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10 September 2019 Control of thiocarbamate-resistant rigid ryegrass (Lolium rigidum) in wheat in southern Australia
David J. Brunton, Peter Boutsalis, Gurjeet Gill, Christopher Preston
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Two field experiments were conducted during 2018 at Paskeville and Arthurton, South Australia, to identify effective herbicide options for the control of thiocarbamate-resistant rigid ryegrass in wheat. Dose–response experiments confirmed resistance in both field populations (T1 and A18) of rigid ryegrass to triallate, prosulfocarb, trifluralin, and pyroxasulfone. T1 and A18 were 17.9- and 20-fold more resistant to triallate than susceptible SLR4. The level of resistance detected in T1 to prosulfocarb (5.9-fold) and pyroxasulfone (4-fold) was lower compared to A18, which displayed 12.1- and 7.8-fold resistance to both herbicides, respectively. Despite resistance, the mixture of two different preplant-incorporated (PPI) site-of-action herbicides improved rigid ryegrass control and wheat yield compared to a single PPI herbicide only. Prosulfocarb + triallate and prosulfocarb + S-metolachlor + triallate did not reduce rigid ryegrass seed set when compared to prosulfocarb applied alone at the higher rate (2,400 g ai ha–1). Pyroxasulfone + triallate PPI followed by glyphosate (1,880 g ai ha-1) as a weed seed set control treatment reduced rigid ryegrass seed production by 93% and 95% at both sites, respectively. These herbicides also significantly improved grain yield of wheat at Paskeville (22%) and Arthurton (38%) compared to the untreated.

Nomenclature: Prosulfocarb; triallate; pyroxasulfone; S-metolachlor; trifluralin; glyphosate; rigid ryegrass, Lolium rigidum Gaudin LOLRI; wheat; Triticum aestivum L. ‘Chief CL Plus'

© Weed Science Society of America, 2019.
David J. Brunton, Peter Boutsalis, Gurjeet Gill, and Christopher Preston "Control of thiocarbamate-resistant rigid ryegrass (Lolium rigidum) in wheat in southern Australia," Weed Technology 34(1), 19-24, (10 September 2019).
Received: 20 March 2019; Accepted: 11 July 2019; Published: 10 September 2019
Herbicide resistance
preplant incorporated
weed control
weed seed set control
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