The rise and fall of clethodim

WeedSmart 2025-26 Webinar Series

Webinar 1: The Rise and Fall of Clethodim

There is a heavy reliance on clethodim for ryegrass weeds in non-GM canola and pulse crops, late breaks and increasing levels of resistance is resulting in poor levels of control.

A recent GRDC Update highlighted growing resistance issues in pulse crops, particularly concerning high rates of clethodim and butroxydim. This session also warned that if clethodim and glyphosate combinations begin to fail in GM canola, the potential loss of paraquat would further limit post-emergent ryegrass control options.

This webinar shared some of the implications of declining clethodim efficacy in canola and pulse-based rotations.

• Peter Boutsalis from the University of Adelaide kicked-off the webinar outlining the current trends around clethodim resistance and how they are shifting over time.
• Grower Bec Marshall, along with WeedSmart agronomists Chris Davey and Greg Condon, shared their experiences around the tools available to manage ryegrass in the face of clethodim resistance.

The team outlined how diverse rotations along with robust pre-emergent programs and crop topping in pulses and canola can contain ryegrass seedbanks.

The addition of circuit breakers such as oaten or vetch hay, brown manure pulses, narrow windrow burning and impact mills also provide a catalyst for reducing numbers. Plus, longer term programs to complement diverse rotations include GM canola, competitive barley varieties and robust cereal pre-emergent herbicides.

Greg Condon

Greg is the WeedSmart southern extension agronomist (Vic and NSW) and is based in Junee, NSW. He runs Grassroots Agronomy with his wife Kirrily Condon. Greg works with growers and industry groups and is passionate about profitable farming systems. Connecting innovative growers with agronomists, stakeholders and researchers is a major focus of Greg’s extension role.

Dr Peter Boutsalis

Dr Peter Boutsalis has been involved in herbicide resistance research from the beginning. His career spans over 30 years, investigating the first cases of Group 2 resistant broadleaf weeds in Australia in the early 1990s. He operates Plant Science Consulting, an Adelaide-based company specialising in commercial herbicide resistance testing and customised herbicide pot trials, and is a researcher with the University of Adelaide.

Bec Marshall

Agronomist and grower, based at Normanville, Victoria, along with her husband Ash, has been adapting their farming system with longer-term strategies for ryegrass control, to overcome multiple resistance in some populations, with a Big 6 approach across their 3300 ha farm.  Incorporating new practices along with attention to detail in existing tactics has provided a systems approach to drive down weed numbers into a low weed seed farming system.

Replay this webinar to hear the latest from leading industry agronomists, researchers and farmers staying ahead of the curve on their weed seed banks.

Boots off, cuppa ready and headphones on!