Annosus root and butt rot

Introduction

Formerly Heterobasidion annosum (Fr. : Fr.) Bref.

Prevention

Disease prevention can be achieved by carrying out forestry activities during the winter, when the snow stays on the ground. Thus, the low temperatures prevent the fungus from sporulating while the fruiting bodies of H. irregulare are under the snow. Spore dispersal is almost nil at that time. When silvicultural operations are carried out in the absence of snow, care must be taken to avoid injuring the roots of the residual trees to minimize infection (Davis and Meyer 2004).

Control

1. Mechanical and silvicultural

The two main infection routes for the disease colonization of freshly cut stumps since less than two weeks and root graft between healthy roots and roots of infected stumps (Epstein 1978).When thinning and final cutting operations are scheduled during warmer months (when the temperature reaches 8°C), simultaneous stump treatment using chemical or biological control agents should also be planned (Laflamme 1994).
In forest sites or plantations that are infected stumps should be extracted and burned after harvesting (Froelich et al. 1978) or the sites should be converted to deciduous species (Legrand and Soutrenon 2008). Manion (1981) believes that no treatment will be effective for a severely infected stand.

2. Chemical

Applying urea to freshly cut stumps promotes colonization of the stump surface by numerous antagonistic fungi (Johansson et al. 2002). Ideally, this treatment should be carried out at the same time as the cutting. Alternatively, it can be done in the days following the harvesting. Treatment of stumps with urea appears to be effective in Europe, but the product in question has not been tested in Canada (Maladies des arbres du Québec 2009).Borax (disodium tetraborate) was used in the past, but it is no longer registered for use in Canada because it was found to have limited effectiveness in plantations where the disease was still present.Currently, there are no products registered specifically for treating Annosus root and butt rot in Canada.

3. Biological

In several European countries, pines have been successfully protected by applying a biocontrol agent, specifically, spores of Phlebiopsis gigantea (Fr.:Fr.) Jül. (syn: Peniophora gigantea (Fr.:Fr.) Massee) to pine stumps. A biocontrol product based on P. gigantea is currently under development in eastern Canada (Maladies des arbres du Québec 2009; Laflamme 1994, 2001; Laflamme et al. 1998). The registration process has been initiated.
Another avenue of research relates to the potential of using mycoviruses as biological control agents that can alter the virulence of H. annosum (Ihrmark et al. 2002).

4. Genetic resistance

H. irregulare affects so many coniferous species that the development of resistant varieties would be impossible.

5. Stages in an integrated disease management program

1. Schedule silvicultural operations in the winter.
2. If winter operations are not feasible, treat cut stump surfaces with urea during harvesting in locations where this is legally permitted.
3. Consider using the biocontrol agent Phlebiopsis gigantea when the product becomes available.
4. Once a Heterobasidion sp. has become established on a forest site, locate the affected area, burn the grubbed-out stumps and convert the stand to deciduous species. The disease expansion in small mortality foci can also be stopped by digging a trench around the dead trees and two additional rows of apparently healthy pines

References

1. Centre collégial de développement de matériel didactique. [SD]. Maladies des arbres du Québec. http://rea.ccdmd.qc.ca/ri/arbres/# consulté le 13 janvier 2009.
2. Davis, C. and Meyer, T. 2004. Field Guide to Tree Diseases of Ontario. Natural Resources Canada, Canadian Forest Service, Great Lakes Forestry centre, Sault Ste. Marie, NODA/NFP Technical report TR-46 (Rev. ed.), 138 pp.
3. Epstein, A. H. 1978. Root graft transmission of tree pathogens. Annual Review of Phytopathology; 16 181-192
4. Froelich, R. C.; Hodges, C. S. Jr. and Sackett, S. S. 1978. Prescribed burning reduces severity of annosus root rot in the south. Forest Science; 24 (1), p. 93-100
5. Johansson, S.M.; Pratt, J.E. and Asiegbu, F.O. 2002. Treatment of Norway spruce and Scots pine stumps with urea against the root and butt rot fungus Heterobasidion annosum—possible modes of action. Forest Ecology and Management vol 157 March 2002 p. 87-100
6. Ihrmark, K.; Johannesson, H.; Stenström E. and Stenlid, J. 2002. Transmission of double-stranded RNA in Heterobasidion annosum. Fungal Genetics and Biology. Volume 36, Issue 2, Pages 147-154.
7. Laflamme, G. 2001. In Biological Control Programmes in Canada, 1981-2000; Heterobasidion annosum (Fries) Brefeld, annosus root rot (Polyporaceae). Wallingford: CABI Publishing, p. 461-464
8. Laflamme, G.; Blais, R. and Bussières, G. 1998. Eradication trial of annosus root rot in red pine plantations. Root and butt rots of forest trees: 9th International Conference on Root and Butt Rots, Carcans-Maubuisson, (France), 1-7 September, 1997. Paris: Institut National de la Recherche Agronomique (INRA), p. 375-380
9. Laflamme, G. 1994. La maladie du rond causée par Heterobasidion annosum. Feuillet d’information CFL27, Centre de Foresterie des Laurentides, Service Canadien des Forêts. Ressources naturelles Canada.
10. Legrand, P. et Soutrenon, A. 2008. Annosus root rot in conifers: from diagnosis to treatment. / Le fomes des résineux: du diagnostic au traitement. Forêt-Entreprise; (178), Paris: Institut pour le Développement Forestier, p. 51-55
11. Manion, P. D. 1981. Tree disease concepts. State University of New York. Prentice-Hall, New Jersey 399p.

Authors

Josée Grondin et Pierre DesRochers

Auditors

Gaston Laflamme