United States Department of Agriculture 

Animal and Plant Health Inspection Service 

Plant Protection and Quarantine

 

 

Importation of Perennial Wall Rocket Leaves, 

(Diplotaxis tenuifolia, (L.) from the 

United Kingdom into the continental 

United States 

Risk Management Document

January 20, 2010 

Plant Health Programs (PHP) 

Regulations, Permits and Manuals (RPM) 

Contact Person: Claudia Ferguson 
Risk Management Document: Wall Rocket Leaves from United Kingdom. 

January 20, 2010 2

1. Introduction 

This document describes the risk management measures for the importation of wall 

rocket leaves, Diplotaxis tenuifolia (L.), from the United Kingdom (UK) into the 

continental United States. The volume of wall rocket to be shipped from the United 

Kingdom to the United States is estimated at less than ten 40 foot long maritime 

containers per year. (USDA, 2008) 

United States Code of Federal Regulations (7 CFR 319.56) authorize importation of fruits 

and vegetables from foreign countries into the United States. Currently, fresh perennial 

wall rocket from the UK is prohibited by these regulations. 

The United States Department of Agriculture, Animal and Plant Health Inspection 

Service (USDA, APHIS) conducted a pest risk assessment (PRA) in response to a request 

to allow imports of fresh perennial wall rocket leaves from the UK into the continental 

United States (USDA, 2008). Two pests of quarantine significance were identified, 

which would be likely to be introduced into the continental United States via leaves of 

perennial wall rocket. This document evaluates the appropriate pest risk management 

measures for these quarantine pests. 

2. Quarantine Pests of Concern for Wall Rocket Leaves from 

the United Kingdom 

The list of quarantine pests of wall rocket leaves from the United Kingdom was prepared 

based on: 

(1) United States Department of Agriculture (USDA), Animal and Plant Health 

Inspection Service (APHIS) records of intercepted pests (USDA, 2007), and 

(2) Scientific literature. 

The pest risk assessment, ‘Importation of Perennial Wall Rocket Leaves (Diplotaxis 

 tenuifolia (L.)) from the United Kingdom into the Continental United States’, A 

Pathway-Initiated Assessment, represents a baseline risk associated with the unmitigated 

importation of fresh leaves of wall rocket from the United Kingdom (USDA, 2008). 

The PRA identified the following two pests, both having a medium risk potential to 

follow the pathway: 

Chromatomyia horticola (Goureau) (Diptera: Agromyzidae) 

Liriomyza strigata (Meigen) (Diptera: Agromyzidae) 
Risk Management Document: Wall Rocket Leaves from United Kingdom. 

January 20, 2010 3

There were no pests identified as having a high risk potential to follow the pathway. 

3. Risk Management Measures

APHIS proposes that fresh leaves of perennial wall rocket grown in the United Kingdom 

may be imported into the continental United States only under the following conditions: 

A) Wall rocket leaves must be imported as commercial consignments only. 

B) Each consignment of wall rocket leaves must be accompanied by a Phytosanitary 

Certificate (PC) with an Additional Declaration (AD) issued by the Department of 

Environment Food and Rural Affairs (DEFRA) bearing the following: “Wall rocket 

leaves in this consignment were inspected and found free from Chromatomyia 

horticola and Liriomyza strigata.” 

4. Rationale for Risk Management Measures 

According to USDA, guidelines for pathway initiated pest risk assessments (USDA, 

2000), pests with ‘Medium’ pest risk potential may require specific phytosanitary 

measures. 

The PRA identified two quarantine pests that could be introduced into the United States 

via the importation of perennial wall rocket from the United Kingdom: Chromatomyia 

horticola and Liriomyza strigata (USDA, 2008). Both are Dipteran leaf miners in the 

family Agromyzidae and both have ‘Medium’ pest risk potentials. In general, leaf miners 

have minimal natural dispersal potential. Larvae remain inside the leaf where the egg 

they hatched from was laid, until they pupate. Adults do not disperse long distances on 

their own. They can be transported through wind currents, but since a successful dispersal 

requires that suitable plant hosts be available at the destination during the relatively short 

lifespan of the miner, this is therefore not a common method of dispersal (CABI, 2007). 

Both the leaf miners produce visible and obvious signs of infestation as small punctures 

in the leaf epidermis and whitish, irregularly linear mines. Pupae or exuviae may be 

present at the end of mines; frass occurs at short intervals along the mines in irregular, 

well-separated grains (CABI, 2006). 

As the damage caused by leaf miners is usually visible, post-harvest treatments including 

washing and culling will reduce or eliminate infested leaves. Port inspectors are capable 

of finding both pests. Requiring an additional declaration with the phytosanitary 

certificate ensures that the wall rocket leaves were grown in UK and are a product of the 

United Kingdom. 
Risk Management Document: Wall Rocket Leaves from United Kingdom. 

January 20, 2010 4

5. Summary

The requirements of a phytosanitary certificate with additional declaration from DEFRA 

will document that the importation is a product of United Kingdom. A Phytosanitary 

Certificate also provides phytosanitary security by requiring DEFRA to conduct 

inspections for pests. 

Importations of wall rocket leaves from the United Kingdom will also be subject to 

inspection at the first port of entry into the continental United States. These 

inspections doubles the number of inspections that each consignment of wall rocket 

leaves receives. 

Author 

Devaiah A. Muruvanda, Ph.D., Senior Risk Manager, USDA, APHIS, PPQ, Regulations, 

Permits & Manuals 

Reviewer: 

Claudia Ferguson, Regulatory Policy Specialist, USDA, APHIS, PPQ, Regulations, 

Permits & Manuals 

6. References 

CABI. 2006. Crop Protection Compendium, 2006 Edition. CAB International, 

 Wallingford, UK. 

CABI. 2007. Crop Protection Compendium. CD-ROM. CAB International (CABI), 

 Wallingford, UK. 

USDA. 2000. Guidelines for Pathway-Initiated Pest Risk Assessments, Version 5.02. 

30 pp. 

USDA. 2008. Importation of Perennial Wall Rocket Leaves (Diplotaxis tenuifolia (L.))

from the United Kingdom into the continental United States. – A PathwayInitiated Risk Assessment. July 2008. United States Department of Agriculture, 

Animal and Plant Health Inspection Service, Plant Protection and Quarantine, 

Center for Plant Health Inspection Service, Plant Epidemiology and Risk Analysis 

Laboratory. Raleigh, NC. 24 pp. 

USDA. 2007 Pest ID Database: United States Department of Agriculture, Animal and 

Plant Health Inspection Service, Plant Protection and Quarantine, Riverdale, MD.