Swiss needle cast of Douglas fir in Victoria. II. Variation in the resistance of provenances.  L.A. Pederick and G.C. Marks.  June 1975.  10 pp. (unpubl.)

SUMMARY

A Douglas fir provenance trial at Narbethong infected with the Swiss needle cast fungus (Phaeocryptopus gaeumannii) was assessed for variation in severity of disease symptoms. Provenances from southern latitudes (California and Southern Oregon) and from higher altitudes were more susceptible to the disease. Provenances from low altitude sources on the Californian coast, which have shown the best potential for growth in Victoria, were poorly represented in the trial, but available evidence indicates that they will be badly affected by the disease.

The least affected provenances in the trial were from low altitudes on the central Oregon coast. These have given reasonably good growth in Victoria. All the trees in the trial were infected. There was no evidence of any absolute resistance to the disease.

Considerable tree to tree variation in apparent resistance was observed. A number of very lightly affected trees were observed in some of the provenances. The provenances and individual trees also varied in the time at which the flushing of the new season’s foliage occurred. The possibility of partial disease escape by late flushing requires investigation.