Aerial spraying is to be used for the first time to target caterpillars of the oak processionary moth.
They feed on oak trees and their hairs contain a toxin that can cause itchy rashes, eye and throat irritations.
Experts will spray Herridge’s and Broom copses near Pangbourne and a privately-owned block of trees nearby .
They will use a bacterial agent that occurs naturally in soil and is authorised for the operation by Natural England, the government’s advisor on the natural environment.
The Forestry Commission said the product, called Bacillus thuringiensis, poses no risk to human or animal health.
The 25 acre woodland area and 2.5 acre block of trees will be sprayed twice in a two-week period.
Stewart Snape, from the Forestry Commission’s plant health service said: “Most oak processionary moth 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.”
Residents are urged not to touch the caterpillars or their nests and to report any sightings.
The caterpillars were first found in the Pangbourne area in 2010.
Just three nests were found last year, compared to several dozen in 2011.