Scientists are warning that a foreign pest invasion could wipe out large swathes of Canada’s ash tree population.

The virulent emerald ash borer was discovered in south-western Ontario last year. Instead of unfurling leaves in the spring, affected trees produce small green beetles.

Forestry experts have been surveying ash trees, which are commonly used to make baseball bats and furniture, to check the spread of the pest but are unsure how to fight it. So far the infestation is limited to a 30km range near Windsor.