By Samantha Collins
Bananas and beans are key crops in Uganda, where more than 7 million people depend on them for carbohydrates and proteins. Yet these crops are vulnerable to insect pest and disease outbreaks that can devastate food production and livelihoods in poor smallholder farming households.
It is estimated that pests and diseases cause a 27 percent loss to annual harvests worldwide - a problem that is becoming increasingly difficult to fight as climate change results in changes in insect behaviour and new pest and disease combinations.
Smallholder farmers are often unable to afford the expensive synthetic chemical treatments that could help reduce the risks of outbreaks, and the treatments can pose risks to workers’ health and the environment. But there is another option which is more sustainable and less expensive: using agricultural biodiversity.
The use of agricultural biodiversity to minimize the risk of crop pest and disease has been the focus of a 5-year Bioversity International project in China, Ecuador, Morocco and Uganda. Using different varieties of a crop, planted together, can reduce farmers’ chances of losing an entire harvest. Different varieties offer different resistant levels to outbreaks, unlike relying on growing single genetically uniform modern varieties.
Two of the six crops studied in the global project, bananas and common beans, were evaluated in terms of the number of varieties grown, the area planted to each variety at household and community level, and the variation of resistance when the variety was grown on its own compared to mixed with other varieties.
“The correlation between the number of varieties and the area sown to each variety was greatest when the pressure from pests and diseases was greatest,” said Carlo Fadda, the Bioversity International scientist who coordinated the project in the field. “For example, when the disease incidence is high, farmers who grow more bean varieties benefit from the diversity in their fields, by experiencing less overall crop damage.”
The study showed that farmers in Uganda already have a good understanding of some of the pests and diseases they could see attacking their crops, especially those that attack the common bean. But they were less familiar with some of those that are not visible to the naked eye, such as nematodes, which is a serious banana pest.
Scientists worked with farmers to devise cropping systems that included a mix of traditional varieties that are also commercially attractive, so the farmers could increase protection against outbreaks and also income opportunities. They also examined the farmers’ beliefs about traditional varieties being more resistant than modern varieties, with encouraging results.
“The project showed that crop diversity can represent an affordable and usable alternative to expensive chemical inputs in some cases, which is especially valuable to poorer farmers,” says Devra Jarvis, principal scientist at Bioversity International. “It increases the options farmers have to manage their production systems.”
Bioversity International scientists hope that the results of this research from the four countries will help promote the use of crop biodiversity as part of sustainable, integrated pest management strategies.
Samantha Collins is a communications specialist at Bioversity International. Bioversity International will be holding a session entitled "Sustainable Use of Agricultural Biodiversity" at the upcoming Global Conference on Agricultural Research for Development which will be held in Punta del Este, Uruguay from 29th October to 1st November.