PESTS AND DISEASES OF FORESTRY IN NEW ZEALAND
Flagging of giant redwoods caused by Botryosphaera dothidea
ACROSS THE PATHOLOGY BENCH- FLAGGING OF GIANT REDWOOD
From Forest Health News 103, Decermber 2000
Flagging of small branches of the giant redwood, Sequoiadendron giganteum , is fairly common in New Zealand. The cankers are often accompanied by resin bleeding and may look very like the symptoms of cypress canker on cypresses. The causal agent, Botryosphaeria dothidea , causes dieback and/or cankers on many host species in temperate and tropical parts of the world. Many classes of woody plants are recorded as hosts; shrubs, fruit trees, ornamentals and plantation trees. In addition to attacking crops such as kiwifruit, apples, pears and currants in New Zealand the fungus is frequently found infecting plantation forest trees. It is associated with leader and branch dieback of both conifers and hardwoods such as species of Eucalyptus . Plants that have been predisposed by other agents such as drought, frost, or weakened from defoliation by disease are most commonly infected. The fungus also colonises dying or recently killed tissues and from this base may exacerbate the initial damage. In the New Zealand plantation forest environment B. dothidea behaves as an opportunistic pathogen that is generally unable to infect vigorous, healthy tissue. In North America it is reported to attack conifers which have been planted far from their native habitat.
(Margaret Dick, Forest Research)
