Update on Tree Health
Dr Ana Pérez-Sierra from Forest Research describes some of the latest diseases affecting trees in Britain
The Tree Health Diagnostic and Advisory Service (THDAS)1 at Forest Research is helping to diagnose, monitor and provide advice about the general health of the nation’s trees, woodlands and forests, working on common diseases as well as on new threats. Although our last five years have been dominated by Chalara2 ash dieback caused by the fungus Hymenocyphus fraxineus, we are also working on a few new diseases that have been recently detected in Britain.
Sweet chestnut blight
Sweet chestnut blight3 is a disease caused by the fungus Cryphonectria parasitica. It was first identified in the UK (southern England) in 2011 and it was eradicated. Unfortunately, the disease was detected at the end of 2016 in western England and in 2017 in east London. The fungus affects the bark of sweet chestnut and enters through fissures or wounds. Stems or branches are girdled by lesions and die. The dead bark becomes visible as a sunken canker and epicormic growth might be observed below the cankered area. This pathogen has caused severe epidemics of American sweet chestnut (Castanea dentata) in North America and European sweet chestnut (C. sativa) in continental Europe.
Sirococcus blight of cedars
Since 2013 Atlas cedars have been suffering from severe shoot blight, cankers and defoliation in Britain caused by the fungus Sirococcus tsugae4. In the spring, affected trees display dead needles on the shoots which show a characteristic ‘pink’ colour; this is very distinctive in Blue Atlas cedar. The fungus can cause up to 70% defoliation and if the cankers affect the main stem (and it is girdled), the tree might die. We have had only a few reports of young trees dying although some affected trees have been removed because they are unsightly. There are no effective control measures for the disease. While good hygiene may reduce the spread of the disease, the fungus is dispersed by rain splash and strong winds are likely to disperse it over longer distances. This fungus can also affect other cedar species and hemlocks.
Neonectria Canker of fir
In 2015, fir trees (Abies spp.) showing dead shoots and branches, cankers and heavy resin flow were reported to THDAS. The fungus Neonectria neomacrospora5 was identified as the cause. Although records of this disease go back more than 100 years in Europe, it was in 2008 that a new and severe canker disease of firs caused by this fungus was reported in Norway. In 2011, the same disease was reported in Denmark and, in 2013, it was included in EPPO (European Plant Protection Organization) Reporting Service as a new emerging disease6. Since 2015 the number of confirmed cases in different Abies spp. has increased.
The management or control of tree diseases is greatly helped by early
detection and prompt action. For this reason we encourage the report of
these and any other tree health concerns through
You can find out more about the work of Forest Research, including their research on pests and diseases, on their website8.