Look beyond herbicides for weed control

  • Jan 02, 2019

Herbicides are not the silver bullet, magic solution to weed problems they once were. New remedies are being sought as herbicides run into all sorts of hurdles.

In the “good old days,” life seemed simpler. You just got advice about what herbicide or tank mix of herbicides to use to control a set list of weeds in a particular crop.

Resistance grows over time

These days, weed populations are becoming increasingly resistant to certain chemistries and replacement herbicides don’t always exist. What’s more, few new chemistries are in development.

On top of that, maximum residue limits, or MRLs, are not always in place or standardized in importing nations. This is also limiting a producer’s options. The KeepingItClean.ca website has been established to help producers sort through the maze of what is and isn’t allowed.

Weed populations are becoming increasingly resistant, few new chemistries are in development and MRLs limit your options. What’s a producer to do?

Take the example of the weed kochia in a lentil crop that’s nearing harvest. In the past, a producer may have applied glyphosate to kill the weeds and start them drying down to make combining easier. But in recent years, a growing percentage of the big Christmas tree-shaped weeds are resistant to glyphosate.

Tank mix partners are available for glyphosate to overcome the resistance issue, but these chemistries may or may not have MRLs established in the countries buying the lentils. Beyond that, glyphosate is under constant attack by activists. Some buyers want to avoid any glyphosate residue, no matter what regulations allow.

Using integrated strategies

Tillage has drawbacks, but new tillage options are being developed including cultivation between crop rows aided by special cameras and software.

More attention is being paid to limiting the return of weed seeds to the soil. The Australian-developed Harrington Seed Destructor is being evaluated in Canada, and other methods are being explored for destroying weed seeds as they exit the combine.

Agronomics are another important tool. Crop rotation, heavier seeding rates, narrower seed rows, intercropping and cover crops can all help crops compete with weeds.

None of these alternatives is a solution by itself. There is no single answer to replacing herbicides. However, there are lessons to be learned from organic producers who have always had to use other strategies.

As producers, we need to adjust our mindset. This means using herbicides more wisely while also exploring other avenues for weed control.

From an AgriSuccess article by Kevin Hursh.