Seasonal development
and life cycle—European canker
The fungus that causes European canker, Nectria galligena, survives the summer as mycelia in shoot
and branch cankers. Cool, wet weather in fall and winter stimulates the formation of spore-bearing structures
on cankers. Spores are moved by splashing rain and commonly infect leaf scars on young shoots and spurs.
Leaf scars are most susceptible to infection during the first hour after leaf fall.
Once infection takes place, the fungus slowly penetrates
bark tissue. Lesions become apparent 2 to 3 months later.
Cankers are formed and may encircle and kill twigs and small
branches. The fungus may cease activity when the weather
warms up and then resumes development when conditions that
favor it return.
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Spores
on the surface of cankers
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