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After eradicating pink bollworm, Arizona farmers hope to use GMO cotton to target other pests

Published on April 29, 2021 | Amanda Morris, Az Central

CASA GRANDE — Dust from a nearby tractor blew thick across Paco Ollerton’s face as he walked across a wide field sprinkled with leftover cotton from last fall’s harvest. The tractor roared along his farm, tilling the soil to prepare for the next planting. 

The cotton seeds Ollerton would plant were bright blue and shimmery, like tiny jewels in his hand. These seeds had been color-coded to signify that they were genetically modified. 

Cotton farmers in Arizona started planting genetically modified cotton in 1996 in an effort to eradicate an invasive species of moth from Asia or Austrailia known as the pink bollworm. Pink bollworm caterpillars eat the seeds of cotton plants and damage cotton fibers, and in the 1990s and early 2000s, they were a big problem in Arizona.

“The damage was devastating,” Ollerton said. “I’ve never seen anything like it before.”

As a third-generation cotton grower who has been farming for 40 years, Ollerton recalls spraying pesticides in his cotton fields seven or eight times per season in an effort to combat the insects, always to no avail.

Planes spraying pesticides had to land in the middle of the field just to clear splattered pink bollworm moths off their windshield so they could safely see while flying, he said, and he and other farmers still lost huge portions of their crops. Sometimes, he said, farmers lost a third of their cotton crop, even after more than a dozen pesticide spray treatments. 

“There was a fleck of cotton here, a fleck of cotton there,” Ollerton recalled. “It was terrible.”

Then farmers tried a new method to combat the insects: planting genetically modified cotton, called Bt cotton, that is toxic to pink bollworms. Now, over a decade later, the pink bollworm is gone.

But it wasn’t just the genetically modified cotton. A recent study from the University of Arizona shows that farmers were able to eradicate the pest with the help of a coordinated, multifaceted program across the Southwest and northern Mexico among university, federal and state scientists, individual cotton growers and the cotton industry. 

The U.S. Department of Agriculture declared that the pink bollworm was eradicated in the United States in October 2018, but lead study author Bruce Tabashnik said the last pink bollworm was found in Arizona in 2012 and effectively eliminated in the state by 2013, a feat he initially didn’t think would be possible.

Genetically modified crops are not a silver bullet, he said, and over-relying on them can quickly cause problems with insect resistance. This has been seen in other areas of the world such as in India, according to Tabashnik, who is also a regents’ professor and head of the Department of Entomology at the University of Arizona. But in this instance, genetically modified crops seem to have allowed Arizona cotton farmers to stay in business.

“Farmers wouldn’t have been able to keep farming without eradicating the pink bollworm,” he said.

His study shows that eliminating the pink bollworm saved cotton farmers in the United States $192 million from 2014 to 2019 and helped reduce pesticide use in Arizona cotton fields by 82%. 

Though it’s been years since a pink bollworm has been spotted in the state, many Arizona farmers like Ollerton continue to use genetically modified cotton, and are turning their eyes toward other types of cotton pests.

In the U.S. corn and cotton are the two most common genetically modified crops grown with toxins in them derived from a bacteria called Bacillus thuringiensis, according to the U.S. Department of Agriculture.

Genetically modified plant seeds are more expensive than conventional seeds and researchers caution that insect resistance is a potential issue that must be managed.

And while farmers, scientists, the EPA and other advocates of the technology say it is safe for humans and poses little to no risk of affecting other parts of the ecosystem, anti-GMO activists argue there could be unknown safety or environmental issues with such crops and some would like to see more independent data and research.

Managing insect resistance

Bacillus thuringiensis is a type of bacteria found in the soil that is toxic to certain insects when eaten, according to USDA research entomologist Jeff Fabrick, who co-authored the University of Arizona study. 

To put these toxins into crops, companies like Bayer take one specific part of the bacteria’s genetic code, called a gene, and insert it into a plant’s genetic code. This gene carries the instructions for making a specific toxic protein and by putting it into the plant’s genetic code, it triggers plants to start producing the protein, according to Graham Head, Bayer’s global head of resistance management.

Instead of spraying the toxin in a pesticide, Head said this technique “lets the plant do the work.”

The toxic protein that the bacteria makes has to bind to receptors in the gut to be toxic for an insect or any other living thing, Fabrick said, much like a lock and a key. Any organism without the right receptor in its gut wouldn’t be affected, he said.

“Really, the beautiful thing about this particular bacterium is that it has evolved over millions of years with the insect …There’s a bunch of steps that have to happen before the protein is actually toxic,” Fabrick said. “It’s very selective and it has very little off-target effects.”

The first toxic protein put into plants by Bayer targeted a family of insect known as Lepidoptera, which includes butterflies and moths such as the pink bollworm. Not every pink bollworm was susceptible to the toxin. If a pink bollworm had any mutations that alter or eliminate its gut cell receptors for the toxin, that insect would be resistant and would not be affected.

Over time, Tabashnik worried that if farmers planted nothing but Bt cotton, all of the regular pink bollworms would die off and the only ones left would be the resistant pink bollworms, which would cause all future generations of pink bollworms to be resistant to the toxin and make managing the population even harder.

Tabashnik said he expected resistance problems would crop up quickly, since the pink bollworms’s short reproductive cycle means the population goes through five generations in one year. In the lab, he said a pink bollworm population became resistant after two generations of exposure to a Bt toxin. Once resistance is established, it’s very hard to reverse it or manage populations.

“When I first heard that the cotton growers in Arizona wanted to eradicate the pink bollworm, I thought it was a really bad idea, and the reason is insects tend to be incredibly adaptable,” Tabashnik said. 

To combat this problem, Arizona farmers were required to plant non-genetically modified cotton as at least 4% of their overall cotton crop so that some non-resistant bollworms would survive and mate with the resistant bollworms. Since Bt resistance is a non-dominant trait, this ensured that the pink bollworm population did not become resistant overall. 

Within 10 years, by 2006, farmers managed to reduce the pink bollworm population in Arizona by 90%, Tabashnik said. Once the population was knocked down, farmers obtained special permission from the EPA to plant 100% genetically modified cotton that year.

At the same time, researchers released sterilized pink bollworms to overwhelm the remaining population and knock down the population size further. For every one wild pink bollworm, Tabashnik said researchers needed to release 200 sterile moths, which would not have been logistically practical unless the pink bollworm population hadn’t already been diminished.

“By itself, the Bt crop is generally not going to allow eradication, so you need to combine it with other tactics,” he explained. “The combination of Bt cotton and sterile moth releases is a marriage made in heaven … it works much better than you’d expect.”

Now, Fabrick said he hopes the success of this method could be applied against other types of insects or against pink bollworms in other areas of the world, such as China, though he acknowledged that the right conditions are needed for success.

In Burkina Faso, a country in western Africa famed for its high-quality cotton, companies introduced Bt cotton in 2008 after being devastated by bollworm pests. But the Bt cotton-growing program essentially failed, according to Brian Dowd-Uribe, a University of San Francisco associate professor who studies social and economic factors around genetically engineered crops.

“It led to $76 million in losses because of inferior lint quality,” Dowd-Uribe said. “The Bt cotton lint wasn’t as good as the conventional cotton lint, so they decided to reverse course.”

That’s because Bt cotton was developed for commercial growers in the United States, where the cotton quality is different than it is in Burkina Faso. Outside of the context where the technology was developed, Dowd-Uribe said Bt cotton may be less likely to be successful depending on different social and environmental factors.

In the U.S., Dowd-Uribe said there’s a highly concentrated seed market among a few companies. Bt crops make up over 80% of corn and cotton crops planted in the U.S., according to Steve Naranjo, the center director of the USDA Arid Lands Agricultural Research Center.

“Because that technology is so pervasive within the cotton and the corn industry, it’s difficult for growers to find cotton or corn that doesn’t have the Bt technology in it,” Naranjo said.

Ollerton said he hasn’t noticed much of a difference between regular cotton and genetically modified cotton in the U.S., except that in some genetically modified cotton varieties, it was harder to open up the cotton bolls for picking.

The companies also set the prices for the seeds they sell, which are patented technology. Ollerton said he typically pays about $400 for a bag of seeds weighing between 43 and 48 pounds. By contrast, he said he paid about $30 for a 50-pound bag of cotton seed in the 1980s, which would be about $150 in today’s dollars.

It’s a price Ollerton is willing to pay, he said, because the technology has helped. He has continued to use the genetically modified cotton even after getting rid of pink bollworms because they are useful against other types of pests as well, such as the native cotton bollworm, also known as a corn earworm.

Targeting additional insects

Over time, Bayer has continued to update its genetically modified cotton, adding other genes from the Bacillus thuringiensis bacteria to make additional toxic proteins in their crops.

In the company’s second version of genetically modified cotton, also known as Bollgard 2 cotton, Bayer added a protein to broaden the amount of insects within the moth and butterfly family that would be affected, Head said.

“The basic concept is that we want to improve the level of control against pests,” Head said.

He also said this helps manage insect resistance because now, insects need multiple mutations to be resistant to both toxic proteins and are less likely to be resistant to both. 

Ollerton said Bollgard 2 cotton helped him control army worms, the cotton leaf perforator and the salt marsh caterpillar, all of which are native species. Tabashnik said none of these species would be eradicated through the use of the genetically engineered cotton, because unlike the pink bollworm, which almost exclusively eats cotton, army worms and the salt marsh caterpillar can survive on other plants as well.

“The cotton bollworm-corn earworm can eat over a hundred different host plants,” Tabashnik said. “So if you were going to try and eradicate it, you would have to think in terms of all its different host plants.”

While the cotton leaf perforator has a narrow diet and mainly eats cotton, he said the lack of sterile insect releases would prevent eradication of this insect population.

In addition to BG2 cotton, Bayer has developed a third generation of genetically modified cotton that Head said increases the plant’s toxicity to a small number of closely related moth and butterfly species in the Lepidoptera family.

“The whole concept here is to keep building on the previous generations of technology,” he said.

Bayer announced it expects to update its cotton plant technology to target sucking pests such as plant bugs and thrips, which lay their eggs under cotton bolls and can cause cotton to rot. Ollerton said plant bugs have been his farm’s biggest problem pest in recent years.

Environmental and health concerns

Naranjo said one variety of genetically modified corn initially produced the Bt toxin in its pollen, which raised concerns over negative impacts on pollinators. Since then, biotechnology companies discontinued that variety.

All current types of Bt cotton and corn have very low levels of toxin in their pollen as well as very little or no Bt toxin in their nectar, he said. Most pollinators are not susceptible to the toxin in the first place, so the risk to pollinators is extremely low.

Head said Bayer has been continually learning and improving their genetically modified crops along the way.

“There is a large amount of control over those things,” Head said. “We get better and better at ensuring that the proteins go at high levels into the plant tissues we’re most interested in and directing it to be at low levels in other tissues as much as possible.”

He said the company has multiple studies and years of data showing that these genetically modified crops are safe for the environment and safe for human health.

“A lot of scrutiny has gone in. A lot of really good experience says that these are great technologies to use,” Head said.

Some researchers argue that the use of genetically modified crops is more environmentally friendly because they reduce the use of potentially harmful pesticides. Broad spectrum pesticide use had harmed beneficial pollinating insects, according to Fabrick, who said that using a targeted approach reduced negative effects on other species.

Naranjo said that while the Bt toxic proteins from genetically engineered cotton can leach into the soil around crops, studies suggest that off-target effects into the soil or into runoff water are not a concern because the toxin is at lower concentrations in the soil and degrades quickly once it leaves the plant and gets diluted in water. 

Some are still wary of genetically modified crops and would like to see more research. Rachel Linden, founder of GMO Free Arizona, said she worries about unintended consequences of the technology. She doesn’t trust the results of studies done by companies that make the technology, such as Bayer, because of allegations that products like RoundUp are linked to an increased risk of cancer.

The International Agency for Research on Cancer, a branch of the World Health organization, reviewed about 1,000 studies and in 2015 labeled glyphosate, an ingredient in RoundUp, as “probably” cancer-causing. However, the company told The Arizona Republic that it “stands fully behind its glyphosate-based products” as safe.

The Environmental Protection Agency also released a report in January stating that the agency did not identify any human health risks associated with glyphosate and that “the benefits outweigh the potential ecological risks when glyphosate is used according to label directions.”

The company announced settlements worth billions of dollars last June against thousands of litigation claims but said the settlement agreements “contain no admission of liability or wrongdoing.”

An EPA spokesperson said the agency identified no risks to soil, water or non-target organisms linked to Bayer’s latest genetically modified cotton products.

Linden still believes RoundUp causes cancer and worries about other products made by Bayer. She believes the EPA and USDA should not rely on studies done by the company to make decisions about their products.

“There’s no reason to trust these companies,” she said. “That is inherently a bad idea: to leave corporations to self-police themselves.”

An EPA spokesperson said regulations are based on “strict scientific standards and extensive input from academia, industry, other federal agencies and the public.”

Christoph Then, the executive director of Test Biotech, a German organization advocating for independent research on biotechnology, said further data and research is needed. Currently, he said conducting independent research is difficult.

“It’s difficult for researchers to get access if they’re not signing agreements with the company, so it’s more or less controlled by the company,” Then said.

In response, Bayer said researchers can usually do research with an academic research license or stewardship agreement with the company. If a researcher is not covered by either, the company “works with the researcher and academic institution to make sure the appropriate agreements are in place.”

In a statement, Bayer said it “is always open to discussions with academic researchers on potential study opportunities.”

Christoph Then also argues that studies on genetically engineered crops don’t always reflect real-world situations. For example, he said company studies sometimes only test one toxic protein at a time, rather than testing them in combination, and that there aren’t enough long-term studies done on continuous consumption of or exposure to the products.

“We agree with industry that we would not expect short-term acute health impacts. But we insist that more complex questions on chronic exposure to these traits … need to be examined,” he said.

He also believes that company-driven research is not always set up to be focused on health and safety, and that the way studies are designed can be biased.

“From our perspective, it’s not science based. They just try to save time and money. But it’s not driven by the perspective of protection of human health or animal health,” Then said.

In response, Bayer said the company follows global standards of good laboratory practices when conducting research to “ensure the quality and integrity of the data.”

More research is needed, Christoph Then said, in light of studies showing immune system reactions in mice exposed to the toxic protein used in Bt crops, including one from the National Autonomous University of Mexico. Another study from the National Autonomous University of Mexico concluded that “although the term ‘toxic’ is not appropriate for defining the effects these toxins have on mammals, they cannot be considered innocuous,” based on such immune system responses.

The company said the results of the study from the National Autonomous University of Mexico showing immune system reactions in mice contradicted “the weight of evidence and history of safe use” of the toxic protein in question. The company also said the study’s test conditions were not realistic when compared with real-world exposure to the toxic protein.

In addition to potential impacts on immune system responses, Then also believes the environmental impacts of Bt crops like corn and cotton should be further studied. He said not enough research has been done on what would happen if the crops spread into the wild.

He pointed to a recent study that demonstrated that genes from genetically modified cotton escaped into the wild in Mexico and changed the way that wild cotton interacts with different insects in the ecosystem. Prior to this, Then said the assumption was that any escaped genes from genetically modified cotton would disappear and not have any impact on native wild plants.

But this study demonstrated that the cross of genes from genetically modified plants into wild cotton plants caused the wild cotton plants to produce differing amounts of nectar and attract different populations of insects as a result.

“We think this is a highly relevant study because it shows the unintended effects,” Then said. “Nobody ever did a detailed study of what Bt cotton does if it starts spreading.”

While these hybrid varieties of cotton have not yet been labeled as invasive, Then said its possible the changes could threaten biodiversity in Mexico or change the ecosystem in unforeseen ways.

The company said the study was not robust enough to support the conclusion that the observed differences were caused by the Bt cotton genes.

In response to concerns over the science behind their products, Bayer said safety was its top priority and that it was committed to information transparency.

“Crop protection and GM crop products are among the most thoroughly investigated and strictly regulated products in the world,” the statement said.

Source: https://www.azcentral.com/story/news/local/arizona-science/2021/04/29/arizona-farmers-genetically-modified-cotton-targets-pests-eliminates-pink-bollworm/6836112002/

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