News from the gardening world
Native ash trees under threat as pest pushes west
Adevastating exotic pest has caused five of the six most prominent ash trees in North America to be a step away from extinction – and now the UK public is being urged to keep a watchful eye out in case it reaches these shores.
The Asian emerald ash borer beetle, native to China, Japan, Taiwan, Korea and the Russian Far east, has decimated the North American ash population, causing the International Union for Conservation of Nature (IUCN) to place the five species on its ‘critically endangered’ Red List. Three species, the white ash, Fraxinus americana, the black ash, F. nigra, and the green ash F. pennsylvanica, are the country’s most dominant species, comprising nine billion trees.
The half inch-long metallic green beetle arrived in Michigan on infested wooden pallets in the late 1990s. Its grubs burrow beneath the bark, feeding on the tree’s living tissues, girdling it and causing it to die within two to three years. Scientists estimate beetles can destroy an ash plantation in just six years.
There’s currently no known method of controlling the pest or resistant species, except the native Asian Manchurian ash, F. mandshurica, although work is on-going to find a solution.
Thankfully, the distinctive beetle hasn’t been found in the UK or the EU, but is currently 150 miles beyond Moscow, travelling west at around 25 miles per year. The Forestry Commission is extremely concerned about the insect appearing in the UK, as it will attack our native ash, Fraxinus excelsior, much of it already weakened or killed by recent outbreaks of chalara, a fungal disease introduced to the UK in 2012.
The beetle has been placed on the UK Plant Health Risk Register and the Forestry Commission is asking the public to become familiar with the borer beetle, reporting any suspected cases. l Visit www.forestry.gov.uk/ emeraldashborer.
Ash trees are an important element in the British landscape
Trees a acked by the emerald leaf borer (below) eventually die back
Tunnelling by grubs destroys living tree tissue