When I read the news in June that Kenya was ready to allow field trials of genetically modified cassava, I called Dr. Hans Herren. Herren won the World Food Prize in 1995 for using biological controls to halt a mealybug infestation that threatened to destroy cassava crops across Africa. With cassava serving as the staple food for much of the continent, the effort saved as many as 20 million lives, by one estimate.
I’d been with Herren at the World Food Prize events in Des Moines, Iowa, in 2013. That was the year the World Food Prize Committee, from its elegant Hall of Laureates building recently renovated with a donation from Monsanto, awarded the prizes to three pioneers in GMO technology. We ate a lot of GM food at the World Food Prize festivities, and we heard a lot about cassava. The crop was again threatened, this time by the brown streak virus, and the industry had the antidote: a GM variety that could prevent the disease. The same one now slated for release in Kenya.
Herren was dismayed in 2013 by the corporate turn the prize had taken. I remembered that he’d won the prize for saving the African cassava, so I asked him what he thought of the new GM cassava. He took me on the longest, most entertaining tangent I could remember. He told me the story of the successful biological control of the cassava mealybug decades earlier. It was a brilliant reminder of what ecological science looks like, and what it has to offer agricultural landscapes that are now so wildly out of ecological balance.
Tracking the cassava mealybug
Herren was fresh out of Berkeley in 1979, an entomologist with an ecology and agronomy degree. He applied for a job at the International Institute for Tropical Agriculture (IITA) working on maize, but when the director saw his resume he grabbed him to work on a mysterious infestation of cassava mealybugs in Africa. First spotted in Zaire (now the Democratic Republic of the Congo), the bugs were spreading rapidly, threatening a crop that served as a staple food for 200 million people across the continent.
Herren clearly enjoyed recounting the tale, giving it the feel of a detective story, a race against time to prevent a ticking biological time bomb from killing millions of African peasant farmers. He toured the sites of the infestation and gathered the available evidence. He said it was striking how devastating the pest was, turning large bushes into thin white stalks. The moist white covering on the remaining stalk looked like a fungus, but it was, in fact, a massive colony of tiny mealybugs.
He concluded that this had to be an invasive species brought into the region from the Americas, the other area where cassava – also known as yuca – originated and is still widely cultivated. And it had to be a species that in the Americas was kept under control, because there were no reports of cassava-killing mealybugs.
Over the course of a year he drove through Mexico, Central America, Venezuela, Brazil, and finally Paraguay searching, in the primary centers of origin of the Manihot genus, to which cassava belongs, for this particular species of mealybug. To his chagrin, he found nothing. But he reasoned that he hadn’t been in every region in every growing season. He’d been in Paraguay during the rainy season; maybe it thrived in the dry season. He asked a colleague, Dr. A. Bellotti, who traveled regularly to the Caacupe research station in Paraguay, to keep looking. Sure enough, Herren got a call. His colleague had found the mealybug.
It turned out that the bug didn’t destroy cassava in Paraguay because a number of insects preyed on it. These so-called beneficial insects are at the heart of the biological control of pests. Products of the long process of domestication of agricultural crops and their evolution, these beneficial insects keep nature in balance. Without them, there is nothing to stop this particular species of mealybug from consuming the cassava. The invasive bug from Paraguay, likely brought onto the continent illegally on cuttings for experimental planting, had arrived without its natural enemies and was feasting on African cassava without any well-adapted enemies.
Fortunately, for such crop-threatening outbreaks the time bomb often ticks slowly. In the two years that Herren and his colleagues had searched for the bug and its antidote, the infestation had spread from the Bas Congo (the region around Brazzaville and Kinshasa) to Maputo in Mozambique, covering the entire African cassava belt, an area about one and a half times the size of the United States.
In a quarantined environment in London, Herren studied the beneficial insects they collected to see which might thrive in Africa without themselves becoming dangerous invasive species. They did the research in London because no cassava is grown there. He said they had to take special precautions to ensure that no bugs would be inadvertently released where they could do their own damage.
Eventually, they identified a small wasp they thought would be safe to bring to Africa. The wasp controlled the pest by laying its eggs in the young mealybugs. The eggs hatched quickly, and the young wasps nourished themselves by eating their mealybug hosts from the inside out, killing them within their first week or so of life. Before they could do any damage, and before they could reproduce. The latter was key to the evolutionary balance, because Herren said mealybugs spread quickly. All the bugs are female, so they reproduce by parthenogenesis, and they each will produce 700 offspring.
Biological pest control – at scale
With a biological antidote in hand, Herren mobilized US$20 million from international agencies to design a multi-year process to introduce the wasp into African cassava-growing regions. He reminded me, more than once, that the funding for his initial research and for the biocontrol campaign came entirely from public sources. And there were no patents to infringe on the rapid and inexpensive dissemination of wasps.
Critics often paint agroecology as useful only on small-scale farms. The mealybug control effort was at scale – massive scale. Researchers spread the wasps through ground operations and even airplane drops, seeding cassava regions with the predators. By 1993, the mealybugs had been brought under control, with the wasps reaching an ecological equilibrium with the destructive pests.
As the World Food Prize committee noted in giving Herren the 1995 award, “Within ten years, Dr. Herren had almost single-handedly developed a chemical-free biological control for the mealybug, eliminated the threat to cassava production, averted disastrous famine, and saved upward of 20 million lives.”
Herren went on to lead IITA’s Plant Health Division, which he created, taking a holistic approach to managing pests and diseases. Later, he joined the International Centre of Insect Physiology and Ecology (ICIPE) in Nairobi, Kenya. He is now President and CEO of the Millennium Institute in Washington, DC.
And the GM cassava?
Herren’s tangent took him back to the alleged breakthrough on GM cassava to fight the brown streak virus. As the World Food Prize fawned over its GM scientists in 2013, Herren answered my question. Most of the products of biotechnology don’t address pressing life and death issues, he explained. They reduce the need to weed your soybean and corn fields, at first, but this comes at a cost for the environment, health, and the farm economy too. With resistance building up, from both the insect and weed sides, new products need to be developed, recreating the old pesticide treadmill.
Where biotech claims it has the solution to a life-threatening problem, the product is often in development for years after the press releases proclaim its life-saving properties. This often results in cuts in funding for more traditional and safer options such as biological control, which unlike GMOs, deal with the cause rather than the symptoms of the problem.
And the GM cure for the brown streak virus? He let out an exasperated sigh. “We had that completely under control. It’s become a problem because they’ve killed off the ecological features that kept it from being a problem. You don’t need GM cassava. You need to restore the ecological balance in the field, you need to restore the soils and provide healthy nutrition for the plants.”
Indeed, the African Centre for Biodiversity has documented the risks of the planned GM release and the existence of resistant varieties that could be propagated in the region.
With the recently announced release of GM cassava in Kenya, I got back in touch with Herren. This was indeed the same GM variety touted seven years earlier as the imminent savior of Africa’s cassavas. Herren’s biological pest control strategies had saved the African cassava before. Could they do it again?
“Yes, absolutely. By investing in co-creation of solutions in which farmers and scientists work together, embedded in the local ecological conditions. Cassava is a very resilient crop and, as we have learned from the mealybug and green-spider-mites biological control, natural solutions do work and are supported by healthy soils and healthy plants.”
The answer is not more technology to overcome nature, he explained, it is understanding nature and working with it to restore balance. “Years of biotechnology research give you one genetically modified plant variety that does one thing. Tackling the cause of the problem beats symptom treatment, every time!”
Herren is encouraged that this year’s World Food Prize is being awarded to Rattan Lal, who is being recognized for his pioneering efforts in the ecological restoration of our depleted soils. I am too. Lal is tackling causes, not symptoms, in our broken food system.
Photo courtesy of Thamizhpparithi Maari, Wikimedia Commons
