Clethodim: evaluation in field experiments for grass-weed control in oilseed rape.

Clethodim, an ACCase inhibitor, is being developed as a potential grass-weed herbicide for use in a number of crops including oilseed rape in the UK. Previous usage in the UK of ACCase inhibitors has led to the development of levels of resistance in Alopecurus myosuroides (black-grass) by various mechanisms. Whilst clethodim efficacy against black-grass is likely to be affected by the commonest form of ACCase target site resistance present in the UK, such resistance to clethodim is only partial and it should still exhibit useful control levels of black-grass in the field. Six field trials during autumn 2011 were carried out with clethodim to evaluate its performance in oilseed rape comparing it with other herbicides with the same mode of action. At 120 g a.i. ha-1, clethodim gave significantly better levels of control than tepraloxydim even though the black-grass populations were known to show resistance to this group of herbicides. The results indicate that of this herbicide group, clethodim could make a significant contribution to UK growers of oilseed rape.