Environmental Conditions Influencing Infection of Norway Spruce Stumps by Heterobasidion annosum and Effect of Urea Treatment : Root and Butt Rots

Uppsala

International Union of Forest Research Organizations, Swedish University of Agricultural Sciences

1994

S. 668-674

11 Lit. Ang.

Bandaufführung

73841

About 60 thinnings (each 50 trees) were made in 30 year-old first generation Norway spruce stands in the southern half of Sweden in various seasons and weather conditions during 4 years. The infection rate of stumps by basidio-spores of Heterobasidion annosum was estimated after 3-15 months. During April-September it was significantly higher than during October-March. Temperature was the most important factor - below 50C very few infections occurred. Urea treatment of thinning stumps was performed using (A) a 20% solution applied by brushing and (B) a 30% solution applied by spraying. The effects of the both treatments were significantly different (p < 0.05): the 20% solution caused 77% reduction in infection rate and the 30% solution a 86% reduction. By applying a series of urea concentrations it was found that at least 50% of what is possible to apply in practice is necessary for a significant decrease in the infection rate.