A tipping point for weed control?

By Herald-Whig
Posted: Dec. 3, 2017 12:01 am

Most Americans consumers don't think about weeds when buying food. But if farmers could no longer control weeds with existing herbicides, Americans would take notice pretty quickly.

"I think the future of cheap food is strongly related to the availability and effectiveness of existing herbicides," said Adam Davis, ecologist in the Department of Crop Sciences at the University of Illinois and USDA Agricultural Research Service.

That is, without working herbicides, food could get a lot more expensive.

Davis and George Frisvold, an economist at the University of Arizona, recently teamed up to consider the possibility that we've reached a critical tipping point in the ability to control agricultural weeds with the herbicides currently on the market.

"If we fully lost chemical control of certain weeds, and if farmers continued with the corn-soybean rotation, they'd be forced to reduce their acreages as they spend more time and money managing weeds," Davis said.

Herbicides fall into one of 16 categories describing their mode of action, or specific target in the plant that the chemical attacks. Because of various regulations and biological realities, a smaller number of herbicide MOAs can be used on any given crop and the suite of weeds that goes along with it.

"In some areas, we're one or two MOAs away from completely losing chemical control for certain weeds," Davis said. "And there are no new herbicide MOAs coming out. There haven't been for 30 years."

It sounds dire, but Davis remains optimistic. "I believe there's hope," he said. "But it requires that we take action to diversify weed management now."

Just what would it take to bring us back from the brink of total weed domination? Davis has a lot of ideas, but one of the big ones is something he calls the "middle way," which bridges the gap between the traditional corn-soy rotation with its heavy herbicide inputs and a diversified organic system.

"You can get about 90 percent there just with a good crop rotation," he said. "Then you build in things like weed suppressive cultivars, banded herbicides, row spacing, cultivation, harvest weed seed control, and all these tactics together can add up to really effective weed management systems. We've shown you can reduce herbicide use by 90 percent in diversified systems and get the same amount of weed control."

Corn genome

More than two decades ago, the corn plant got a huge boost with the announcement of the National Plant Genome Initiative.

The historic research effort to map the corn genome -- supported and shepherded by the National Corn Growers Association -- has resulted in significant economic and environmental dividends for farmers and society.

"The NPGI didn't just build a bridge between scientific discovery and real-world solutions for corn. It laid the groundwork for a new interstate highway of discovery," said Pam Johnson, an Iowa farmer who chaired NCGA's Research and Business Development Action Team and later served as NCGA president.

NPGI has funded more than $1.5 billion of genomic research to date, and the undertaking continues to send ripples through the scientific community and agriculture.

At 2.5 billion base pairs covering 10 chromosomes, this genome's size is comparable to that of the human genome which explains why the data generated will keep scientists sorting and exploring for decades to come.

The new, emerging picture of corn helps researchers better understand its evolution and history. The crop was domesticated from a Central American grass called teosinte some 10,000 years ago. Much of the genetic diversity of maize, however, reaches nearly five million years back.

"Today we are still investigating what each of the genes does with a new initiative called Genomes to Fields. It's a big puzzle that we don't have a complete map for yet, but the potential benefits and advances are mind-boggling," Johnson said. "The data we have contains answers like the best way to adapt corn to different climates, develop more efficient corn plants, use less energy growing it, sequester more carbon and increase the supply of food and feed."