Distribution of phytophthora root rot and eucalypt dieback along the proposed route of the Gas and Fuel Corporation natural gas pipeline, between Pakenham and Wollert.  P. J. McHugh, F. G. Neumann and G. C. Marks.  July 1983.  16 pp. + App. (unpubl.)

SUMMARY

The results are presented of a preliminary low-intensity survey during May 1980, and of two more detailed follow-up surveys during April 1982 and 1983, for the presence of Phytophthora cinnamomi Rands (phytophthora root disease) in soils, and of eucalypt dieback, along the proposed 88 km route of a Gas and Fuel Corporation natural gas pipeline between Pakenham and Wollert. In the three surveys, a total of 180 composite soil samples (each consisting of five 0.20-0.25 kg sub-samples) were tested for incidence of the pathogen in grassland, pasture and forest areas traversed by the route. In the 1983 survey, sampling was concentrated in forested rather than agricultural areas, as the former are known to be more vulnerable to the disease and have sustained less disturbance to soils and vegetation.

The pathogen was isolated at only 13.8 per cent of total sample points, though its distribution along the route was probably more widespread than assessed. Infected soil samples were taken from grassland and pasture, though most came from forested areas. Eucalypt dieback was observed near 13.3 per cent of total sample points, but only about 20% of these were infected with P. cinnamomi. In a few cases, dieback was associated with infestations by foliage-sucking psyllid insects (Psyllidae:Glycaspis spp.). Along most of the route, the soils and the vegetation had already been substantially disturbed as a result of various human activities such as roading, farming, mining and selective logging. Also, much of the vegetation appeared tolerant to the disease. It was therefore concluded that (1) any soil disturbance associated with the proposed construction works would only have a minor influence on the incidence of phytophthora root disease, and (2) hygiene measures are not warranted.