The importance of field records
If you don’t have a record of what’s been sprayed on which field over the past 5 years, it’s time to start one. If you only have product names in your records, they need to be translated into herbicide Groups. For example, if you find that you have been spraying Group 1 herbicides for 4 out of the past 5 years on the same field, it may explain why your weed control program is losing
Crop rotationRotating crops annually adds diversity to the field cropping system, and diversity increases the sustainability of the system. It provides the platform for long-term weed management. A well-planned crop rotation can:
- Reduce the impact of weeds, insects and diseases, leading to higher yields
- Lower input costs in some rotational crops
- Use more competitive crops to control weeds in some years
- Help manage crop residue
- Provide diversified marketing options
- Give you the option to choose different herbicide Groups
Seed competitive varieties and increase seeding rates to enhance a crop's ability to compete more effectively with weeds. Varying seeding dates and decreasing row spacings are other options. Even herbicide-resistant weeds are still susceptible to crop competition for space, moisture, sunlight and nutrients.
A very effective way to prevent herbicide resistance is to seed your problem field last*. Delaying seeding allows the weeds to grow so you can eliminate them.*Source: 5 year UK study supports this seeding later
If tillage is an option, for minimum till or no-till operations the consideration of selective tillage adds a tool to your toolbox. Focus on problematic weed patches.
Crops that get a head start on weeds through proper fertility are going to be more competitive. Plan a fertility program for the crop; feed the crop, not weeds.
Sample collection for HR testing
If, after going through these warning signs, you suspect that you have a resistant weed population, collect a sample of the plants and/or seeds for testing. See Resources for contact information for herbicide resistance testing sites.
Proper sample collection that includes multiple plants and/or adequate seed volume is critical for accurate testing. Testing labs will provide specific guidance for sample submissions.