According to BBC, the fall armyworm poses a major threat to food security and agricultural trade, warns the Centre for Agriculture and Biosciences International (Cabi).
It says farmers' livelihoods are at risk as the non-native larvae threatens to reach Asia and the Mediterranean.
The Food and Agriculture Organization plans emergency talks on the issue.
The armyworm, so called because it eats its way through most of the vegetation in its way as it marches through crops, is native to North and South America but was identified for the first time in Africa last year. BBC reports.
Cabi chief scientist Dr Matthew Cock said: "This invasive species is now a serious pest spreading quickly in tropical Africa and with the potential to spread to Asia.
"Urgent action will be needed to prevent devastating losses to crops and farmers' livelihoods."
Scientists think the caterpillar or its eggs may have reached the continent through imported produce.
Once established in an area, the adult moths can fly large distances and spread rapidly.
Dr Jayne Crozier, of Cabi, said the armyworm's presence had now been confirmed in west Africa and was thought to be present in the south and east of the continent, many parts of which relay on maize for their staple diet.
"It's possibly been there for some time and it's causing a lot of damage now," she told BBC News.
"The recent discovery of fall armyworm in Africa will be a huge threat to food security and also to trade in the region."
The FAO is to hold an emergency meeting in Harare between 14 and 16 February to decide emergency responses to the armyworm threat.
Zambia has used army planes to spray affected areas with pesticides.