The latter is more virulent, capable of infecting an entire tree and killing it over a few years time, whereas the North American strain limits itself to the first few metres of the stem.

[4] Another reason behind the high potency of the European strain is that trees are unable to defend themselves from the fungus during winters, as the fungus can remain active at temperatures as low as -5°C[5] Early signs of a Scleroderris canker infection includes a purple tint in the needles and, more evidently, the falling off the needles in the wrong season.

A severe Scleroderris canker infection can sometimes be disastrous, as the fungus survives on the pine cones, killing any new seedlings within two years.

[citation needed] Chances of infection increase greatly if the previous winter has been mild and the spring season is cool and wet, due to the active temperature.

Infection occurs in damaged buds and proceeds downwards into the stem, and ascospores are released from November to July.