Some oats are wilder than others

Oat variety trial. Williams WA, October 2000. From left: unnamed variety, Euro and Winjardie.

Keep an eye on your wild oats — you may find that you have not one but two species, and that the herbicide that works for one does not necessarily work for the other.

Research at the University of Melbourne indicates that 85 per cent of wild oat infestations in the wheatbelt of eastern Australia and 50 per cent in Western Australia are a mixture of two species.

Weed population ecologist Geoff Barry is studying the two species (Avena fatua and A. sterilis) and has shown significant differences in their ecology and herbicide sensitivity. An infestation containing both species can be more difficult to manage. The project is supported by the Federal Government and farmers through the GRDC.

The research has identified significant differences in the emergence, growth and development of these two species. A. sterilis is less dormant and has a greater emergence following the break of season than A. fatua. In addition, flag leaf appearance, flowering and shattering in A. sterilis occur about a week earlier than in A. fatua, while plants of A. fatua have a greater biomass and leaf area at maturity.

Of 30 wild oat infestations tested, a number were found to be resistant to Achieve (Group A — dim) and Hoegrass (Group A — fop). Different infestations showed different resistance patterns. For example, in one of the infestations studied, A. sterilis showed resistance to both herbicides while A. fatua was resistant to only Hoegrass.

Which have you got?

A. fatua is more frequent in samples from Victoria, southern NSW and Western Australia, while A. sterilis is more frequent in samples from northern NSW and southern Queensland. (See maps.)

The two species can only be distinguished at seed maturity. There are no reliable means of identification at the seedling or mature plant stage. A. sterilis is similar to cultivated oats in that the seeds (usually 2-3 in number) of a spikelet remain intact and are shed from the plant as a single unit. In A. fatua all seeds of a spikelet shed from the plant as separate units.

Program 3.3.2

Contact: Mr Geoff Barry 03 8344 9856

Region National, North, South, West