Southern Africa has been struck by a pestilence so severe farmers have invoked plagues of biblical proportions.

Hungry caterpillars called fall armyworms are on the move across the continent from Zambia southward. In early February, South Africa’s agricultural department issued a report, noting that for the first time that this unfamiliar pest had been spotted in the country’s Limpopo province.

“Little is known on how this particular pest entered Southern Africa,” the report said. “Since this pest is very new in Africa, very little is known on its long term effects.” It was positively identified as the fall armyworm a few days later.

“It has come in like one of the 10 plagues of the Bible,” said Ben Freeth, who operates a commercial farm in Zimbabwe, to South Africa’s Sunday Times. “It’s widespread and seems to be spreading rapidly. It can lay up to 2,000 eggs and its life cycle is very quick.”

Armyworms – which will grow into are moths and not, technically speaking, worms – are so named for their ability to destroy massive amounts of crops, in the manner of troops trampling over a countryside. Writing at the Conversation, Kenneth Wilson, who is studying the use of biological parasites to battle crop pests at England’s Lancaster University, described the recent havoc as the combination of two species: a surge in the population of the native African armyworm, plus the fall armyworm, an invader from the Americas.

African armyworms eat in hordes as dense as 1,000 caterpillars per square meter, Wilson noted, stripping maize plants bare. The newcomers may be no less destructive.

“Only time will tell,” he wrote, “what the full impact of this armyworm invasion will have.”