Researchers are examining the status of Phytophthora ramorum, known as sudden oak death, and Phytophthora kernoviae. Both diseases have been found in the UK, mainly in Cornwall.
The Forestry Commission started a national re-survey of England and Wales in June and it will be completed in August.
A second survey will cover previously unsurveyed woods in Devon, where an outbreak of sudden oak death has been found, while surveyors will also check on disease spread as part of a forest condition survey across the UK.
