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Phytophthora ramorum

(Sod, Sudden Oak Death)

Overview

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Macro-fungus. This fungus infests several species of oak trees and causes increased mortality in a short period of time after the development of cankers that girdle the tree. The fungus is spread by spores, can be easily spread to other locations in nursery material , and there is no treatment available once trees develop cankers.

Common Names

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Common Names in English:

Ramorum Blight, Ramorum Dieback, Sod, Sudden Oak Death

Description

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Physical Description

Species Phytophthora ramorum

Hyphae are highly branched, contorted, dendritic . Chlamydospores , produced on hyphal tips , are at first hyaline , then darken to cinnamon brown, 30-90 µm. Sporangia are semi-papillate, 30-90 µm, and deciduous. Oospores have not been observed. Infected trees develop bleeding or oozing cankers on the lower trunk . Cankers produce a reddish-brown to tar-black viscous seep that is sticky. Cankers are generally found in the lower 10 feet of the stem and are above the soil line . Underneath the outer bark of the infected tree, a dark line separates the necrotic tissue from the healthy tissue. Foliage on the infected tree, in the advanced stage, quickly changes from green to yellow to brown.

Habitat

Forests of three main types are affected in the North American region: Mixed Evergreen-Bay-Arbutus (fairly dry open forests with a grass and dense shrub understory ), Tanoak - Douglas-fir (wetter forest, frequently with Vaccinium as understory), Coast Redwood (usually more open, often with tanoak as the major understory). Found to infest the following plant species: Lithocarpus densiflorus (tanoak), Quercus agrifolia (coast live oak), Quercus parvula var. shrevei (Shreve's oak), Quercus kelloggii (black oak), Vaccinium ovatum (huckleberry), Rhododendron spp. (rhododendron and azalea), Arbutus menziesii (arbutus), Arctostaphylos manzanita (manzanita), Acer macrophyllum (bigleaf maple), Aesculus californica (California buckeye), Umbellularia californica (bay laurel), Viburnum X bodnantense (hybrid viburnum), Lonicera hispidula (California honeysuckle), Heteromeles arbutifolia (Christmasberry), Rhamnus californica (coffeeberry), Sequoia sempervirens (coast redwood), Pseudotsuga menziesii (Douglas-fir).

Biome: natural forest , planted forests

Ecology: Increased mortality of the host species : tanoak, coast live oak, and black oak. Tanoaks are a dominant hardwood in CA and OR forests and die in a short period of time following the onset of symptoms. Sudden die-offs of tanoak trees have negative visual, social, and ecological impacts .

Biology

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Reproduction

Spores.Sporangia, zoospores , chlamydospores

Taxonomy

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Similar Species

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Members of the genus Phytophthora

There are approximately 149 species in this genus. Here are just 100 of them:

P. agaves · P. alni · P. alni alni · P. alni multiformis · P. alni uniformis · P. aquatica · P. avicennae · P. avicenniae · P. bahamensis · P. batemanensis · P. boehmeriae · P. botryosa · P. brassicae · P. cactorum · P. cactorum var. cactorum · P. cajani · P. cambivora · P. canavaliae · P. capsici · P. carica · P. caricae · P. cinchonae · P. cinnamomi (Littleleaf Disease) · P. cinnamomi var. cinnamomi · P. cinnamomi var. parvispora · P. cinnamomi var. robiniae · P. citri · P. citricola · P. citrophthora · P. clandestina · P. colocasiae · P. cryptogea · P. cryptogea begoniae · P. cryptogea var. cryptogea · P. cyperi · P. cyperi-bulbosi · P. cyperi-iriae · P. cyperi-rotundati · P. devastatrix · P. devastrix · P. drechsleri · P. drechsleri var. cajani · P. drechsleri var. dracaenicola · P. drechsleri var. drechsleri · P. epistomium · P. eriugena · P. erythroseptica · P. erythroseptica var. erythroseptica · P. erythroseptica var. pisi · P. europaea · P. fagopyri · P. fischeriana · P. fragariae · P. fragariae var. fragariae · P. fragariae var. oryzobladis · P. fragariae var. rubi · P. gonapodyides · P. hedraiandra · P. hibernalis · P. himalayensis · P. humicola · P. idaei · P. ideai · P. ilicis · P. imperfecta var. imperfecta · P. infectans · P. infestans · P. infestans var. infestans · P. inflata · P. insolita · P. inundata · P. ipomoeae · P. iranica · P. irritabilis · P. italica · P. japonica · P. jatrophae · P. katsurae · P. kernoviae · P. lateralis · P. leersiae · P. lepironiae · P. macrochlamydospora · P. meadii · P. medicaginis · P. megakarya · P. megasperma · P. megasperma medicaginis-sativae · P. megasperma var. glycinea · P. megasperma var. megasperma · P. melonis · P. mexicana · P. mirabilis · P. multivesiculata · P. murrayae · P. mycoparasitica · P. nemorosa · P. nicotianae · P. nicotianae van · P. nicotianae var. nicotianae

Bibliography

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More Info

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Notes

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Contributors

Identifiers

Last Revised: 2008-08-20