infected by the asexual spores traveling through the plant, causing the berries to harden, turn cottony on the inside, and dry out instead of maturing. The berries are filled with a cotton-like fungus and are generally yellowish with tan stripes or blotches at maturity, making them unmarketable. It results in important economic impacts on many cranberry marshes, particularly in Wisconsin.
Common spot of strawberry is one of the most common and widespread diseases afflicting the strawberry. Common spot of strawberry is caused by the fungus Mycosphaerella fragariae. Symptoms of this disease first appear as circular, dark purple spots on the leaf surface. Mycosphaerella fragariae is very host-specific and only infects strawberry.
Botryotinia polyblastis is a fungal plant pathogen that causes Narcissus Fire of daffodils, genus Narcissus.
Botrytis squamosa is a fungus that causes leaf blight on onion that is distinctly characterized by the two stages – leaf spotting followed by blighting. The pathogen is an ascomycete that belongs to the family Sclerotiniaceae in the order Helotiales. The lesions start out as whitish streaks and take on a yellow tinge as they mature. They cause yield losses up to 30%. This fungus is endemic to the USA and has also been reported in Europe, Asia, and Australia. Typical management of this disease includes chemical fungicides with significant efforts being made to establish a means of biological control.
Phytophthora hydropathica is an oomycete plant pathogen that is found in aquatic environments such as irrigation and river water. The pathogen was previously classified as P. drechsleri Dre II before being categorized as its own distinct species. P. hydropathica has been primarily found in association with ornamental plant nurseries. The pathogen has been isolated throughout the Southern United States, as well as internationally in Mexico, Italy, and Spain.
Botrytis elliptica is a necrotrophic fungal pathogen which infects species of plants in the Lilium genus, causing the disease commonly known as Lily Gray Mold. The symptoms of Lily Gray Mold include the appearance of water-soaked spots on leaves which appear white and increase in darkness with age, ranging from gray to brown. These spots may cover the entire leaf, complemented with a gray webbing, containing the fungal spores. The leaves will appear wilted and branches may die back. In addition to leaves, petals, stems, and buds may be infected, and this gray webbing will eventually cover the plant, feigning the appearance of gray flowers. Infected buds often rot. Lily Gray Mold disease, if not properly treated, will appear each year with increasing vigor.