HIGHLAND nature lovers have been warned not to remove tree material to help prevent the spread of a giant moth which could destroy Scotland's pine forests.

People visiting woodland in the Kiltarlity area near Inverness have been urged not to take away pine needles, branches or twigs because of the threat to the country's native trees.

Forestry Commission Scotland is trying to stop the spread of a localised population of the pine-tree lappet moth. Its caterpillars can cause large-scale damage to pine plantations. The moths, which can grow to 8cm, were first found in Scotland in the Highlands in 2004 and a breeding population was confirmed in 2009. Since then, strict control measures have been put in place to avoid the spread of the destructive insect.

They originate in continental Europe, Russia and Asia, where they causes large-scale damage to pine plantations, sometimes over thousands of hectares.

Outbreaks last up to eight years in some parts of its range.

Studies suggest that climate change over the coming decades may make Scotland – especially the drier east of the country – a more favourable breeding ground for the moths.

Hugh Clayden, the commission's tree-health policy adviser, said: "The potential threat comes from the caterpillars of this large moth, which feed mainly on pine needles and can completely strip trees of their foliage if outbreak conditions arise.

"Taking any foliage or woody material away from affected forests could potentially help these moths to move to other areas so we are asking members of the public to assist us by leaving such material in the forest as it could harbour either eggs or caterpillars of the pine-tree lappet moth."

The moths can produce up to 250 eggs each and lay them on needles, twigs or bark between late May and the middle of August. The caterpillars – which can also grow to 8cm – feed until the first frost arrives before traveling down the tree trunks to spend winter underground.

They re-emerge in early spring and travel back up the tree to feed again.

In Scotland, adult male pine-tree lappet moths were first caught in 2004 in a pine plantation to the west of Inverness, and then in the river Beauly catchment area but the presence of this moth was not reported to the commission until 2008.

The commission, responsible for protecting and enhancing the 1.6 million acre national forest estate, set up an Outbreak Management Team in late 2008 to deal with the moth.

A contingency plan was put in place, a key part of which was introducing immediate controls on the movement of timber from the outbreak area.

Mr Clayden added: "Our initial timber movement controls bought us the time needed to investigate the life cycle, potential origins and likely impacts of this impressive moth.

"Based on that expert advice we now feel able to reduce the level of timber movement controls so that woodland owners can resume active management of their forests – which, in the longer term, is by far the best way to keep them healthy and resilient to the wide variety of insect pests and tree diseases found in the natural environment.

"But that's not to say that we are giving the all-clear or being complacent about the potential threat from the pine tree lappet moth.

"We will still be monitoring the area and working with an Outbreak Management Team to ensure our response remains balanced and risk-based.

"And everyone using these woodlands can help us by taking simple measures to prevent this moth from spreading outside the area."