The potential of copper sulphate to control Phytophthora cinnamomi during bauxite mining in Western Australia

Abstract

Bauxite mining in Western Australia occurs in forest infested with Phytophthora cinnamomi. The mining company Alcoa identified the need for a treatment to eradicate P. cinnamomi from relatively small volumes (<60 m³) of topsoil and gravel. This study examined the efficacy of copper sulphate (CuSO₄) in eradicating P. cinnamomi within 2 h and after 5 days. Both agar and in vitro soil tests were used. Concentrations up to 137.5 mg/L Cu²⁺ in potato-dextrose agar did not kill or totally inhibit growth of the pathogen. Vermiculite infested with P. cinnamomi was added to topsoil and gravel treated with concentrations up to 5 g CuSO₄/kg soil. Direct plating of vermiculite and baiting of soils with leaves of Pimelea ferruginea and cotyledons of Eucalyptus sieberi were used to determine the disease-suppressing ability of CuSO₄. Applications of up to 5 g CuSO₄/kg soil were insufficient to kill P. cinnamomi after 2 h exposure in both soil types. However, infection of baits in gravel did not occur after 5 days exposure. The results indicate that CuSO₄ application would not be appropriate where rapid and total eradication of P. cinnamomi is required but it may be valuable where the aim is to significantly reduce the risk of spreading the pathogen.