Two-Year Survival of Gremmeniella abietina Conidia Collected on Branches Left on the Ground after Pine Harvesting

Gaston Laflamme,Danny Rioux

doi:10.3390/f6114055

Abstract

In 1972, it was reported that viable ascospores and conidia of Gremmeniella abietina, North American race, were present on dead branches up to 10 months after they were killed. In Sweden, the survival period of conidia of G. abietina, European race, was reported to be over 18 months. We investigated the viability of conidia produced by G. abietina, European race, over a 2-year period in eastern Canada. Infected branches with pycnidia were left on the ground in June 2006. Branches were sampled every month during three growing seasons. Conidia germination was tested monthly and showed a very high rate of germination (76%–98%) from July 2006 to August 2007. Very few pycnidia were detected in the fall of 2007 and in May 2008. In June and July 2008, no pycnidia could be observed, the shoots being in an advanced stage of decomposition. In light of these observations, it is recommended to delay pine plantation until after two growing seasons following harvesting of diseased pine trees.

Highlights

The fungal pathogen Gremmeniella abietina (Lagerb.) Morelet causes shoot blights and cankers, symptoms of a disease known as scleroderris canker, mainly found on two-needle pines
In 2007, the germination rate was very high from May to August but no conidia could be found from September to November 2007 as pycnidia appeared dry and empty
The fact that G. abietina stopped producing pycnidia in September 2007, in contrast to the previous year where it continued until late in the fall (November), suggests that the dry climatic conditions observed at that time could have affected sporulation, even though it is most likely the result of the degeneration of the pathogen into the decaying shoots

Summary

Introduction

The fungal pathogen Gremmeniella abietina (Lagerb.) Morelet causes shoot blights and cankers, symptoms of a disease known as scleroderris canker, mainly found on two-needle pines. The names “European race” or “European strain” were given to distinguish this exotic pathogen from the native North American one [2]. It is equivalent to the A type [3] or the large tree type [4] of G. abietina reported in Europe. None of these designations (race, strain, type) have any taxonomical value [5].

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Conclusion