Invasion of the Superweeds – Diagnosing the Enemy –

Scott M. Swinton is a professor of agricultural, food and resource economics at Michigan State University. He developed WEEDSIM, a computer program to help farmers choose profitable weed control strategies.

Roundup Ready™ crops let corn and soybean farmers rely on a single weapon. A single weapon is predicable, and any warrior who is predictable is open attack by opponents that can adjust. Roundup resistant weeds have done just that.

A choice between higher environmental costs and higher food costs for nonchemical weed control.

To overcome these new “super weeds,” farmers need to take a leaf from Sun Tzu’s “The Art of War”: study the opponent and find its weaknesses. The past 30 years of research into weed management have yielded two important keys to understanding the weaknesses of weeds.

The first key is to study the weeds in the crops. How many weeds are there? Just a few weeds may not cause enough crop damage to be worth the effort and cost of weed control. Which weed species are present? All weeds are not equal. Some weeds get bigger and do more damage than others.

There are many herbicides to choose from, and some kill certain weeds better than others. Computer programs can help farmers decide whether a herbicide is worthwhile and, if so, which one is most cost-effective. WeedSOFT is one program developed by researchers at 17 land-grant agricultural universities that can help farmers find the weapon to exploit their enemies’ weaknesses.

The second is to be unpredictable. Farmers who grow Roundup Ready™ crops may find that glyphosate is nearly always the most cost-effective choice, but the wise warrior also understands the value of surprise. Relying on the same herbicide will eventually favor those weeds that can mutate to survive.

There are many strategies farmers can use to vary their attack. They can change herbicides. They can use tillage. They can also rotate different types of crops. Rotating summer crops (like corn and soybean) with winter crops (like wheat and canola) can break up weed cycles.

Alas, studying the enemy takes time and effort. Just as antibiotic-resistant germs have forced physicians to spend more time on diagnosis, so glyphsate-resistant weeds will force farmers to spend more time on weed diagnosis. This will raise their weed control costs. Unfortunately, many herbicide substitutes for glyphosate are more toxic, so the public may have to choose between higher environmental costs and higher food costs for nonchemical weed control.

Invasion of the Superweeds – Room for Debate Blog –

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