The Western Australia Department of Agriculture last year undertook glass house and field research and investigated various aspects of the double knockdown treatments at Merredin and Avondale.

The research was funded by the Grains Research and Development Corporation and undertaken by the Department in collaboration with Western Australia Herbicide Resistance Initiative of the University of Western Australian.

Department research officer Abul Hashem said the research demonstrated the benefits of double knockdown.

"When the double knockdown herbicides are applied at the three to six leaf stage, glyphosate followed by Spray.Seed^® or Spray.Seed^® followed by glyphosate was equally effective and gave good ryegrass control," Dr Hashem said.

"At the one leaf stage of ryegrass, both the herbicides alone or in sequence were relatively less effective," he said.

"Glyphosate followed by Spray.Seed^® was most effective when a two-day interval was allowed between the two applications. Spray.Seed^® followed by glyphosate was most effective when a two to five-day interval was allowed between applications."

Dr Hashem said the research found less herbicidal efficacy was observed when less than two day intervals were allowed between the knock down herbicides. However, the efficacy of the treatment was only slightly reduced by a longer interval between sprays.

Glyphosate and Spray.Seed^® applied individually were more effective when applied at 10 am and 4 pm than at 1 pm. Dr Hashem said researchers would need to verify this finding in the coming season to determine whether it was an issue in late autumn or early winter under field conditions.

When glyphosate was followed by Spray.Seed^® or Spray.Seed^® followed by glyphosate, spraying the herbicides at different times of day did not affect ryegrass survival.