GBOLUMUE, Liberia, Feb 6 (Reuters) - Martha Kermel holds out rail-thin arms covered with a latticework of scratches from her encounter with a plague of caterpillars that has devastated crops and spread fear through this corner of West Africa.
"They scratched my arms when they moved," said Kermel, a mother of four, telling how the small creatures poured down onto her from the tree branches overhead as she set out from her village to a rice farm cultivated by her community in Liberia.
That was two weeks ago. Now the millions of caterpillars which covered the road and nearby bushes have retreated into cocoons, or hatched already into moths ready to spawn a new generation of grubs here or further afield.
The insects can travel up to 60 miles (100 km) a day, and have already crossed the border to Guinea, an agriculturally rich country and the source of many of Liberia's food imports.
That has set alarm bells ringing in neighbouring Ivory Coast, the world's top cocoa grower and an important producer of coffee, rubber, palm oil and other cash crops.
The creatures were first thought to be army worms, a moth caterpillar, but they were identified this week as the young of another kind of moth, the Achaea catocaloides, which are also known to damage cocoa and other tree crops.
For the time being, the moths are headed north, and experts in Ivory Coast said this week they should avoid Ivory Coast's valuable cocoa belt, which produces about 40 percent of world supply.
But they remain a risk to Ivory Coast's central borderlands, which produce around 100,000 tonnes of cocoa and 70,000 tonnes of robusta coffee a year.
For Kermel, the threat is more immediate.
She and her family, subsistence farmers like most people in the area, live 10 miles (16 km) south of the border with Guinea and 45 minutes by foot from the nearest passable road.
When the bugs attacked, Kermel had nowhere to go, and worried about feeding her children.
She said the "kotin", as locals call the pests, fouled the creek near her home with their faeces, turning the water black.
Every day since then, she and her children have had to walk several miles to the main road to gather water at a borehole.
The Liberian governent has said the caterpillars are threatening the food security of 350,000 people, and President Ellen Johnson-Sirleaf declared a national state of emergency.
Jewel Howard Taylor, a senator who was married to Charles Taylor, a former president and warlord in Liberia's devastating 1989-2003 civil war who is now on trial for war crimes, donated 150 bags of rice and tarpaulins, clothes and blankets.
That kind of help will be insignificant if the moths continue to spread and multiply.
The infestation may be linked to a long rainy season, cold weather at the start of the year, or climate change and deforestation forcing caterpillars to seek food elsewhere, scientists and Liberian ministry officials said this week.
"I think this is a seasonal threat. From our experience in Benin, the moth will disappear by early or mid-March," Georg Goergen, an entomologist at the International Institute for Tropical Agriculture (IITA), told Reuters.
While the caterpillars feed on trees, adults belong to a group known as fruit-sucking moths for their penchant for piercing ripening fruit and sucking out the juice, often causing the fruit to rot and drop prematurely.
Spray teams, each member with a plastic tank of insecticide strapped to their back, have started work. But Jobson Momo, an agricultural programme officer in the town of Carey, said his team did not have enough pesticide, protective gear or vehicles.
The entire first wave of Liberia's caterpillars has now turned into moths. Scientists at the Ministry of Agriculture fear they are are now reproducing and could cause secondary and tertiary waves of infestations that, if uncontained, may destabilise an already volatile region.
"This is a wake-up call, a call that gives neighbouring countries adequate time to mount an early warning system to detect and manage this problem," said Braima James, an IITA project manager.
Ivory Coast's National Centre for Agronomic Research has sent experts to Liberia to find out more about the caterpillars and see if any are headed towards their border.
Guinea, which borders both countries and is in a chaotic state after a December military coup, says a string of villages near the Liberian border is already infested.
"The equipment we have means we can only spray up to a height of 6 metres (yards), whereas some trees are 30 metres high. We absolutely must have air support," Sikoun Wague, spokesman for Guinea's Agriculture Ministry, told Reuters.
"These insects suck the sap from trees and leave tonnes of waste in channels and water courses, which are then unusable for two weeks," he said.
Across the border in Liberia, Kermel has, luckily, already harvested her rice crop. But while she and her relatives waited for the caterpillars to disperse, they should have been planting for the next season.
The delay could cause a weak yield next harvest.
John Kulah was less lucky. He had cropped his upland rice but lost all his swamp rice, which ripens later, to the bugs.
"They eat and eat and eat, so greedy," he said angrily.
"We have to farm to live," said Kulah, who has now slashed out a new field in the bush, well away from the dahoma trees which attract the caterpillars. With nine children to feed, he hopes the next wave of caterpillars doesn't come.
"What are we supposed to do then?" (Additional reporting by Saliou Samb in Conakry, Ange Aboa in Abidjan and David Lewis in Dakar; Editing by Alistair Thomson and Sara Ledwith)
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