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Management of Pinus sylvestris stands infected by Gremmeniella abietina

aspects of tree survival, growth and regeneration after the severe outbreak in 2001

Bernhold, Andreas (2008). Management of Pinus sylvestris stands infected by Gremmeniella abietina. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2008:27
ISBN 978-91-85913-60-2
[Doctoral thesis]

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Abstract

The pathogen Gremmeniella abietina causes severe damage to native Pinus sylvestris and introduced Pinus contorta var. latifolia in Sweden. The recent G. abietina outbreak in 2001–2003, caused by the large tree type (LTT), affected at least 480,000 ha of middle-aged P. sylvestris stands and forced Swedish forest owners to sanitary clear-cut large areas of valuable forests. There was, however, little knowledge of survival and growth loss of infected trees and risks involved in replanting P. sylvestris in the G. abietina-infected slash. In this thesis, G. abietina disease incidence on P. sylvestris seedlings planted after sanitation felling was studied, with and without removal of infected P. sylvestris slash. Furthermore, survival and vitality of G. abietina in the slash was studied by spore germination tests of pycnidia collected from infected slash at regular intervals. One year after planting, G. abietina pycnidia were found on 32% of the control seedlings and total infection, including stem cankers, reached 44%. Removal of infected slash reduced the number of infected seedlings by 50% and seedling mortality by 27%, one year after planting. The vitality of G. abietina in the slash was as high in pycnidia collected in 13- to 18-months-old slash as in pycnidia collected in fresh slash. It is recommended to wait at least two years after sanitary fellings before replanting with P. sylvestris. To improve the accuracy of predictions of mortality and growth losses in infected, pole-sized P. sylvestris stands, mortality, diameter growth and insect colonisation were monitored and related to crown defoliation in four 40-year-old stands in 2001–2005. Of the killed trees, 84% were at least 90% defoliated the year before they died and trees with less than 90% defoliation were only killed in the initial phase of the outbreak. A majority of the trees were killed directly by G. abietina whereas less than one third died after colonisation by pine shoot beetle (Tomicus piniperda), a pest that was mainly found on dead trees or trees with at least 95% defoliation. A greater fraction of small trees died and generally did so more rapidly than larger trees. Regression analysis indicated that a mean defoliation of 2/3 of the crown resulted in an average loss of 50% in diameter increment. Based on this study, a defoliation limit of 75–80% is recommended for sanitary cutting of P. sylvestris trees in the initial phases of an outbreak, and a limit of ca. 90% for trees that survive the initial phases of an outbreak. The interest in the productive P. contorta as an alternative to P. sylvestris is currently increasing in Sweden. To study the resistance of P. contorta to LTT G. abietina, seedlings of P. contorta and P. sylvestris were planted in gaps of an infected 40-year-old P. sylvestris stand in 2005. After two years, 45% of the P. contorta seedlings and 32% of the P. sylvestris seedlings were infected. However, mortality was lower and the mean length of infected tissue on surviving seedlings significantly shorter in P. contorta (3.9 cm) compared to P. sylvestris (10.4 cm). Furthermore, 47% of the P. contorta seedlings had developed new leader shoots in 2007, compared to 19% of the P. sylvestris seedlings. Histopathological examinations of infected shoots showed that both P. contorta and P. sylvestris produce ligno-suberised boundaries that are involved in the active defence in the shoots, preventing major crown dieback. The results indicate that P. contorta is more resistant to LTT G. abietina than P. sylvestris.

Authors/Creators:Bernhold, Andreas
Title:Management of Pinus sylvestris stands infected by Gremmeniella abietina
Subtitle:aspects of tree survival, growth and regeneration after the severe outbreak in 2001
Year of publishing :2008
Volume:2008:27
Number of Pages:55
Papers/manuscripts:
NumberReferences
ALLI. Witzell, J., Bernhold, A. & Hansson, P. (2006). Survival and vitality of Gremmeniella abietina on Pinus sylvestris slash in northern Sweden. Forest Pathology. 36, 406-412. II. Bernhold, A., Witzell, J. & Hansson, P. (2006). Effect of slash removal on Gremmeniella abietina incidence on Pinus sylvestris after clear-cutting in northern Sweden. Scandinavian Journal of Forest Research. 21, 489–495. III. Bernhold, A., & Witzell, J. Tree mortality, increment loss and foliage recovery in middle-aged Pinus sylvestris following defoliation by Gremmeniella abietina and subsequent attack by Tomicus piniperda (Submitted manuscript) IV. Bernhold, A., Hansson. P., Rioux, D., Simard, M. & Laflamme, G. Resistance to Gremmeniella abietina (EU race, large tree type) in introduced Pinus contorta and native Pinus sylvestris in Sweden (Submitted manuscript).
Place of Publication:Umeå
ISBN for printed version:978-91-85913-60-2
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agrovoc terms:pinus sylvestris, pinus contorta, godronia, slash, disease transmission, regeneration, growth, survival, fungal diseases, sweden
Keywords:defoliation, diameter increment, disease resistance, fungal pathogen, growth loss, lodgepole pine, Pinus contorta, sanitation, Scleroderris canker, Scots pine, slash.
URN:NBN:urn:nbn:se:slu:epsilon-2168
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-2168
ID Code:1732
Department:(S) > Dept. of Forest Ecology and Management
Deposited By: Andreas Bernhold
Deposited On:10 Apr 2008 00:00
Metadata Last Modified:02 Dec 2014 10:13

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