The name says it all. A legion of fall armyworm caterpillars descends on the fields, leaving behind destruction before marching on. Once a field is infested, the voracious larvae destroy up to 50% of the harvests, according to the Food and Agriculture Organization of the United Nations (FAO). Maize, one of the staple foods in sub-Saharan Africa, is particularly affected. The fall armyworm causes up to 18 million tonnes of maize crop losses every year. More than 300 million people are affected by consequences that hunger and poverty.
Farmers can breathe a sigh of relief
It all started with a stowaway from America. First discovered in 2016, the fall armyworm quickly became a serious pest. It proliferated at breakneck speed and is now widespread in all countries south of the Sahara.
Meanwhile, farmers on the continent have been using synthetic pesticides to fight the pest – to no avail. Many of the chemicals do not reach the caterpillars inside the plants and instead kill important beneficial native insects and the armyworm’s natural enemies. Additionally, the pest’s offspring often develop resistance to synthetic pesticides. What follows are serious negative consequences for the health of farmers and the environment.
But farmers will soon be able to breathe easy: researchers have made a breakthrough in controlling the fall armyworm ecologically. They found three native ichneumon wasp species that can restore the natural balance between pests and beneficial organisms. In a field trial in Kenya, researchers released hundreds of thousands of these parasitic wasps in maize farms infested by fall armyworms, with astonishing results: the released wasps wiped out up to 55% of the pests. “The parasitic wasps work synergistically by attacking the pest’s eggs and larvae”, explains Dr Samira Mohamed, a researcher at the International Centre of Insect Physiology and Ecology (icipe) in Nairobi, Kenya.
Integrated measures help
More wasps will be bred after the encouraging field trial in Kenya. “There are plans for mass releases of these beneficial insects in other maize-growing areas in Kenya. We are also planning, together with national partners, to expand the release to other countries in eastern and southern Africa,” explains Sevgan Subramanian, Head of the Environmental Health Theme at icipe. However, a lack of technical capacity for propagating the wasp species in different countries presents a major challenge.
Demonstrating alternative methods of pest control is therefore all the more important. One of these methods is push-pull farming, which which was developed by icipe. Biovision helps to disseminate the method and supports its adaptation to new agricultural conditions. A study showed that armyworm-infested fields managed with push-pull faced around 80% less damage than normally managed fields. The average number of armyworm larvae per plant was 82.7% lower in the push-pull fields than in monoculture maize fields. Yields were also significantly higher.
Other environmentally friendly methods, such as intercropping or using organic pesticides, are also important components of a sustainable strategy. For millions of sub-Saharan farmers, these measures will be essential for survival.