The Autumn armyworms: Dangerous caterpillars

The small caterpillar - no bigger than four centimeters - is not as harmless as it looks here. When thousands of these small pests fall into a field, the harvest is quickly destroyed. The wandering pests gnaw across the whole country.

Spodoptera frugiperda (that is the name of the army worm in Latin) likes corn. He eats the leaves, but above all he bites through the inside of the plant. Corn is the most important nutrient supplier, especially in the south of the African continent. The FAO estimates that the pest can destroy more than three-quarters of a crop.

These spot-camouflage caterpillars crawl from field to field as if they're marching in to battle - that's why they are called "armyworms." In huge numbers they march from grasslands on to crops, where they eat everything in sight.

On their way to adulthood, the seemingly never-ending caterpillars pass through six stages: from the tiny, transparent larvae to the almost four centimeters long moths. If they grow up, they pupate - the process of becoming a moth - just under the surface of the ground.

After three weeks of feasting on crops and grass, the transformation begins. Then we see the metamorphosis to the "Noctuidae" - an owl-like butterfly.

And this is how the creature looks in all its splendor. With a wingspan of just under four centimeters, the nocturnal moths provide fast and efficient offspring - with females laying up to 1000 eggs in their lifetime. With no frost in the African climate you could find up to 12 generations in just a single year.

Small, light and greedy: The moths can spread quickly over hundreds of kilometers in favorable winds throughout the continent. At the beginning of 2016, the Autumn armyworm was first detected in Nigeria, a year later it was already flying about 5000 kilometers further south. Europe is by no means too far away, experts warn.

The United Nations is already warning of a new crawler plague across Africa. "Pests do not know any national borders," says the UN Organization for Food and Agriculture (FAO). Originally, the butterfly species originates from the tropical regions of the American continent. From there they were towed to Africa.

Resistant Plants, Sand, or Chemistry: Farmers in North and South America have tested many compounds against creeping armyworms. It is best to fight the pest with pesticides, but some have already shown resistances. Experts suggest to dig trenches around the affected field. That way the caterpillars can be easily killed when they try to reach the neighboring field.