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.