Taking their cue from a naturally occurring phenomenon, scientists based at New South Wales Department of Primary Industry’s Wagga Wagga Agricultural Institute have been exploring the potential of Australian eucalyptus to control major weeds and crop diseases.
The NSW DPI research team, under the guidance of leading weed expert Dr Hanwen Wu, has identified essential oils from several eucalyptus species that they believe can help combat agrochemical resistance in plant pests and pathogens – among farmers’ biggest challenges this decade.
The allelopathic effect of eucalyptus trees, where chemicals they release suppress plant growth in the understorey, is commonly seen in the landscape and we applied a scientific approach to investigate that observation,” explained Dr Wu.
“Laboratory tests showed that some eucalyptus oils, from a selection of 40 species, were able to completely suppress fungal growth of three major diseases, wheat yellow leaf spot and crown rot and canola sclerotina stem rot.
“We screened 300 eucalyptus species on weeds, including annual ryegrass, barley grass, fleabane, silverleaf nightshade and wild radish, to find that even at low concentrations some eucalyptus oils were able to prevent germination and growth of weed seeds.”
There’s enormous potential for further exploration of the use of eucalyptus essential oils as bioherbicides for weed management, Dr Wu noted.
“With rapidly growing herbicide resistance and no new molecules developed in the last 25 years, which could offer new modes of action to control weeds, these naturally occurring oils could be a gift from nature,” he said.
“We now need to find out how these oils work to inhibit weeds and diseases so we can adopt the technology for use in agricultural production and to safeguard the environment.”
Further study of eucalyptus species, and the subsequent identification of the bioactive compounds in these species, could provide “chemical leads” for the development of new herbicides, with new modes of action, the researchers noted.
With an estimated 800-plus eucalyptus species in Australia, the discovery has immense potential to offer farmers across the nation a new, cost-effective and sustainable way of managing weeds and crop diseases.
Dr Wu and his team’s research was funded by the NSW Government Weeds Action Program 2014-2015, with support from Meat & Livestock Australia (MLA) and the Graham Centre for Agricultural Innovation – an alliance between DPI and Charles Sturt University.