In fight against African pests, researchers point to natural-born killers

Many African farmers are suspicious of natural pesticides, despite their significant benefits.
Researchers say it is high time to tap African farmers’ knowledge of naturally occurring pesticides.
Researchers say it is high time to tap African farmers’ knowledge of naturally occurring pesticides.

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Africa - BOGOR, Indonesia — They’re green. They’re flowery.

And to many of the insects that ravage crops in Africa, they’re deadly.

Call it a “back to nature” approach to pest management: With infestations still threatening the food security of many smallholder farmers in Africa and global demand growing for produce free of synthetic pesticides, researchers say it is high time to tap African farmers’ knowledge of naturally occurring pesticides to make such botanical solutions efficient, affordable and accessible.

“Current pest management technologies are not accessible to those who need them,” said Phosiso Sola, Senior Scientist at the Center for International Forestry Research (CIFOR). “Those pesticides that get to smallholder farmers are often out of date or adulterated.”

Sola is the lead author of a new study on botanical pesticides in Africa, which makes the case for deeper investment in plant-based products.

She pointed out that up to 30 percent of crop yields were lost before harvesting and during storage in sub-Saharan Africa because farmers cannot protect them adequately from parasites.

Meanwhile, synthetic pesticides pose health risks to their users and may shut them off from lucrative export markets such as Europe and the U.S., where regulations on chemical residues are getting stricter, the publication notes.


In this context, the authors see botanical products as an attractive alternative: “The high diversity of African plant species with pesticidal properties and existing indigenous use of such plants by resource-poor farmers suggest that there is scope for developing a strong market that meets local as well as international demand for more ecologically benign pest control,” they write.

Yet despite their appeal, botanical pesticides are currently underdeveloped in Africa.

“Studies show that many more farmers know about them than use them — by deduction, there is a certain amount of doubt,” said Philip Stevenson, a professor of plant chemistry at the University of Greenwich’s Natural Resources Institute and a co-author of the paper.

“The main reason is that synthetic pesticides are promoted more effectively and farmers think they are more efficient — which includes a part of misinformation when you realize the resistance to them that has been building up,” Stevenson added. He also mentioned the influence of some religious groups who denounce the use of plants as witchcraft.


Many botanical pesticides are currently used in a low-tech way, with farmers growing or collecting selected plants and using their flowers, leaves or bark in crude form to combat infestations of insects or fungi in crops. Such traditional techniques yield inconsistent results, which has contributed to reinforcing the image of botanicals as less reliable than synthetic pesticides.

Botanical pesticides produced on a commercial basis by smallholder farmers could increase household incomes, and if used could increase food security by reducing yield losses

Phosiso Sola

This gap is where science is now needed to turn plant-based products into a viable alternative, according to Stevenson. “We don’t need research to find new plant species — we have enough — but rather to learn how to grow and use them more efficiently and sustainably,” he said.

While researchers noted a complete lack of interest for botanicals among the multinationals that currently produce synthetic pesticides, they remarked that Chinese and Indian companies had successfully converted some tropical plants such as neem into commercial sprays.

They believe there is a middle ground for researchers and commercial investors to develop plant-based products in Africa, for use by African farmers.

The paper analyzes examples of well-known botanical pesticides such as pyrethrum, an insecticidal flower grown in East Africa that generates significant export revenues for the region’s local farmers. Inefficiency and financial problems at the Kenyan state-owned monopoly that processed pyrethrum had triggered the industry’s decline, according to the study, but there are now opportunities for private investors to revive it.

The tephrosia shrub is also known across Africa to kill insects. A more scientific approach to its use could help farmers select the best varieties and the most efficient techniques to draw insecticide from its leaves.

“It would be possible to produce plant material and pack it in tea-bag-like containers so that farmers can make their own extract without having to grow it or dry the leaves, thus creating business for entrepreneurs,” Stevenson said. Such cheap insecticide, he said, could become the first ever accessible to some smallholder farmers in poorer regions of sub-Saharan Africa.


To enable such developments, researchers highlight the need for African governments to adapt existing regulations designed with botanical pesticides in mind.

“There is no policy framework for the production and distribution of botanicals. It’s very difficult to conduct the research to bring them to market,” Sola said.

While some countries such as Kenya have moved to adapt registration requirements more specific to each type of pesticide, in most countries the cost is often too high for potential local producers of botanicals.

For example, “while synthetic products have a simple list of chemical contents, plant products include multiple chemicals, and you cannot begin to conduct toxicology studies on each of them,” Stevenson said.

Researchers say African governments could foster vibrant domestic industries by opening simpler avenues to support botanicals value chains — including incentives for conservation where their collection or cultivation may threaten forests, as in the case of promising species found in the wild such as species of Lippia and Securidaca.

“Botanical pesticides produced on a commercial basis by smallholder farmers could increase household incomes, and if used could increase food security by reducing yield losses,” Sola said.

Not to mention the export of low-residue fruit and vegetables so eagerly sought by Western consumers.

For more information about the topics of this research, please contact Phosiso Sola at

This research was funded by the European Commission and forms part of the CGIAR Research Program on Forests, Trees and Agroforestry.

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