Research on using biodiversity to reduce pests and diseases

The challenge

Cercospora Leaf Spot and Berry Blotch disease on a coffee leaf, Costa Rica. Credit: Bioversity International/C. Zanzanaini

Pests and diseases are a natural part of any ecosystem. What farmers fear are the outbreaks or epidemics that can cause high yield losses. Worldwide farmers lose an average of 10-16% of their annual harvest to pests and diseases, but cases vary widely by crop, region and threat - losses for one farmer can be up to 100% of crops in one season to a single pest or disease. These losses take a heavy toll on local and regional food supplies whether it be wilt diseases in banana, bean fly and rust in beans, leaf blight in maize or blast in rice.

Climate change is also affecting pest and disease outbreaks. Insects already consume 5 to 20% of major grain crops. A recent paper estimates that for the three most important grain crops—wheat, rice, and maize—yield lost to insects will increase by 10 to 25% per degree Celsius of warming.

Common pest and disease control methods include using pesticides, physical barriers, crop rotation and natural pest enemies. However, less is understood about how crop varietal diversity could improve pest and disease management.

Bioversity International's research approach:

Our research shows that using agricultural biodiversity and a series of low-tech management practices are effective, cost-efficient and environmentally-friendly ways to manage pests and diseases for increased productivity and reduced loss.

We conduct research at different scales, from a variety within a crop to the species and landscape level. Using diversity for pest and disease management also encourages farmers to maintain local diversity on their farms, an important source of genetic materials that could be used for breeding resistant varieties in future.

We work through local and international partnerships with communities, researchers, government actors and development agencies to develop solutions that can then be taken to scale.

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Removing single diseased stems

Credit: Bioversity International/G. Blomme

For close to two decades, Xanthomonas wilt has devastated banana production across East Africa. Previous recommendations for control were often reported as labour intensive and tedious, with many smallholder farmers reluctant to adopt them. But that is changing thanks to an easier, cheaper option developed by Bioversity International and partners which is helping to restore banana productivity to smallholder farm families in the Democratic Republic of Congo (DRC) and across east and central Africa.

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Crop variety mixtures - a recipe for success

Credit: Bioversity International/R. Nankya

A new study shows that farmers in Uganda who grow varietal mixtures of beans and of bananas perceive a yield increase of up to 28%. The results are boosting farmers' motivations to make more use of agricultural biodiversity to achieve more resilient production.

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Using intraspecific crop diversity in 4 countries

Intraspecific diversity in field plots to test for resistance to ALS, Anthracnose, and beanfly, Uganda. Credit: Bioversity International/D.Jarvis

Since 2006, Bioversity International and partners have been working with farmers and national researchers in China, Ecuador, Morocco and Uganda, to see how diversity within a crop, can add value to pest and disease management.

The research focuses on traditional and modern varieties of six crops: banana, barley, common bean, faba bean, maize and rice. Field trials across all four countries have consistently shown that using more varieties of a crop increases resilience to pests and diseases, reducing the likelihood of severe outbreaks and damage to crops.

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Stopping the coffee borer beetle in its tracks

Fragmented coffee production landscape, Costa Rica. Credit: Bioversity International/DeClerck

The coffee borer beetle has spread to almost all coffee producing regions and is resistant to most pesticides.
Fragmenting agricultural landscapes by increasing the diversity of cropping systems increases distance between crops and acts as a physical barrier to pests like the coffee borer beetle.

Bioversity International work with CIRAD and CATIE demonstrates that maintaining forest adjacent to coffee reduced movement of coffee borer beetle by 86% – it takes > 400 linear meters of sugar cane, 400 of pasture, and less than 150 of forest to serve as a barrier.

Forests also provide bridges to aid wildlife movement through agricultural lands and they attract pest predators – like the yellow warbler who likes to eat coffee borer beetles.

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