Ryegrass control: Renewed interest in trifluralin

Notice warning farmers not to rely on a single chemical for weedkilling

Researchers at the Institute for Integrated Agricultural Development at Rutherglen, Victoria, have been studying the effectiveness of a pine resin-based formulation of controlled release trifluralin for the control of annual ryegrass in minimum-tillage wheat, as part of a weeds study supported by growers through the GRDC.

In a three-field experiment they compared different rates of herbicide and methods of incorporation. "The herbicide was applied to bare ground before Matong wheat was direct-drilled into the treated soil using either a narrow (50 mm) point drill or direct-drilled then cultivated with a tined implement to simulate sowing with a full combine," said project scientist Allison Chambers.

"We found that both the emulsifiable concentrate (EC) and the controlled release (CR) formulations of trifluralin worked well in controlling annual ryegrass while managing to maintain good wheat yields in both simulated full combine and direct-drilled treatments.

"Ryegrass numbers were reduced from 312 plants/m2 to between 23 (EC trifluralin, full combine) and 80 plants/ m2 (CR trifluralin, full combine) in one year. A similar trend was observed in the other two years. In addition to providing reasonable ryegrass control, all treatments effectively controlled hogweed/wireweed germination," said Ms Chambers.

"These are initial results and will be combined with those from company experiments to determine if label recommendations for the use in minimum tillage can be made," she said.