Oak wilt is a disease affecting oak trees in North America caused by the fungus Ceratocystis fagacearum.
The four species of North American budworm, the larval stages of particular types of moth, can damage a range of conifer species, some of which are grown in the UK.
So far oak wilt and North American budworm have not been identified in the UK but there is a risk they could be accidentally imported, the Forestry Commission said.
New information listed on the Forestry Commission website includes details of contingency plans which would come into effect in the event of an outbreak, alongside information on how to identify the pests or disease, susceptible species and control measures.
Tree affected by oak wilt in Texas, USA - image: Flickr/Bob Shrader
Plant health team manager for Forestry Commission England Andy Hall said:
"The protections against these pests getting in are stringent, but we cannot afford to be complacent. I therefore encourage everyone who works with trees and timber to familiarise themselves with the information about these threats, to remain vigilant for any sign of them, and to immediately report any cases they suspect."