When resistance is confirmed on farm, we often think only of the increased herbicide costs. There are a number of other costs growers might incur, however. These can include:
- Crop yield loss
- Reduced commodity prices due to increased dockage
- Reduced land values
- Costs of mechanical and cultural control measures
- Changes to crop rotation
All things considered, the cost of proactively implementing herbicide resistance strategies is lower than the cost of managing reactively. This requires a different approach to weed control.
In some cases, non-chemical (cultural) management may be required, such as the strategic use of tillage, increased seeding rates, weed seed destructors, etc. When it comes to herbicides, layering products offers the best means of control.
What is herbicide layering?
Herbicide layering is the practice of using multiple herbicide groups and active ingredients, at different application timings, to control the same resistance-prone weeds.
In practice, herbicide layering means starting with a pre-seed herbicide application that includes both a burnoff and extended weed control product. The burnoff product controls the emerged weeds, while the residual activity of the other herbicide product keeps weeds from germinating during the vital early weeks of crop development. Afterwards, a post-emergence application containing one or more herbicides with different modes of action can be used.
In total, two, three, or even four unique modes can be more strategically applied throughout the season.
Keep an eye on the forecast
Variable environmental conditions can impact how effective herbicide layering can be, however. As a result, having a well-planned early weed control program is critical. Learn more here.
Spraying during warm and sunny daytime conditions, and when nighttime lows don’t dip below 4° Celsius, is the best overall strategy. This is particularly true when trying to control larger perennials and winter annuals. The more receptive weeds are the better, so if weeds have been damaged by frost, try and hold off. If weeds are damaged by frost or not actively growing, they will not metabolize the herbicide properly at the site of action. The end result of this can be opening the window to herbicide-resistance development and overall lack of weed control.
When using a soil-applied herbicide that requires a rainfall for activation, try to time your extended weed control application just prior to moisture accumulation to ensure the herbicide is washed off the crop trash and moved into a soil solution for germinating weed uptake.
Look for flexible, powerful products
Overall, having a well-planned early weed control program can really support profitability. A well-timed early application of Command Charge herbicide and glyphosate, for example, can help combat resistant-kochia and cleavers.