KATHMANDU, Nepal – The annual rush to the hills by villagers keen to harvest a rare aphrodisiac fungus dubbed “Himalayan Viagra” has emptied rural schools in Nepal and forced them to shut, a local official said Tuesday.

Parents, students and even teachers have left home in pursuit of “yarchagumba”, a high-altitude caterpillar fungus which is eagerly sought for its reputed sexual enhancement.

“In this district alone, about 8,000 students have left school for the expedition,” Prakash Subedi, an official at Jajarkot district education office, told AFP.

“Without the students, there’s no point running the school so we close them. Even the teachers go to collect it,” Subedi said. Some schools might hold extra classes in the autumn so children’s education does not suffer, he added.

Yarchagumba, which in Tibetan means “summer grass, winter worm,” is produced when Cordyceps fungus spores attack a caterpillar larva underground, kill it and cause a mushroom to sprout out of its head.

Nepalese villagers flock to high meadows each spring in search of the specimens.

China and other Asian markets have huge appetites for the obscure fungus, pushing prices above $11,500 per pound (450 grams) and putting its value somewhere between silver and gold.

“We urge the parents not to take their children along with them,” Subedi said, adding that parents typically ignore the plea because children can earn up to 100,000 rupees ($1,140) during the harvest.

No definitive research has been published on the qualities of “Himalayan Viagra”. But Chinese herbalists believe the fungus — an excellent balance of yin and yang, as it is both animal and vegetable — boosts sexual performance.

Boiled in water to make tea, or added to soups and stews, it is claimed to cure a variety of ailments from fatigue to cancer.

In recent years researchers have claimed that despite regulatory measures such as a tax imposed on harvesters to control the fungus population, supplies are declining, perhaps due to over-harvesting.

In 2011 a Nepalese court convicted 19 villagers over the 2009 murder of a group of farmers during a fight over harvesting rights.

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