This weekly Wednesday post is from council member, David Carmichael. David is a Landscape Technician with PEI’s Department of Agriculture and Forestry. Today’s topic is European larch canker.
European larch canker, caused by the fungus Lachnellula willkommii, is a serious disease in many parts of Europe. The disease is also present in Japan, China, and Russia. In North America, the disease is only found in the Maritime Provinces of New Brunswick, Nova Scotia and Prince Edward Island and in five counties in Maine, USA.
The disease was mistakenly introduced to P.E.I. on European larch trees seedlings planted for trial purposes in the Grand River area of the Island. Unfortunately, the intended seedlings were infected with European Larch Canker upon introduction. The disease is currently regulated both in Canada and the USA. Source: Canadian Food Inspection Agency.
All larch species (Larix sp.) are potential hosts.
As the name of this disease suggests, the fungal pathogen (Lachnellula willkommii) that is the responsible agent for this disease causes large numbers of cankers to form on the branches and trunks of infected trees. The appearance of cankered areas is the first sign of the disease.
Seedlings and young trees are killed through girdling, ie, the cambium (the growth layer that makes the trunk and branches grow thicker) around the circumference of the trunk or main branch is damaged. Initially, the cankers, which are caused by lesions of the cambium and result from a scarring process, appear as swellings on the smaller branches or as depressions in the larger branches.
The cankers are accompanied by exudations of resin, which can become very abundant. This gives the cankers a shiny, slightly bluish appearance. In addition, during certain periods of the year, fruiting bodies of the fungus appear on or near the cankers. They are white and hairy and resemble small cups with yellow orange centres. Larch needles on the small stems or branches above the cankers wither in the spring or become discoloured early in the fall. Source: Natural Resource Canada
The presence of cankers on the trunk is usually a sign that the disease is in an advanced stage. This is accompanied by a significant loss of foliage.
For control, contact the Canadian Food Inspection Agency 902-566-7290 for confirmation if trees with symptoms are found outside the regulated area. Contact the J. Frank Gaudet Tree Nursery, Community, Lands and Environment at 902-368-4714 for confirmation of trees with symptoms found inside the regulated area.