Developing custom plans for pesticide-resistant weeds

For farmers, it’s an all-too-familiar problem: To protect their crops from invasive weeds, they apply pesticides to their fields, only to see pesticide-resistant weeds rear their heads – with the vicious cycle continuing as farmers turn to a second (or third) round of pesticides that also prove ineffective.

How can farmers break this cycle? A standard pesticide application process won’t cut it: Simply put, there’s no one-size-fits-all solution.

Precision agriculture tools

Instead, the future of farming lies in customised weed treatment. And the future is here: With precision agriculture tools, farmers can efficiently and precisely detect which of the more than 8,000 species of weeds are sprouting in their fields.

Armed with this information, farmers can apply treatments tailored to specific weed types, preventing the overuse of costly chemicals and the development of pesticide resistance.

Here’s how the problem took root – and how farmers can respond.

The rise of resistant weeds

While weeds have been resisting herbicides since the mid-20th century, recent decades have seen the problem get worse. Take glyphosate, which became an increasingly popular pesticide after the glyphosate-tolerant soybean was introduced to the market in 1996, followed in 1997 by glyphosate-tolerant corn.

29 weed species resistant to glyphosate by 2014

As researchers at the University of Nebraska note, 29 weed species had become resistant to glyphosate by 2014. Pigweed is one such species, as the Scientific American highlighted in a 2018 report. Glyphosate-resistant pigweed can have anywhere from 5 to 160 copies of the gene that makes the plant protein glyphosate attacks, compared to the typical 2 copies.

It’s not just glyphosate: Popular herbicides like Pursuit, Classic, Roundup, AATrex, Callisto, Laudis, Impact, Armezon, and Express are all ineffective against at least one weed type, the University of Nebraska researchers point out.

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While weeds have been resisting herbicides since the mid-20th century, recent decades have seen the problem get worse. – Photo: Hans Prinsen

Multiple herbicide resistance

The rise in resistance has been accompanied by the emergence of an especially challenging phenomenon: multiple herbicide resistance, or cross-resistance. When the response to a weed’s herbicide resistance is to resort to a different, stronger herbicide, this is often the unintended consequence – and it’s proving costly.

In the United States alone, herbicide resistance costs the agriculture industry an estimated $10 billion per year. Moreover, taking an imprecise, trial-and-error approach to herbicide application imposes a heavy toll on both farmers’ resources and the environment – ultimately damaging crop production.

For instance, some herbicides have been linked to the plunge in the native bee population, with farmers in China now having to resort to the arduous task of hand-pollinating plants.

Given this state of affairs, it’s time for an overhaul of weed treatment.

Customising weed treatment

Even slight variations in geography, weed species, weather, time of application, and other environmental conditions can influence the effectiveness of treatment. UV light from the sun, for example, inactivates some herbicides. Though not affected by UV light, researchers have found that glyphosate is less effective if applied after 4:00 pm or before 10:00 am.

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Weed mapping using precision agriculture tools brings significant cost savings, reduces herbicides’ environmental impact, and reduces the risk that weeds will become resistant. – Photo: Stadje Media

Smarter treatment decisions

The wide range of variables involved is precisely why precision agriculture tools are increasingly farmers’ best allies. By pinpointing the exact types of weeds in farmers’ fields, these tools can drive smarter treatment decisions so that weeds don’t become needlessly resistant and farmers don’t resort to overuse of herbicides.

For instance, Taranis’ Weed Identification Platform combines artificial intelligence, computer vision, satellite, and drone imagery technology to inform farmers which kinds of weeds are attacking their crops.

Taranis’ Variable Rate Prescription Engine, meanwhile, creates “spray specific zones,” dividing fields into separate areas based on what types of weeds exist in each area and creating tailored treatment plans for the different weeds.

Targeted, data-driven application of herbicides – not continued trial-and-error and overuse – is the way forward

These techniques may sound promising in theory – but do they work in practice?

Researchers have found that weed mapping using precision agriculture tools brings significant cost savings, reduces herbicides’ environmental impact, and reduces the risk that weeds will become resistant.

Targeted, data-driven application of herbicides – not continued trial-and-error and overuse – is the way forward. Farmers who implement precision agriculture tools for weed control have reported savings ranging from 20% to 90% – a vital benefit at a time of shrinking margins.

More profit for farmers

Harnessing precision agriculture and adding precision spraying and variable rate spraying to their weed management toolboxes, farmers can maximise their crop output while optimising their management of both natural and economic resources. That means more profit for farmers – and more quality food to feed a growing global population.