H2: Distribution of invasive non-native species and plant pests and diseases

Interim Interim

Short description

This indicator will show changes in the distribution of non-native invasive species and plant pests that have already established in England. Preventing the spread of invasive non-native species limits their ability to disrupt ecosystems and cause economic damage. Plant pests and diseases cause significant negative impacts and it is often more difficult to prevent their entry and establishment, therefore limiting spread is critical in preventing negative impact on native species and ecosystems. This indicator will utilise distribution data for a reference subset of priority invasive species and plant pests and diseases as an indication of the success of biosecurity measures in controlling their spread.

This indicator is not available for reporting in 2021 in a finalised form. An interim indicator is presented here that shows trends in the number of additional tree pests and diseases becoming established in England since the year 2000. These data are published annually in the Forestry Commission’s Key Performance Indicators report. Further development is required to identify species for inclusion and develop the indicator drawing on existing data.


This indicator enumerates those additional tree pests and diseases formally considered as becoming ‘established’ by the UK Plant Health Risk Group within a rolling 10-year period. Establishment is defined as ‘perpetuation, for the foreseeable future, of a pest within an area after entry’. This is the definition produced by the Secretariat of the International Plant Protection Convention.

Trend description

The number of additional tree pests and diseases becoming established in England within a rolling 10-year period fell from a peak of 7 in 2000-09 to a low of 3 in 2007-16. It then increased again to 5 in 2009-18 before falling to 4 in 2010-19 (the most recent 10-year period for which data are available). In all, 11 tree pests and diseases became established in England in the 19 years from 2000 to 2019 and of these, the 4 to become ‘established’ between 2010 and 2019 are:

  1. Chalara dieback of Ash (Hymenoscyphus fraxineus), considered established in 2012;

  2. Oriental chestnut gall wasp, considered established in 2016;

  3. Sweet chestnut blight caused by the fungus Cryphonectria parasitica, considered established in 2017; and

  4. The Elm zigzag sawfly (Aproceros leucopoda), considered established in 2018, following a rapid expansion across Europe from eastern Asia.


Choose categories from the dropdowns below to see different breakdowns of the data. Some will not be available until a higher level is chosen.

This table provides metadata for the interim or final indicator presented above.

Indicator name

Distribution of invasive non-native species and plant pests and diseases

Indicator reference


Outcome Indicator Framework theme

Biosecurity, Chemical and Noise

Headline indicator status

Exotic and invasive non-native species

Relevant goal(s) in the 25 Year Environment Plan
  • Enhancing biosecurity
Relevant target(s) in the 25 Year Environment Plan
  • Managing and reducing the impact of existing plant and animal diseases; lowering the risk of new ones and tackling invasive non-native species
  • Reaching the detailed goals to be set out in the Tree Health Resilience Plan
Position in the natural capital framework
  • Pressure on natural capital assets
Related reporting commitments
  • Relevant to the Convention on Biological Diversity
  • May provide evidence in support of Climate Change Risk Assessments under the Climate Change Act (2008)
Geographic scope


Status of indicator development


Date last updated

11 June 2021