Plant pests

Plant pests include insects, other invertebrates, bacteria, fungi, viruses and other pathogens which affect the health of plants or plant products by feeding on them or causing disease.

What is a PRA

The process of identifying appropriate phytosanitary measures required to protect plant resources against new or emerging pests and regulated pests of plants or plant products is called pest risk analysis (PRA). Within the International Plant Protection Convention PRA is defined as:

"The process of evaluating biological or other scientific and economic evidence to determine whether an organism is a pest, whether it should be regulated and the strength of any phytosanitary (plant health) measures to be taken against it".

PRAs may also be conducted on commodity imports to determine whether they provide a pathway for pests to enter the importing country or area. This document provides a very brief summary of Defra’s approach to PRA.

PRA standards

There are international standards that set out what to consider when conducting a PRA. PRAs vary in length from simple expert judgements ("does not feed on plants" or "tropical pest, no host plants grow in Europe") to longer technical documents containing detailed assessments of biological factors, climate maps, and estimated costs and benefits of the measures needed to inhibit the entry of a pest into an area, or to eradicate a pest outbreak. Further information can be obtained from the IPPC

The UK has a flexible approach to PRA and uses a variety of PRA templates appropriate to the issue being considered

PRA authors

PRAs are technical assessments written by plant health scientists to inform decisions by plant health policy makers.

PRA limitations

PRAs give a snapshot of the analysis at a particular time, and although we do revise them, they may go out of date as new information comes to light.

All risk analyses have to cope with areas of uncertainty where evidence is lacking, inconclusive or contradictory. For organisms that do not occur in the UK our experts have to use their judgement in extrapolating from available data to assess how a pest might behave under UK conditions on UK crops and wild plants. If there is a wide range of uncertainty about the risk we may commission research to fill gaps in the risk analysis. Until more is known we take a precautionary approach.

Specific treatments may be mentioned in a PRA as examples of control measures which are applied in areas of the world where the pest is established. These should not be regarded as recommendations: indeed the treatments may not be approved for use in the UK.

The PRA region/area

Defra’s PRA focus is generally on the risk to the UK.  Plant health is a devolved matter, but Defra’s focus on the UK risk situation is facilitated through a UK co-ordination approach involving input from Scotland, Wales and Northern Ireland.

The Wildlife and Countryside Act

For some organisms the conclusion of the PRA is that the risk is low and statutory action by the plant health service to exclude or eradicate the organism is not warranted. However it is still an offence under section 14 of the Wildlife and Countryside Act 1981 for any person to release or allow to escape into the wild any animal which is of a kind which is not ordinarily resident in and is not a regular visitor to Great Britain in a wild state, or which is listed on Part I of Schedule 9 to the Act. The release does not have to be deliberate or intentional. Further information on preventing the release of plants and animals into the wild is available.