Aerial Spraying Not The Answer

Oak Processionary Moth

Butterfly Conservation is extremely disappointed that the Forestry Commission is going ahead with aerial spraying of a protected wildlife site to control the Oak Processionary Moth.

The charity believes that the procedure will potentially harm a wide range of wildlife in the wood and would set a bad precedent.

Although Butterfly Conservation understands the need to control this potentially harmful species, it does not feel that blanket aerial spraying is the best method and is very concerned that it will kill other butterflies and moths that exist as caterpillars in the area and harm a wide range of other wildlife.

The site near Pangbourne in Berkshire is an important refuge for wildlife and a designated Site of Special Scientific Interest (SSSI.  It is home to rare butterflies such as the Silver-washed Fritillary and White Admiral with the Purple Emperor regularly seen in the vicinity.

The Scarlet Tiger moth is found on-site as are several nationally scarce micro-moths.

Moths play a vital role in the food chain and are important food for birds and bats, many of which rely on moth caterpillars to feed their young. Spraying at this critical time of year will have a huge impact on native species, some of which may even become locally extinct as a result.

The spraying will involve the use of a strain of the bacteria Bacillus thuringiensis (known as Bt for short).

The strain of Bt is known to kill a wide range of butterfly and moth caterpillars, as well as beetles and flies. Additionally, there is no guarantee that spraying will be successful in eradicating the Oak Processionary.

The Oak Processionary is a native of parts of Europe and is thought to have arrived in the UK as eggs laid on young oak trees imported from the Continent.

On the continent caterpillars can damage oak trees by feeding on the leaves, sometimes causing severe leaf loss and potentially leaving the trees vulnerable to other threats. Their hairs are highly irritant and can become airborne and cause respiratory problems in some cases.

Attempts have been made in many other countries to control the moth and have so far proved inconsistent.

The moth has become established in parts of London where it is known to be expanding its range, so spraying this one area is unlikely to control its spread.

Dr Martin Warren, BC Chief Executive, said: "Blanket aerial spraying of a designated wildlife site sets a very bad precedent and is an extremely crude control mechanism – the approach is akin to using a sledgehammer to crack a nut.

“We believe that a far better method would be to conduct a detailed survey of the conspicuous nests and spray them individually, as they have done in other areas."

Butterfly Conservation will be monitoring the impact closely to see what damage is caused and how quickly populations recover after spraying.