Preferred name: Epitrix subcrinita
Authority: (Leconte)
Taxonomic position: Animalia: Arthropoda: Hexapoda: Insecta: Coleoptera: Chrysomelidae
Other scientific names: Epitrix subcarinata Crotch
Common names in English: western potato flea beetle
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Notes on taxonomy and nomenclature EPPO Categorization: A1 list
EU Categorization: Emergency measures
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EPPO Code: EPIXSU

As with most Epitrix, Epitrix subcrinita are primarily specialists on Solanaceae. Adults feed above ground on leaves while larvae feed on roots. Due to the subterranean habitat of the larvae most host records are based on adults feeding on foliage. Many of these records may be incidental as adult flea beetles are known to opportunistically feed on plants that they are not able to complete their lifecycle on (Clark et al., 2004). Under laboratory conditions Landis (1948) reported rearing E. subcrinita to adulthood on Capsicum frutescens, Solanum dulcamara, Solanum villosum, Solanum tuberosum, and a single larva was successfully reared on the non-solanaceous plant Cucurbita pepo.

Host list: Capsicum frutescens, Datura innoxia, Hyoscyamus niger, Leucophysalis nana, Lycium, Nicandra physalodes, Nicotiana alata, Nicotiana attenuata, Physalis alkekengi var. franchetii, Physalis lobata, Physalis longifolia, Physalis pubescens, Solanum carolinense, Solanum dulcamara, Solanum lycopersicum, Solanum melongena, Solanum nigrum, Solanum rostratum, Solanum triflorum, Solanum tuberosum, Solanum umbelliferum, Solanum villosum

E. subcrinita occurs throughout western North America including Canada, the United States, and Mexico. It is also reported from Guatemala and Peru, but due to the high diversity of species in the neotropics and the lack of any formal revisions these records should be treated with some caution until more taxonomic research is conducted. There are currently no known introduced populations of E. subcrinita.

North America: Canada (Alberta, British Columbia, Saskatchewan), Mexico, United States of America (Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, Wyoming)
Central America and Caribbean: Guatemala
South America: Peru

Due to the lesser agricultural impact of E. subcrinita compared to E. tuberis in North America its biology and control methods have not been as well studied, particularly in recent years. The distribution and seasonality of the two species in Washington state were studied in Webster (1932), seasonality of adults and tuber damage in British Columbia were studied by MacCarthy (1953), overwintering patterns were studied by Davis and Landis (1947), host rearing tests were performed by Landis (1948), and the life history of beetles from western Washington State were studied by Jones (1944). 

Adult E. subcrinita feed on leaves and produce ‘shot-hole’ symptoms while the larvae feed on roots and tubers. The Jones (1944) study is the most complete study of the biology of E. subcrinita. Under laboratory conditions the full life cycle of E. subcrinita was found to take an average of 49.2 days at approximately 21° C. In western Washington state they have two broods in July and September with the highest population in September. The beetles disperse by flying low to the ground on calm days mostly after noon.

E. subcrinita overwinters as adults, primarily in vegetative litter (Davis and Landis, 1947).

Symptoms

Both larvae and adults have chewing mouthparts. The adults riddle the leaves with small circular holes (1.0-1.5 mm diameter) that produce the characteristic ‘shot-hole’ symptom in the potato foliage, which is common to all Epitrix species. The adult insects can be detected on the foliage and jump promptly when approached. On windy days, they are less active.

Tuber damage by E. subcrinita is generally regarded as lesser than that of E. tuberis based on some studies (e.g. Jones, 1944), but other research has found that they are capable of creating damage comparable to that of E. tuberis as described by Hoerner & Gillette (1928) (MacCarthy, 1950). Different types of tuber injury can be produced by the larval feeding. The larva may tunnel underneath the skin, producing winding superficial trails (‘worm-tracks’) or may feed outside, penetrating only partially into the potato, almost at a right angle to the surface (Hoerner & Gillette, 1928), originating a pit which mostly penetrates up to 3 mm but may reach 6 mm, and later becomes filled with dark corky material, described as ‘slivers’ (Gentner, 1944; Wallis, 1953; Morrison et al., 1967). ‘Slivers’ may show on the tuber’s surface as a black point, or a raised rugose elevation in the skin (‘pimples’). The ‘worm-track’ type of injury is the most easily recognizable. Rough skin, deep cracks and scab-like lesions are sometimes associated with the larval attack.

Morphology

The genus Epitrix is a group of small flea beetles with uniform appearance which can be recognized by the presence of characteristic rows of setae on the elytra (Deczynski, 2016). The morphological identification to species is made by specialists, on the basis of the habitus and genitalia of the adult insects. The identification keys and illustrations presented in EPPO Standard PM 7/109 (2) (EPPO, 2017) allow E. subcrinita to be distinguished from the related potato species E. cucumeris, E. papa and E. tuberis. Out of these species E. subcrinita is distinctive due to its brown, brassy color.

The immature stages of E. subcrinita have not been formally described, but are similar in appearance to other Epitrix larvae such as E. cucumeris and E. tuberis.

Eggs

The eggs are whitish, spherical and minute.

Larva

The larvae are whitish with a brown head, slender, cylindrical, and about 5 mm long.

Pupa

The pupa is white and approximately 2.5 mm long.

Adult

The adults are small brassy dark brown beetles with rows of short white hairs across the elytra, 1.76-2.27 mm long, with testaceous antennae. The hind femurs are enlarged, adapted to jumping.

Detection and inspection methods

Detection is made by visual inspection of the foliage of potato or other host plants, looking for shot-hole symptoms and adult flea beetles. On potato, the tubers are inspected visually for symptoms of larval injury (EFSA, 2019). The ‘worm-track’ type of injury is the most easily recognizable. The ‘slivers’ are best detected if the potato tubers are peeled with a knife.

The identification of the species requires the collection of insect specimens for analysis. Adult specimens may be collected with a sweep-net or with a mouth aspirator. The larvae are very difficult to detect and collect because of their small size and translucent color, and also because of their feeding behavior. When present at potato harvest, the larvae may be hidden inside the ‘worm tracks’, or may expose the terminal part of the abdomen protruding outside the tuber, while feeding.

The identification of all E. subcrinita stages can be made reliably by non-specialists, using molecular methods (DNA barcoding on cytochrome c oxidase subunit I (COI) gene) (EPPO, 2016a; Germain et al., 2013; Mouttet et al., 2016). The reference sequences of these species are available in EPPO-Q-bank and BOLD databases.

Adult E. subcrinita can fly, and this is one of the main means for local dispersal of the species (Jones, 1944). Additionally, some hosts of E. subcrinita can be common weeds in disturbed areas such as Solanum nigrum and S. dulcamara. Populations on these hosts can serve as reservoirs to infest agricultural areas, and due to the close proximity of these weeds to human dwellings their spread may be aided by human transport and corridors of host plants such as roadside weeds.

The main pathway for long distance spread is through the commercial transport of potato tubers (seed or ware potatoes), when associated with soil and plant debris (EPPO, 2016b; 2017). 

When potatoes are harvested in an infested field, adults, pupae and larvae of E. subcrinita may be present in the stubble, soil, and tubers. Adult beetles may be carried passively on the surface of potatoes, or with the soil adhering to potato tubers. This possibility would be higher in exports of seed potatoes, because potatoes are not washed.

The soil of host plants for planting could also contain and spread immature stages of the pest (EPPO, 2011).

Economic impact

The amount of damage caused by E. subcrinita to potato tubers has been debated due to conflicting results. The tuber flea beetle E. tuberis which often co-occurs with E. subcrinita is known to make tunnels in the tubers which can reduce the value of the crops. Some research has indicated that this damage is associated with E. tuberis and weak or absent when only E. subcrinita is present (Webster 1932, Jones 1944, Fulton & Branham 1960). However, under laboratory conditions MacCarthy (1960) found that E. subcrinita produced tuber damage comparable to that of E. tuberis.

The reduction of the leaf area by adult feeding should have a minor impact on yield losses, because it is compensated by the fast growth of the potato plants, as demonstrated experimentally by Senanayake et al. (1993) for E. cucumeris. However, young plants grown after the emergence of the beetles can be killed by high populations with significant feeding (Webster & Baker, 1929). 

Control

Contemporary methods of control for E. subcrinita have not been studied due to its minor status as a pest in North America compared to the more destructive E. tuberis. Methods of control used for E. tuberis and other Epitrix species, such as IPM strategies combining cultural measures for reducing the population of overwintered adults with insecticide treatments, may work for E. subcrinita as well. E. subcrinita tend to overwinter in vegetative litter while E. tuberis mainly overwinters in the soil, so destruction of litter may also help to reduce winter survival (Davis and Landis, 1947).

Phytosanitary risk

The present distribution of E. subcrinita in North America indicates that the species would find suitable climatic conditions in the EPPO region. 

It is difficult to predict the potential economic impact of E. subcrinita due to the uncertainty of how much tuber damage they will cause in the field. If their damage is minimal then their impact would be comparable to that of Epitrix cucumeris, but if they exhibit tuber tunnelling behaviours then their impacts would be closer to E. tuberis. Since there are no known introduced populations of E. subcrinita it is uncertain how they would behave in a novel environment. 

One could expect E. subcrinita to develop one or two generations per year in many of the potato-growing areas of Central and Northern Europe (EPPO, 2011), and possibly also in southern regions. While E. subcrinita could be controlled chemically, its presence could lead to a generalized use of insecticides on potato, rather than the occasionally targeted use against Leptinotarsa decemlineata, as at present in most EPPO countries. The problem would arise even more acutely in countries where L. decemlineata has not been introduced (EPPO, 2011). Furthermore, the control of E. subcrinita would be critical in several EPPO countries, namely in a majority of the EU countries where insecticides used in North America are no longer authorized.

The import of seed potatoes from third countries is prohibited in several EPPO member countries, namely in the EU (EU, 2016), but sometimes authorized under derogation procedures, e.g. from Canada into the EU (EU, 2003).

Following the accidental introduction of the species E. papa and E. cucumeris in Portugal and Spain, E. subcrinita is subject, together with E. cucumeris, E. papa, and E. tuberis, to measures by several EPPO member countries to prevent their introduction and spread within the EPPO region. 

Specific requirements related to E. cucumeris, E. papa, E. subcrinita and E. tuberis are recommended for seed potatoes (except micropropagative material and minitubers) and ware potatoes to be imported from third countries. According to EPPO Standard PM 8/1 (EPPO, 2017) seed potatoes should be washed or brushed so that they are free from plant debris with no more than 0.1% w/w of soil remaining; and where appropriate subject to transitional arrangements (pest-free area for E. subcrinita and origin from a pest-free potato production and distribution system for the pest, according to EPPO Standard PM 3/61 (EPPO, 2019)). Ware potatoes should either (a) originate from a pest-free area for E. subcrinita and E. tuberis according to EPPO Standard PM 3/61 (EPPO, 2019) or (b) measures as described in EPPO Standard PM 9/22 (EPPO, 2016b) for E. subcrinita should be implemented to ensure that there is no risk of spreading this pest, or (c) there should be absence of plant debris with no more than 0.1% w/w of remaining soil.

Additional requirements are recommended for soil or growing medium attached to rooted host plants from countries where E. subcrinita occurs (removal of soil and growing media, or production in a pest free area, or in a pest-free place under protected conditions, or production under screened greenhouse conditions with appropriate monitoring in the framework of a bilateral agreement) (EPPO, 2011).

Bienkowski AO & Orlova-Bienkowskaja MJ (2017) World checklist of flea beetles of the genus Epitrix (Coleoptera: Chrysomelidae: Galerucinae: Alticini). Zootaxa 4268, 523-540. 

Clark SM, LeDoux DG, Seeno TN,  Riley EG,  Gilbert AJ, Sullivan JM (2004) Host plants of leaf beetle species occurring in the United States and Canada. Special Publications of the Coleopterists Society 2, 476 pp.

Davis EW & Landis BJ (1947) Overwintering of potato flea beetles in the Yakima Valley. Journal of economic entomology 40, 821-824.

Davis EW, Landis BJ & Randall TE (1948) A potato resistant to tuber infestation by flea beetle larvae. Journal of Economic Entomology 41, 10-12.

Deczynski AM (2016) Morphological systematic of the nightshade flea beetles Epitrix Foudras and Acallepitrix Bechyné (Coleoptera: Chrysomelidae: Galerucinae: Alticini) in America north of Mexico, PhD thesis, Clemson University (USA).

Döberl M (2000) Beitrag zur Kenntnis der Gattung Epitrix Foudras, 1860 in der Paläarktis. Mitteilungen des Internationalen Entomologischen Vereins 25, 1–23.

EFSA (2019) Schenk M, Camilleri M, Diakaki M & Vos S. Pest survey card on Epitrix cucumeris, Epitrix papa, Epitrix subcrinita and Epitrix tuberis. EFSA supporting publication EN-1571. https://doi.org/10.2903/sp.efsa.2019.EN-1571 

EPPO (2011) Pest Risk Analysis for Epitrix species damaging potato tubers. EPPO, Paris (FR). http://www.eppo.int/QUARANTINE/Pest_Risk_Analysis/PRA_intro.htm [accessed on 17 February 2016].

EPPO (2016a) EPPO Standard PM 7/129 (1) DNA barcoding as an identification tool for a number of regulated pests. EPPO Bulletin 46, 501-537. https://doi.org/10.1111/epp.123494

EPPO (2016b) EPPO Standard PM 9/22(1) National regulatory control system for Epitrix species damaging potato tubers. EPPO Bulletin 46, 556-566. https://doi.org/10.1111/epp.12349 

EPPO (2017) EPPO Standard PM 7/109(2) Epitrix cucumeris, Epitrix papa, Epitrix subcrinita, Epitrix tuberis. EPPO Bulletin 47, 10–17. https://doi.org/10.1111/epp.12362 

EPPO (2017) EPPO Standard PM 8/1(2) Potato Commodity-specific phytosanitary measures. EPPO Bulletin 47, 487–503. https://doi.org/10.1111/epp.12418 

EPPO (2019) EPPO Standards PM 3/61(2) Pest-free areas and pest-free production and distribution systems for quarantine pests of potato. EPPO Bulletin 49, 480–481. https://doi.org/10.1111/epp.12617 

EU (2003) Commission Decision 2003/61/EC of 27 January 2003 authorising certain Member States to provide for temporary derogations from certain provisions of Council Directive 2000/29/EC in respect of seed potatoes originating in certain provinces of Canada. Official Journal of the European Communities L23/31.

EU (2016) 2016/2031 of the European Parliament and the Council of 26 October 2016 on protective measures against pests of plants. Official Journal of the European Union L317/4.

Fulton HG & Banham FL (2019) A brief history of the tuber flea beetle, Epitrix tuberis Gent., in British Columbia. Journal of the Entomological Society of British Columbia 57, 47-49.

Gentner LG (1944) The black flea beetles of the genus Epitrix identified as cucumeris. Proceedings of the Entomological Society of Washington 46, 137-149.

Germain J-F, Chatot C, Meusnier I, Artige E, Rasplus J-Y & Cruaud A (2013) Molecular identification of Epitrix potato flea beetles (Coleoptera: Chrysomelidae) in Europe and North America. Bulletin of Entomological Research 103, 354-62. https://doi.org/10.1017/S000748531200079X 

Jones EW (1944) Biological studies of two potato flea beetles in eastern Washington. Journal of Economic Entomology 37, 9-12.

Landis BJ (1948) Plants upon which tuber flea beetles and western potato flea beetles propagate. Journal of Economic Entomology 41, 6-10.

MacCarthy HR (1950) A comparison of potato tuber damage by two flea beetles: Epitrix tuberis Gent and Epitrix subcrinita Lec. Journal of the Entomological Society of British Columbia 47, 42.

MacCarthy HR (1953) Further evidence of tuber damage by the western potato flea beetle. Journal of Economic Entomology, 46(4), 688-689.

Morrison H, Gentner L, Koontz R & Every R (1967) The changing role of soil pests attacking potato tubers. American Potato Journal 44, 137–144.

Mouttet R, Germain JF & Cruaud A (2016) Molecular identification of Epitrix potato flea beetles (Coleoptera: Chrysomelidae) in Europe and North America – CORRIGENDUM. Bulletin of Entomological Research 109, 559-559. http://dx.doi.org/10.1017/S0007485316000559

Seeno TN & Andrews FG (1972) Alticinae of California, Part I: Epitrix Spp. (Coleoptera: Chrysomelidae). The Coleopterists Bulletin 26, 53-61. Retrieved May 22, 2020, from www.jstor.org/stable/3999405 

Senanayake DG, Pernal SF & Holliday NJ (1993) Yield responses of potatoes to defoliation by the potato flea beetle (Coleoptera: Chrysomelidae) in Manitoba. Journal of Economic Entomology 86, 1527-1532.

Wallis RL (1957) Seasonal abundance and host plants of the tuber flea beetle in the Rocky Mountain region. Journal of Economic Entomology 50, 435-437.

Webster RL (1932) Injury and distribution of potato flea-beetle in Washington. Journal of Economic Entomology 25, 976-980.

Webster RL, & Baker WW (1929) Potato flea-beetles in Washington Epitrix subcrinita LeConte: Epitrix cucumeris Harris. Journal of Economic Entomology 22, 897-900.

This datasheet was prepared in 2020 by Anthony Deczynski. His valuable contribution is gratefully acknowledged.

EPPO (2024) Epitrix subcrinita. EPPO datasheets on pests recommended for regulation. https://gd.eppo.int (accessed 2024-12-22)

This datasheet was first published online in 2020. It is maintained in an electronic format in the EPPO Global Database. The sections on 'Identity', ‘Hosts’, and 'Geographical distribution' are automatically updated from the database. For other sections, the date of last revision is indicated on the right.