Triphine Mukandanga, a potato farmer in Cyanika Sector, Burera District, describes the 2026 planting season as a difficult one that has left her questioning whether to continue with the crop after late blight disease affected her harvest in a way she had not expected.

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Late blight is a disease that attacks potato plants, creating dark spots on leaves, stems, and tubers. It can quickly destroy crops, especially in wet and humid conditions.

"I have been farming potatoes for years, but this season was discouraging. I planted 360kg of seeds on my 11 acres, expecting over 3.6 tonnes, but I barely harvested 800kg,” she recounts.

Mukandanga explains that her farm uses a standard calculation: one acre can hold about 25 medium seeds or 40kg of larger seeds, with an average of 100kg producing roughly a tonne. Yet, the late blight disease undermined her expectations.

To fight the disease, she sprayed a mix of chemicals nearly twice a week. "I was using about three bottles of Cypermethrin, each costing Rwf1,200, mixed with three bottles of Rudomir,” she explains.

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"Even with all that, the disease kept spreading because of the heavy rains. We were spraying so often, I can’t even count how many times.”

The rising cost of inputs has added to her woes. "Two years ago, Dithane was Rwf6,000, now it is Rwf8,000; Rudomir went from Rwf1,000 to Rwf1,500, and Cypermethrin from Rwf800 to Rwf1,200,” she notes.

Faced with diminishing returns, Mukandanga is now considering a shift. "I am thinking of growing other crops while I wait for the land to recover,” she says.

Christella Uwase, a potato seed multiplier in Gicumbi District and founder of Bountiful Farmers Ltd, said multipliers face rising challenges on the field. She grows varieties including Kinigi, Kirundo, and Ndamira.

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"Yields are falling while costs keep rising, which is discouraging. Multipliers’ work is also affected due to the disease,” se says.

Having visited the genetically modified potato trials, she said their yields are higher and resistant to disease. "Varieties that don’t need pesticides will boost our profits and allow us to invest elsewhere. We can’t wait to get them.”

Late blight, a big challenge

In a visit to Rwanda this month, Janet Fierro, the Communications Manager at the Feed the Future Innovation Lab for Legume Systems Research at Michigan State University, told the media that late blight disease costs the global economy between $7 billion and $8 billion every year.

"Today, we believe that science has given us the answer to late blight,” Fierro said.

She noted that while late blight is no longer a major concern for potato growers in the United States, the same technologies used there are now being adapted for regions where the disease remains devastating.

She explained that biotechnology has helped address problems such as bruising and water damage in the US.

"It’s very exciting to see that you can take something like technology and apply it to each individual part of the world. In sub-Saharan Africa, late blight is a big issue,” Fierro added.

In Rwanda, trials conducted on two varieties, Ndamira and Victoria, by the Rwanda Agriculture and Animal Resources Development Board (RAB) under the project in collaboration with African Agricultural Technology Foundation (AATF) show what that resilience could mean in practice.

Anastase Nduwayezu, a Senior Scientist and Coordinator of Potato Research and Technology Transfer in RAB, said trials comparing improved and non-improved varieties revealed significant yield differences, even without the use of pesticides.

During Season A of 2025, which began in November 2024, improved Ndamira produced an average of 450 grammes per plant, compared with 320 grammes for the non-improved variety. Improved Victoria recorded the same average yield, while the non-improved Victoria produced about 200 grammes per plant.

In Season B of 2025, yields were analysed in tonnes per hectare. Improved Victoria produced 33.93 tonnes per hectare, compared with 2.75 tonnes for the non-improved variety. Improved Ndamira yielded 30.81 tonnes per hectare, against 9.15 tonnes for its non-improved counterpart.

"All trials were conducted at the RAB station in Musanze on plots measuring 26 metres by 16.6 metres.”

Further trials in Season A of 2026 expanded to multiple RAB stations, including Rwerere in Burera District, Tamira in Rubavu District, and centres in Nyamagabe and Musanze.

While comprehensive results from all sites are still being compiled, early findings from Nyamagabe show improved Ndamira yields rising from 34.9 tonnes per hectare to 35.5 tonnes. Improved Victoria increased to 34 tonnes per hectare from 14.4 tonnes.

At Rwerere, improved Ndamira yields rose from 24.9 tonnes per hectare to 30.9 tonnes, while improved Victoria produced 19.5 tonnes per hectare compared with 5.4 tonnes for the non-improved variety.

"All varieties were tested under the same conditions, without the use of pesticides,” Nduwayezu said.

Cutting costs, reducing health risks

Abed Mathagu, Manager of the Rwanda AgriBiotech Project at the AATF, said the core advantage of the new potatoes lies in resistance to late blight.

"The potato does not require spraying for this disease, so farmers save money and the yield which is destroyed by this disease,” he said.

Mathagu stressed that the biotechnology involved does not introduce foreign substances but enhances resistance using traits from existing potato varieties.

Similar potatoes, he noted, have already been approved for cultivation in the United States and are undergoing regulatory processes in Kenya, Nigeria, Bangladesh and Indonesia.

Beyond productivity, reduced pesticide use could also carry public health benefits. According to the World Health Organisation, exposure to large quantities of pesticides can result in acute poisoning or long-term effects including cancer and reproductive health problems.

Regulatory pathway and broader biotech work

Athanase Nduwumuremyi, Senior Research Fellow and Roots and Tubers Programme Coordinator at RAB, said the biotech potato work is part of a broader effort focusing on maize, cassava and potatoes.

The biotech project aims to develop varieties resilient to climate change and major diseases, while reducing farmers’ dependence on chemical inputs.

"For potatoes, I have seen that they can have their produce doubled compared to the other varieties,” Nduwumuremyi said.

He explained that the varieties under testing, Victoria and Ndamira, are already familiar to farmers, having been cultivated in Rwanda for several years. The current work focuses on improving their resistance rather than replacing them.

The next step, he said, is to seek registration of the varieties through the Rwanda Inspectorate, Competition and Consumer Protection Authority (RICA), a process that may involve additional trials before approval.

Similar biotech efforts are underway in cassava, targeting cassava brown streak disease, locally known as Kabore, a viral infection for which no pesticide treatment exists. In maize, researchers are addressing fall armyworm damage while also developing drought-resistant varieties.

Across Africa, at least 10 countries including Rwanda, Kenya, Ethiopia, Sudan, Egypt, Eswatini, Ghana, Nigeria and Mozambique, have approved various biotech crops, ranging from insect-resistant cotton and cowpea to herbicide-tolerant soybean and pest-resistant maize.