Control of Heterobasidion in Norway Spruce Stands: The Impact of Stump Cover on Efficacy of Urea and Phlebiopsis gigantea and Implications for Forest Management

Astra Zaluma,Uvis Skola,Lauma Bruna,Talis Gaitnieks,Patrick Sherwood,Jonas Rönnberg

doi:10.3390/f12060679

Abstract

This study investigated the efficacy of Rotstop®, a native Latvian Phlebiopsis gigantea strain and 35% urea solution in combination with a stump cover treatment to control against natural spore infection by Heterobasidion spp. upon precommercial thinning of Norway spruce in three stands growing on former agricultural lands. The major findings were that (i) infection rates of Heterobasidion spp. on stumps treated with the native P. gigantea strain, Rotstop® or urea are similar when stumps are uncovered, and (ii) stump cover promotes stump colonization by the Latvian P. gigantea strain and Rotstop®, leading to a significantly smaller relative area colonized by Heterobasidion spp., as well greater efficiency against Heterobasidion in comparison with urea. Covering of stumps appears beneficial for controlling Heterobasidion stump colonization and may be valuable to forest owners if used in small-scale operations, but it is impractical in automatized thinnings, where managers should consider using regular Rotstop® without covering the stumps.

Highlights

Heterobasidion annosum sensu lato (Fr.) Bref. is a species complex of necrotrophic, root and white rot pathogens of conifers, comprising five species distributed in the NorthernHemisphere [1]
Three of the species are native to Europe: (i) Heterobasidion annosum sensu strictum (Fr.) Bref., primarily a pathogen of Scots pine (Pinus sylvestris L.) and other pines and conifers; (ii) Heterobasidion parviporum Niemelä & Korhonen, a pathogen of Norway spruce (Picea abies (L.) Karst.); and (iii) Heterobasidion abietinum Niemelä & Korhonen, largely a pathogen of silver fir (Abies alba Mill.) and other Abies species
The aims of this study were to test the control efficiency of Rotstop®, a native Latvian Phlebiopsis gigantea strain and urea as control agents against natural spore infection of Heterobasidion spp. on pre-commercial thinning stumps of Norway spruce on former agricultural lands, and to analyze the effect of stump coverage on urea and biological control agent (BCA) efficacy

Summary

Introduction

Heterobasidion annosum sensu lato (Fr.) Bref. is a species complex of necrotrophic, root and white rot pathogens of conifers, comprising five species distributed in the NorthernHemisphere [1]. In intensively managed forests and plantations, Heterobasidion spp. is a major threat to timber production, owing to growth reduction and increased tree mortality, with financial losses estimated as more than 790 million euros per year in Europe alone. Is a major threat to timber production, owing to growth reduction and increased tree mortality, with financial losses estimated as more than 790 million euros per year in Europe alone These calculations do not include wind and storm damage in decayaffected stands, damage that may be or may become (due to climate change) extremely significant [1] and references therein.

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