The large pine weevil destroys saplings
Scientists have drafted in billions of microscopic parasites to help in the fight against a pest which can decimate newly planted trees.
The large pine weevil is capable of killing up to 75% of saplings if insecticides are not used.
But now Forestry Commission Wales has turned to nematodes - tiny invertebrate parasites - to fend off the attacks.
Its biological testing unit in Powys said the micro-bugs could reduce damage to conifer plantations by up to 40%.
Experts working at the commission's Welsh silvicultural operations (WSO) unit in Welshpool, said Entomopathogenic nematodes (EPNs) would help reduce the use of insecticides.
"Using insect parasitic nematodes to control the pine weevil is completely natural and has also allowed me to greatly reduce the amount of chemicals that I need," said Tony Westley, who is heading the project.
EPNs are colourless roundworms that can only be seen through a microscope, says the commission.
They attack and kill pine weevils within 48 hours by locating them under the bark and entering them through natural body openings.
Over the last two years WSO has successfully treated more than 1,111 acres (450Ha) in Wales, and also at Kielder forest in Northumberland and several sites for United Utilities.
Adult pine weevils feed on the bark and the lower part of the stem on young trees, explained the commission.
They added that EPNs occured naturally in the environment and a number of species were found in cultivated fields, roadside verges, forests and heath land in the UK.
The nematodes used in Wales are bred in vats by a company in Littlehampton, West Sussex.
Forestry Commission Wales is responsible for looking after the 320,000 acres (130,000 ha) of public forests owned by the Welsh Assembly Government.