A risk calculator for glyphosate resistance in Lolium rigidum (Gaud.).
BACKGROUND
Glyphosate resistance has been confirmed in 58 populations of Lolium rigidum (Gaud.), a major weed of crops in southern Australia. Extensive use of glyphosate in conjunction with minimal soil disturbance has been identified as high risk for resistance to that herbicide. Land managers need a simple method for rapid assessment of the risk of resistance occurring as a result of past and proposed future management practices. Modelled on risk assessment nomographs, a simple calculator for indicating the risk of evolved glyphosate resistance in L. rigidum is described.


RESULTS
The calculator uses the generations since first use and the frequency of use of glyphosate in combination with historical cultivation levels as critical factors for determining the risk of glyphosate resistance evolution. Based on the management history of a field, a land manager can graphically determine a glyphosate resistance risk for that field.


CONCLUSIONS
The calculator enables the farmer or the advisor to assess the risk of a weed's population becoming resistant and modify practices accordingly to manage for sustainable glyphosate use. The risk calculator could be modified for other herbicides and different weed species.
Stanton
Rex A
RA
EH Graham Centre, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia. Rex.Stanton@dpi.nsw.gov.au
Pratley
James E
JE
Hudson
David
D
Dill
Gerald M
GM
D005998:Glycine / Q000031:analogs & derivatives*; D053209:Herbicide Resistance / Q000235:genetics; D006540:Herbicides; D008129:Lolium / Q000235:genetics*; D049451:Nomograms; D018570:Risk Assessment / Q000379:methods; D000097797:Glyphosate
D005998:Glycine; D006540:Herbicides; D000097797:Glyphosate