Taxonomic information	Current valid scientific name: Nacobbus aberrans (Thorne, 1935) Thorne and Allen, 1944 Synonyms: Anguillulina aberrans Thorne, 1935, Nacobbus batatiformis Thorne and Schuster, Nacobbus serendipiticus Franklin, Nacobbus serendipiticus bolivianus Lordello, Zamith and Boock ame used in the EU legislation: Nacobbus aberrans (Thorne) Thorne and Allen Name used in the Dossier: – Order: Rhabditida Family: Pratylenchidae
Group	Nematoda
EPPO code	NACOBA
Regulated status	EU status: Annex IAI Non‐ EU: A1 list: Brazil (2018), Paraguay (1995), Uruguay (1995), Bahrain (2003), Jordan (2013), Uzbekistan (2008), Georgia (2018), Russia (2014), Turkey (2016), Ukraine (2010), EPPO (1981) A2 list: Argentina (2019) Quarantine pest: Morocco (2018), Israel (2009), Norway (2012)
Pest status in Peru	Present, restricted distribution (EPPO, online)
Pest status in the EU	Absent
Host status on Ullucus tuberosus	In CABI (2020) and EFSA Journal (2018), ulluco, Ullucus tuberosus is recorded as a host of Nacobbus aberrans.
PRA information	Nacobbus aberrans, the false root‐knot nematode is a species complex (=N. aberrans sensu lato) comprising more than one species (Reid et al., 2003; Vovlas et al., 2007). It is a root endoparasite with mobile (juveniles and immature adults) and immobile developmental stages (sedentary mature females). According to the host preferences N. aberrans is classified into three groups (potato, sugar beet and bean group) (Franco and Main, 2008, EFSA, 2018). According to the EFSA Scientific Opinion on pest categorization of N. aberrans published in 2018, all populations of N. aberrans sensu lato are highly polyphagous and could attack and cause severe damage to many important host plants in the EU. Yield losses reported on crops infected by N. aberrans depend on initial density, climatic conditions, soil type and crop cultivar and average 65% for potato in the Andean region of South America, and 55% and 36% for tomato and bean, respectively in Mexico (Inserra et al., 2004; EFSA, 2018). The false root‐knot nematode is adapted to different climatic conditions and has been reported from temperate and subtropical regions of North (USA, Mexico) and South America (Argentina, Bolivia, Chile, Ecuador and Peru) (EFSA Journal, 2018). South American populations are able to develop at temperatures of 10–25°C (Anthoine et al., 2006). N. aberrans is widely distributed in the areas of oca and ulluco production (Bridge et al., 2005) and is considered the most common pest of potato and other Andean crops including ulluco in the temperate highlands of the Andean regions (Manzanilla‐Lopez et al., 2002; Franco and Main, 2008). In the Andes, it is associated with potatoes at temperatures of 15–18°C (Mai et al., 1981). Although ulluco roots can be heavily attacked, information on the economic impact of N. aberrans as a limiting factor of ulluco production is poor (Bridge et al., 2005). According to Bridge et al. (2005), the response of ulluco to the attack of N. aberrans as well as Atalodera andina indicates the possibility of an available resistant gene base. In the answers provided by Peru to the questions raised by the working group, it is stated that distribution of false root‐knot nematode in Peru is restricted. The nematode causes damage to potatoes; however, its attacks are rare. According to SENASA, no false root‐knot nematode attacks were detected on ulluco. N. aberrans is quarantine plant parasitic nematode pest posing a high risk for the EU agriculture if introduced either with infested plants (plants for planting) or soil attached to plants. Unwashed/unbrushed ulluco tubers are contaminated with soil and could pose a significant risk of introduction of plant parasitic nematodes, including N. aberrans into the EU. Cleaned ulluco tubers intended for consumption, that are essentially free from soil present a lower risk for quarantine plant parasitic nematodes, but washing (or brushing) does not reduce the risk of nematodes associated with tubers infected with certain endoparasitic nematodes, including N. aberrans. Although N. aberrans may be present inside ulluco tubers, the risk which is generally associated with the end use of ulluco is considered low as the ulluco will be processed for consumption – tubers will be heat treated. Plant residues like peels or culled tubers may, however, still pose certain risk, if they are not properly removed of or treated.
Other relevant information for the assessment
Symptoms	Main type of symptoms	The above‐ground symptoms of N. aberrans attack are not very specific. They appear as irregular patchy areas of infested plants manifested in poor growth, wilting and leaf chlorosis. The symptoms caused by the false root‐knot nematode attack are more obvious on the roots, on which root galls are developed mainly along the root axis and at the root tips. These galls are similar to those caused by Meloidogyne spp. Gall shape may vary with nematode density, biological race and root size (Brodie et al., 2005). Galls are not so pronounced on tubers.
	Presence of asymptomatic plants	Tubers and roots inhabited by the vermiform and motile stages of N. aberrans escape any visual inspection. The absence of symptoms (galls) in certain plants is possible and the presence of N. aberrans within tubers of ulluco may be overlooked (EFSA, 2018).
	Confusion with other pathogens/pests	Galls formed by N. aberrans may be confused with symptoms caused by root‐knot nematodes (Meloidogyne spp.). For proper nematode identification, it is therefore necessary to use morphologic characters or molecular tools.
Host plant range	N. aberrans is a highly polyphagous nematode parasitising more than 90 plant species from 21 botanical families including potatoes (Solanum tuberosum L.), sugar beet (Beta vulgaris L.), tomato (Solanum lycopersicum L.) and beans (Phaseolus vulgaris L.) (EFSA Journal, 2018). Other hosts (EFSA Journal, 2018): Amaranthaceae (Amaranthus sp., A. hybridus L., A. hypochondriacus L., A. quitensis H.B. & K., A. retroflexus L., A. spinosus L., Bassia (=Kochia) scoparia (L.) Voss); Apiaceae (Daucus carota L.); Asteraceae (Eupatorium azangaroense Sch. Bip., Baccharis salicifolia (Ruiz and Pav) Pers., Gaillardia pulchella Fouger, Lactuca sativa L., Simsia amplexicaulis Pers., Tagetes mandonii Sch. Bip., Taraxacum officinale L., Tragopogon porrifolius L.); Basellaceae (Ullucus tuberosus Caldas); Brassicaceae (Brassica campestris L., B. juncea (L.) Czern. & Cass. (=B. japonica), B. napus (L.) Rchb. Napobrassica Group, B. nigra (L.) Koch, B. oleracea L., B. rapa L., Calandria albis Kunth., Capsella bursa‐pastoris (L.) Medic., Matthiola sp., Raphanus sativus L., Sisymbrium irio L.); Cactaceae (Coryphantha vivipara Britt. and Rose, Escobaria (=Mammillaria) vivipara (Nutt.) F. Buxb, Mamillaria vivipara (Nutt.) Haw., Opuntia fragilis Haw., O. macrorhiza Engelm. (= tortispina Nutt.); Caryophyllaceae (Spergula arvensis L., Stellaria media (L.) Vill.; Chenopodiaceae (Atriplex confertifolia (Torr. and Fr_em.) S. Wats, Chenopodium album L., Chenopodium ambrosioides L., Ch. murale L., Ch. nuttalliae Saff., Ch. quinoa Willd., Salsola kali L. var tenuifolia Tausch, Spinacia oleracea L.); Convolvulaceae (Ipomoea batatas Lam.); Cucurbitaceae (Cucumis sativus L., Cucurbita maxima Duchesne, C. pepo L.); Fabaceae (Physalis spp., Pisum sativum L., Trifolium sp.); Lamiaceae (Origanum vulgare L.); Malvaceae (Abelmoschus (=Hibiscus) esculentus Moench, Alcea rosea L., Anoda cristata (L.) Schlecht., Malva parviflora L.); Nyctaginaceae (Mirabilis jalapa L.); Oxalidaceae (Oxalis tuberosa Molina); Plantaginaceae (Plantago lanceolata L.); Polygonaceae (Fagopyrum esculentum Moench.); Portulaceae (Portulaca oleracea L.); Solanaceae (Solanum sp., Capsicum annuum L., C. annuum L. var. Glabriusculum (Dunal) Heiser & Pickersgill (=C. baccatum L.), C. frutescens L., C. pendulum Willd., C. pubescens Ruiz & Pav., Cestrum roseum H.B. & K., Cyphomandra betacea Sendt., Datura ferox L., D. stramonium L., Nicotiana tabacum L., Solanum acaule, S. andigena Juz. and Buk., S. chacoense Bitter, Solanum chmielewskii (C.M.Rick, Kesicki, Fobes & M.Holle) D.M.Spooner, G.J.Anderson & R.K.Jansen, Solanum hirsutum, Solanum hybrids, Solanum infundibuliforme, Solanum megistacrolobum, S. melongena L., S. nigrum L., Solanum peruvianum Mill., Solanum pimpinellifolium Mill., S. rostratum Dun., S. triquetrum Cav., Solanum sparsipilum); Tropaeolaceae (Tropaeolum tuberosum Ruiz. et Pav.); Zygophyllaceae (Tribulus terrestris L.).
Pathways	– Plants, plants for planting (tubers, roots) – Subterranean plant parts intended for consumption (e.g. edible ulluco tubers) – Soil and growing media as such or attached to plants – Soil and growing media attached to machinery, tools, packaging materials etc.
Surveillance information	In the dossier (Sections 1 and 2), it is stated that pest surveys are permanently carried out on various crops, including Andean tubers, such as ulluco. Staff of SENASA periodically inspect the fields for the presence of symptoms caused by specific pests and take samples that are sent to appropriate laboratory at SENASA. The results of the laboratory are sent to the nearby SENASA headquarters so that it communicates with the producer and appropriate management measures are taken. According to Peru, there are no information on nematode ‘outbreaks’ on ulluco. The nematodes are therefore considered minor pests of ulluco.