font settings and languages

Font Size: Large | Normal | Small
Font Face: Verdana | Geneva | Georgia
Languages:

Discula destructiva

(Dogwood Anthracnose)

Overview

[ Back to top ]

Macro-fungus. Discula destructiva is a fungus that has caused serious losses to North American native flowering dogwood (Cornus florida) and other native and introduced species (C. nuttallii and C. kousa, respectively) of dogwood found in the natural environment and in ornamental plantings . Infection is more likely to occur at higher elevations and on moist to wet sites, and shade increases the risk of infection and mortality . Spores are washed onto new leaf tissue during periods of wet weather or sprinkler irrigation . Spores of D. destructiva land on shoots and leaves penetrating them directly and causing the quick death of the plant tissue due to the production of several toxins by the fungus. Larger trees often die 2 to 3 years after the first symptoms are found in the leaves. Management of D. destructiva is not readily available, but there are strategies available to enhance high value and ornamental populations of dogwoods through extensive care of individual trees.

Common Names

[ Back to top ]

Common Names in English:

Dogwood Anthracnose

Description

[ Back to top ]

Physical Description

Species Discula destructiva

The USDA Forest Service: Northeastern Area (UNDATED) states that, "Conidiomata of D. destructiva may form on necrotic leaf or bark areas. Masses of white to salmon colored conidia ooze as cirrhi from the reddish to dark brown conidiomata during wet weather." The USDA Forest Service: Southern Region (UNDATED) adds that, "Initial symptoms of D. destructiva are small tan leaf spots that develop into large tan blotches. Often a purple border occurs between dead and healthy tissues and occasionally the entire leaf is killed."

Habitat

The USDA Forest Service: Southern Region (UNDATED) states that, "Infection begins in leaves and spreads to twigs and branches, which dieback . Main-stem infections cause cankers , which kill the trees . In the South, infection is most likely at higher elevations and on moist to wet sites. Shade increases risk of infection and mortality ."

Biome: disturbed areas, natural forest , planted forests, urban areas

Ecology: The USDA Forest Service: Northeastern Area (UNDATED) states that, "D. destructiva Infections often progress down the petioles of blighted leaves into shoots , resulting in cankers . Direct infection of shoots, resulting in tiny cankers, may occur on C. florida during spring and fall . Girdling cankers typically develop at leaf nodes, causing twig dieback . On C. nuttallii , fall blighting of terminal leaves is common, resulting in death of terminal buds. Twig dieback is most common in the lower crown following years of extensive spring or fall leaf blighting. As a result of twig dieback, succulent shoots proliferate on the lower trunk and main branches of affected trees . These branches are very prone to infections, which may progress into the main stem Multiple cankers can girdle individual branches or kill the entire tree." The USDA Forest Service: Southern Region (UNDATED) adds that, "Cankers may not be present on all the dead trees. Larger trees often die 2 to 3 years after the first symptoms are found in the leaves." The fungal growth and virulence at 28 C and higher is significantly decreased (Ning and Blackwell, 2002).

Biology

[ Back to top ]

Reproduction

Asexual reproduction by conidia produced in structures called acervuli; sexual reproduction unknown (Redlin, 1991).Pecknold et al. (2001) states that, "On the underside of the leaf spots the fruiting structures of the causal fungus D. destructiva, may be visible as small raised tan or brown specks scattered randomly over the lesion surface. Spores from these structures are washed onto new leaf tissue during periods of wet weather or sprinkler irrigation . If cool wet weather persists leaves may become severely blighted. "The Plant Disease Diagnostic Clinic (2001) states that, "Reproductive structures of D. destructiva form underneath leaf spots and on the surface of twig cankers . Huge amounts of asexual spores are formed inside and, in the spring , ooze out in slimy beige clusters . Local dispersal of the spores occurs by splashing rain while long distance dispersal may also occur via insects and birds. Transportation of diseased stock into new areas spreads the disease as well, especially into areas where dogwoods are not native . Spores of the fungus land on shoots or leaves penetrating them directly causing the quick death of the plant tissue due to the production of several toxins by the fungus." Redlin (1991) states that D. discula produces acervular and subcuticular conidiomata on leaves and twigs of the host. Conidia are ellipsoidal and nonseptate. A sexual state is unknown.

Taxonomy

[ Back to top ]

Similar Species

[ Back to top ]

Members of the genus Discula

There are approximately 44 species in this genus:

D. africana · D. albersi · D. attrita · D. betulina · D. bicarinata · D. brenckleana · D. bulweri · D. bulwerii · D. calcigena · D. calcigena barbozae · D. calcigena discina · D. campestris · D. caricis · D. ceanothi · D. cheiranthicola · D. cytosporea · D. destructiva (Dogwood Anthracnose) · D. dianthi · D. echinulata · D. fraxinea · D. junci · D. kriegeriana · D. leacockiana (Madeiran Land Snail) · D. lignicola · D. lyelliana · D. nyeli · D. oxytropis · D. peckiana · D. pinicola · D. polymorpha · D. polymorpha alleniana · D. polymorpha arenicola · D. polymorpha depressiuscula · D. polymorpha senilis · D. pulvinata · D. pyri · D. rotula · D. runcinata · D. tabellata (Madeiran Land Snail) · D. tectiformis · D. testudinalis (Madeiran Land Snail) · D. testudinalis testudinalis · D. tetrica · D. turricula (Cima Discula)

Bibliography

[ Back to top ]

More Info

[ Back to top ]

Notes

[ Back to top ]

Contributors

Identifiers

Last Revised: 2008-10-01