Associate Professor David Lee, University of the Sunshine Coast
Forestry operations in native forests, environmental plantings and planted forests are major disturbance events, leading to abundant coppice/seedling/juvenile growth that is ideal for the development of Myrtle Rust (Austropuccinia psidii) and endemic fungi of leaves/stems e.g. Quambalaria pitereka. Myrtle rusts’ interaction with endemic fungi and impact on recovery of these disturbed forests are unknown. This project will complement PBSF029 which focusses on the impact of Myrtle rust following fire disturbance. In addition, we will evaluate several untested novel fungicides for efficacy against these diseases.
Objectives and Impact
Objective: Myrtle rust and endemic fungi impacts onyoung environmental plantings, and coppice regrowth in native forests following forestry operations (e.g. thinning), are unknown. We aim to quantify disease impact on growth and test novel fungicides to manage these impacts, encouraging ecosystem recovery and forest establishment.
Methods: Establish replicated field trials (2 locations in Southeast-QLD/NNSW) to examine current impact of myrtle rust and endemic fungi on environmental plantings and regrowth forests following forestry operations (Theme 3.2 MR Action Plan). Target species include important native forest Myrtaceae species: e.g. C. citriodora (spotted gums comprise 80% of native forest timber harvested in Queensland), E. cloeziana (Gympie messmate) and Melaleuca species (paperbarks). We will allow natural fungal infection and inoculate coppice/young trees with myrtle rust/endemic fungi to quantify disease impact on tree growth and evaluate efficacy of untested novel fungicides that could protect the species (Theme 4.3 MR Action Plan).
Trials evaluating the impact of the exotic pathogen Austropuccinia psidii (causing myrtle rust) and the endemic pathogen Quambalaria pitereka (causing Quambalaria shoot blight: QSB) were established at two locations in southeast Queensland. These trials were set up on sites that had recent forestry operations including tree planting and harvesting operations which resulted in coppice regrowth. Three myrtaceous species were included in the study: Eucalyptus cloeziana, E. siderophloia and Corymbia citriodora subsp. variegata.
Two-year old E. cloeziana trees appeared to have reach a stage (height) where they had outgrown susceptibility to myrtle rust. However, Corymbia citriodora subsp. variegata trees at the same age were being moderately impacted by QSB. Coppice regrowth of these species was more impacted by the fungal pathogens than intact trees.
Three fungicides were also evaluated during this study (one commercial fungicide and two novel fungicides). All had beneficial effects against the fungal diseases in terms of disease incidence or tree growth.
The efficacy of the two novel fungicides warrants further investigation which may lead to an application for APVMA registration.