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.
Readiness and links to data
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.
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:
Chalara dieback of Ash (Hymenoscyphus fraxineus), considered established in 2012;
Oriental chestnut gall wasp, considered established in 2016;
Sweet chestnut blight caused by the fungus Cryphonectria parasitica, considered established in 2017; and
The Elm zigzag sawfly (Aproceros leucopoda), considered established in 2018, following a rapid expansion across Europe from eastern Asia.