Barnyard grass develops herbicide resistance

Glyphosate resistance was first documented in Australia in 1996 at a site in Victoria. Since then, there have been a number of other sites reporting glyphosate resistance. So far, only annual ryegrass populations had been reported with glyphosate resistance in Australia. The Glyphosate Resistance Register contains information regarding all the known glyphosate-resistant weedDescription The inherited ability of a plant/weed to survive a dose of a herbicide normally lethal to that species. Authoritative On-line References and Resources http://www.weedscience.org/in.asp The International Survey of Herbicide Resistant Weeds monitors the evolution of resistant species and assesses their impact. All confirmed instances of new cases are listed. populations present in Australia. The register is managed by Dr Chris Preston of the Plant & Food science department at the University of Adelaide.

In a news alert dated January 29, 2007 the Department of Primary Industries (DPI) has warned one of the state's most prolific weeds has developed resistance to glyphosate.

The herbicide is one of the last weapons farmers are able to use in the control of barnyard grass (Echinochloa colona), which competes with summer crops and fallows. One plant can produce up to 42,000 seeds. The mature plant grows taller than rice and competes with the crop for resources like sunlight and soil nutrients. It is also an alternate host for tungro (RTD) and rice yellow dwarf (RYD) viruses as well as for corn pests.

Barnyard grass can reduce corn yields by 20%. The DPI's technical specialist for weeds, Andrew Storrie, says growers are running out of control options with a number of weeds now developing resistance to key herbicides: "Growers are left with few options as there is already resistance to herbicide mode-of-action groups A, B and C overseas, and one population in northern NSW is resistant to atrazine - group C."

Mr Storrie also stressed that growers would have to act now if they are to have any hope of controlling barnyard grass in the future, as the weed has a long-lived seedbank and develops quickly.

"Spray with a high rate of paraquat or SpraySeed® - a second application might be needed if the plants are large – and keep controlling new germinations until the end of the season.”

Read full article published by DPI here.

Note: Sprayseed® is a branded product containing paraquat and diquat, both active substances are from the same chemical family.