A groundbreaking bioherbicide takes a bite out of Kenya's hunger

When Catherine Wanjala woke up in the morning and saw the little purple flowers in her maize field in western Kenya, it would break her heart. The sprinkling of pretty blossoms was a terrible omen; her field was riddled with witchweed, a parasitic plant that attaches to the roots of crops like maize and sorghum, starving them of nutrients.

“Seeing my plants shrivel up and turn yellow would make me cry,” says Wanjala, recalling the time two years ago when the plant wreaked havoc and decimated the family’s income.

Wanjala is hardly the only farmer grappling with witchweed’s curse. Across sub-Saharan Africa, the plant known scientifically as striga hermonthica causes an estimated US$7-14 billion of damage yearly, wiping out harvests and hitting the livelihoods of more than 100 million people.


Now, thousands like Wanjala are fighting back - with an environmentally friendly fungal bioherbicide that’s gaining ground in Kenya - and soon elsewhere in eastern Africa, with support from the World Food Programme (WFP).

Produced by Kenya-based social enterprise Toothpick, it uses locally sourced fungal spores and counts among just a few bioherbicides being commercialized in the world. Unlike a chemical herbicide, the spores target witchweed and are unlikely to cause harm to other plants or humans, making the treatment both safer and more effective.

Farmers coat their seeds with the product before planting. For a cost of just 2,000 Kenyan shillings (US$15.50) per acre, the bioherbicide can boost maize yields by up to 60 percent.

“It’s one thing to have an amazing bioherbicide, but it’s another to prove its efficacy to rural farmers and encourage them to use it,” says Michael Njagi, who oversees WFP Kenya’s work tackling witchweed. “That’s where the World Food Programme stepped in.”

WFP's innovation team and the Farm to Market Alliance – a group working with farmers that includes private sector partners - collaborated with Toothpick to establish over 60 demonstration plots across western Kenya. The initiative not only showcased the bioherbicide’s effectiveness to farmers, but also provided them with hands-on training in its application. Farmers the alliance works with helped others like Wanjala access key inputs like fertilizers, along with markets.

“When they see that you spend 2,000 shillings and your return on investment is over 28,000 shillings, it’s a no brainer,” Njagi said.

One more shot

For many like Wanjala, the bioherbicide has been a life changer. Studies show female farmers, who make up the majority of smallholder maize growers in Kenya, are particularly vulnerable to the perils of agriculture. As those responsible for their family’s food security, they understand the full impact of failed harvests from factors like extreme weather or deadly pests.

“It was a really hard time for me and my family,” recalls the mother of two of her losing battle against witchweed. “I had no food even for my kids. We had to settle for having one meal a day.”

Wanjala’s children dropped out of school. She had to borrow money from relatives to get by. Her marriage suffered. But this year things changed, when she learned about the bioherbicide. 

“We've met numerous farmers, some of whom were at the brink of giving up on agriculture. Others had given up on farming,” says Toothpick scientist Loise Kioko. “We had to convince them to just give it one more shot.”

Beyond its effectiveness, the Toothpick bioherbicide has another powerful asset. Unlike its chemical counterparts, it offers a more sustainable and environmentally friendly solution to treating weeds.

“Chemical herbicides pose a significant threat to our environment,” says Pauline Kiamba, a WFP land and water expert in Kenya. “They contaminate soil and water, harm beneficial insects and vital pollinators, disrupt the delicate balance of the soil microbiome and devastate biodiversity.”

By next year and with WFP’s support, Toothpick aims to introduce its bioherbicide to 110,000 farmers like Wanjala across western Kenya - and eventually expand across East Africa, starting with neighbouring Uganda.

Wanjala for one, is sold. She’s seen her yields grow ninefold, to 270kg per harvest, and her earnings have soared.

Thanks to her extra income, “my children have not been sent home for school fees or anything else," Wanjala says, "and they can now study with no interruptions like other children."

Wanjala’s relationship with her husband has also improved. “We do not have to stress each other about many issues,” she says, “as we’re both working to build better lives.”

The WFP Innovation Accelerator in Munich and the WFP Kenya Country Office Innovation team are supporting the bioherbicide initiative for farmers in Kenya. 

WFP wants to thank New Zealand and Norway for supporting the bioherbicide project. 

Learn more about WFP's work in Kenya