Liberia: UN-led team gives new hope for containing devastating caterpillar plague

A team of scientists has identified the caterpillars that swarmed across northern and central Liberia devouring crops and contaminating water supplies as an easier to control species than was previously thought, the United Nations Food and Agricultural Organization (FAO) announced today.

After a three-day fact-finding visit to seven of the areas affected by the outbreak, the FAO-led experts established that the insects were not armyworms, as had been reported, but larvae of another moth species, Achaea catocaloides rena.

The caterpillar infestation swept across some 100 villages in Liberia and six communities in neighbouring Guinea, in some cases overrunning buildings and sending residents fleeing in panic, causing President Ellen Johnson-Sirleaf to declare a national emergency last week. According to Liberian authorities, the emergency involved about 500,000 villagers.

It had been feared that much worse was in store as armyworms – one of the most destructive of insect pests – bore into the ground, out of reach of pesticides, form protective cocoons around themselves, waiting to re-emerge as moths able to fly up to 1,000 kilometres and lay 1,000 eggs.

Achaea catocaloides rena, however, pupate on the ground under fallen leaves making it relatively easier to destroy the cocoons and limit further infestation.

The four-man team, comprised of FAO experts from Ghana and Sierra Leone and two local entomologists, reported villagers destroying cocoons by stamping on them or collecting and burning them, which will not be enough to prevent their spread to plants and crops.

The caterpillars have already polluted water bodies and damaged crops such as coffee, cocoa, plantain, bananas and wild flora, and large adult moth populations had also contaminated the environment with their powdery scales, which could cause allergies.

Some staple food crops such as maize, rice, sorghum and millet, which are scarce during this dry season, had been left largely undamaged. The team said the caterpillars moved to other food sources after eating through the leaves of the Dahoma trees where they mainly reside.

The experts warned that although it is positive news that these caterpillars pupate on the ground “emergency preparedness for secondary and tertiary outbreaks are not in place as a preventive measure.”

FAO is in discussions with the Liberia Ministry of Agriculture and other partners on how to contain the infestation after confirmation of the identity of the caterpillars. The agency noted that this is also an opportunity to develop a better response system against migrant pests in the sub-region based on monitoring, early warning, bio-control, capacity building and contingency planning.