Forestry Commission turns to aerial spraying to tackle oak processionary moth in Pangbourne woodland

The Forestry Commission is planning aerial spraying of an area of woodland near Pangbourne in West Berkshire during May, and is reassuring residents that it poses no risk to human or animal health.

A helicopter will spray the woodland twice over a seven to 14-day period. This is the time when caterpillars of the oak processionary moth (OPM), which is a risk to tree, animal and human health, are emerging from eggs in oak trees.

The product sprayed will be Bacillus thuringiensis (Bt), a bacterial agent which occurs naturally and widely in soil. The Forestry Commission says Bt is very safe when used by fully qualified operators in compliance with the strict health, safety and environmental protection regulations governing its use.

Natural England, the government's advisor on the natural environment, has given authorisation for the operation.

The main 10-hectare area to be treated comprises Herridge's and Broom Copses, part of which is privately owned and part of which is public woodland managed by the Forestry Commission. Another privately owned 1ha block of trees nearby will also be treated.

If successful the operation would mark a big step forward in efforts by the Commission and West Berkshire Council to eradicate the pest from the Pangbourne area, where only three nests were found in 2012, down from several dozen the previous year.

Forestry Commission plant health service representative Stewart Snape said: "We know there could be OPM in the woodland because we found a nest in it last year. Most OPM treatment is done by spraying individual trees from the ground, but it's much more difficult to find and treat the pest in a woodland environment than in trees in a park or street, with a significant risk that some will be missed.

"The most effective way to treat the woodland is to spray it from a helicopter using an ultra-low-volume spray system to minimise the amount of Bt used. Helicopters can fly lower and slower than fixed-wing aircraft, and therefore target the spray very accurately.

In addition, the downdraft from a helicopter's rotor helps to achieve much better penetration of the foliage than fixed-wing aircraft or ground spraying can achieve.

"We have also agreed to conduct a five-year environmental monitoring programme which includes bird, bat, moth and butterfly surveys."

Pangbourne residents whose oak trees have been found to be infested with OPM have been working with the Commission, West Berkshire Council and an authorised contractor since 2010 to have their trees sprayed. The aerial spraying of these dense woodland areas will significantly support the eradication project.

OPM is a risk to oak trees' health because its caterpillars feed on the leaves, and in serious cases they can defoliate whole trees, leaving them vulnerable to other pests and diseases.

OPM is a native of southern Europe which was accidentally introduced to Britain. The small Pangbourne outbreak was discovered in 2010, and the eradication programme led by the Forestry Commission and West Berkshire Council has reduced it to only three nests found in 2012.

  • Local residents with enquiries specifically about the aerial spraying may contact Martin Townsend 01865 777810,
  • More-general enquiries about OPM in Pangbourne should be directed toArthur Cullen at West Berkshire Council on 01635 519675 or
  • Reports of sightings of the caterpillars can be found at
  • Anyone with an itchy or painful skin rash or a sore throat and irritated eyes after being near oak trees in these areas should consult their GP or NHS 111. Health information is available on the Public Health England website at under 'oak processionary moth'.

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