Onion weed control in medic pastures - a herbicide evaluation

Onion weed (Asphodelus fistulosusis) is a significant pest of crops and pastures on many soil types on upper EP. Onion weed that germinates in the pasture phase often results in thick stands of large plants that require repeated herbicide application and/or cultivation to control prior to a crop phase. Cultivation prior to sowing is a widespread practice to control the weed and reduce the residues to manageable levels. However, cultivation can expose the soil to erosion.Onion weed in pastures regularly sets seed prior to the end of the growing season, ensuring the seed bank is replenished and the weed persists in every phase of the rotation. A key strategy to reduce the impact of onion weed, and the need for cultivation, is to reduce growth and seed set in the pasture phase of the rotation. Non-selective herbicides can control actively growing onion weed plants, but pasture growth is also affected.Previous trials by the UNFS group, MDB NRM, and PIRSA have shown the following herbicides can provide adequate control of onion weed in non-selective situations:Paraquat and double knocks of paraquatGlyphosate plus metsulfuron methyl mixtures (+/- paraquat second knock)Glyphosate plus LVE ester 2,4- D plus metsulfuron methyl,( +/- paraquat second knock)ChlorsulfuronSpray SeedAllianceThis trial was established to investigate herbicide control of autumn/winter germinating onion weed in the pasture phase, while maintaining the productivity of the medic pasture. This trial evaluated the herbicide control of young actively growing onion weed in a vigorous medic pasture. The herbicides, with the exception of paraquat, were chosen to minimise the impact on the medic biomass production.