Herbicide resistance means weeds are winning

A combination of new and old technology will be needed to maintain an upper hand in the never-ending battle against weeds.

Herbicide resistance is making many weeds more difficult to control. Meanwhile, a number of herbicide options are facing potential restrictions.

Some of the restrictions are international, such as glyphosate in Europe, but we’ll still feel the ramifications here.

Many lentil crops will be cursed with yellow flowered weeds this summer courtesy of wild mustard that’s Group 2 resistant.

One option is an old active ingredient called metribuzin, which is available as Sencor and Squadron. The product has a lot of shortcomings, but it’s likely to make a comeback if Group 2 products such as Odyssey and Solo can no longer do the job.

Registered post-emergent wild oat control options no longer exist for canaryseed. Plant breeding may eventually re-establish a wild oat control option, but in the meantime, producers will need to rely on Avadex, a pre-emergent product that was one of the very first wild oat control products.

Avadex, purchased from Monsanto by the much smaller Gowan a number of years ago, has a bright future because it offers a different mode of action for wild oat control in a range of cereal crops.

New herbicide options are under development for flax and mustard and better brassica weed control is desperately needed for chickpeas. However, chemistry won’t be the only answer.

Watch for some smart tillage options in the years ahead. Tillage between rows has to be precise because of the narrow row spacing of most prairie crops, and more accurate GPS signals might make this possible. Another possibility is recognition software that can identify crop rows.

Meanwhile, wick weeders, an old technology, take advantage of the height difference between crops and weeds. The wicks, wet with a product such as glyphosate, are moved above the canopy, where the chemical is wiped on the taller weeds. Weed competition has already taken a heavy toll on the crop by that stage, but wick weeders can prevent some weeds going to seed. It’s more a Band-Aid than a solution, but it may see a resurgence when all else has failed.

The CombCut, which was on display at Canada’s Farm Progress Show in Regina, was developed by an organic producer in Sweden so that the blades slide through a crop and cut stiffer stemmed weeds. Blade angle and spacing are adjustable, and brushes on a reel keep the material moving over the knives.

The CombCut can remove broadleaf weeds from a cereal crop, or it can cut weeds above the crop canopy. The machine mounts on the front or the back of a tractor and is controlled with a three-point hitch.

A price tag of more than $40,000 for a 28 foot machine means it isn’t something to try out on a whim.

However, conventional agriculture will need to keep an eye on the weed control advances made by the organic industry as well as advances in other countries.

The Harrington Seed Destructor from Australia is a heavy and expensive unit pulled behind a combine to crush weed seeds. A lot of weed seeds were removed that way when more producers collected chaff for cattle feed in this country.

A good post-emergent herbicide can provide weed control that’s close to 100 percent.

As specific products become less effective or are removed from the market, we’ll need to accept products and techniques that are less than perfect.

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