Dunstan, W.A., Hardy, G.E.St.J., Colquhoun, I.J. and Shearer, B.L. (2006) Basal bark application of phosphite and the control of Phytophthora cinnamomi: a preliminary study with Banksia spp. and Eucalyptus marginata. In: Proceedings of the 3rd International (IUFRO) Conference on Phytophthora in Forests and Natural Ecosystems, 11 - 18 September 2004, Freising, Germany.
The efficacy of basal bark application (BBA) of phosphite to control infection by Phytophthora cinnamomi was compared with established application methods in two field experiments. In Banksia menziesii and B. attenuata, BBA was compared with trunk injection and high volume foliar spray (FS). In Eucalyptus marginata (Jarrah), BBA was compared with trunk injection only. Efficacy of treatments was assessed by measuring colonisation of stems artificially inoculated with P. cinnamomi (in situ for Banksia spp., and in excised stems for E. marginata). FS treatment was most effective in reducing colonisation by P. cinnamomi in B. attenuata and B. menziesii, (68%, p = 0.00002 and 60%, p = 0.00002, respectively), followed by BBA [52%, P = 0.00004, and 45%, p = 0.00003). Injection was effective in B. menziesii (42% reduction, p = 0.00006), but the reduction in colonisation in injected B. attenuata was not significantly different from untreated controls. In Jarrah, stem colonisation was reduced by 33% in injected trees (p = 0.003), but BBA was ineffective. Application time for BBA was 26-43% of that for other treatments. However, the cost of the carrier (modified heptamethyltrisiloxane) made BBA treatment 1.5-1.8 times more expensive per unit of basal area than the other methods.