This week's work is being carried out during off-peak daytime hours, and traffic management may be required on some sections.
The council's Cabinet Member for Highway Management Councillor Stuart Hughes said: "Our regular tree inspections found that these trees have ash dieback (ADB) and they now need to be removed for public safety reasons. The work is being co-ordinated to take place outside of peak times in order to minimise disruption."
He added: "We’re continuing to take a proactive approach in managing ash dieback by regularly monitoring and inspecting ash trees across Devon when in leaf. While we will remove trees when necessary, we are supporting a replanting programme that includes a diverse range of native trees in order to reduce the impact on the environment."
Devon County Council leads the Devon Ash Dieback Forum, established in 2016 to address the risks of the disease.
The council has already removed around 100 trees infected with ADB and said it was also managing reports of around a further 400 trees near the highway, many privately owned, which will require felling in the next few months.
Ash make up around a fifth of Devon's trees, and all are considered vulnerable to ADB.