The initiative aims to find a home-grown biocontrol inoculum for Striga, which threatens many of Africa’s staple crops
One of the world’s toughest weeds is literally getting a taste of its own medicine in Africa.
Striga, a parasitic weed that has caused continued havoc on the African continent, is slowly but surely feeling the effects of an ingenious initiative — the Toothpick Project, now nearing commercialization.
Striga (witchweed) is the No. 1 pest threat to food security in Africa. The devastating invasive parasitic weed attacks the most important staple crops in Africa, including corn, sorghum, millet, dryland rice, sugar cane and cowpea, and now it has been identified in wheat in Sudan.
Although $30 million has been invested in finding Striga solutions, the damage has been getting worse over the last two decades. In a survey in three counties in Kenya, “all corn fields in western Kenya are impacted by Striga to some degree,” said Claire Baker with the Toothpick Project. “We’ve also heard reports that 50 percent of arable land in Tanzania is impacted by Striga.”
Baker, co-founder and director of the Toothpick Project and Toothpick Company Ltd., said according to papers published more than a decade ago, Striga results in US$9 billion in crop loss per year at the hands of smallholder farmers.
“About 40 million smallholder farms have Striga,” said Baker. “It strangles (corn) and other crops, attacking at the roots before the plants even come up above ground, resulting in 20 to 100 percent reduction in crop yield.”
The Toothpick Project has been in the works for more than a decade in Africa and is now approaching commercialization. It’s been a long haul, but the team that has brought it this far is dedicated to improving the fortune of corn — and other crops — farmers in Africa, 80 percent of whom are women.
The research starts with David Sands with Montana State University, who has been working on biocontrol solutions for years. Sands developed a biocontrol technology that flips plant pathology and puts the plant disease to work to kill the targeted weed — in this case, Striga hermonthica.
“Biocontrol of weeds has always been on the mind of plant pathologists for a long, long time,” said Sands. “We work with fungi, we work with bacteria or viruses, and they all attack weeds. We knew there ought to be some way to use these natural fungi to attack weeds and not have to use chemicals.
“Our strategy was to find Striga attacked by a fungal disease, Fusarium oxysporum. We then selected the most virulent strains of that fungi,” added Sands.
Fusarium oxysporum (f.sp. strigae), or Foxy, is a host-specific plant pathogen with 200 forms, each attacking a different species of plant. The challenge was that in nature, the pathogen seeks a balance with its host and it only wilts about 40 percent of the Striga weed. The team investigating the problem realized they needed a higher success rate than that if they were going to meet Striga head-on.
“So, we selected for Foxy strains excreting higher levels of certain amino acids, such as tyrosine and leucine, plus methionine,” said Sands. “These amino acids harm the Striga, but they don’t harm the crop. And so, the Striga count goes down by about 90 percent, increasing the total crop yield.
“It’s been a really good solution because it’s host-specific, which means it won’t hurt other plants, it’s non-GMO for countries that are limiting GMO action, and it’s safe for humans and animals,” added Sands.
To confirm the product is safe to humans and the environment, the Foxy strains have been tested by two independent toxicology labs (VA Tech and U of Nairobi) that have identified no known fusaria toxins.
The next challenge for the team was to figure out how to distribute Foxy to the farmers for use. The team worked with agronomist and farmer Florence Oyosi of Maseno, Kenya, and with the Kenya Agricultural and Livestock Research Organization (KALRO). In the early development of the technology, Oyosi helped create the toothpick delivery product for smallholder farmers.
The three strains of Foxy that were isolated from wilted Striga weeds and then selected for specific excretion of tyrosine, leucine and methionine amino acids were grown onto a wooden toothpick/dowel and dried, and all three are stored in a sterile, sealed canister (called FoxyT14, trademarked as Kichawi Kill in Kenya) of cooked and cooled rice. The farmer simply shakes the container twice a day for three days, and after the three days, all the rice is inoculated with FoxyT14. The farmer then plants about a teaspoon of inoculated rice with each corn seed. With the virulence enhancement, FoxyT14 kills the parasitic weed, Striga, instead of just wilting it.
With a Gates Foundation grant, the team, led by Henry Sila Nzioki, a plant pathologist with KALRO, did proof of concept trials in Kenya with 500 farmers in 2014 and 2015. The average yield increase of the corn crop? A whopping 56.5 percent. Over the past four years, the team has conducted regulatory trials and is awaiting registration of the system.
In 2018, the team launched a social enterprise based in Kakamega, Kenya, called the Toothpick Company Ltd. This organization celebrates public private partnership through its close relationship with KALRO, as well as the German non-governmental organizaion Deutsche Welthungerhilfe e V.
“Manufacturing is at the KALRO-Katumani biocontrol lab, and this is run by Sila Nzioki,” said Baker. “This distribution is then passed to the Toothpick Company where we partner with NGOs, community-based organizations, farmer groups and the ministry of agriculture, and through those entities, we deliver to village-based farmers.”
Although they are still awaiting registration, expected within the next three months, the work continues.
“We’re still working in the fields,” noted Baker. “We currently have 42 trained farmers to be village-level inoculum producers, and in September, these farmers prepared and planted over 600 demonstration plots in five counties in western Kenya.
“This is part of an enterprise — each of those farmers will have a micro business, and they will be earning profit off of their sales to their own customer base.”
The Toothpick Project doesn’t stop there.
“We are moving forward in Kenya with our goals to scale by 2025,” said Baker. “However, Striga is across sub-Saharan Africa so it’s really critical that we expand our reach.”
Next steps are to train a science team to understand regulatory harmonization, to expand distribution methods and to expand to other target weeds.
“In the next year, we anticipate working with each of our scientists, called the Pan-African Biocontrol Science team, to isolate and select their virulence-enhanced strains from each country,” said Baker. “We are also going to conduct our second training, which was earlier cancelled because of COVID, and are working on ways to train virtually.”
Promisingly, the team is seeing persistence of the treatment over time.
“In fact, at our original research plots (they’ve been untreated for years), Striga is no longer present and crops are doing well,” said Baker. “Our scientist couldn’t even get Striga to grow there when he planted Striga seeds. We haven’t conducted a longitudinal study yet but over the next five years we should have a better understanding of how farmers should schedule their treatments for the greatest benefit at the lowest cost.”
The emergence of wheat as a host for Striga emphasizes the importance of this control method not just in Africa.
“As far as we know, only wheat fields in Sudan have Striga, but if it spreads, we’ll have a huge problem on our hands.”
Baker emphasizes “we do have a global goal of shifting weed management from synthetic herbicides to a newly developed bioherbicide market.”
She anticipates that success in Africa will lead to game-changing adoption of bioherbicides elsewhere.