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Pasture competition key to beating parthenium weed 13 May 2013

New research has identified the best pasture species for Queensland graziers to out-compete parthenium weed and potentially increase stocking rates.

Dr Stephen Adkins of the University of Queensland ran trials at Mungallala, Injune and Kilcoy from October 2011 to March 2012 with funds from the National Weeds and Productivity Research Program, managed by the Rural Industries Research and Development Corporation.

“The trial at Mungallala in the south west showed tall finger grass, Rhodes grass, Queensland blue grass and Wynn cassia to suppress weed growth by over 80 per cent,” Dr Adkins said. “The native Queensland blue grass provided the best fodder biomass of the 11 species tested.”

At Injune in the central west, tall finger grass was the only species to strongly suppress parthenium weed. This was followed by butterfly pea at 66 per cent, buffel grass at 65 per cent and Wynn cassia at 61 per cent.

“In this area the best fodder yields came from buffel grass followed by butterfly pea,” he said

The grazing trial at Kilcoy in the south-east showed the best forage production was obtained with a mix of Rhodes grass, butterfly pea and green panic. In another trial, atro and buffel grass performed strongly.

Parthenium weed is most commonly found in the rangelands and summer cropping areas of Queensland and northern New South Wales, but it has now spread into the Gulf Country of the Northern Territory and into Western Australia. 

Each plant produces around 20,000 seeds, which can germinate and start producing the next generation of seeds in just four weeks.

“The weed has a big impact on the beef industry, mainly through reducing land carrying capacity and increasing management costs,” Dr Adkins said.

“So far 11 biological control agents have been identified, tested and released for parthenium weed. Interestingly, the trial at Kilcoy was hampered by the presence of the Mexican beetle (Zygogramma bicolorata) that was introduced to attack the weed.

“However, while biological control is an important weapon, it isn’t the only answer. It needs to be combined with other strategies - pasture competition, herbicides, cultivation and improving the general cleanliness and health of the land.”

Parthenium weed possibly originated in Mexico, but it has genetically adapted to a wide range of environments and spread at an extremely alarming rate. It has now exploded across the globe, invading some 30 countries including large tracts of India and Eastern Africa.

Dr Adkins was the lead presenter on parthenium weed at the 4th International Tropical Weeds Science Conference in Thailand in January 2013. He said different countries are taking varied approaches to attempting to control parthenium weed.

“Ethiopia is one of the latest countries to release biological control agents, but in India where each state has its own weed control strategies, biocontrol is not widely supported,” he said. 

“They are meeting with mixed success, and in some areas the weed is causing extreme allergy problems.”

More information about identifying parthenium can be found here: http://www.weeds.org.au/docs/parthenium_weed_mgt_guide.pdf