Fall armyworms are native to the Americas and were first spotted in Nigeria and Togo last year, though they have already caused damage to staple crops in Zambia, Zimbabwe, South Africa and Ghana

A plague of crop-destroying fall armyworm caterpillars has spread to East Africa where officials confirmed their presence for the first time in Uganda on Friday.

An outbreak of the caterpillars in several southern African nations has already raised alarm with the UN Food and Agriculture Organisation warning they pose "a huge threat to food security".

Uganda's Agriculture Minister Vincent Ssempijja said the presence of the innocuous looking but hugely destructive brown caterpillar had been confirmed in over 20 districts of the country.

"This will negatively impact on the nation's food and nutrition security," Ssempijja told a press conference in Kampala.

An estimated 10.9 million people already don't have enough to eat in Uganda, according to a UN report on food insecurity released last month.

Fall armyworms are native to the Americas and were first spotted in Nigeria and Togo last year, with one theory saying that they arrived in Africa on commercial flights from South America or in plants imported from the region.

They have already caused damage to staple crops in Zambia, Zimbabwe, South Africa and Ghana while reports suggest Malawi, Mozambique and Ghana may also be affected.

Irrigation systems, like the one shown in Pretoria, South Africa, can be used to dispense pesticides to combat the armyworm infestation, but some have begun to develop a resistance

The caterpillars eat maize, wheat, millet and rice—key food sources in southern and eastern Africa, where many areas are already struggling with shortages after years of severe drought.

They also attack cotton, soybean, potato and tobacco fields.

Chemical pesticides can be effective, but fall armyworms have developed resistance in their native Americas.

In Uganda the caterpillars were spotted in May last year. Samples had to be sent to Australia to determine if they were the native Africa armyworm—less destructive and which responds to pesticides—or the fall armyworm.

"If nothing is done we could lose up to 15 percent of our maize production," said senior agriculture minister official Okasai Opolot.

Uganda produces close to four million metric tons of maize grain annually, contributing to the livelihoods of more than 3.6 million households, according to government statistics.

Kampala has set aside one billion shillings ($280,000, 257,000 euros) for emergency response work including distribution of pesticides and educational materials for farmers.

Explore further Emergency UN meeting in Harare over armyworm outbreak

© 2017 AFP