Reviewing options for smallholder farmers in the war against fall-armyworm in Africa

Spodoptera frugiperda, the fall armyworm (FAW), is one of the world’s worst agricultural pests. This polyphagous noctuid is native to the American tropics and subtropics and was first detected in West Africa in 2016. It has spread across the continent, subsequently invading Asia. FAW has wreaked havoc on maize production of smallholder farmers, who often have limited access to insecticides, fertilisers and hybrid seed.
Our objective was to synthesise published knowledge on what farmers can do to minimise damage. We used a systems-model. Our target parameter was the degree of damage caused by FAW and we defined the system as a smallholder maize field with the system boundary as the field edge. We conducted a systematic review using Web of Science, resulting in 219 initial hits. We retained 85 articles of which 12 were reviews. We classified potential influences into climatic, cultivar, cultural practices, and treatment factors. Treatment factors were subdivided into “input toxicity to humans and the environment”, labour requirement and “cost-benefit ratio”. “neighbouring fields” and “landscapes” were considered as outside the system boundary.
In SSA to date, cultivar type has had little impact on FAW damage. However, FAW-tolerant cultivars have recently been imported from the Americas and national breeding programmes have started to cross them with those used locally. Bt-maize is rarely available in Africa. Synthetic insecticides are the most widely used control option, but many are classified as moderately hazardous. Biopesticide use is constrained by availability and cost although their use can be profitable. Early planting significantly reduced FAW-damage as did no-till and frequent weeding. Intercropping with beans decreased FAW-damage, while pumpkin increased it. The push-pull technique whereby grasses, often Brachiaria or Pennisetum, are grown around the field, attracting the FAW and Desmodium, a repellent legume, is grown within the field, to drive it away, has been successful. However, seed availability and high labour are adoption constraints.
In conclusion, using synthetic insecticides is currently the most efficient way to reduce damage by FAW and increasing profitability. Environmentally safer options are currently limited by their high cost, higher labour requirement and low availability. Increasing the access to, availability of and utility of environmental-friendly options, will thus be key to decreasing the effects of FAW without compromising human and environmental health.