Woodlands in Berkshire are being treated for the very first time with chemicals sprayed from a helicopter.
It's to get rid of a type of caterpillar that is causing a headache for both trees and the people living there.
Caterpillars of the oak processionary moth attack oak tree leaves, making the tree vulnerable to other pests and diseases.
Each caterpillar is covered in over 60,000 tiny hairs which can cause painful skin rashes for humans, as well as eye and throat problems.
Martin has been to find out more.
Pictures in the report courtesy of Julien Bressy and Mark Townsend/Gristwood & Toms