Scientists warn that parts of southern Africa already hit by record droughts now face another potential food crisis because of the invasion of the crop-eating pest, known as the “fall armyworm.”

What is the fall armyworm?

It is not actually a worm, but a hungry caterpillar that eats crops before turning into a moth. It is a new pest, not to be confused with the similarly named “African armyworm,” which has been present in the region for many years.

Where did it come from?

It is native to the Americas, but experts are not sure how it reached Africa. One theory is that the eggs or the caterpillars hitched a ride in some imported produce, or even made it on board commercial flights.

Why is it such a threat to farming?

• It is very hungry (and not picky) — This pest targets maize (the primary food crop in many of the areas where the pest has been identified) and other cereal crops, plus cotton, soybean, potato and tobacco crops. When it does invade, up to three-quarters of the crop can be destroyed.
• Unknown enemy — Governments, communities and farmers have no previous experience of dealing with the new pest, which may be even harder to deal with than its native equivalent.
• It is fast  —According to the UN’s Food and Agriculture Organisation, it has taken only eight weeks for the pest to spread to the six southern African countries where there are suspected infestations.
• It is hard to find — The fall armyworm burrows right into the stem of maize plants, concealing itself from view and preventing farmers from spotting the problem early.
• Bad timing  — It comes after two years of record droughts, which have already affected more than 40 million people in the region, making 15 per cent less food available, according to the UN.