NSW DPI principal research scientist, Hanwen Wu, said tests from 22 samples received last year indicated resistance to glyphosate is common in southern New South Wales.

"We found no resistance to haloxyfop (Group 1) and need more samples from cropping paddocks to determine the overall resistance status in southern NSW," Dr Wu said.

"Samples from cropping paddocks only are needed, ideally 30 mature seed heads with tiny black seeds from 10 different plants in each paddock.

"We know glyphosate control of feathertop Rhodes grass has been variable in southern New South Wales and Group 1 herbicides are prone to developing resistance.

"With feathertop Rhodes grass continuing to spread south, where it devalues pasture and reduces productivity, this survey will allow us to benchmark herbicide resistance in southern NSW to help growers better manage this invasive weed."

Test results will be sent directly to farmers and will help inform a joint Grains Research and Development Corporation (GRDC) and NSW DPI research project. Led by Dr Wu, the project is investigating management tactics best suited to southern New South Wales.

Farmers are asked to place seeds in an envelope labelled with the date of collection, the farmer's name, mobile phone number, nearest town and GPS location, if available.

Samples can be sent to:
Feathertop Rhodes grass
NSW Department of Primary Industries
Wagga Wagga Agricultural Institute
PMB Pine Gully Road
Wagga Wagga NSW 2650