Lemon tree with phytophtora 02 - collar rot

Collar rot is a symptomatically described disease that is usually caused by any one of various

fungal A fungus (: fungi , , , or ; 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 one of the tradit ...

and

oomycete The Oomycetes (), or Oomycota, form a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms within the Stramenopiles. They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction o ...

plant pathogens. It is present where the pathogen causes a lesion localized at or about the

collet A collet is a segmented sleeve, band or ''collar''. One of the two radial surfaces of a collet is usually tapered (i.e a truncated cone) and the other is cylindrical. The term ''collet'' commonly refers to a type of chuck that uses collets ...

between the stem and the root. The lesions develop around the stem eventually forming a "collar". Observationally, collar rot grades into "basal stem rot", and with some pathogens is the first phase of "basal stem rot" often followed by "root rot". Collar rot is most often observed in seedings grown in infected soil. The pathogens that cause collar rot may be species or genera specific. But generalist pathogens such as '' Agroathelia rolfsii'' (aka ''Sclerotium rolfsii'' or ''Athelia rolfsii'') are known to attack over 200 different species. While bacteria caused collar rot is not common, trees infected with

Fire blight Fire blight, also written fireblight, is a contagious disease affecting apples, pears, and some other members of the family Rosaceae. It is a serious concern to apple and pear producers. Under optimal conditions, it can destroy an entire orchard ...

(''Erwinia amylovora'') may develop collar rot. Non-parasitic collar rot may be caused by winter damage. Calonectria collar rot of papaya

The symptomatically described disease Southern blight is often the first observed precursor of the collar rot caused by the fungus '' Agroathelia rolfsii''. Causally known as Sclerotial blight, ''Agroathelia rolfsii'' survives in the soil as

sclerotia A sclerotium (; : sclerotia () is a compact mass of hardened fungal mycelium containing food reserves. One role of sclerotia is to survive environmental extremes. In some higher fungi such as ergot, sclerotia become detached and remain dormant u ...

, and in infected decomposing plant material as

mycelia Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fo ...

. Collar rot that is caused by the oomycete ''

Phytophthora ''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species cause economic losses on crops worldwide, as well as environmental dam ...

'' is causally called Phytophthora collar rot, and is a common disease of fruit and nut trees, as well as other flowers and crops. ''Phytophthora'' species remain in the soil, as spores, and in infected plant tissue, as mycelia, so absent control measures (sterilization, toxic applications) the disease continues so long as susceptible plants are grown in that soil. __TOC__

Hosts and agents

* In

carnation ''Dianthus caryophyllus'' ( ), commonly known as carnation or clove pink, is a species of ''Dianthus'' native to the Mediterranean Basin, Mediterranean region. Its exact natural range is uncertain due to extensive cultivation over the last 2,00 ...

s (''

Dianthus caryophyllus ''Dianthus caryophyllus'' ( ), commonly known as carnation or clove pink, is a species of '' Dianthus'' native to the Mediterranean region. Its exact natural range is uncertain due to extensive cultivation over the last 2,000 years. Carnations ...

'') by '' Alternaria dianthi'', * In chili (''Capsicum'') by ''

'', * In

cinchona ''Cinchona'' (pronounced or ) is a genus of flowering plants in the family Rubiaceae containing at least 23 species of trees and shrubs. All are native to the Tropical Andes, tropical Andean forests of western South America. A few species are ...

(''Cinchona officinalis'') by '' Phytophthora quininea'', * In Chinese evergreens ('' Aglaonema'') by '' Fusarium subgutinans'', * In coffee plants (''Coffea'') by '' Gibberella stilboides'', * In

dogwood ''Cornus'' is a genus of about 30–60 species of woody plants in the family Cornaceae, commonly known as dogwoods or cornels, which can generally be distinguished by their blossoms, berries, and distinctive bark. Most are deciduous ...

s (genus ''Cornus'') by '' Phytophthora cactorum'' where the disease is also called "crown canker", * In eggplant/brinjal (''Solanum melongena'') by '' Sclerotinia sclerotiorum'' and ''Sclerotium rolfsii'', * In elephant foot yams (''Amorphophallus paeoniifolius'') by ''Sclerotium rolfsii'', * In fruit and nut trees by a variety of pathogens including ''

Sclerotium rolfsii ''Agroathelia rolfsii'' is a corticioid fungus in the order Amylocorticiales. It is a facultative plant pathogen and is the causal agent of "southern blight" disease in crops. Taxonomy The species was first described in 1911 by Italian mycol ...

'', ''

Alternaria ''Alternaria'' is a genus of Deuteromycetes fungi. All species are known as major Phytopathology, plant pathogens. They are also common allergens in humans, growing indoors and causing hay fever or hypersensitivity reactions that sometimes lead t ...

'' and ''

'', * In groundnut/peanut (''

Arachis hypogaea The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), goober pea, pindar (US) or monkey nut (UK), is a legume crop grown mainly for its edible seeds. It is widely grown in the tropics and subtropics by small and large ...

'') by ''

Aspergillus niger ''Aspergillus niger'' is a mold classified within the ''Nigri'' section of the ''Aspergillus'' genus. The ''Aspergillus'' genus consists of common molds found throughout the environment within soil and water, on vegetation, in fecal matter, on de ...

'' which also causes wilt and crown rot, and by ''

Lasiodiplodia theobromae ''Lasiodiplodia theobromae'' is a Plant pathology, plant pathogen with a very wide host (biology), host range. It causes rotting and Forest dieback, dieback in most species it infects. It is a common post harvest fungus disease of citrus known as ...

'', * In hardwoods and conifers by ''

Phytophthora cinnamomi ''Phytophthora cinnamomi'', also known as cinnamon fungus, is a soil-borne water mould that produces an infection which causes a condition in plants variously called "dieback", "root rot", or (in certain '' Castanea'' species), "ink disease". O ...

'', * In

maize Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...

(corn, ''Zea mays'') by ''

'', * In

papaya The papaya (, ), papaw, () or pawpaw () is the plant species ''Carica papaya'', one of the 21 accepted species in the genus '' Carica'' of the family Caricaceae, and also the name of its fruit. It was first domesticated in Mesoamerica, within ...

by '' Calonectria'', * In

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

s by both ''Phytophthora'' and '' Diplodia pinastri'', * In

rhododendron ''Rhododendron'' (; : ''rhododendra'') is a very large genus of about 1,024 species of woody plants in the Ericaceae, heath family (Ericaceae). They can be either evergreen or deciduous. Most species are native to eastern Asia and the Himalayan ...

, China aster, marigold, gloxinia and

zinnia ''Zinnia'' is a genus of plants of the tribe Heliantheae within the family Asteraceae. They are native to scrub and dry grassland in an area stretching from the Southwestern United States to South America, with a centre of diversity in Mexic ...

by '' Phytophthora cryptogea'', * In

sunflower The common sunflower (''Helianthus annuus'') is a species of large annual forb of the daisy family Asteraceae. The common sunflower is harvested for its edible oily seeds, which are often eaten as a snack food. They are also used in the pr ...

s by ''

'', and by '' Phytophthora cryptogea''. * In

sweet potato The sweet potato or sweetpotato (''Ipomoea batatas'') is a dicotyledonous plant in the morning glory family, Convolvulaceae. Its sizeable, starchy, sweet-tasting tuberous roots are used as a root vegetable, which is a staple food in parts of ...

es (''Ipomoea batatas'') by ''Sclerotium rolfsii'', * In

tobacco Tobacco is the common name of several plants in the genus '' Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the ...

by '' Sclerotinia sclerotiorum''. * In

tomato The tomato (, ), ''Solanum lycopersicum'', is a plant whose fruit is an edible Berry (botany), berry that is eaten as a vegetable. The tomato is a member of the nightshade family that includes tobacco, potato, and chili peppers. It originate ...

es (''Solanum lycopersicum'') by '' Alternaria solani'',

Related diseases

* Rootstock blight''Symptoms of rootstock blight can be confused with Phytophthora collar rot.'' * Stem rot

References

{{Reflist Crop diseases Tree diseases Eudicot diseases Fungal plant pathogens and diseases Water mould plant pathogens and diseases