Analysis of Cronartium flaccidum lesion development on pole-stage Scots pines
2000
Kaitera, Juha
Historical and current lesion development and sporulation of Cronartium flaccidum was investigated in a stand of artificially seeded pole-stage Pinus sylvestris in northern Finland. An average of 6.5 lesions developed per infected tree, most of them occurring on a minority (25%) of the trees. During the monitoring period of five years, fresh aecia appeared mainly in 7â10-year-old shoots, the age of the shoots bearing aecia varying between 3â20 years. Aecia appeared for the first time most frequently in 5â10-year-old shoots. Infection waves occurred, whereas lesions were formed most frequently in shoots formed in various years through the 1980s. After the lesions started to sporulate, sporulation in most lesions that finished sporulating during the monitoring period lasted for 1â2 years. The aecia in between 47% and 59% of the infected shoots developed annually over a longer length in proximal direction than in distal direction next to the previous yearâs infection. The aecia-bearing distal part of the shoot was longer in between 19% and 37% of the shoots.
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