BMP for Herbicide Resistance in Turfgrass

At the recent Australian Turfgrass conference there was significant discussion on increased herbicide resistance problems being experienced by turfgrass managers. This is especially evident for those managing Poa in warm season grasses, but others are also seeing problems with other turfgrass weeds.

It is important that turfgrass managers now implement proper Integrated Weed Management strategies to ensure they get performance from current herbicides in the future and don’t increase their herbicide resistance problems.

In preparation for a workshop at the conference I conducted a review of several strategies on managing herbicide resistance in agricultural situations. From this I developed a list of Best Management Practices to Reduce Herbicide Resistance Risk in Turfgrass which I presented at the conference. While the list may need some review and modification I feel it is a good starting point for the industry.

  1. Understand the biology of the weeds present – it is impossible to make a management plan without good understanding of the biology and ecology of the weed(s). These include germination requirement, emergence patterns, life cycle, seed dormancy, mode of dispersal.
  2. Focus on preventing weed seed production and reducing the number of weed seed in the soil seedbank – management of the soil seed bank is critical for successful long term weed control. This involves minimizing deposits and maximizing withdrawals out of the bank.
  3. Use weed-free turf, soil, seed etc. – the use of materials contaminated with weeds can bring in new weeds and deposit more seed into the soil seed bank.
  4. Scout routinely – inspecting regularly and recording the presence of weeds will make the implementation of control measures more successful. Photographs, Apps and new technology like drones can all help with this process.
  5. Follow Crop Life Australia & HRAC resistance management guidelines – these organisations publish guidelines on the frequency of herbicide use designed to reduce the risk of herbicide resistance development.
  6. Use multiple herbicide mechanisms of action (MOAs) that are effective against the most troublesome weeds or those most prone to herbicide resistance – rotation and tank mixing of herbicide mode of actions are two of the fundamental strategies of herbicide use that will delay the development of herbicide resistance.
  7. Apply the labeled herbicide rate, at recommended weed sizes, with correct conditions, adjuvants and water volumes – herbicide labels detail information of product rates, weed size, environmental conditions, adjuvants and water volumes which maximize efficacy of the product.
  8. Emphasize cultural practices that suppress weeds by using turf competitiveness – the best defence against weed invasion is having healthy and actively growing turf which can compete against weeds.
  9. Use mechanical and biological management practices where appropriate – alternative methods of weed control to herbicides are perhaps more difficult to implement in turfgrass management that in agricultural situations, but where their use is possible they can be extremely important.
  10. Prevent movement of weed seed or vegetative propagules – transfer of weeds on machinery, clothing and other equipment and tools can introduce weeds from one area to another.
  11. Prevent an influx of weeds by managing fence lines and surrounding areas – weed control is often concentrated on the highly maintained turf surfaces while weeds may flourish in other areas where they can flower and set seed which then is introduced to the turf surfaces.
  12. Develop a Plan and maintain records: an invaluable reference guide – the old saying that “fail to plan is a plan to fail” is very true for management of herbicide resistance. Plan’s need to take the long-term view over several seasons to ensure correct programming of herbicides to manage resistance development.

Herbicide resistance will continue to increase as a management issue for turf managers. It is been over 30 years since a new mode of action herbicide was discovered. So don’t expect a silver bullet to come on the market which will solve your weed management problems. When new successful herbicide treatments are discovered they need to be used according to sound agronomic decision to ensure they remain effective tools into the future.