Cornus anthracnose

Cornus anthracnose is a fungal disease that kills leaves and young shoots of some North American Cornus species (dogwoods). Infections cause dead blotches on leaves and die-back of young stems.

Cornus anthracnose

Quick facts

Common name Cornus anthracnose
Scientific name Discula destructiva
Plants affected Cornus florida, Cornus nutallii and Cornus kousa
Main symptoms Dead blotches on leaves, stem die-back
Caused by Fungus
Timing Late spring onwards

What is cornus anthracnose?

Cornus anthracnose is a fungal disease caused by Discula destructiva, which arrived in the UK from North America in the late 1990s.

It infects and kills the leaves and young shoots of some North American Cornus species (dogwoods). Cornus florida is particularly susceptible, Cornus nuttallii and Cornus kousa may also be attacked. Native UK Cornus species appear unaffected.

Damage occurs from late spring until leaf fall in the autumn.

Symptoms

You may see the following symptoms:

  • On leaves: Spots and blotches of dead tissue appear. Under wet conditions, the blotches expand and the leaf shrivels and falls. A severe attack can completely defoliate a tree
  • On stems: Young stems die back and under wet conditions tiny raised pimples can be seen on the bark
  • Bark cankers have been reported on susceptible Cornus species in the USA

Cornus anthracnose
    Cornus anthracnose

    Control

    Non-chemical control

    • There is anecdotal evidence that the disease varies in severity from year to year, so raking up and destroying infected leaves may be helpful in reducing the amount of infection in the following year
    • Choose resistant species. The most susceptible species are Cornus florida and C. nuttallii and, to a possibly lesser extent, C. kousa. In studies in the USA, C. controversa and C. sericea were also susceptible. Native European Cornus species in the UK appear unaffected. There is currently insufficient information available for other species

    Chemical control

    The fungicides tebuconazole (Bayer Fungus Fighter Concentrate), tebuconazole with trifloxystrobin (Bayer Fungus Fighter Plus), and triticonazole (Scotts Fungus Clear Ultra and Scotts Fungus Clear Ultra Gun) are approved for use against various fungal diseases on ornamental plants and could be used, but there is no specific information on their efficacy and no claims are made by the manufacturers for control of this particular disease.

    Inclusion of a fungicide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.

    Download

    Fungicides for gardeners (Adobe Acrobat pdf document outlining fungicides available to gardeners)

    Links

    Chemicals: using a sprayer
    Chemicals: using safely and effectively
    Chemicals: storing and disposing safely

    Biology

    The fungus Discula destructiva causes extensive damage in North America to the native Cornus species, which are an important landscape feature. The disease is known there as anthracnose and was first noted in the 1970s. The fungus is not thought to be native to North America, but its origins are unknown. It was first detected in the UK in the late 1990s and was probably introduced accidentally on infected plant material.

    The fungus produces very small, pimple-like fruiting bodies on dead leaves and stems and in wet weather minute spores are released from these and  dispersed by rain-splash, wind-blown rain and, probably, by animals and birds. Wet conditions are required for infection.

    No other spore types are known and it is assumed that the fungus can remain dormant in affected twigs and bark during the winter, to produce fresh spores the following spring.

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