Trunk infection of eucalypts by Phytophthora cinnamomi Rands – a preliminary report.  G. C. Marks, I. W. Smith and F. Y. Kassaby.  June 1982.  17 pp. (unpubl.)

SUMMARY

Phytophthora cinnamomi Rands (phytophthora root rot) was isolated from the root collar and major roots of dead and wilting Eucalyptus sieberi L.A.S. Johnson (silvertop), E. regnans F. Muell. (mountain ash) and E. obliqua L’Hérit. (messmate stringybark) growing in infected soil in widely scattered locations in the coastal region of Victoria. Inoculation experiments show that P. cinnamomi infects the cambial zone, producing a spreading lesion under the bark in susceptible species; in resistant species the lesion is small. Kino veins are formed around the lesions in both susceptible and resistant species. Externally the lesions are inconspicuous and can only be detected by kino exudations, thus they are easily confused with other forms of damage.

Inoculation experiments on eucalypts confirmed the results obtained by Rands with Cinnamomum burmanni (Nees) Blume. They showed that the fungal activity was intermittent, and that there may be differences in pathogenicity of isolates and in susceptibility of trees within a species. The fungus was found to overwinter in the rhytidome (outer bark), even in cooler regions of Victoria, and field resistance to dieback disease was related to stem infection resistance. The results suggest that P. cinnamomi can kill susceptible eucalypt trees by girdling the root collar and/or major roots.

Also published:

Marks, G.C., Smith, I.W. and Kassaby, F.Y. (1981)  Trunk infection of Eucalyptus spp. by Phytophthora cinnamomi Rands a preliminary report.  Aust. For. Res. 11: 257-67.