Needle Damage in Sitka Spruce Caused by Early Autumn Frosts

Abstract

Autumn frosts preceded by warm weather cause distinctive needle browning symptoms on young Sitka spruce trees which have completed shoot elongation. Damage is invariably confined to needles of the current year and typically consists of pink or reddish-brown patches in the centres of needles. Needles clustered around the apical buds are usually unaffected but in extreme cases all current year's needles may be entirely reddish-brown. These symptoms were reproduced on young plants by experimentally freezing them in a programmed chamber. Widespread damage was observed in the field in October 1971, September 1972 and September 1979 and assessments of field trials showed that damage was most severe on southerly provenances and on trees deficient in phosphorus.