Managing Weed Resistance - Parrish and Heimbecker, Limited

15 ways to manage weed resistance in Western Canada

Weed resistance in Western Canada isn’t new and it’s not going away.

There’s no easy way to wrestle resistant biotypes to the ground. Weed species resistant to certain herbicides were first discovered in Western Canada in the early 1970s and the list continues to grow every year. Herbicide resistant weeds are coming to a field near you – if they’re not already there.

But don’t give up. Practicing good chemical rotation, using high quality certified seed, well-timed tillage, and a dozen other strategies will help you manage weed resistance in your fields.

Herbicide resistance weeds don’t just appear

You can ignore them but once herbicide resistance in a weed species develops in a field, the problem doesn’t go away. You need to manage the threat proactively.

Weed control becomes a much more complex issue once resistant weeds show up in your fields. If you suspect a weed is resistant, confirm the type of resistance by having it analyzed. Your P&H Retail can help with this test.

Following is a list of integrated management strategies to combat herbicide resistant weeds. Although each strategy might only make a small difference, put together they can proactively delay the serious threat of weed resistance.

Integrated weed management strategies

  1. Rotate crops: An agronomically sound crop rotation allows you to use different herbicide groups. This will reduce the threat of selection for resistant weeds.
  2. Tank-mix: Use tank mixes and herbicides with multiple modes of action to ensure broad spectrum weed control. Also practice herbicide layering, such as the use of a pre-emergent herbicide applied in the fall to control weeds emerging early in spring followed by in-crop herbicides with a completely different mode of action.
  3. Use the high rate: Rates of herbicides can vary. Use the higher rate to consistently control weeds.
  4. Seed early: Early seeding in a clean field gives the crop a competitive advantage over weeds. Use tillage or pre-emergent herbicides to provide a competitive advantage for the crop prior to and during the critical weed-free period.
  5. Use certified seed: Avoid planting weeds back into your fields by using certified seed. High germination and vigor provide a quick emergence of the competitive crop. Shallow seeding also speeds up crop emergence.
  6. Keep crop records: Keep accurate and detailed field crop records so you remember crop rotation, which herbicides you’ve used, etc.
  7. Scout fields: Don’t wait to scout fields. Get out early to understand what weeds are present and their growth stage.
  8. Don’t leave weed escapes: Control weed escapes before they go to seed. Escapes add weed seeds to the seed bank. This compounds the threat in following years.
  9. Choose varieties carefully: Choose competitive crop varieties and seeding rates to optimize plant populations. An early, healthy, thick crop is more competitive than a thin, stressed crop. A healthy crop with a good plant population also provides competition during herbicide timing, which enhances herbicide efficiency.
  10. Watch row spacing: Seeder row spacing can impact weed control. Narrower rows increase the crop’s competitiveness and speed up the crop canopy enclosure. You don’t necessarily need to change seeding equipment for weed management. However, consider row spacing and weed resistance when purchasing the next seeder.
  11. Test unusual weeds: If you notice unusual patches of weeds showing up in fields, test them for resistance.
  12. Consider fall-seeded crops: Grassy weeds such as wild oats can’t compete with fall-seeded crops like fall rye or winter wheat. Perennial crops like alfalfa are also competitive once established.
  13. Mow weed patches: Mowing weed patches before they go to seed or silaging can reduce the weed seed bank buildup in fields.
  14. Clean equipment: Cleaning tillage and harvest equipment can prevent transferring weed seeds from field to field. Clean newly acquired equipment before putting it to use on the farm since stowaway weed seeds can be spread into clean fields.
  15. Manage fertilizer: Fertilizer management can also impact weed management strategies. Careful placement of fertilizer gets the crop off to a great start.

Your local P&H Retail Agronomist is familiar with current weed issues in the area and can provide information on best management strategies to control weeds in your fields.