Bugs and biogas: Kenyan farmers get creative to fight 'devil's' cactus

  • By Caroline Wambui
  • 27/09/2019

Men on the communally-managed Makurian Group Ranch in Kenya's Rift Valley load a prickly pear cactus they have chopped down into put in a wheelbarrow in Laikipia County, Kenya, July 31, 2019. Thomson Reuters Foundation/Caroline Wambui


LAIKIPIA, Kenya, Sept 26 (Thomson Reuters Foundation) - Armed with rakes, hoes and machetes, a group of ranchers hacked at the spiky cactus plants sprouting all over their land, chopping them into pieces and carting them off in wheelbarrows.

In many parts of the world, the prickly pear (opuntia) is used as natural fencing and decoration, thanks to its flat, fleshy pads, colourful flowers and purple fruits.

But across Kenya's arid northern areas, where grazing land is already depleted by frequent droughts, the cactus has become a nightmare for cattle ranchers and livestock herders.

Farmers at the communally managed Makurian Group Ranch in Laikipia County in Kenya's Rift Valley say the non-native, invasive plant destroys the grass that feeds their animals and can make them sick when they eat it.

"Despite our ruthless battle with opuntia, the cactus has rendered thousands of acres into a wasteland and won't go away," lamented Jackson Mukurinu, a farmer at the ranch who has lost more than 800 goats and 85 cows after they fed on the cactus.

Hoping to loosen its grip on grazing land, farmers, charities and scientists are working together to eradicate the plant with methods ranging from feeding it to insects, to turning it into fuel.


The prickly pear was brought to the area by colonisers in the early 1900s, said Protas Osinga, a livestock officer in Laikipia.

Over time, a warming climate and rapid population growth have transformed it from a popular crop into an uncontrollable menace, he said.

During the droughts and prolonged dry spells that have become increasingly common in Kenya over the past decade, the cactus is often the only vegetation that can thrive, he noted.

Livestock, birds, elephants and baboons often have no choice but to feed on the cactus, and when they do, they disperse its seeds as they move around the area. Kenya's expanding population, meanwhile, has stoked demand for milk and meat, motivating farmers to increase their herds with more animals spreading the cactus seeds, Osinga added.

Highly resistant to drought and able to re-sprout from the smallest piece of root, the prickly pear grows aggressively and is remarkably difficult to remove, said Lerina Legei, 80, an elder at the Makurian ranch.

In the past five years, over half of the more than 1,200 farmers living in the area have been forced to move to other parts of the ranch after the cactus overran their land, he said.

"Livestock is our livelihood and opuntia - having no competition - has conquered the land by suffocating the native crops, leaving no grass for our livestock," said 42-year-old rancher Florence Kakweri.

She moved her family last year after the plant's domination rendered them "helpless".

Osinga, the livestock officer, told the Thomson Reuters Foundation that about two-thirds of the ranch's 6,640 hectares (16,400 acres) had been invaded by the prickly pear so far.


The plant's impact does not stop at killing pasture, said Richard Karmushu, chairman of the Makurian Group Ranch.

It also exacerbates land erosion, as animals looking for grass manoeuvre around the cactus and eventually carve paths in the soil, he explained. Rain then washes away the weakened earth, leaving deep gullies crisscrossing the farm.

When farmers remove the cactus, it leaves behind deep, bare patches that are prone to further degradation, Karmushu noted.

Even worse, the plant's effect on livestock is so devastating that Kenya's cattle farmers have taken to calling it the "devil's cactus".

Ranchers at Makurian say their animals are often blinded by the plant's sharp spines as they try to reach the grass growing underneath it.

And while both humans and animals can safely eat the nutrient-rich prickly pear once its spines are removed, if ingested whole, the thorns can cause inflammation or infection that are sometimes fatal, said Osinga.


Simon Mbuki, programme manager for the aid agency World Vision, said tackling the cactus requires a range of measures.

The charity is helping Kenyan pastoralists in four counties find ways to control the plant, he said - for example, by providing the tools the Makurian ranchers are using to cut away the plant from their land.

World Vision's four-year project, launched in summer 2018, has so far managed to clear the cactus from 70 hectares, Mbuki said.

Because physically removing it can damage the soil, scientists have also been experimenting with a biological eradication method: tiny, cactus-eating insects.

Working with the Kenya Plant Health Inspectorate Services, pastoralists at Ol Joji Ranch in northern Kenya have introduced millions of cochineal bugs, sap-sucking insects that feed only on cactus, to their land.

The ranchers reported that the bug - also commonly used to produce a red dye - can wipe an area clear of cactus while leaving the soil intact.

Some have also found ways to turn the nuisance plant into a money-maker by using it to create juice, wines, oils and biogas.

Environmental scientist Francis Merinyi, who grew up in Laikipia, started making biogas from prickly pears when looking for a sustainable way to eliminate the cactus.

Last year, he founded the company Cactigas to buy unwanted plants from farmers to turn into clean fuel.

The process involves chopping the cactus up into a paste that is diluted with water and left to ferment.

It eventually starts releasing methane and other gases, which are collected, purified and stored in tanks for heating and cooking.

"When you make biogas, you utilise the entire plant as compared to making juice or wine," noted Merinyi.

The paste can also be used as organic fertiliser to add nutrients back into land degraded by a dry spell or a cactus invasion, he said.


Njenga Kahiro, Laikipia County's water and environment minister, said the local government was committed to helping farmers tackle the cactus.

Besides supporting initiatives by charities and companies like Cactigas, the government is also working to persuade farmers to keep fewer animals and embrace zero grazing, which involves feeding cows cut grass instead of putting them out to pasture.

Both methods help reduce the movement of cattle and curb the dispersal of the cactus, Kahiro noted.

He said officials were also training farmers to breed their own cochineal bugs to feed on the cactus.

At Makurian ranch, farmer Mukurinu is desperate for any method that will rid his land of the prickly pear - and put a stop to the injuries he and his family get while uprooting it.

"I hope it will be eradicated for good so that as a family we can enjoy the many benefits (of the land) that we used to."

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