By George Grow
22 July, 2017

A species of armyworm has spread to over 20 African countries and threatens Africa's main food crop -- maize.

The warning comes from the United States Agency for International Development, or USAID.

Joseph Huesing works as an advisor to USAID. He suspects the fall armyworms were transported to Africa from the American state of Florida or islands in the Caribbean.

Huesing says the insects are attacking maize crops -- also known as corn -- in African countries south of the Sahara desert.

"From Nigeria and Ghana, all the way to South Africa to Ethiopia," he told VOA. "The most recent one is South Sudan, which reported fall armyworm infestation toward the end of June."

Huesing thinks fall armyworms are a big threat to African agriculture. When they invade a maize field, he said, the insects can eat 30 percent or more of the crop. They also eat other crops.

A Challenge to Control

The fall armyworms got their name from fall, or autumn -- the time of year when they do the most damage in the northern United States. The first published report describing their presence in Africa appeared in early 2016. It suggested the insects had already been there for a year.

A crop-eating armyworm is seen on a sorghum plant at a farm in Settlers, northern province of Limpopo.
A crop-eating armyworm is seen on a sorghum plant at a farm in Settlers, northern province of Limpopo.

For several reasons, the fall armyworms may pose more problems for farmers than the African armyworm, which is native to Africa.

Fall armyworms can reproduce continuously under warm, moist conditions, says Yene Belayneh of USAID. He noted that they can feed off of more than 80 species in 27 plant families.

As adults, fall armyworms can fly up to 100 kilometers a day if pushed by winds. Some armyworms have found a ride on modern aircraft.

For this reason, Belayneh said, communication is especially important. "If there is an outbreak, for example in Ethiopia, alerting Sudan or Eritrea would be a wise thing," he said.

In fact, the insects are in Ethiopia. The country's Plant Protection Directorate reported that as of July 10, fall armyworms have infested more than 440,000 hectares of crops. It said that about 305,000 hectares had been protected.

Harder to detect

But chemical treatments may be less effective with the new invaders than with the African armyworms. The fall armyworm enters "the plant and feeds from inside," says Belayneh. This makes the insect harder to recognize and harder to kill.

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