## Importation of Perennial Wall Rocket Leaves ( Diplotaxis tenuifolia (L.)) from the United Kingdom into the continental United States

A Pathway-Initiated Risk Assessment

September 2008

Revision 002

Agency Contact:

United States Department of Agriculture Animal and Plant Health Inspection Service Plant Protection and Quarantine
Center for Plant Health Science and Technology Plant Epidemiology and Risk Analysis Laboratory 1730 Varsity Dr., Suite 300 Raleigh, North Carolina 27606 USAPerennial wall rocket from the U.K.

Rev. 002 October 07, 2008 ii 

### Executive Summary

In this document we assessed the risks associated with the movement of fre sh leaves of perennial wall rocket, Diplotaxis tenuifolia (L.), into the continental United States. It was prepared by risk analysts at the USDA Animal and Pl ant Health Inspection Service.

We listed pests that affect pere nnial wall rocket throughout the worl d if populations of that pest were reported in the United Kingdom. The table li sting the pests should not be interpreted to infer that a direct association of a given pest on perennial wall rocket within the UK was reported in the scientific literature, or that all pests known to affect perennial wall rocket in the world are
listed.

Quarantine pests likely to follow the pathwa y selected for further analyses include: Chromatomyia horticola and Liriomyza strigata . We qualitatively analyzed these quarantine pests using the methodology described in the US DA-APHIS Pathway-Initiated Commodity Risk Assessment Guidelines 5.02. Accordingly, we ex amined the biology of each pest within the context of the Consequences of Introduction and the Likelihood of Introduction, and estimated
the baseline Pest Risk Potential. Both C. horticola and L. strigata were rated to have a Medium pest risk potential. Based on this assessment, por t-of-entry inspections may be insufficient to safeguard U.S. agriculture and phytosanitary meas ures should be implemented in order to reduce phytosanitary risk.Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 iii 

### Table of Contents

Executive Summary.............................................................................................................. .......... ii
Table of Contents.............................................................................................................. .............iii
1. Introduction................................................................................................................ ................. 1
2. Risk Assessment ............................................................................................................. ............ 1 2.1. Initiating Event: Proposed Action...............................................................................1
2.2. Assessment of Weed Potent ial of Perennial Wall Rocket ..........................................2 2.3. Previous Risk Assessments, Deci sion History, and Pest Interceptions ......................2 2.4. Pest Categorization .....................................................................................................3 2.5. Quarantine Pests Likely to Follow the Pathway.........................................................8 2.6. Consequences of Introduction.....................................................................................8
2.7. Likelihood of Introduction..........................................................................................11 2.8. Conclusion: Pest Risk Potential and Phytosanitary Measures....................................13
3. Authors and Reviewers....................................................................................................... ...... 14
4. References.................................................................................................................. ............... 15 Appendix A: Risk Management Options for the im portation of leaves of perennial wall rocket, Diplotaxis tenuifolia (L.), from the United Kingdom................................................................... 19
A1. Introduction............................................................................................................... ..19 A2. Mitigation Options ......................................................................................................19 A3. Summary .................................................................................................................... .22
A4. Literature Cited ........................................................................................................... 23Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 1 

### 1. Introduction

This pest risk assessment was conducted and re viewed by staff at the Pest Epidemiology and Risk Analysis Laboratory (PERAL ) of the United States Departme nt of Agriculture (USDA). We examined the unmitigated risks associated with the leaves of fresh Diplotaxis tenuifolia (L.) imported from the United Kingdom, given that sta ndard industry post-harv est practices for leafy vegetables (e.g. lettuce, celery, greens, etc) will be used. In packinghouses, standard practices include trimming, washing, and sorting (Cantwel l and Kasmire, 2001). Field-packing does not guarantee appropriate washing and so rting; therefore, for the purposes of this risk assessment, we assume only packinghouse handling occurs (Can twell and Kasmire, 2001). Should the UK wish export to the United States additional plant parts besides the leaves of D. tenuifolia (e.g., stems), or if it is determined that the above post-harve st practices are not occu rring, this analysis may
need to be amended.

Diplotaxis tenuifolia has several common names including perennial wall rocket, narrow-leaved wall-mustard, wild rocket and wild arugula. For the purposes of this risk assessment, D. tenuifolia will be referred to as “pere nnial wall rocket” as per the import request from the UK. Perennial wall rocket is a drought-tolerant, ev ergreen sub-shrub in the family Brassicaceae [=Cruciferae]. It has edible leaves that are similar in flavor to Eruca sativa (arugula) but stronger. Perennial wall rocket can be added to mixed salads, but is generally considered too strong to be used in quantity on its own.

This risk assessment is qualitative, with risk being expressed in terms of high, medium or low rather than probabilities or frequencies. The de tails of the methodology and rating criteria can be
found in the Pathway-Initiated Pest Risk Assessments: Guidelines for Qualitative Assessments,
Version 5.02 (PPQ, 2000).

Regional and international plant protection organizations such as the North American Plant Protection Organization (NAPPO ) and the International Plan t Protection Convention (IPPC) provide standards for conducting pest risk an alyses (IPPC, 2007: ISPM #11; NAPPO, 2004). The methods used to initiate, conduct, and report this assessment, as well as the use of biological and phytosanitary terms are based on these standards. The IPPC standards describe three stages of pest risk analysis: Stage 1, Initiation; Stage 2, Risk Assessment; and Stage 3, Risk Management. This document satisfies the requir ements of IPPC Stages 1 and 2.



### 2. Risk Assessment

2.1. Initiating Event: Proposed Action

This commodity-based, pathway-initiated assessme nt is written in response to a request for USDA authorization to allow impor ts of a particular commodity presenting a potential plant pest risk. In this case, the importation into th e United States of leaves of wall rocket, D. tenuifolia (L.), from the United Kingdom is a potential pathwa y for introduction of exotic plant pests. Title 7, Part 319, Section 56 of the United States C ode of Federal Regulat ions (7 CFR §319.56) provides regulatory authority for the importation of fruits and vege tables into the United States.Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 2 2.2. Assessment of Weed Potential of Perennial Wall Rocket

The initial step in conducting a commodity-based risk assessment, after receiving a request for its importation, is to analyze its potential to become a w eed. We presented the results of the weed screening for D. tenuifolia below (Table 1)

. Perennial wall rocket is considered a weed in many parts of the world, including the United States. Ho wever, because it is al ready widely distributed throughout the continental United States, and be cause we believe the risk of weediness associated with importing perennial wall rocket fo r consumption is Low, this screening did not prompt a pest-initiated pest risk assessment.

Table 1. Assessment of the Weediness Potential

Commodity: Leaves of Diplotaxis tenuifolia (L.) species (Brassicaceae)

Phase 1: Diplotaxis tenuifolia is apparently distributed in the following United States: Alabama, Arizona, California, Connecticut, De laware, Florida, Idaho, Illinois, Indiana, Massachusetts, Maine, Maryland, Michigan, New Mexico, New Jersey, New York, Ohio, Oregon, Pennsylvania, Texas, and Virginia. It does not appear to be widespread in any state.

Phase 2: Is the species listed in:
Yes Geographical Atlas of World Weeds Holm et al

. , 1979
No World’s Worst Weeds Holm et al

. , 1997; Holm et al

. , 1977
No Report of the Technical Committee to Evaluate Noxious Weeds for Federal Noxious Weed Act Gunn and Ritchie, 1982
No Economically Important Foreign Weeds Reed, 1977
Yes Weed Science Society of America list WSSA, 1989
Yes Are there any references indicating weediness? e.g

., AGRICOLA, CAB, Biological Abstracts, AGRIS; search on “species name” combined with
“weed.”

Phase 3: Although this species is listed as a weed , it is widely distributed through out the
United States and is not c onsidered a quarantine weed.

2.3. Previous Risk Assessments, Decisi on History, and Pest Interceptions

No decision history exists for this commodity, nor have any pr evious risk assessments been done. Currently 7 CFR §319.56 prohibits the entry of fresh perennial wall rocket from the United Kingdom into the United States. No other country currently exports wall rocket into the United
States.

APHIS maintains a database of pl ant pests intercepted at U.S. ports of entry (PestID, 2007). We found no pest interceptions at any U.S. ports of entry on/with/in Diplotaxis from anywhere in the
world.Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 3 2.4. Pest Categorization

Below we list the pests associated with perennia l wall rocket (in any country) that also occur in the United Kingdom (Table 2). In th is list we identify the followi ng: (1) the presence or absence of these pests in the United States, (2) the gene rally affected plant part or parts, (3) the quarantine status of the pest with respect to the United States, (4 ) whether the pest is likely to follow the pathway and enter the United States on commercially exported perennial wall rocket, and (5) pertinent citations for either the distri bution or the biology of the pest. We eliminated many organisms from further cons ideration as sources of phytosan itary risk on perennial wall rocket from the United Kingdom because they do not meet the definition of a quarantine pest.

Table 2 . Pests associated with perennial wall rocket, Diplotaxis tenuifolia (L.), and also present in the United Kingdom Pest Geographic
distribution Host association
reference Quarantine pest Plant part
association Follow pathway

ARTHROPODA Acari: Tetranychidae Bryobia praetiosa Koch UK (CABI, 2007); US (PestID, 2007) Laffi, 2001 No N/A N/A

Tetranychus urticae
Kock UK, US (Bolland et al

. , 1998) Bolland et al

. , 1998 1 No N/A N/A

Collembola: Sminthuridae

Sminthurus viridis L. UK (CABI, 2007; CABI, 1973); US (Alaska) (CABI, 1973) Raimo et al

. , 2005 Yes Leaves (CABI, 2007) No 2

INSECTA Coleoptera: Chrysomelidae Phyllotreta sp. UK, US (Konstantinov and Vandenberg, 2001) Ciampolini et al

. , 2001;
Konstantinov and Vandenberg,
2001 No N/A N/A

Diptera: Agromyzidae Chromatomyia horticola (Goureau,) [= Phytomyza horticola Goureau] UK (CABI, 2007) Spencer, 1990 3 Yes Leaves Yes

1 Based on its association with Diplotaxis viminea.

2 Sminthurus spp. are tiny hexapods likely to be removed from leaves with even minimal washing and not likely to remain in the pathway through harvest and processing.

3 Based on association with genus Diplotaxis

.Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 4 Pest Geographic
distribution Host association
reference Quarantine pest Plant part
association Follow pathway Liriomyza strigata (Meigen) UK (Pitkin et al

. , 2008) Pitkin et al

. , 2008; Spencer, 1973; Spencer,
1990 4 Yes Leaves Yes

Phytomyza rufipes Meigen UK (CABI, 2007; Spencer, 1973), US (Spencer, 1973) Spencer, 1973; Spencer, 1990 4 No N/A N/A

Diptera: Cecidomyiidae

Dasineura brassicae (Winnertz) UK (CABI, 2007) Stelter, 1992 Yes Fruits, Seeds (CABI, 2007) No

Diptera: Drosophilidae Scaptomyza flava (Fallen) [= Scaptomyza apicalis Hardy] UK (Pitkin et al

. , 2008); US (Fisher et
al

, 2000) Pitkin et al

. , 2008 No N/A N/A

Hemiptera: Aphididae Lipaphis erysimi
Kaltenbach UK (CABI, 2007); US (CABI, 2007) Singh et al

. , 2004 No N/A N/A

Hemiptera: Pentatomidae Eurydema oleracea (L.) [= Strachia oleracea ] UK (Douglas and Scott, 1865) CABI, 2007; Arkhipov, 1985;
Schaefer and Panizzi, 2000 5 Yes Leaves

, seeds, flowers,

stems (Schaefer and Panizzi, 2000) No 6

Lepidoptera: Crambidae

Hellula undalis (Fabricius) UK (Kimber, 2008), US (HI) Robinson et al.,
2008 4 Yes Leaves

, stems No 7

Lepidoptera: Geometridae Eupithecia pulchellata Stephens UK (Scoble, 1999) Zhang, 1994 8 Yes Leaves

, Stems No 9

4 Based on association with genus Diplotaxis.

5 Eurydema spp. are pests of all crucifers (Schaefer and Panizzi, 2000) and E. oleracea in particular feeds on a wide range of cruciferous crops (Arkhipov, 1985; CABI, 2006).

6 Eurydema spp. are large, very conspicuous, highly mobile, external feeders. Thus, they are very unlikely to remain on the commodity through harvest and processing.

7 This pest may follow the pathway on commodities such as ca bbage, because larvae can tunnel into the main stem in seedlings and feed on leaves and by tunne ling into leaf petioles (Kessing and Mau, 2007). Wall rocket differs greatly from cabbage in structure, however, and the pest is highly unlikely to be hidden inside the loose leaves, especially if post harvest washing practices are followed.

8 The host range is not well defined, bu t according to Zhang (1994) this pest feed s on various Cruciferae (=Brassicaceae).

9 Adults are highly mobile external feeders, not likely to re main in the pathway through harvest and processing. Larvae and eggs are likely to be removed from l eaves with even minimal washing.Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 5 Pest Geographic
distribution Host association
reference Quarantine pest Plant part
association Follow pathway Lepidoptera: Lyonetiidae Bedellia ipomoeae Bradley UK (CABI, 2007) US (Zhang, 1994) Zhang, 1994 No N/A N/A

Lepidoptera: Pieridae

Pieris brassicae
Linnaeus UK (CABI, 2007) PPQ, 1984 Yes Leaves No 10

Pieris rapae Linnaeus UK, US (Zhang, 1994) Zhang, 1994 11 No N/A N/A

Pontia daplidice
Linnaeus UK 12 (Zhang, 1994; Eeles, 2007) CABI, 2007; Zhang, 1994; Eeles, 2007 13 Yes Leaves

, Stems No 11

Lepidoptera: Pyralidae Evergestis extimalis Scopoli UK (Fitter and Peat, 1994; Robinson et
al

., 2008) Robinson et al.,
2008 Yes Fruit, Seed (Fitter and Peat, 1994) No

Evergestis forficalis
Linnaeus UK (Zhang, 1994; CABI, 2007) Mazzei et al

. , 2007; Zhang,
1994 14 Yes Leaves

, Stems No 15

FUNGI & CHROMISTANS 16
Albugo candida (Pers.:Fr.) Kuntze [Oomycetes: Peronosporales] UK (Anonymous, 2003), US (Farr et al

. , 2007) Anonymous, 2003; Farr et al

. , 2007 No N/A N/A

Erysiphe cruciferarum Opiz ex L. Junell [Ascomycetes: Erysiphales] UK (Anonymous, 2003; Braun, 1995b) US (Farr et al

. , 2007) Braun, 1995b;
Farr et al

. , 2007 No N/A N/A

10 Larvae are occasionally found within some host vegetables, and pupae are sometimes attached to fresh or dried vegetables or crating. For example, it has been inte rcepted at U.S. ports of en try from France, Greece, Ital y, Portugal, Scotland, and Spain; but only on Brassica oleracea (cabbage, broccoli, cauliflower, etc.) or as a hitchhiking pest on containers and tiles.
Given the loose-leaf structure of Diplotaxis spp., if all postharvest practices an d visual inspection are in place, the likelihood of introduction should be negligible.

11 Based on its association with Diplotaxis virgata.

12 Rare migrant to UK, but occasionally seen in large numbers.

13 The host range is not well defined, but this pest is associat ed with various Cruciferae (CABI, 2006; Zhang, 1994; Eeles, 2007)

14 Mazzei (2007) list this species on Diplotaxis; Zhang (1994) lists it at a pest of “Brassica and wild Cruciferae.”

15 Adults are highly mobile external feeders, not likely to remain in the pathway through harvest and processing. Although larvae feed in the heart or amongst young spun leaves of some crucifers, because wall rocket’s leaves are loose (unlike cabbage, for example), it is likely that larvae and eggs would be removed from leaves with even minimal washing.

16 Taxonomy according to Farr et al., 2007; Kirk, 2004.Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 6 Pest Geographic
distribution Host association
reference Quarantine pest Plant part
association Follow pathway Fusarium oxysporum
Schlechtendah [Ascomycetes: Hypocreales] US, UK (CABI, 2007) Garibaldi et al

. , 2003 No N/A N/A

Peronospora parasitica (Pers.:Fr.) Fr. [Oomycetes: Peronosporales] UK (Anonymous, 2003); US (Farr et al

. , 2007) Farr et al

. , 2007;
Garibaldi et al

. , 2004 No N/A N/A

Plasmodiophora
brassicae Woronin [ Plasmodiophoromycetes : Plasmodiophorales] UK (Anonymous, 2003); US (Farr et al

. , 2007) Farr et al

. , 2007 No N/A N/A

Pseudocercosporella capsellae (Ellis & Everh.) Deighton [Ascomycetes: Mycosphaerellales] UK, US (Farr et al., 2007) Braun, 1995a 17 No N/A N/A

Sclerotinia sclerotiorum (Lib) de Bary [Ascomycetes: Helotiales] UK (Farr et al

. , 2007); US (Farr et al

. , 2007) Farr et al

. , 2007;
Garibaldi et al

. , 2005 No N/A N/A

Thanatephorous
cucumeris (A.B. Frank) Donk Anamorph: Rhizoctonia solani
J.G. Kuhn [Basidiomycetes: Ceratobasidiales] UK, US (CABI, 2007) Nicoletti et al

. , 2004 No N/A N/A

BACTERIA 18
Xanthomonas campestris

pv. campestris (Pammel) Dowson [ Xanthomonadaceae ] UK, US (CABI, 2007) Raio and Giorgini, 2005 No N/A N/A

VIRUSES Pepino mosaic potexvirus [PepMV] UK (restricted distribution) (Jones, 2005), US (CABI, 2007) Córdoba et al.,
2004 19 No N/A N/A

17 Host association was made with members of the same genus, Diplotaxis erucifolius and D. muralis (Braun et al., 1995b). This pathogen also attacks many other genera in the Brassicaceae family (Farr et al., 2007).

18 Taxonomy according to Euzeby, 2007.

19 Host association was made with the member of the same genus, D. erucoides (Córdoba et al., 2004).Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 7 Pest Geographic
distribution Host association
reference Quarantine pest Plant part
association Follow pathway Turnip mosaic virus [Potyviridae] TuMV UK, US (Brunt et al

. , 1996 onwards;
ICTVdB Management, 2006; CABI, 2007) Rimmer et al

. , 2007; CABI,
2007 20 No N/A N/A

Turnip yellow mosaic tymovirus TYMV UK (Rimmer et al

. , 2007) Brunt et al

. , 1996
onwards 21 Yes Whole Plant (Brunt et al

. , 1996 onwards) No 22

20 A specific reference for TuMV occurring on Diplotaxis was not found, however the host range for this virus is very broad, encompassing hundreds of species an d numerous plant families (Rimmer et al, 2007; CABI, 2006). It is possible Diplotaxis tenuifolia is also susceptible; therefore it was included on this list.

21 Association of TYMV with D. tenuifolia was based on experimental conditions, not found naturally infected in the field (Brunt et al

. , 1996 onwards). Host range is larg ely limited to Brassicaceae (Rimmer et al

. , 2007).

22 TYMV is primarily transmitted by certain beetles in the Ch ysomelidae and Curculionidae fami lies or by mechanical means (Rimmer et al., 2007). Phyllotreta sp. is the only beetle identified in this pest list for U.K. wall rocket. Species of Phyllotreta are vectors of TYMV (Rimmer et al., 2007), but due to th e external feeding nature of the beetle and processing of the commodity, they are unlikely to follow the pathway and th erefore would not be present to vector the virus to live
hosts in the United States. Within the United States it is also unlikely that D. tenuifolia salad greens, imported for consumption, will be exposed to the v ectors necessary for transmission or be discarded in close proximity to live Brassicaceae host plants. Therefore, we considered that the pathogen would not follow the pathway.Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 8 Other organisms included on the pest list (Table 2) , but not chosen for fu rther scrutiny, may be potentially detrimental to agriculture in the United States. The following are reasons for not subjecting them to further analysis: they are well established and widespread in the United States; they are mainly associated with plant pa rts not included with the commodity; they may be associated with the commodity, but are not e xpected to remain with the commodity during processing; or, they have been intercepted on rare occasions, as biological contaminants, at the ports of entry during commodity inspections and w ould not be expected to be frequently found in commercial shipments.

2.5. Quarantine Pests Likely to Follow the Pathway

In our review of the literature, we identified 30 pests that may be associated with perennial wall rocket in the United Kingdom (Table 2). Most of the other pests were not considered quarantine pests of the continental United States. Furthermor e, of the quarantine pests, we found only two that were likely to stay with the commodity through harvest, processing, and shipping. Such pests are said to “follow the pathway” and we an alyzed them in the next section. These were the leafminers (Diptera: Agromyzidae) Chromatomyia horticola Goureau, and Liriomyza strigata (Meigen).

We did not further consider quarantine pests not expected to follow th e pathway. Should any of these pests be intercepted in shipments of the commodity, however, qua rantine action may be taken at the port of entry and additi onal risk analyses may be conducted.

2.6. Consequences of Introduction

In this section we assessed the undesirable consequences that may occur from the introduction of quarantine pests. For each quarantine pest, we ra ted the potential conseque nces of introduction in
five areas called “Risk Elements.” The Risk El ements include: Climate/Host Interaction, Host Range, Dispersal Potential, Economic Impact, and Environmental Impact. These elements reflect the biology, host range and climatic/geographic di stribution of each pest and are supported by biological information on each of the analyzed pest s summarized in this section. For each risk element, we assigned pests a rating of Low (1 point ), Medium (2 points) or High (3 points). The ratings were determined using the criteria in the Risk Assessment Guidelines, Version 5.02 (PPQ, 2000) (see for more details).

The major sources of uncertainty present in this ri sk assessment are similar to those in other risk assessments. They include the use of a developing or evolving process (Orr et al

. , 1993; PPQ, 2000), the approach used to combine risk elemen ts (Bier, 1999; Morgan and Henrion, 1990), and the evaluation of risk by comparisons to lists of factors within the guide lines (Kaplan, 1992; Orr
et al

. , 1993). To address this last s ource of uncertainty, the lists of factors were interpreted as illustrative and not exhaustive. This implies that additional biological information, even if not explicitly part of the criteria, can be used when it is releva nt to a rating. Other sources of uncertainty are the quality of the biological info rmation and the amount of information available on the regional flora and fauna. Inherent biological va riation within a popul ation of organisms introduces uncertainty as we ll (Morgan and Henrion, 1990).Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 9 For each pest, we summed the five Risk Elements to give a Cumulative Risk Rating. These risk ratings are qualitative estimates of the severity of the impact each pest would have, in terms of economic and environmental consequences, should each pest establish and spread in the
continental United States. The Cumulative Risk Ratings for each pest are summarized below (Table 3).

Chromatomyia horticola Goureau (Diptera: Agromyzidae) Risk Rating

Risk Element #1: Climate/Host Interaction Chromatomyia horticola is found throughout tropical, subtropical, and temperate Asia, Europe, and Africa (CABI, 2007). Ba sed on this distribution we estimated
that C. horticola could become established in Plant Hardiness Zones 5-10 in the United States (PERAL, 2008). One or more of its potential hosts occurs in these zones (NRCS, 2007). High (3)

Risk Element #2: Host Range Chromatomyia horticola is a highly polyphagous species that feeds on crops in many different families including: Alliaceae, Anacardiaceae, Asteraceae, Brassicaceae, Caryophyllaceae, Chenopodiaceae, Cucurbitaceae, Fabaceae, Ranunculaceae, and Umbelliferae (CABI, 2007). Some of the major crops attacked include onions ( Allium spp.), Brassica spp., lettuce ( Lactuca sativa ),
beans (Phaseolus spp.), and peas ( Pisum spp.) (CABI, 2007; Spencer, 1973). High (3)

Risk Element #3: Dispersal Potential Chromatomyia horticola has a relatively high biotic potential. Females lay as many as 50 eggs per day, and may lay mo re than 300 in their lifetime (CABI, 2007). Depending on the region, C. horticola generally has three or four generations per year.

In general, leaf miners have minimal na tural dispersal potential. Larvae remain inside the leaf where the egg they ha tched from was laid, until they pupate. Adults do not disperse long distances on their own. They can be transported through wind currents, but because windborne transfer requires that suitable plant
hosts be available at the destination duri ng the relatively shor t lifespan of the fly, this is probably not a common method of dispersal (CABI, 2007). Movement of economic crop hosts, if containing early stages of the pest, may effectively transfer the species to new areas. Despite the large-scale movement of plants of European and Asian origin into thes e regions, the species has not become established in the Americas or Australasia (CABI, 2007). Medium (2)

Risk Element #4: Economic Impact Chromatomyia horticola is a very serious pest almost everywhere it is established (CABI, 2007). Infestations on seedlings ar e especially seriou s as the plants quickly stop developing, and either wilt or die. Infestations on older plants can be less serious, but still cause yi eld reductions (CABI, 2007).

In northern Europe, C. horticola often seriously damages glasshouse crops of
tomatoes and lettuce. In the Mediterran ean, it damages both glasshouse and field crops, especially Cicer, Brassica and Pisum species, and similarly in Japan to High (3)Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 10

Chromatomyia horticola Goureau (Diptera: Agromyzidae) Risk Rating

Allium

, Cucurbita

, Mentha and Vicia species (CABI, 2007). The pest can transfer plant pathogens during leaf visiting by the females, or even by males feeding at the leaf punctures made by the female (CABI, 2007).

Introduction of the pest could cause loss of regional and domestic markets since the fly is not present in Western Hemisphere. Risk Element #5: Environmental Impact Chromatomyia horticola poses a potential threat to plants in the United States listed as Threatened or Endangered, such as Allium munzii (CA), Cucurbita
okeechobeensis ssp. Okeechobeensis (FL), Helianthus eggertii (AL, KY, TN), H. paradoxus (NM, TX), H. schweinitzii (NC, SC) (USFWS, 2007). Chemical control programs are unlikely to be initiated against this pest, since those already in place for the control of other pestiferous leaf miners, such as Liriomyza sativae
Blanchard or L

. trifolii (Burgess), are likely to be equally effective against C

. horticola . However, C. horticola could be the target of biological control programs, as for other introduced Agromyzidae (e.g., Hawaii; (Culliney and Nagamine, 2000)). High (3)

Liriomyza strigata (Meigen) (Diptera: Agromyzidae) Risk Rating

Risk Element #1: Climate/Host Interaction The complete geographic distribution of L. strigata is unknown. It is found in the Palaearctic region, throughout Western Eur ope, but the eastern limit of its range is unknown (Spencer, 1973). Based on its known distribution, we assume it can
survive in at least four Plant Hardines s Zones of the United States, and perhaps more (PERAL, 2008). One or more of its potential hosts occurs in these zones (NRCS, 2007). High (3)

Risk Element #2: Host Range Liriomyza strigata is a highly polyphagous species that feeds on over 180 genera in 31 different families (Spencer, 1973). Main vegetable crops attacked include Beta vulgaris (Chenopodiaceae), Lactuca spp. (Compositae), and Pisum sativum L. (Fabaceae) (Spencer, 1973). High (3)

Risk Element #3: Dispersal Potential Species of Liriomyza have a relatively high biotic potential. Lifetime fecundity varies greatly by species, but ranges be tween 100 and more than 600 eggs per female (Parrella, 1987).

In general, leaf miners have minimal na tural dispersal potential. Larvae remain inside the leaf where the egg they ha tched from was laid, until they pupate. Adults do not disperse long distances on their own. They can be transported through wind currents, but because windborne transfer requires that suitable plant
hosts be available at the destination duri ng the relatively shor t lifespan of the fly, this is probably not a common method of dispersal (CABI, 2007). Movement of economic crop hosts, if containing early stages of the pest, may effectively Medium (2)Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 11

Liriomyza strigata (Meigen) (Diptera: Agromyzidae) Risk Rating transfer the species to new areas. Howe ver, despite having a large host range, including many crops, this species has a re latively restricted global distribution. Risk Element #4: Economic Impact According to Spencer (1973) , large populations of L. strigata are rarely found in a single plant; therefore, larv al damage to mature plants is generally negligible, and young plants are not normally attack ed. Chemical control programs are unlikely to be initiated against this pe st, since those already in place for the
control of othe r species of Liriomyza are likely to be equally effective against it ; therefore, the presence of this specie s is unlikely to si gnificantly increase production costs. Introduction of the pe st could cause loss of regional and domestic markets since it is apparently not present in the Western Hemisphere, Africa, Asia, or the Pacific (CABI, 2007). Medium (2)

Risk Element #5: Environmental Impact Liriomyza strigata is highly polyphagous (Spencer, 1973) and could potentially attack plants listed as Threatened or Endange red in 50 CFR §17.12 (e.g., Campanula robinsiae, endangered in FL; Helianthus paradoxus threatened in TX and NM; H. schweinitzii endangered in NC and SC) (USFWS, 2007). Chemical control programs are unlikely to be initiated against this pest, since those already in place for the control of other pestiferous leaf miners, such as Liriomyza sativae
Blanchard or L

. trifolii (Burgess), are likely to be equally effective against L. strigata . However, this pest could be the targ et of biological c ontrol programs, as has occurred with other introduced Ag romyzidae (e.g., Hawaii; (Culliney and Nagamine, 2000)). High (3)

Table 3 . Risk ratings for Consequences of Introduction.
Pest Climate/ Host
Interaction Host Range Dispersal
Potential Economic Impact Environ. Impact Cumulative Rating Chromatomyia
horticola High (3) High (3) Medium (2) High (3) High (3) High (14)

Liriomyza strigata High (3) High (3) Medium (2) Medium (2) High (3) High (13)

a Low risk = 5-8 points =, 9-12 points = me dium risk, and 13-15 points = high risk. T

2.7. Likelihood of Introduction

Likelihood of introduction is a func tion of two risk elements: 1) the quantity of the commodity imported annually and 2) pest opportunity, which c onsists of five criteri a that describe the potential for pest survival along the pathway. Details of these two Risk Elements and their rating criteria are provided in PPQ ( 2000). We summarized the ratings and cumulative scores for Likelihood of Introduction below (Table 4).Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 12 2.7.1 Quantity Imported Annually The quantity expected to be im ported annually is reported by the exporting country in the import request document. We converted this amount into standard units of 40-foot-long shipping containers. In this case, the UK has indicated th at the volume of wall rocket shipped to the United States is expected to be betwee n 100-150,000 kg annually, which is less than 10 containers per year. Therefore, we rate d this risk element Low for both pests.

2.7.2. Survive Post-Harvest Treatment This risk element evaluates the efficacy of standa rd post-harvest treatments in terms of the likely mortality of pests exposed to the treatments. In the absence of further information, we assumed minimal post-harvest treatments, including wash ing and culling, will be used in processing perennial wall rocket in the UK. Because damage is usually obvious, we think the leaf miners are likely to be culled during this pro cess. Therefore, we rated both pests Low for this risk element.

2.7.3. Survive Shipment According to information provided by the United Kingdom, perennial wall rocket would be air freighted directly from London to Orlando or Miami, Florida. Immediately before flight, each consignment would be vacuum-cooled and insulated. Chromatomyia horticola and L. strigata are both cold tolerant pests, and we assume that more than 10 percent would survive shipment under these conditions. Therefore, we rated the risk of shipment survival as High for both pests.

2.7.4. Not Detected at Port-of-Entry Chromatomyia horticola and L. strigata are leaf miners that produ ce visible and obvious signs of infestation (see Figs. 1 and 2) and port inspector s are capable of readily identifying both pests. Therefore, we rated the likelihood of these pest s escaping detection at ports of entry as Low

.

Figure 1 . Leaf mines of C. horticola on Pisum sp. (source: Crop Prot ection Compendium, 2007 Edition. CAB International, Wallingford, UK, 2007)Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 13 Figure 2 . Leaf mines of Liromyza strigata on Sonchus (The Leaf and Stem Mines of British flies and other pests, http://www.ukflymine s.co.uk/Flies/Liriomyza_strigata.html)

2.7.5. Imported or Moved Subsequently to an Area with an Environment Suitable for Survival Perennial wall rocket from the UK is likely to be sold in every state. We assume that demand will be proportional to the size of the consumer population in potential markets, and that any
infestations would be distribu ted equally among consignments.

Based on what is known about the curre nt geographical distributions of C. horticola and L. strigata , these pests would likely survive in much of the United States, or at least Plant Hardiness
Zones 6-10. States within these zones contain more than 89 percent of the U.S. population (PERAL, 2008). Moreover, this region include s several of the most populous states (e.g

., Illinois, New York, Ohio, Pennsylvania) to which a significant percenta ge of perennial wall rocket imports would likely be diverted. Thus, we estim ated a High risk associated with the likelihood that both pests will be moved to suitable habitat in the United States.

2.7.6. Come into Contact with Host Material Suitable for Reproduction
Because C. horticola and L. strigata have very broad host ranges, a nd host plants are distributed throughout the United States (NRCS, 2007), suitable host material should be widely available for both pests. However, in this case perennial wa ll rocket will only be imported for consumption. Both pests have a limited capacity for natural di spersal and remain on their host plants except as adults, and adults are poor flyers with re latively short life spans. In order for both C. horticola
and L. strigata to become established via perennial wall rocket imported for consumption,
infested leaves would have to be placed outdoors in proximity to host material. Since this is not likely to occur, we considered both pests to ha ve a Low risk of coming into contact with host material via this pathway.

2.8. Conclusion: Pest Risk Potential and Phytosanitary Measures

We summed the values for the Consequences an d the Likelihood of Intr oduction to yield Pest Risk Potential values (PPQ, 2000) (Table 5). This is an estimate of the relative risk associated with the importation of perennial wall rocket from the United Kingdom. We used the following scale to interpret these totals: low risk = 11- 18 points, medium = 19-26 points, and high = 27-33 points.Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 14 Pests with a Pest Risk Potential value of Low do not require specific mitigation measures,
whereas a value within the Medium range indicates that specific phytosanitary measures may be necessary. The PPQ Guidelines state that a Hi gh Pest Risk Potential means that specific phytosanitary measures are strongly recommende d, and that port-of-ent ry inspection is not considered sufficient to provi de phytosanitary security.

Possible pest mitigation options are outlined in the appendix, but the choice of appropriate phytosanitary measures to mitigat e risks is undertaken as part of Risk Management and is beyond the scope of this document.

Table 4 . Risk Ratings for Likelihood of Introduction Pest Quantity Imported Survive
PostHarvest
Treatment SurviveShipment Not
Detected
at Portof-Entry Moved

to Suitable
Habitat Contact
with
Host
Material Cumulative Rating a

Chromatomyia
horticola Low (1) Low (1) High (3) Low (1) High (3) Low (1) Medium (10)

Liriomyza strigata Low (1) Low (1) High (3) Low (1) High (3) Low (1) Medium (10)

a Low risk = 6-9 points, Medium = 10-14 points, and High = 15-18 points

Table 5 . Pest Risk Potentials Pest species Consequences of
Introduction Likelihood of
Introduction Pest Risk Potential

Chromatomyia horticola High (14) Medium (10) Medium (24) Liriomyza strigata High (13) Medium (10) Medium (23)



### 3. Authors and Reviewers

Plant Epidemiology and Risk Analysis Laboratory
Center for Plant Health Sc ience and Technology (CPHST)

Authors: Alison Neeley, Entomologist Heather Hartzog, Plant Pathologist
Reviewers: Robert Schall, Plant Pathologist Marina Zlotina, EntomologistPerennial wall rocket from the U.K.

Rev. 002 October 07, 2008 15 

### 4. References

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Rev. 002 October 07, 2008 17 PERAL. 2008. Plant Hardiness Zones of the United States: Area and Population Analysis. United States Department of Agriculture, An imal and Plant Health Inspection Service, Plant Protection and Quarantine, Center fo r Plant Health Science and Technology, Plant Epidemiology and Risk Analysis Labor atory (PERAL), Raleigh, NC. 6 pp.
PestID. 2007. Pest Identification Database (PestID). United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine. https://mokcs14.aphis.usda.gov/aqas/l ogin.jsp. (Archived at PERAL) Pitkin, B., W. Ellis, C. Plant, and R. Edmunds. 2008. The leaf and stem mines of British flies and other insects. Diplotaxis, wall rocket s [Brassicaceae]. Last accessed March 12, 2008. http://www.ukflymines.co.uk/Keys/DIPLOTAXIS.html. PPQ. 1984. Pests Not Known to Occur in the United States or of Limited Distribution, No. 47: Large White Butterfly ( Pieris brassicae ). United States Depart ment of Agriculture, Animal and Plant Health Inspection Servi ce, Plant Protection and Quarantine (PPQ) , Riverdale, MD. 941 pp. PPQ. 2000. Guidelines for pathway-initiated pest ri sk assessments (Version 5.02). United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine (PPQ), Riverdale, MD. 30 pp. Raimo, F., G. Miccio, R. Nicoletti, and F. Ja nssens. 2005. Damage by sp ringtails on perennial wallrocket ( Diplotaxis tenuifolia ). Informatore Fitopatologico 55(1):44-47. Raio, A., and M. Giorgini. 2005. Infections of Xanthamonas campestris pv. campestris on rocket crops in Campania, south Italy. Informatore F itopatologico 55(7/8):58-60. Abstract Only. Reed, C.F. 1977. Ecologically important fore ign weeds. Agricultu ral Handbook No. 498. US Government Printing Office, Washington, D.C. 746 pp. Rimmer, S. R., V. I. Shattuck, and L. Buchwa ldt. 2007. Compendium of Brassica Diseases APS Press, St. Paul, MN. 117 pp. Robinson, G.S., Ackery, P.R., Kitching, I.J., Beccaloni, G.W., and L.M. Hernandez. 2008. HOSTS- a database of the world’s Lepidopteran hostplants. Last accessed September 15, 2008. http://www.nhm.ac.uk/research-cura tion/research/proj ects/hostplants/ Schaefer, C.W., and A.R. Panizzi. 2000. Heter optera of Economic Importance. CRC Press, Boca Raton, FL. 828 pp. Scoble, M. J. 1999. Geometrid moths of the world. Natural History Museum, London. 1016 pp. Singh, B., S.K. Gupta, and D.R. Kotwal. 2004. Sc reening of some Brassica species and their strains for resistance to mustard aphid ba sed on aphid infestation Environment and Ecology 22(Spl-3):565-568. Spencer, K.A. 1973. Agromyzidae (Diptera) of Economic Importance. Dr. W. Junk B.V., Publishers, The Hague, 418 pp. Spencer, K.A. 1990. Host Specializa tion in the World Agromyzidae (Diptera). Kluwer Academic Publishers, Dordrecht, The Netherlands, 444 pp. Stelter, H. 1992. Studies on gall midges XXXIII: Dasineura species (Diptera: Itonididae) in shoots of cruciferous plants. Beitrage zur Entomologie 42(1):197-205. USFWS. 2007. Threatened and Endangered Specie s System (TESS). United States Fish and Wildlife Service (USFWS). http://ecos.fws .gov/tess_public/TESSWebpage. (Archived at PERAL) WSSA. 1989. Composite List of Weeds. Weed Science Society of America. Zhang, B.C. 1994. Index of ec onomically important Lepidop tera. CAB International, Wallingford, UK. 599 pp.Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 18Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 19 

### Appendix A: Risk Management Options for the im portation of leaves of perennial wall rocket, Diplotaxis tenuifolia (L.), from the United Kingdom

A1. Introduction

In this PRA we identified only two quarantine pe sts that could be introduced into the United States via the importation of perennial wall rocket from the United Kingdom: Chromatomyia
horticola and Liriomyza strigata. Both are Dipteran leaf miners in the family Agromyzidae and both had Medium pest risk potentials.

According to PPQ (2000), pests with Medium pest risk potential may require specific phytosanitary measures. This section presents possi ble risk mitigation strategies that PPQ risk managers may wish to consider when deciding if and what risk management measures should be
undertaken. The actual choice of risk mitigation measures is not addressed in this document but details are published in the Federal Register as quarantine notices.

The proposed importation of fresh perennial wall rocket from the United Kingdom, if approved, would be regulated by amendment to existing fruits and vegetables regulations (7 CFR § 319.56). The appropriate level of protection may be achieved through the a pplication of a single phytosanitary measure, such as inspection or a quarantine treatment, or a combination of

measures.

The Plant Protection Act (7 U.S.C. § 7701-7786, 2000) defines ‘systems approach’ as “...a defined set of phytosanitary proce dures, at least two of which ha ve an independent effect in mitigating pest risk associated with the moveme nt of commodities.” Similarly, the FAO Standard for Integrated Measures for Pest Risk Management proposed that a systems approach be defined as, “The integration of different pest risk ma nagement measures, at least two of which act independently, and which cumulatively achieve th e desired level of phytosanitary protection” (IPPC, 2007: ISPM #14). Systems approaches ar e employed by an importing country as an alternative to the use of single measures that achieve an appropriate level of phytosanitary protection when a single phytosanitary measure is nonexistent, infeas ible or undesirable.

Combining specific mitigation measures to pr ovide overlapping or sequential safeguards is distinctly different from applying single m itigation methodologies such as fumigation or inspection. Specific measures may be selected from a range of pre-harvest and post-harvest measures (e.g., surveys, inspections, sanitation, ch emical treatments, etc.) and include mitigation measures to compensate for uncertainty. PPQ uses systems approaches for the importation of many commodities including Unshu oranges from Japan (7 CFR § 319.28), tomatoes from Spain, France, Morocco, and Western Sahara (7 CFR § 319.56 28), and peppers from Israel (7 CFR § 319.56 24). These programs have performed successfully for many years.

A2. Mitigation Options

A2.1. Establishment of Pest Free Areas A pest free area (PFA) is defined as “an area in which a specific pest does not occur as demonstrated by scientific evidence and in wh ich, where appropriate, th is condition is beingPerennial wall rocket from the U.K.

Rev. 002 October 07, 2008 20 officially maintained” (IPPC, 2007: ISPM #s 4 and 5). As a sole mitigation measure, the establishment of pest free areas or pest free pl aces of production may be co mpletely effective in satisfying an importing country’s appropriate level of phytosanitary protection (IPPC, 2007: ISPM #s 4 and 10). This option has been successful in practice, eliminating the need for postharvest commodity treatments to achieve probit-9-level secu rity (e.g., TDOA, 2003). Establishment and maintenance of pest free areas or production sites are to be in compliance with international standards [e.g., IPPC, 2007: ISPM #s 4, 5 and 10; NAPPO, 2004).

A2.2. Establishment of Area s of Low Pest Prevalence According to the IPPC (2007: ISPM #22), an area of low pest prevalence may comprise all of a country, part of a country, or part s of several countries, in which a particular pest species occurs at low population densities and which is or are su bject to effective surv eillance and control or eradication measures (IPPC, 2007: ISPM #10) . Procedures for the establishment and maintenance of areas of low pest prevalence ar e to comply with inte rnational standards (e.g., IPPC, 2007: ISPM #22; NAPPO, 20 03). For example, elements of an operational plan for
establishment and maintenance of such areas mi ght include a geographic description to delimit the area; specification of an upper limit to pest densities; m eans to document and verify all necessary procedures and maintain records; specification of phytosanitary procedures (e.g., survey, pest control); and movement controls to prevent pest entry or re-entry into the area. The
international standards recommend that the exporting country cons ult with the importing country in the early stages of implementation to ensure that importing country requirements are met. In particular, target or threshold population densities defining an area of low pest prevalence are to be established in consultation with the importing country.

Any protocol for establishing and maintaining a pest free area or area of lo w pest prevalence is also to include a pest-reporting procedure and emergency action plan to address target pest detections in the pest free or low-preval ence zones (IPPC, 2007: ISPM #s 10 and 22; NAPPO, 2003, 2004). Combined with inspection, effective IPM programs achieving low pest prevalence may be a possible mitigation option for both leaf miners but should be verified by conducting an official survey or lot freedom based on inspection of shipping lot.

A2.3. Control/Suppression Programs A control program may be used to suppress or eliminate pests from fields or prevent infestation. Generally, such programs should not be used as stand-alone mitigation options, but may be used in combination with other measures as part of a systems approach. Successful control programs typically include monitoring, cu ltural, biological and chemi cal components (Dreistadt, 1994). The components of the control program must be clearly defined for use in a systems approach (IPPC, 2007: ISPM #14).

In controlling Agromyzid leaf miners, chemical tr eatment of seedlings can be very effective in preventing the initial laying of eggs (CABI, 2007). However, only using insecticides to control leaf miners is not generally an effective long-te rm strategy. When insecticides are used heavily,
resistant strains of flies become dominant and the non-selectivity of the insecticides also kills off natural predators and parasites. Prolonged appli cation can result in expl osive populations of the pest (CABI, 2007).Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 21 In greenhouses, the introduction of Hymenoptera parasites can be ex tremely effective, especially during the first period of leaf mine development. Irradiated (and hence sterile) males are also a very effective method of reducing egg-layi ng. Limited success has also been obtained by exposing yellow sticky traps cl ose above the growing plants, as the males tend to fly low between plants and in general are more mobile than the females (CABI, 2007).

A2.4. Phytosanitary Certification Inspections
These may provide an acceptable level of protection when used as part of a systems approach. The crop should be sampled and inspected peri odically during the gr owing season and after harvest. Survey results must be negative for issu ance of a certificate. St atistical procedures are available to verify the confidence in declaring an area pest-free based on negative survey results (e.g., Venette et al

. , 2004; Barclay & Hargrove, 2005).

Yellow sticky traps and water pan traps are very effective in monitoring Dipteran leaf miners (CABI, 2007) and are by far the simplest and mo st inexpensive method of monitoring (Rosen, 1990). Additionally, plants can be carefully examin ed for presences of damage and visible pest stages. Sampling plans can be developed to give precision on estimates of pest population levels.

A2.5. Packinghouse procedures Washing the commodity and removing obviously inf ected or infested material may reduce the likelihood of introducing quarantin e pests into the United States with a shipment. Packinghouse operations should include at least the follo wing (Cantwell and Kasmire, 2001): trimming; cleaning with chlorinated water (concentrations could vary from 50 to 200 ppm active chlorine); sorting and grading to eliminate defective produc ts (including any leav es damaged by pests).

A2.6. Quarantine treatments Quarantine treatments normally provide probit-9 s ecurity by killing 99.9968 percent or more of the target organisms.

Irradiation at 400 gy : Recently, APHIS published a final rule establishing “a minimum generic dose of 400 Gy for all plant pests of the class In secta other than pupae and adults of the order Lepidoptera” for “all regulated arti cles (i.e., fruits, vegetables, cu t flowers, and foliage)” (Shea, 2006). Irradiation is not appropriate for all comm odities, however, and more research may be
needed to determine the tolerance of wall rocket is to irradiation. If irradiation is used, measures should be implemented to ensure the phytosanitary security of the consig nments after treatment to prevent re-infestation. Irradiation may not kill all internal insects; the endpoint of treatment may be inactivation, sterilization, or preventing ma turation of larvae. Ther efore, the presence of live larvae in a treated consignment would not necessarily result in its rejection, provided appropriate safeguarding measures ha d been used (IPPC, 2007: ISPM #18).

Fumigation – Methyl bromide fumigati on (T101-n-2) is currently approved as a quarantine treatment for leaf miners on herbs and leafy ve getables (PPQ, 2006). However, perennial wall rocket is not specifically listed, and therefore, not currently approved, but because several close relatives are listed, it is likely only minimal res earch would be needed to add wall rocket. Hence, methyl bromide fumigation would be expected to provide probit-9 security against both pests.Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 22 A2.7. Pre-shipment programs Inspection, treatment, or other risk mitigation m easures performed in the field and packinghouse should be under the direct supervision of qualified APHIS and DEFRA personnel, and in accordance with specified phytosanitary procedures . Such programs require all aspects of the application of any required phytos anitary measures to be monitored, and also aim to identify shortcomings or opportunities for program improvements (IPPC, 2007: ISPM #14). Provision should be made for the formal recognition of approved areas, sites, or producers, as well as the specification of conditions for revoking approvals or refusing certificat ion for export to the
United States.

A2.8. Point-of-entry sampling and inspection If a preclearance program is not implemented, then inspection at port of entry is necessary. Upon arrival in the United States, consignments should be inspected, with particular attention given to paperwork and seals on vehicles, to ascertain that the chain of cu stody has remained intact. Portof-entry inspection may provide an acceptable le vel of protection against obvious pests when used as part of a systems approach. A ra ndom sample from each consignment should be inspected to detect a pest infestation rate of 10 percent or greater (PPQ, 2007).

Leaves should be carefully examined as out lined in the APHIS Fruit and Vegetable Manual (PPQ, 2008): Inspectors should look for leaf miner larvae and signs of larv ae such as frass and holes in the leaves. When examining leaves, in spectors should also look for discolored paths under the leaf surface and the pr esence of mines inside the le af. Using a probe or knife, inspectors should extract the leaf miner larvae by pricking the leaf surface at the end of a path and looking for small larvae.

A3. Summary

Options for risk mitigation are summarized below (Table A1).

This document does not purport to es tablish specific work plans or to evaluate the quality of a specific program or systems approach. It iden tifies risks and provides information regarding known mitigative measures. The sp ecification and implementation of measures, as would be described in an operational work plan, is beyond the scope of this document.

Table A1 . Summary of risk mitigation options for Chromatomyia horticola and Liriomyza strigata on perennial wall rocket from the UK Measure(s) Pests Efficacy
Pest-free areas or areas of low pest prevalence Both When conducted in compliance with international standards (e.g., IPPC, 2007: ISPM #s 4 and 10; NAPPO, 2004) this method meets requirements for appropriate level of protection Suppression /Control

program Both pests of concern could be managed, at least in part, Research required on effectiveness of methods proposed.Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 23 Measure(s) Pests Efficacy with a control program, whether cultural, chemical, or mechanical means, but the program should include monitoring and inspection to verify effectiveness. Control
must be used in combination
with other measures. Phytosanitary Certification Inspection and Monitoring Both, but must be used in
combination with other

measures. A phytosanitary certificate guides inspection efforts in UK and alerts U.S. inspectors to pests of concern with this commodity. Packinghouse procedures, including washing and visual culling Both, but must be used in
combination with other

measures. Research required on efficacy.

Point-of-entry sampling and inspection following guidelines in PPQ fruit and vegetables manual Both, but must be used in
combination with other

measures. Sample size must be adequate to
detect infestation

Irradiation, generic dose 400 Gy, combined with low pest prevalence Both Approved by APHIS; research may
be needed to determine tolerance of
wall rocket to irradiation Methyl bromide fumigation T101-n-2 Both, but must be used in
combination with other

measures. Approved by APHIS to treat leaf miners, on leafy vegetables. Research required to demonstrate efficacy on perennial wall rocket. Port-of-entry sampling and inspection combined with packinghouse procedures Both Given the medium pest risk potentials of both pests and the obvious damage they cause on leaves, a combination of packing house procedures and port-of-entry sampling and inspection may effectively mitigate risk.

A4. Literature Cited

7 CFR § 319.28. U.S. Code of Federal Regu lations, Title 7, Part 319.28 (7 CFR § 319.28 – Unshu oranges from Japan). 7 CFR § 319.56 28. U.S. Code of Federal Regula tions, Title 7, 319.56 28– Tomatoes from Spain, France, Morocco, and Western Sahara. 7 CFR § 319.56 24. U.S. Code of Federal Regula tions, Title 7, Part 319.56 24– Peppers from
Israel. 7 U.S.C. § 7701-7786. 2000. Plant Protection Ac t, Title 7 United States Code § 7701-7786.Perennial wall rocket from the U.K.

Rev. 002 October 07, 2008 24 Barclay, H. J., and J. W. Hargrove. 2005. Probability models to facilitate a declaration of pestfree status, with special reference to tsetse (Diptera: Glossinidae). Bull. Entomol. Res. 95(1):1-11. CABI. 2007. Crop Protection Comp endium. CD-ROM. CAB Interna tional (CABI), Wallingford,
UK. Cantwell, M. I., and R. F. Kasmire. 2001. Post harvest Handling Systems: Flower, Leafy, and Stem Vegetables. in A. A. Kader, (ed.). Postharvest Technology of Horticultural Crops. University of California, Oakland, CA. Dreistadt, S.H. 1994. Pests of Landscape Trees an d Shrubs: An Integrated Pest Management Guide. University of California, Davis, California. IPPC. 2007. International Standards For Phytosan itary Measures, 1 to 29 (2007 edition). Food and Agriculture Organization of the United Nati ons, Secretariat of the International Plant Protection Convention (IPPC ), Rome, Italy. 376 pp. NAPPO. 2003. Guidelines for the establishment, maintenance and verification of areas of low pest prevalence for insects. NAPPO Regional Standards for Phytosanitary Measures No.
20. Ottawa: Secretariat of the North Ameri can Plant Protection Or ganization (NAPPO). NAPPO. 2004. Guidelines for the establishment, ma intenance and verification of fruit fly pest free areas in North America. NAPPO Regional Standards for Phytosanitary Measures No.
17. Ottawa: Secretariat of the North Ameri can Plant Protection Or ganization (NAPPO). Rosen, D. 1990. Armoured Scale Insects: Their Biology, Natural Enemies and Control, Volume 4B. Elsevier, Amsterdam, Netherlands. Shea, K. 2006. Treatments for Fruits and Vegetabl es. Rules and Regulations. Final Rule. Federal Register: January 27, 2006. (FR Doc. 06-746) 71(18):4451-4464.
TDOA. 2003. Texas Rio Grande Valley Mexican Fruit Fly, Anastrepha ludens , (Loew) [sic] Protocol—2003/2004. Unpublished report. Texas Department of Agriculture (TDOA). PPQ. 2000. Guidelines for Pathway-Initiated Pest Risk Assessments, Version 5.02. United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine (PPQ). http://www.aphi s.usda.gov/ppq/pra/commodity/cpraguide.pdf. PPQ. 2006. Treatment Manual (05/2008-25). United Stat es Department of Agriculture, Animal and Plant Health Inspection Service, Plan t Protection and Quarantine (PPQ). 782 pp. PPQ. 2007. Agricultural Quarantine Inspect ion Monitoring (AQI M) Handbook (10/2007-05). United States Department of Agriculture, An imal and Plant Health Inspection Service, Plant Protection and Quarantine (PPQ). 196 pp. PPQ. 2008. Fresh Fruits and Vegetables Import Manual (06/2008-35). United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine (PPQ). 616 pp. Venette, R. C. and E. E. Davis. 2004. Chili thrips/yellow thrips, Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) Mini Pest Risk Assessment. Uni v. of Minnesota, St. Paul, MN. 31 pp.