Pesticide efficacy is decreasing
If you’ve ever colored Easter eggs — I mean the old-fashioned way, with food-coloring, not with those plastic wraparounds — then you know that when you mess up, you have two options: rinse them off with some white vinegar and start over, or forge ahead, layer even more color on top, and hope that something presentable emerges.
Okay, so that metaphor’s a bit of a stretch, but that’s what came to mind when I read, earlier this week, that scientists at the University of Nebraska, Lincoln, have engineered a new category of transgenic crops. The new plants — which include broad-leafed greens such as soybeans, tomatoes, and tobacco — harbor a bacterial gene that makes them resistant to an herbicide called dicamba.
“But we have Roundup!” you cry. “Why do we need anything else?” Well, because Roundup (active ingredient: a chemical called glyphosate) isn’t working as flawlessly as it used to. According to the story in Science (sorry, subscription only), 24 percent of farmers in the northern Midwest and 29 percent in the South say they have glycophate-resistant (GR) weeds. Crop scientists in Argentina, Brazil, and Australia report GR grasses popping up too.
Which is hardly a surprise when you consider the loads of the chemical we’ve dumped on our fields in the past few decades. In 1995, U.S. farmers used 4.5 million kilograms of glyphosate; today they use 10 times that amount. And glyphosate-resistant crops (better known as “Roundup Ready”), first engineered by Monsanto in 1986, now dominate the market. Today, more than 90 percent of soybeans and 60 percent of the corn are glyphosate resistant. With many farmers using glyphosate as their sole herbicide, we’ve essentially ensured that mavericks would eventually sprout. “The selective pressure for weeds to develop resistance has been huge,” Stephen Duke, a plant physiologist at the USDA’s Agricultural Research Service told Science.
Now plant researchers are hoping to alleviate some of that pressure by introducing dicamba into the mix. If farmers can rotate between dicamba-resistant (DR) and glyphosate-resistant crop varieties, they say the likelihood of weeds gaining a foothold will fall. The new plants also feature an interesting safety mechanism that should help stave off weeds: the dicamba resistance gene (taken from a bacterium) lives only in the plants’ chloroplasts. Because chloroplast DNA is only inherited through the maternal side, this means that the GM gene can’t be spread through the male pollen. It’s a reproductive stopgap of sorts.
But the researchers themselves don’t seem so confident that Mother Nature won’t soon outsmart even this clever maneuver. Monsanto, which has licensed the dicamba technology, is hard at work on “gene stacking” — combining genes for multiple herbicide resistance into one plant. “We have the technology today to develop herbicide resistance to anything we want to,” Jerry Green, a weed scientist with DuPont Crop Protection told Science.
Yes, we have the technology. That’s not the point. How and whether we should use that technology seems to me to be the more relevant issue. Our love affair with glyphosate is showing the first signs of an ugly breakup, and instead of changing (or reversing) course, we’re simply forging ahead with more chemical solutions, more layers of genetic dye.
Perhaps the most disturbing part of it all, though, is that when the first dicamba-resistant soya goes into production — in three to seven years, according to Monsanto — no one will probably notice. Without a cogent system of labeling standards, consumers will have no idea that this has gone to market, and the mainstream press (sorry, Science and Nature) certainly won’t cover it. It’s not so much that I’m fearful of a hazard to human health by ingesting these foods (a Twinkie probably has more ingredients to worry about); it’s the damage these GM crops do to the greater environment that’s so troubling. These mighty duos of herbicide and herbicide-resistant crops create a vicious loop that we’ve been happy to run in because there’s profit to be had. The fallout, though, is biodiversity itself. The widespread planting of these GM marvels to the exclusion of all else wreaks havoc on ecosystems, on levels we can see and on those we don’t yet understand. It would be nice, at least, if as voters and consumers, we could have a say in the matter … Because while this egg may look pretty on the surface, I have a feeling it’s already rotten inside.