By MaryAnne Musilo

The wheat diseases stem rust and yellow rust have slashed yields across Kenya, but on a 360-acre wheat farm in Kabarak, Nakuru County, a change in fungicide chemistry and spray strategy has restored harvests by more than 50 percent., withPhilip Moi’s farm last year harvesting up to 28 bags of wheat per acre, compared to 16–20 bags before.

“Before changing the fungicides, we used to harvest 16 to 20 bags of 90kg per acre,” said Erick Kigen, a supervisor at the farm.

For several seasons, the farm had relied mainly on Tabibu 500SC, whose active ingredients are thiophanate-methyl, a benzimidazole, and hexaconazole, a triazole. The same chemistry was used repeatedly and sprays were done more as a routine than because of disease pressure. 

But yellow rust and stem rust are not very sensitive to thiophanate-methyl, so it’s record in clearing them tends to be poor, on top of which it has a history of triggering strengthening resistance over just a few seasons.

Hexaconazole has a better record with the rusts and is less likely to trigger resistance, but studies in China and New Zealand have found changes in treated fungi that decrease their sensitivity to the pesticide.

For Erick, using the pair, the stem rust and yellow rust had become steadily harder to control, especially during cold and rainy periods when the fungal diseases were spreading fast. 

But on switching to a mixture of active ingredients promoted by agrochemical company BASF as a T4 spray programme, the farm quickly regained its yields.

“After changing the fungicides, the yields rose to 28 bags per acre, with one acre having the least harvest of 25 bags. In that acre we used to plant grass, which I think could be the factor that contributed to the small harvest. Though the pesticides are expensive, the results are good,” said Erick.

Instead of depending on one main product, the T4 now rotates several fungicides. Priaxor, which contains fluxapyroxad, an SDHI, and pyraclostrobin, a strobilurin. Abacus Advance, which contains epoxiconazole, a triazole, and pyraclostrobin. Ceriax 149.8 EC, which combines fluxapyroxad, pyraclostrobin and epoxiconazole, and Rex, containing a triazole such as epoxiconazole. 

These ingredients attack the fungus in different ways, helping to improve control and reduce the risk of resistance when used in rotation.

“We start by spraying Priaxor, which stops the fungus from growing and protects the crop early.”

“After that, we use Abacus Advance, which helps both prevent and cure wheat diseases as the crop continues to grow.”

“We then spray Ceria 149.8 EC, which controls many diseases and helps avoid resistance when used in rotation.”

“Later in the season, we apply Rex to protect the leaves and stems so the crop stays green and fills grain properly.”

“All these sprays together make up the T4 spray programme, where wheat is protected step by step through its growth stages, unlike using only Tabibu and another product, which gives weaker and uneven disease control,” said Erick.

The farm grows the Robin wheat variety, chosen for its grain quality and post-harvest stability. 

“This variety is good but it has poor resistance to stem rust and yellow rust, which is why it requires up to four fungicide sprays to deal with the disease.”

Wheat rust is very common in Kenya. A 2023 study by CIMMYT of 132 wheat fields in the north and central rift found 102 rust infections, of which 60 were stem rust and 42 were yellow rust. 

But the amount of rainfall makes a difference to the severity.

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“This season we have only sprayed three times. When it is rainy, we spray about five times. The fungicides are expensive, for example the Ceriax, we buy at Sh30,000 for 5 litres, which can only spray 15 acres,” he said.

The farm uses tractors to spray, and also hires tractors for harvesting at Sh3,000 per acre.

“In harvesting, we wait for the wheat to dry while in the shamba, then we hire someone to confirm the moisture. The Cargill company where we sell our wheat requires 13.5 percent moisture, which is difficult to get. We mostly get it at 14 percent or 15 percent. The company deducts 1.5kg per bag as a penalty,” said Erick.

Prices fluctuate by season as the moisture fluctuates. “In 2024, we sold at Sh5,000 per sack and last season we sold at Sh4,600.”

Bird damage is another major challenge, with the farm hiring about 30 people daily to scare birds away, paying each Sh600 per day.

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