Detecting resistance in imported perennial ryegrass seed lots

Key points • This work studied the level of herbicide resistance in imported ryegrass seed lots to understand the risks associated with this pathway for introducing herbicide resistance onto New Zealand farms. • None of the ryegrass had resistance to glyphosate. • Twenty of the 28 Lolium perenne seed lines tested from overseas (mostly turfs) had some resistance to Group 1 and 2 herbicides. Eight had no detectable resistance to Group 1 and 2 herbicides. • It is safer to assume that resistance is present in any imported seed line.