POTENTIAL OF FUNGAL ISOLATES FOR THE BIOLOGICAL CONTROL OF SAFFRON THISTLE (CARTHAMUS LANATUS) IN AUSTRALIA
NS CRUMP1, GJ ASH1 and A NIKANDROW2
1Farrer Centre for Conservation Farming, Charles Sturt University, PO Box 588, Wagga Wagga 2678, Australia; 2 Agriculture and Veterinary Research Centre, Orange 2800, Australia
Background and objectives
In Australia, the major constraint to the application of classical biological control for saffron thistle is its genetically similar background to safflower (Carthamus tinctorius) . However no consideration has been given to the use of inundative biological control. This paper outlines the suitability of a fungal pathogen for inundative biological control of saffron thistle.
Results and conclusions
The host range of the Phomopsis sp. was tested by inoculating 29 species, from four different families. Six species within the family Asteraceae, Centaurea sp., Carthamus tinctorius, Lactuca sativa, Dorotheanthus sp. and Chrysanthemum morifolium were killed 3-5 days after inoculation. Severe lesions were recorded on Centaurea solstistialis, Senecio madagascariensis and Arctotheca calendula. In summary, no economically important plants which would be found in the same environment as saffron thistle were killed by Phomopsis sp. Therefore it appears feasible to continue investigations on the use of Phomopsis sp. as a mycoherbicide for saffron thistle. Furthermore, the susceptibility of other weed species promotes the advantage of using Phomopsis sp. as a biocontrol agent.
The most limiting factor of mycoherbicide development is the fungal pathogen's requirement for moisture to infect the plant. Studies on the dew period requirement of Phomopsis sp. on saffron thistle has shown that a period of 2 days' moisture is required to incite complete plant mortality. This dew period must not be delayed after application of the pathogen. Further studies are now focusing on additives which could be combined with the fungus to reduce the dew period requirement and increase plant mortality.