The weeds are winning in the arms race between biotechnology and biology. Kumar claims that growers believe that chemical companies will come up with a new herbicide. Even if such an amazing product was possible, there is a greater danger. Evidence is mounting that weeds can metabolize herbicides and break them down before they even do their job. Palmer amaranth could have developed resistance to weed killers yet to be discovered. Kumar said that this resistance is not something Kumar created in a laboratory. It's all around us, everywhere.
They will always respond to any threat they are trying to put them under. The evolutionary pressure that lawn mowers apply to plants causes them to grow outward rather than upward. They keep their blades away from the ground, and this is when they start to look more like weeds. Rice farmers who weed their paddies by hand ignore grasses that look similar to rice seedlings. This allows the imitators of the weeds to reproduce, making hand-weeding even more difficult. The persistence and speed with which herbicide-resistant populations of weeds have overtaken American farmland is a result of decades of industrial agriculture. Roundup was so common that many plants like Palmer amaranth developed resistance.
Roundup was introduced by Monsanto in the mid-1970s. It worked better than any other weedkiller on the market and was dirt cheap. Kumar claims that Roundup was so effective. It worked no matter where it was applied. This herbicide gets at the root cause of the problem.
Roundups supplement, an innovation that drove sales even higher, was introduced two decades later: Roundup Ready seed. Roundup Ready seeds could be used to grow genetically modified plants. They can withstand spray after spray of herbicide. Farmers could simply plant Roundup Ready seeds and wait for the weeds to emerge before spraying the entire field with Roundup. All other crops died quickly. This revolutionized weed control. Farmers no longer had to purchase a wide range of expensive herbicides every year, or till their fields every season.
Roundup Ready soybeans were first introduced by Monsanto in 1996. The paired products were quickly adopted by farmers: In 2011, approximately 94 percent of the soybean acres in the United States had been planted with Roundup Ready seeds. Similar trends were followed by corn and cotton. The U.S. glyphosate usage increased by more than 300% between 1990 and 2014. Stephen Duke, a former researcher at USDA, said that glyphosate was so effective and cheap that almost everyone used it for nearly 20 years.
The Palmer amaranth is incredibly well-adapted to overcoming resistance, and it does so very quickly. It is a native of the Southwest. The leaves were once eaten by the Cocopah, Pima and Pima tribes. The Navajo used the seeds to make meal. The pigweed began to spread eastward and became a serious threat for the crops in the South by the mid-1990s.
While cash crops are almost identical, farmers buy new genetically engineered seed every year that contains the glyphosate tolerance trait. Palmer amaranth is blessed with incredible genetic diversity. It reproduces sexually through obligate outcrossing. Female plants can produce hundreds of thousands of seeds every year. Random mutations in plants that were able to withstand herbicide sprays gave them the ability to reproduce. After Roundup was applied to a field, all weeds except for the resistant Palmer amaranth were eradicated, the pigweed was free to spread. Researchers planted one Roundup-resistant Palmer Amaranth plant into each of four fields of genetically altered cotton in one study. The weeds choked the cotton and the crop died within three years.
