Suzanne's Mom's Blog

Photo: Delaware Agriculture
Mark VanGessel, Professor of Weed/Crop Management at the University of Delaware, with an invasive palmer amaranth plant.

Agribusiness presents all sorts of challenges these days. For one, weeds are becoming resistant to Roundup, the herbicide that has received so much attention for causing cancer. And having a huge number of acres makes it hard to find a paying crop to plant on alternative years, which can help improve the soil.

A report at Civil Eats, rebroadcast by Public Radio International, got me interested in Australia’s superweed problem. In it, Virginia Gewin explained how near-desperation was causing to farmers to get creative.

“In December, C. Douglas ‘Bubba’ Simmons III left his corn and soybean farm in northwest Mississippi to visit the dryland wheat fields in Western Australia, a region considered to be the herbicide resistance capital of the world. Plagued with unwelcome intruders such as annual ryegrass and wild radish that have evolved resistance to several herbicides, Australian farmers have been forced to develop new approaches to manage weeds — and their seeds. It hasn’t been easy. Farmers there are paying roughly 27 percent more per acre due to increased management and yield loss, according to Bayer.

“Simmons visited several farms in the southern half of the state of Western Australia with three other U.S. farmers and a weed scientist. … Simmons, eager to learn from growers who have faced similar weed concerns, was inspired by Aussie ingenuity. It remains to be seen whether their mechanical and cultural solutions will work in the U.S., given Australia’s much drier landscape. …

” ‘I think Mississippi might even be considered ground zero for the number of herbicide-resistant weeds we have,’ he says. ‘It’s a constant battle from mid-March to mid-November.’

“The long growing season and warmer climates in some parts of the South allow noxious weeds to thrive. But ‘superweeds’ that refuse to die when sprayed with herbicides have been taking over crop land across the U.S. farm belt and beyond. Globally, 255 different weeds have developed resistance to 163 different herbicides, but the most concerning are the 43 that have developed resistance to glyphosate (the main chemical in the widely used weed killer Roundup). These weeds compete with crops for space, water, and nutrients in the soil — and they’re beginning to impact many farmers’ yields. …

“Palmer amaranth, an aggressive pigweed that has devastated crops in the South and Midwest, is one of the worst. Each plant can produce at least 100,000 seeds, and, when left unchecked, they can grow to be taller than some people. …

“ ‘We really need to think about other methods,’ says [Christy Sprague, a Michigan State University professor and weed extension specialist who also traveled to Australia]. It won’t be easy. Farms have gotten larger and larger, so it’s unclear what physical approaches can be incorporated into current farming systems. Cover crops also show promise in suppressing weeds, for example, University of Arkansas weed scientist Jason Norsworthy found that a cereal rye cover crop suppressed roughly 83 percent of palmer amaranth. But their use among farmers is only growing slowly. …

“ ‘Our mantra—keep the weed seed bank as low as possible,’ says Lisa Mayer, manager of the Australian Herbicide Resistance Initiative and WeedSmart at the University of Western Australia. In other words, control these seeds, and keep them from turning into new weeds. To that end, farmers have developed a number of approaches to catch and destroy the seeds. Some pile the wheat chaff into lines behind the combine, which can be collected or burned. They also use the Harrington Weed Seed Destructor, a device that pulverizes weed seeds as the grain is harvested.

“These methods have proven to kill 95-99 percent of the annual weed seed produced. In combination with some herbicides, weed populations have been reduced to around 1 plant per square meter, which lowers the potential for resistance. …

“Simmons says the big takeaway he learned from his Australian counterparts was the need for farmers to help develop new tools for the fight against weeds. Despite the often-intense pressure to continue buying herbicides, Simmons says growers can’t continue as if there’s only a single tool in the toolbox.” More here.

I can’t help thinking smaller farms are the answer, but can they feed a planet that already has too much hunger?

Photo: University of Delaware Carvel REC
The root structure of the invasive palmer amaranth weed makes it almost impossible to eradicate. And it produces a huge number of seeds.

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