Epidemiology of Scleroderris lagerbergii in central Ontario

Abstract

DORWORTH, C. E. 1972. Epidemiology of Scleroclerris 1agcrbel.gii in central Ontario. Can. J. Bot. 50: 751-765. Scleroderris canker (Scl~roclerris Iugerbergii Gremmen) has damaged conifers in Europc for nearly a century. The disease has intensified in the Great Lakes region of North America during the past several decades, and the fungus could spread throughout the North Temperate Zone. Attacks by S. Ia,yerbergii are most severe in topographical depressions and the resulting disease was thought to be associated with frost damage. Observations in depressions that resembled frost pockets indicated that extensive damage to regeneration of Pitz~rs resitrosa Ait. could be attributed primarily to amplified spore deposition in the depressions and rapid intensification of the disease in the presence of prolonged periods of high relative humidity. Topographic projections, photographs, temperature profiles, and spore collection data support this thesis. Vertical restriction to foliage within ca. 1.5 n~ of the ground is attributed to radiation fog that prolongs the incubation period afforded the fungus. Effects of edaphic variation, ground vegetation, and snow cover are evaluated. Snow is accorded importance in ~iiodifying extremes of winter and early spring teniperat~~res to the advantage of the fungus. Frost damage and infection by S. lagerbergii both result in !,!antation failures in topographic depressions. DORWORTH, C. E. 1972. Epidemiology of Sclerorlerris lagerbergii in central Ontario. Can. J. Bot. 50:751-765. Le chancre scleroderris (Scleroderris lagerbergii Grernmen) a endoniniage les conifires en Europe depuis environ un siicle. La maladie s'est intensifiee dans la region des Grands Lacs de I'AmCriq~~e du Nord au cours des recentes dtcennies et le champignon pourrait s'etendre dans toute la zone temperee de l'heniisphire nord. Les attaques par S. lagerbergii sont les plus graves dans les depressions topographiques, et on a cru que la maladie qui s'y developpait etait associee aux donimages causes par le gel. Des observations dans des depressions, qui ressemblaient a des poches de froid, indiquent que les donimages iniportants dans la regeneration de Pitzus resitrosa Ait. pouvaient &tre attribues a une deposition accrue des spores dans les depressions e t a une proliferation rapide de la maladie au cours de periodes prolongees d'huniiditt relative elevee. Des projections topographiques, des photographies, des profils de tempkrature et les resultats de recoltes de spores supportent cette thtse. Le fait que la maladie soit restreinte au feuillage situe a moins de 1.5 m du sol est attribue i la brume de condensation qui prolonge la periode d'incubation offerte au champignon. Les effets de la variation kdaphique, du couvert vegetal et de la couverture de neige sont evalues. Une certaine importance est accordbe a la neige qui modifie les extremes de temperature en hiver et au debut du printemps 5 I'avantage du chanipignon. Le dom~nage cause par le gel aussi bien que I'infection par S. lagerbergii provoquent des echecs ...

Differential reaction in Pinus spp. to inoculation by various isolates of Ascocalyx (Gremmeniella) abietina

“…The cankers here described are similar to those associated with stem infections oi Pinus in North America, where stem canker is the symptom most often associated with the disease often called "Scleroderris canker" (DORWORTH 1981).…”

“…may comprise two varieties (ETTLINGER 1945;MORELET 1980;UOTILA 1983), or at least three physiologically races or serovars, namely Asian, European and North American (DORWORTH and KRYWIENCZYK 1975). In general, each of these races attacks a different range of hosts and produces a different disease syndrome (DORWORTH 1981).…”

Infection experiments with Gremmeniella abietina on seedlings of Norway spruce and Scots pine

“…As mentioned, the fungus is favoured in nature by high humidity (DORWORTH 1972), low summer temperatures (PETXISTO and REPO 1987), and mild winter temperatures (MAROSY and PATTON 1987). High humidity may be necessary to ensure superficial survival (cf.…”

About phytopathological and histological aspects of Norway spruce dieback in the Orlické hory Mts.

“…In such places, the trees are more often damaged by frosts. Moreover, the spores may recirculate, thus intensifying the amount of inoculum (DORWORTH 1972). Sometimes the disease has been found to be more frequent on higher levels above the sea (ROLL-HANSEN 1972;ROLL-HANSEN and ROLL-HANSEN 1973).…”