Food dye is to be sprayed on an area of forestry near Inverness in an effort to better understand how pesticides might work against tree diseases and pests.
Forestry Commission Scotland said the aerial spraying trial planned for between 1-10 August would not involve pesticides.
The test would be done over forestry near the hill Meall Mor south of Inverness.
The area involved would be closed to the public during the trial.
The commission said any future use of pesticides to control the spread of diseases and pests would be a "last resort".
The trial involving food dye would be weather dependent.