Botryosphaeria-canker and blight of Giant Sequoia - Botryosphaeria dothidea
Symptoms / species
Impact / measures
Initially or with only slight infections, single twigs and branches turn brown and die. Typical are patches of brown parts scattered in the crown: in this stage similar to other fungal diseases (e.g.Phomopsis juniperivora! Later on, or in case of intense infection, larger areas of the crown die. On the twigs and branches numerous cankers with resin flow. At the border of the cankers or on dead twigs blackish, dot-like fruiting bodies, containing colorless, spindel-shaped spores measuring 8-10 x 24-32 µm and sometimes also minute comma-shaped microspores.
Affected tree species
Leaf; Stem; Shoot/Twig/Branch;
Botryosphaeria dothidea is a weak parasite, known to cause dieback of numerous plant species as a consequence of various stress factors. In Giant Sequoia pathogen activity is related to long lasting high summer temperature: in Austria (esp. in the eastern parts of the country) this happened in 2003, 2010 and 2013. Rainfall during such warm periods enables optimal conditions for spore production and infection. Thus this fungal species, which grows very well at temperatures of 30°C and more, can be regarded as an example for climate change effects. Infection occurs often through wounds (also wounds by pruning!).
Curative measures If Giant Sequoia trees are well supplied with water, they are usually able to heal cankers by callusing. Therefore the trees should be watered in dry summers(if possible). Bottlenecks in water supply may also be a consequence of unfavorable site conditions - this has to be considered in planting Giant Sequoia in urban areas. If the cankers already affect the stem, the tree should be felled, since a healing is unlikely in that stage. For hygienic reasons, dead material should be removed. Pruning equipment should be disinfected. With young plants, fungicides can be applied (see official register of Plant Protection).
Botryosphaeria dothidea: symptoms
Botryosphaeria dothidea>:early infection stage
Botryosphaeria dothidea: heavily infested branch
Botryosphaeria dothidea: twig-canker with resin flow
Botryosphaeria dothidea: fruiting bodies of the asexual stage