Efficacy of Chemical and Biological Stump Treatments for the Control of Heterobasidion occidentale Infection of California Abies concolor.

Adrian L Poloni,Richard C Cobb,Christopher A Lee,Matteo Garbelotto

doi:10.3390/pathogens10111390

Adrian L Poloni, Richard C Cobb + Show 2 more

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https://doi.org/10.3390/pathogens10111390

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Abstract

We conducted an experimental evaluation of treatments to limit Heterobasidion occidentale infection of white fir (Abies concolor) stumps and wounds in California mixed conifer forests. We tested the efficacy of urea, borate, and a mixture of two locally collected Phlebiopsis gigantea strains in preventing pathogen colonization of fir stumps and separately, urea and borate as infection controls on experimental stem wounds. These were paired with a laboratory test on ~100 g wood blocks with and without a one-week delay between inoculation and treatment. Urea, borates, and Phlebiopsis treatments all significantly reduced the stump surface area that was colonized by H. occidentale at 84%, 91%, and 68%, respectively, relative to the controls. However, only the borate treatments significantly lowered the number of stumps that were infected by the pathogen. The laboratory study matched the patterns that were found in the stump experiment with a reduced area of colonization for urea, borates, or P. gigantea treatments relative to the controls; delaying the treatment did not affect efficacy. The field wound experiment did not result in any Heterobasidion colonization, even in positive control treatments, rendering the experiment uninformative. Our study suggests treatments that are known to limit Heterobasidion establishment on pine or spruce stumps elsewhere in the world may also be effective on true firs in California.

Highlights

Heterobasidion species occur across the northern hemisphere and severely impact a range of conifers including, but not limited to, the widespread economically and ecologically relevant genera Pinus, Abies, and Picea [1]
We found no evidence of differences in ambient spore loads across stands the two stands where we performed the stump H. occidentale colonization prevention experiments
Our findings suggest that the effects of these topical treatments may be tical to that applied in the laboratory wood block experiment where pathogen growth was beneficial to decrease white fir stump infection, and Heterobasidion root disease, common, there is no basis to conclude that the pathogen was unviable in the solution

Summary

Introduction

Heterobasidion species occur across the northern hemisphere and severely impact a range of conifers including, but not limited to, the widespread economically and ecologically relevant genera Pinus, Abies, and Picea [1]. These pathogens are largely, but not exclusively, endemic causes of Heterobasidion root disease, a root and butt rot disease which is one of the most important diseases impacting conifers in the northern hemisphere [2,3]. Identifying management options that can limit root disease establishment and/or impacts and the development of butt rots that affect tree vigor could be a worthwhile effort to sustain the health of forest resources in much of the northern hemisphere. Management of forests with fir components may benefit from actions that are meant to limit infection of stumps and trees by H. occidentale

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