Two Pinus sylvestris stands in each of four research areas in different parts of Finland were pruned during the period May 1985-April 1986. Test prunings were carried out 16 times in all eight stands during the year. Every other pruned tree was inoculated with conidia of the canker fungus Phacidium coniferarum. Pruning damage surveys were also carried in 50 pine stands pruned during 1981-84. The most susceptible pruning period was from October to December. The safe pruning season ended in autumn when the five-day mean temperature decreased below 7 degrees C. The unsafe pruning season ended when the temperature remained permanently below 0 degrees C. The mycelia of the fungus were pathogenic in the inoculations made from October to March. The fungus commonly occurred in slash and in pines wounded during the autumn. P. coniferarum has a one-year life cycle. Recommendations are made for avoiding unsafe pruning times in the different regions of Finland.

Damage on Scots pine (Pinus sylvestris L.) caused by Gremmeniella abietina (Lagerb.) Morelet was assessed in the summer of 1992 in sixty-seven stands in eastern Lapland. The area and severity of damage were smaller and lighter than had earlier been estimated and occurred especially in stands in the first-thinning stage or in middle age. Significant new infection of 1991 occurred in stands previously heavily infected by G. abietina near the Kemihaara river, lake Naruska, the Naruska river, the Tuntsa river and lake Vilma. Fresh damage occurred mainly in the lower or middle parts of the Scots pine canopies.