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Wheat farmers in Kenya battle new race of stem rust disease

A sister strain of highly virulent Ug99 stem rust disease is devastating wheat crops in Kenya, putting smallholder farmer livelihoods at risk.

wheat farmers in kenya
Wheat breeder Sridhar Bhavani (L) speaks with smallholder farmer Simon N’gang’a in his stem-rust infected wheat field. CIMMYT/Julie Mollins

NJORO, Kenya (CIMMYT) — Simon Ng’ang’a does not give up without a fight.

As a smallholder farmer in Kenya’s Rift Valley region, he has contributed for 10 years to the country’s wheat production, which averages around half a million metric tons a year.

Ng’ang’a’s autumn wheat crop failed – his meager 5 hectares (12 acres) of the high-yielding, disease resistant “Robin” wheat variety was struck by a new strain of stem rust disease.

It was reduced to shriveled grain and transformed into papery chaff instead of a valuable harvest.

“I was expecting to earn something to put in my pocket to give to my family, to encourage my children so they can be farmers like their father,” he said.

“Now they see how I’ve done they’re going to go for other jobs, but this was the job I was thinking they could do because I have the machinery to work the field.”

Largely dependent upon the rain-fed agriculture and climatic conditions found at altitudes of 1,500 meters (4,900 feet), Kenya’s wheat yield is small compared to the world’s top grower China, which produces about 120 million metric tons a year. However, wheat is the second most important crop in Kenya after maize.

The stem rust that destroyed Ng’ang’a’s crop, a sister strain of the dangerous Ug99 rust so named because it originated in Uganda, chokes plant nutrients in the stem, preventing the proper formation of wheat kernels. Epidemics of the disease can cause severe losses.

Ng’ang’a was growing Robin, a wheat variety developed by breeders at the International Maize and Wheat Improvement Center (CIMMYT), tested at the Kenya Agricultural Livestock & Research Organization (KALRO) and released to farmers to plant in their fields.

It’s a hardy variety, said wheat breeder Sridhar Bhavani, who heads the CIMMYT stem-rust screening nurseries in East Africa.


Older wheat varieties that farmers grew in the area were yielding about 4.5 metric tons per hectare, but improved varieties such as Robin now produce a yield up to 30 percent higher depending on farm management practices, Bhavani said.

“We’ve been racing to try and combat stem rust, to prevent the spread of the disease by breeding wheat varieties that contain resistant genes. The temporary solution is to spray fungicide,” he said.

“The reason Simon lost his crop is because he was not aware of the new race and failed to apply fungicide at the correct time and dosage, stem rust can cause losses of up to 100 percent.”

Ug99 has so far been detected in Ethiopia, Eritrea, Iran, Kenya, Mozambique, Rwanda, South Africa, Sudan, Tanzania, Uganda, Yemen and Zimbabwe. International scientists, governments and policymakers have been working under the umbrella of the Borlaug Global Rust Initiative project to develop disease-resistant varieties that governments can release through their National Agricultural Research Systems (NARS).

The aim is to develop and release disease-resistant wheat varieties that can be planted in about 5 percent of primary risk areas in all countries. The major fear among scientists is the potential impact of Ug99 if it spreads into the Asian breadbasket of India and China.

“The migration of this disease across geographical borders has an important significance because it indicates it’s widespread and can affect wheat production and food security on a global scale,” said Bhavani, who spends most of his working hours at the quarantined KALRO test site not far from Ng’ang’a’s farm in the Njoro region, about 200 kilometers (124 miles) northwest of the capital Nairobi.

“We’ve now identified eight variants within the Ug99 lineage throughout Africa, showing that Ug99 has a complex virulence to several genes previously believed to be resistant,” Bhavani added, pointing out some telltale rust-colored pustules on nearby wheat stalks.


To combat the threat of stem rust to wheat – as a line of defense for food security – scientists have developed and released 45 resistant wheat varieties. Most vulnerable countries have protectively produced Ug99 resistant varieties on at least 5 percent of their wheat-growing area.

Such resistance breeding in conjunction with fungicide has kept the spread of Ug99 disease in check so far.

Only a few kilometers from Ng’ang’a’s field, largeholder farmer Oliver Nightingale hired airplanes to spray his crop with fungicide after his farm equipment was sabotaged. Nightingale has been a wheat farmer for 23 years, but his vast tract of land has been farmed by his family since 1906 when his grandfather arrived as an immigrant in the early 20th century.

Nightingale, who has seen his wheat yields soar since he started planting the Robin variety, practices conservation agriculture, which means he barely tills the soil, letting the crops benefit from natural nutrients.

“Robin is good, high-yielding hard wheat – in the first couple of years we had no disease, but now we’re seeing it come out, although we haven’t cut down on our fungicide use,” Nightingale said, adding that the Robin variety has increased his yields by a third largely due to the density of the grain.

His overhead costs are equivalent to about 12 bags of wheat per acre. He used to be pleased when he had a yield of 20 bags per acre, but now he’s disappointed if he doesn’t get 30, he said.

“Timely application of fungicides can ensure a crop is protected,” Bhavani said. “Large-scale farmers can invest in enough spray, but small scale farmers may lose their crops because they are resource poor – that’s their biggest limiting factor.”

Wheat makes up about 12 percent of calories in Kenya, The country has two main rainy periods and no specific wheat-growing seasons, allowing the crop to be harvested year round.

The World Food Programme (WFP) estimates that 1.5 million people will be in need of food assistance through early 2015. Both WFP and the Kenyan government provide food aid in the country.

“I’m going to be back in the field again,” N’gan’ga said. “I won’t lose hope. If I get more financing, I will go back and do better.”