Southern Africa: Introduced Pests Threaten Crops after Severe Drought

1 February 2017 Mervyn Piesse, Research Manager, Global Food and Water Crises Research Programme


American armyworms, a species of caterpillar, were first reported in West Africa in mid-2016. The introduced pest has since spread to Zambia, Zimbabwe and Malawi. The Southern African outbreak was first detected in Zambia, where 124,000 hectares of maize, almost ten per cent of the country’s crop, have been affected. American armyworms are known to affect almost 100 plant species, including economically important food crops such as maize, millet, sorghum, rice, wheat and sugar cane. Cowpea, groundnut, potato, soybean and cotton have also been known to be affected.


Maize is the most important food crop in Southern Africa. In 2016, the region imported large amounts of the grain as domestic production declined due to drought. It is believed that American armyworms could have been introduced through the importation of maize from South America. As drought conditions ease in some parts of the region, an outbreak of armyworms threatens to slow the recovery.

A regional maize supply deficit of more than five million metric tons is forecast for 2016/17. As the region typically produces a three million metric ton surplus, this indicates a significant decline in production.

Armyworms are present in seven of Zimbabwe’s eight provinces and, in some parts of the country, 70 per cent of the maize crop is affected. It has experienced the most severe outbreak of any country in the region and is still recovering from the 40 per cent reduction in maize production in 2015/16. The pest poses a significant threat to the country and has dealt a significant blow to the government’s food self-sufficiency programme.

There are unconfirmed reports of the pest in the South African provinces of Limpopo, North-West and Free State, but specimens need to be analysed before remedial action is taken. The collected specimens appear very similar to American armyworms, leading some to “strongly suspect” that the pest has spread to South Africa.

South Africa produces almost half of the maize produced in Southern Africa and an outbreak of armyworms in the country could have devastating consequences. As South Africa is in a better position to control any potential outbreak of armyworms, however, it is unlikely to experience the same levels of crop loss as other countries in the region.

As growing conditions have improved since 2016, South African farmers have planted more maize. Market estimates suggest that production could reach 13 million tonnes, which is a 65 per cent increase on 2016. Provided production exceeds about 10.5 million tonnes, South Africa will be in a position to resume exporting maize. As South Africa is likely to be in a position to export maize, and its farmers are better able to control the spread of pests, it could stand to benefit from the outbreak of armyworms in the region.

If the Southern African region is heavily affected by the introduced armyworm, it will look to South Africa to meet the shortfall in maize production. South Africa, however, might not be able to fully satisfy regional maize demand and, if so, parts of Southern Africa will depend on maize imports from outside the region for a second consecutive year.

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