Are “Super Weeds” on the Agricultural Horizon?

One of the biggest developments in agriculture in the last few decades – or perhaps ever – was the creation of seeds and crops that are resistant to herbicides. Being able to spray chemicals over wide fields of crops indiscriminately while being assured that it will harm only the weeds is an obvious advantage.

To date, the most popular herbicide – and strains of crops resistant to said herbicide – has been glyphosate, better known as Roundup. Today, “Roundup Ready” varieties account for 90 percent of the U.S. soybeans and 70 percent of its corn and cotton. And though many predicted that weeds would never evolve a resistance to the herbicide, dozens of species have done just that.

So, naturally, the industry is working on new crops that are resistant to Roundup and a host of other chemicals. The point being, if you can spray two – or several – different varieties, no weed will be able to withstand the onslaught.

However, weed ecologist David Mortensen of Penn State University fears that weeds will be able to do just that.

In a recent paper, Mortensen argues that it is indeed possible for species of weeds to gain tolerance to several different chemicals at the same time. In fact, he believes it is likely. Of course, farmers and industries could always just develop new ones, right?

Well, maybe.

In a more unlikely series of events – but not entirely implausible, Mortensen argues – weeds could develop new processes that change the fundamental ways with which they deal with chemicals in general. Plants could evolve changes in how they detoxify themselves or metabolize chemicals, making them better at getting rid of toxins or otherwise rendering them harmless. If that happens, the plants would become resistant to many chemicals, not just to those to which a few site-of-action mutations apply, which give resistance to specific chemicals.

Others argue that these sorts of mutations could never come to be. The number and scope of mutations necessary would likely render any weeds that develop them to be sickly, not grow well and perhaps even die off on their own. Plus, the chances of developing that many mutations at the same time necessary for these drastic changes is slim.

But Mortensen still believes it is possible.

By spraying several different chemicals on fields in intense quantities for numerous years, the selective pressures for these types of mutations will be great. And if there aren’t any other weeds around to compete, even mutations that allow a plant to survive but cripples it could survive.

In fact, Mortensen believes such plants may already be out there. When people go out to the fields to get samples of weeds that have survived spraying, they get the healthiest looking ones, not the sickly ones. However, it is these sickly ones that might have the beginnings of the fundamental changes needed to survive multiple pesticides.

In the end, Mortensen is really just advocating for a different way of farming. Instead of using boat loads of chemicals, he advocates the use of an Integrated Weed Management (IWM) method. Using crop rotation, cover crops, competitive crop cultivars, the judicious use of tillage, and targeted herbicide applications has been shown to work as well as traditional herbicide use while reducing the amount used by up to 94 percent.

And for those who don’t believe weeds could ever evolve those incredibly unlikely series of mutations, obviously you have not seen Jurassic Park.

Life always finds a way.


About bigkingken

A science writer dedicated to proving that the Big Ten - or the Committee on Institutional Cooperation, if you will - is more than athletics.
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