The UK Government appears to have finally stopped taking claims of pest-free status in other EU countries and the integrity of the EU plant passport system at face value, writes Dr Terry Mabbett.

AT a recent OPM workshop, the Forestry Commission (FC) announced 98 interceptions of Thaumetopoea processionea (oak processionary moth – OPM) across the United Kingdom during summer/autumn 2019, with over 60 recorded in the UK’s OPM protected zone. Infestations originated on oak tree planting material imported from other European Union countries. A few had come in from Belgium and Germany but the vast majority entered the UK on trees imported from the Netherlands.

Perhaps seeing an opportunity to replace these clearly high-risk oak tree imports from the Netherlands, the Italian National Plant Protection Organisation notified the UK’s DEFRA on the establishment of a pest-free area (PFA) for OPM in the Pistoia nursery district, and some parts of the Montemurlo municipality in Tuscany. This was done in October 2019 but the UK government, apparently stung by so many OPM interceptions this year, promptly requested more evidence to ensure that the PFA claimed by the Italian authorities demonstrated the required international standards and also met recently tightened UK import requirements.

DEFRA said that until satisfactory evidence of compliance with required standards is received, any imports from this area will not be allowed into the UK. Should any imports of oak trees (other than Quercus suber) with a girth at 1.2 m above the root collar of 8 cm or more be received from suppliers on or after the 4th October 2019 from within the designated PFA, a statutory notice will be issued by the Plant Health and Seeds Inspectorate (PHSI) requiring the trees to be destroyed or re-exported.

With respect to oak trees that arrived before 4 October, UK importers should have informed Animal and Plant Health Authority (APHA) within five days of arrival, said DEFRA.

Recently strengthened UK legislation requires that oak imports into and movements within the UK’s OPM protected zone can only take place if the oak trees concerned (i.e. those with a girth at 1.2 m above the root collar of 8 cm or more) meet the following requirements:

1. Have been grown throughout their life in places of production in countries in which Thaumetopoea processionea L. is not known to occur;

2. Have been grown throughout their life in a protected zone which is recognised as such for Thaumetopoea processionea L. or in an area free from Thaumetopoea processionea L., established by the national plant protection organisation in accordance with ISPM (International Standards For Phytosanitary Measures) No 4; or

3. Have been grown throughout their life in a site with complete physical protection against the introduction of Thaumetopoea processionea L. and have been duly inspected at appropriate times and found to be pest-free.

DEFRA said any imports of oaks from the Italian PFA would have entered the UK under Option/Proviso No 2 (above) but until such time that adequate evidence was provided by the Italian authorities, the PFA in Tuscany would not meet the requirements of Option/Proviso No 2. 

All landings of oak plants in England and Wales have to be pre-notified to APHA to facilitate targeted inspections for pests and disease, which can include both a physical and documentary check. Equivalent arrangements are in place for Scotland and Northern Ireland.

The timing of this stand-off is probably no accident. Following the entry of OPM-infested oak trees exported from the Netherlands into the UK, and with the likelihood of restrictions on such exports as a result, then Italian growers may have seen an opening for the export of their own oak tree-planting material into the UK.

For its part, the UK government appears to have finally stopped taking claims of pest-free status in other EU countries and integrity of the EU Plant Passport system at face value. However, in the case of OPM it is almost certainly too late, with OPM expected to be all over the place in the UK during 2020.

Only those on the spot in Italy know for sure whether the designated area in Tuscany is free from OPM and not at risk from this pest in the future. However, it is worth remembering that, as early as 2008, Italian scientists were carrying out aerial spraying against OPM in Turkey oak woods in Tuscany.


Hoppit, Andrew (2019) OPM Interceptions. OPM Workshop at ‘Friends House’, Euston, London. 9 October 2019.

Roversi, P.F. (2008) ‘Aerial spraying of Bacillus thuringiensis var. kurstaki for the control of Thaumetopoea processionea in Turkey Oak Woods’, Phytoparasitica 36(2):175-186.