Taxonomic information	Current valid scientific name: Eulecanium excrescens Synonyms: Lecanium excrescens Name used in the EU legislation: – Order: Hemiptera Family: Coccidae Common name: excrescent scale, wisteria scale Name used in the Dossier: Eulecanium excrescens
Group	Insects
EPPO code	–
Regulated status	The pest is neither regulated in the EU nor listed by EPPO. Eulecanium excrescens is listed in the UK Plant Health Risk Register but archived in 2020 as considered to pose a low risk to the UK (DEFRA, online).
Pest status in the UK	Eulecanium excrescens is present in the UK as introduced species since at least 2000 (MacLeod and Matthews, 2005 Dossier Section 5.0) with restricted distribution to the Greater London Area (e.g. Bishops Strotford, Hornchurch, London, Maidenhead, Roystone, Wickford) where it is considered an ‘established exotic pest' (MacLeod and Matthews, 2005). Outside this area, E. excrescens has been reported in a few localities of the neighbouring county of Hertfordshire (Salisbury et al., 2010) and more recently (2021) in Gloucester (GBIF, online). According to the Dossier Section 5.0, the pest is present in the UK: not widely distributed and not under official control.
Pest status in the EU	Eulecanium excrescens is absent from the EU (García Morales et al., online).
Host status on Acer	Acer pseudoplatanus is a host for E. excrescens (Malumphy, 2005).
PRA information	Pest Risk Assessments available: – CSL Pest Risk Analysis for Eulecanium excrescens (MacLeod and Matthews, 2005) – Scientific opinion on the commodity risk assessment of Malus domestica plants from United Kingdom (EFSA PLH Panel, 2023); – UK Risk Register Details for Eulecanium excrescens (DEFRA, online).
Other relevant information for the assessment
Biology	Eulecanium excrescens is a polyphagous soft scale native to Asia (China) and introduced in the US, where it is present in California, Connecticut, New York, Oregon and Pennsylvania (MacLeod and Matthews, 2005; Malumphy, 2005); in Europe it is present only in the UK (Malumphy, 2005; GBIF, online). It is absent from Africa, Central and South America and Oceania (García Morales et al., online). There is no scales have specific information about the number of life stages of E. excrescens. However, soft three development stages: eggs, nymphs (two or three instars) and adult (Camacho and Chong, 2015). The nymphs of E. excrescens are orange or pale brown with rectangular whitish encrustations on their surface; the first‐instar nymphs are mobile (crawlers) and disperse actively by crawling away from their mothers or passively by wind or phoresis. Both nymphs and adults of soft scales (except adult males when present) feed on twigs and leaves sucking phloem and often producing large amount of honeydew (Camacho and Chong, 2015). In the UK, E. excrescens is a parthenogenetic species and has one generation per year; the nymphs overwinter and reach maturity in April. The large globular adult females (10–13 mm) are dark brown, covered by grey powdery wax. They lay eggs in May, each female lays about 2,000 eggs. The crawlers emerge in May–June and settle to the underside of leaves; in autumn, before the leaf fall, they move from the leaves to the woody parts to overwinter (Malumphy, 2005).
	Eulecanium excrescens can spread naturally by crawling of first‐instar nymphs on very short distances, and passively via air currents and wind of the same development stage. No specific information on the natural dispersal of E. excrescens is available, which is considered ‘likely slow’ (MacLeod and Matthews, 2005). However, it is known that some soft scale crawlers may be dispersed by wind to 55 m to > 4 km (Camacho and Chong, 2015). Passive transport of nymphs on medium–long distance is also possible by phoresis mostly with birds and ants, and human‐assisted spread may occur via infested plants.
Symptoms	Main type of symptoms	Only a non‐specific leaf loss and slow dieback may be sometimes observed as a symptom on plants strongly attacked by E. excrescens, as a result of large amount of sap removed by the scale. The main evidence of the pest attack is the presence of colonies of adults and nymphs producing honeydew on the stem and branches. Adults of E. excrescens are large size (10–13 mm in length/diameter), and this make the pest easy to detect, since no other soft scale species raises that size in the UK.
	Presence of asymptomatic plants	There is no information on the presence of asymptomatic plants, although initial infestations caused by a few insects may go unnoticed.
	Confusion with other pests	In the UK, other six species of Eulecanium are found (Malumphy, 2005) but none raises the size of adult females of E. excrescens, therefore no confusion with other species is possible at that stage. The nymphs may be confused with those of other Eulecanium, as well as with other soft scale species and need to be examined in laboratory for identification with the support of diagnostic keys.
Host plant range	Eulecanium excrescens feeds on a wide host plant range including Acer pseudoplatanus, Juglans regia, Malus spp., Prunus dulcis, P. armeniaca, P. persica, Prunus spp., Pyrus communis, Ulmus spp. and Zelkova serrata. In the UK, the scale also attacks some vines species as Ceanothus sp., Podranea ricasoliana, Parthenocyssus quinquefolia, P. tricuspidata and mostly Wisteria spp. The latter appears to be the preferred host genus as it is in the US (Malumphy, 2005; Salisbury et al., 2010).
Reported evidence of impact	Eulecanium excrescens is a sap sucker able to damage host plants by removing large quantities of sap, so causing weakening, leaf loss and dieback; large amount of honeydew is also produced, reducing photosynthesis and disfiguring ornamental plants in parks and gardens (MacLeod and Matthews, 2005). In China, E. excrescens is regarded as a pest damaging fruit orchards of Malus, Prunus and Pyrus (MacLeod and Matthews, 2005). In the US, the scale is included in the list of pests harmful to hazelnut (Corylus avellana) production in Oregon (Murray and Jepson, 2018); not regarded as a pest of economic importance in California (MacLeod and Matthews, 2005). Impact on ornamental Wisteria may be relevant in case of heavy infestation, as these vines are often cultivated in gardens and for covering walls and buildings in the UK. No information on damage on Acer was found.
Evidence that the commodity is a pathway	The pest occurs on bark. Although the source of infestations in the UK is unknown (MacLeod and Matthews, 2005) and no interception is recorded (EUROPHYT/TRACES, online), plants for planting (except seeds bulbs and tubers) are pathways for E. excrescens according to DEFRA (online). The commodities including dormant plants are pathways for the pest.
Surveillance information	Eulecanium excrescens is not under official control and surveillance in the UK, as does not meet criteria of quarantine pest for Great Britain (Dossier Section 5.0).