Research Articles Mixing it up in Uganda: Biodiversity bugs pests

What do you do when a crop you are growing tastes good and sells well, but is frequently attacked by pests and diseases? You could apply an array of pesticides, herbicides and fungicides to your farm, but this could have long-term repercussions on your own health and the health of your soil. If you are a smallholder farmer, you might not be able to afford to buy these chemical inputs. 

Recent findings from our trials in Uganda confirm the effectiveness of one agricultural biodiversity tactic: mix it up! While intercropping to reduce pest and disease outbreaks is not a new practice; in Uganda, we have been investigating with our partners, how planting different varieties of the same crop in mixtures can also reduce pest and disease damage. 

What have we found? That mixing varieties resistant to certain pests and diseases, with those which are more susceptible, significantly reduces the incidence of that pest or disease. In our trials with common bean varieties, we found that the highest decreases in damage are when at least 50% of a resistant variety is mixed into the plot – in this case, a traditional variety known as Kasirira.

We have had similar success with banana varieties. Ugandan farmers working with us have reported that the presence of weevils that attack banana plants reduced by 75%, and we are also discovering traditional varieties that are resistant to crippling banana diseases such as Black Sigatoka.

A key aspect of our research is tapping into the diversity of traditional varieties that exist in Uganda. Many farmers prefer traditional varieties to hybrid varieties because they taste better and are more suitable to their traditional ways of cooking and eating.

“Although the yield of this [hybrid variety] is good,” said Teopista, one of the banana farmers we work with. “It is too hard when cooked and gets cold too fast. The market price is very low so I mostly brew it into a beer. The traditional variety sells at four times the price.” This preference also means that it is easier to encourage farmers to grow traditional pest- or disease-resistant varieties. 

Using diversity has other benefits too. Planting varieties with different maturing times means that farmers can maintain consistent cash flow and stable food availability throughout the year. “Part of our work includes training farmers on how to select better quality and clean seeds to guarantee better yields; when to plant certain crops or varieties, and how to keep a record of their yields,” said Rose Nankya Bioversity International’s project manager in Uganda.

One of our trained farmers, Joy Mugisha, added, “I now write down how many bean pods I get per plant, how many kilos I get compared to what I planted and how much I sold it for. This helps me plan better for the next crop and I can negotiate better with my buyers because I can show them all the numbers.”   

“Knowing the difference between clean and diseased seeds has helped me a lot,” reported farmer Jovaille Muhoozi. “Before I used to harvest 10kg from planting 5kg of seed. Now I get 40kg from every 5kg of seed I plant, so I’ve started planting 10kg of each different variety!”

As we continue to try different mixtures of beans and mixtures of banana in Uganda, we are also working with partners to improve access to and awareness of traditional resistant varieties and how they can help improve yields overall. Bioversity International has organized seed diversity fairs and established a community seedbank in Uganda’s Sheema district, which now provides more than 200 farmers in the area with 30% of their common bean supply. A second seedbank welcomed and managed by communities has more recently been established in Nakaseke district, Central Uganda.

For more information, view this paper on our bean fly study in Uganda, this scientific poster or visit the resources on our Pests and Diseases page. 

This work is part of a global programme working in China, Ecuador, Morocco and Uganda on using crop varietal diversity in integrated production and pest management. It is supported by the International Fund for Agricultural Development (IFAD), the Swiss Agency for Development and Cooperation (SDC), the Food and Agriculture Organization of the UN (FAO), and the United Nations Environmental Program (UNEP) Global Environmental Facility (GEF).

In Uganda, our partners include: the Plant Genetic Resources Center of National Agriculture Research Laboratories (NARO), the Crop Protection Department of the Ministry of Agriculture, Animal Industry and Fisheries, the Ministry of Local Government, National Agricultural Advisory Services, the Mbarara and Kachwekano Zonal Agriculture Research and Development institutes, Advocates Coalition for Development and Environment, CARITAS Nakaseke and the Uganda National Farmers Federation.

This work contributes to the CGIAR Research Programon Water, Land and Ecosystems.