Are jarrah (Eucalyptus marginata)trees killed byPhytophthora cinnamomior waterlogging?

Eucalypt decline in Australia, and a general concept of tree decline and dieback

“…However, the expression of disease associated with P. cinnamomi throughout temperate Australia varies with environmental conditions (Shearer and Smith, 2000). Dieback has been associated with very wet and/or dry seasons on poorly drained sites affected by human management such as tree cutting, earthworks and severe fires (Marks et al, 1975;Fagg et al, 1986;Davison, 1997;Shearer and Smith, 2000). Whether or not Phytophthora is exotic in parts of its range (Pratt and Heather, 1973), root disease is associated with human disturbance.…”

“…However, the term is also applied to relatively sudden deaths of trees and patches of understorey associated with root rots, drought or waterlogging (e.g. Davison, 1997;Fensham and Holman, 1999;Rice et al, 2004). Both uses may include the symptoms defined as dieback by the Society of American Foresters (Podger, 1981).…”

Resolving confusions about jarrah dieback - don’t forget the plants

“…The only possible way that P. cinnamomi could damage jarrah roots sufficiently to cause severe water deficits to develop, is if infection occurs simultaneously in the tension wood of all major roots. This has not been observed in many of the investigations into the deaths of groups of jarrah trees (Harding 1949;Stahl and Greaves 1959;Podger et al 1965;Podger 1968;Shea et al 1982;Davison 1997), although infection at the root collar does occur occasionally (Dell and Wallace 1981;Shearer et al 1981;Crombie and Tippett, 1990;Hardy et al 1996).…”

“…For example this was the only symptom seen in dead jarrah trees that had been waterlogged 11 months earlier, following exceptionally heavy rainfall and increased discharge of water into the site from nearby roadworks (Davison 1997). In vertical roots 75 % of the sapwood vessels were tylosed, while 25 % were tylosed in horizontal roots.…”

“…Tree deaths were on sites where waterlogging had been observed (Waring 1950;Hamilton 1951;Loneragan 1961;Davison 1997), there were large numbers of tylosed xylem vessels in the root sapwood (Harding 1949;Stahl and Greaves 1959;Davison 1997) and there were no symptoms of consistent fungal lesions or insect damage (Harding 1949;Stahl and Greaves 1959;Podger et al 1965;Davison 1997). Only one other investigation into tree deaths mentions tyloses, which in this instance were associated with P. cinnamomi lesions (Dell and Wallace 1981).…”