Setaria Herbicide Control Trial

By Shane Oster, Chairman

December 2011

This research trialled various pre-emergent herbicides, post-emergent herbicides and a combination of both for the control of Setaria Verticillata in lucerne seed crops. The trial was undertaken from 1 December 2009 to 15 October 2010.

Historically there have been many herbicides registered in lucerne which have been used for the control of Setaria but deciding has been the most effective has only ever been anecdotal. This research was conducted simply to provide efficacy data. As such rates above that listed on the labels were used with some products to identify whether it improved the level of Setaria control. Growers should be consulting their advisor about resistance management strategies and appropriate label rates prior to the application of herbicides on their fields.

The research was divided into three trials. Pre-emergent and post emergent herbicides were used as well as a combination of both.

Results

The results from the RIRDC-funded Setaria Herbicide Control Trial clearly showed that the best control is achieved by using a combination of both pre-emergent and post-emergent herbicides. The best registered pre-emergent herbicide in the trial was Spinnaker. With Spinnaker coming off patent in the last couple of years, the prices have dropped dramatically, with 140g/hectare (or 400ml/hectare) now costing less than $20.00/hectare.

For best results, pre-emergent herbicides such as Spinnaker can be applied on the first seed watering, or preferably on the first watering for the year, which may have been for hay production. This allows the pre-emergent herbicides to tackle the weeds as they germinate.

To obtain optimum control, this needs to be followed up by a post-emergent herbicide. In the trial, Select proved to be the most effective post-emergent herbicide.

Clean out results certainly support the belief that the paddock is the best place to remove Setaria. Large amounts of lucerne were often lost in order to remove the Setaria and product a marketable product. 

In the trial, all of the pre-emergent herbicides were tank mixed with Sprayseed to remove a germination of 1 leaf Setaria. Areas which missed this treatment had by far the worst levels of Setaria contamination. Although it is not recommended in most situations to apply Sprayseed at that time of year, it does highlight the fact that it is still best to control Setaria while it is small.

For more information on this RIRDC-finded trial, you can either contact Lucerne Australia, or go to the RIRDC website and download either a trial factsheet or a full version of the trial results for free.

Go to: Seed Success: Setaria sp Control in lucerne for the factsheet.