This study examined the ability of foliar applications of the fungicide
phosphite to contain colonisation of
Phytophthora cinnamomi in a range of plant species
growing in natural plant communities in the northern sandplain and jarrah
(Eucalyptus marginata) forest of south-western
Australia. Wound inoculation of plant stems with
P. cinnamomi was used to determine the efficacy of
phosphite over time after application. Colonisation by
P. cinnamomi was reduced for 5–24 months after
phosphite was applied, depending on the concentration of phosphite used, plant
species treated and the time of phosphite application. Plant species within
and between plant communities varied considerably in their ability to take up
and retain phosphite in inoculated stems and in the in planta concentrations
of phosphite required to contain P. cinnamomi. As spray
application rates of phosphite increased from 5 to 20 g
L–1, stem tissue concentrations increased, as did
the ability of a plant species to contain P. cinnamomi.
However, at application rates of phosphite above 5 g
L–1 phytotoxicity symptoms were obvious in most
species, with some plants being killed. So, despite 10 and 20 g
L–1 of phosphite being more effective and
persistent in controlling P. cinnamomi, these rates are
not recommended for application to the plant species studied. The results of
this study indicate that foliar application of phosphite has considerable
potential in reducing the impact of P. cinnamomi in
native plant communities in the short-term. However, in order to maintain
adequate control, phosphite should be sprayed every 6–12 months,
depending on the species and/or plant community.
Distribution of saltmarsh plant communities associated with environmental factors along a latitudinal gradient on the south-west Atlantic coast