Epitrix tuberis
(tuber flea beetle)

Pictures

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Identity

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Preferred Scientific Name

• Epitrix tuberis Gentner, 1944

Preferred Common Name

• tuber flea beetle

International Common Names

• English: flea beetle, tuber
• French: altise des tubercules

EPPO code

• EPIXTU (Epitrix tuberis)

Taxonomic Tree

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• Domain: Eukaryota
•     Kingdom: Metazoa
•         Phylum: Arthropoda
•             Subphylum: Uniramia
•                 Class: Insecta
•                     Order: Coleoptera
•                         Family: Chrysomelidae
•                             Genus: Epitrix
•                                 Species: Epitrix tuberis

Notes on Taxonomy and Nomenclature

Top of page Epitrix is a relatively large genus. There are more than 90 recognized species distributed across all biogeographic realms (Seeno and Andrews, 1972). Prior to Epitrix tuberis being described as a new species by Gentner (1944), potato flea beetles found in western states of the USA were considered to be Epitrix cucumeris, the potato flea beetle found in eastern states. Morphologically, E. tuberis was separated from E. cucumeris on the basis of its densely punctate pronotum, more widely separated eyes, subparallel elytral margins and subdepressed disc on the elytra.

Description

Top of page Eggs

The eggs are elliptical, 0.5 mm long and 0.2 mm wide, whitish, with a reticulate surface (Neilson and Finlayson, 1953).

Larva

First-instar larvae are 1 mm long, and white to cream. Final-instar larvae are slender and cylindrical, 5.3 mm long and 0.8 mm wide, whitish with a brown head (Neilson and Finlayson, 1953).

Pupa

Pupae are 2.5 mm long and 1.5 mm wide across the mesothorax, and uniformly white (Neilson and Finlayson, 1953).

Adult

The adults are 1.5-2.0 mm long, dull black to reddish-black with brown to yellow antennae. Legs are reddish and become lighter towards the tarsi (Seeno and Andrews, 1972). They have expanded hind femurs.

Distribution

Top of page E. tuberis is native to northern Colorado, USA. Gentner (1944) gives an account of its initial spread to Nebraska, Oregon and Washington. It has since spread to California, New Mexico, South Dakota and Wyoming (USA), and to British Columbia and Alberta (Canada), during the latter half of the twentieth Century. The species is still spreading.

See also CABI/EPPO (1998, No. 68).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Risk of Introduction

Top of page E. tuberis is categorized as an A1 quarantine pest by the European and Mediterranean Plant Protection Organization, Russia, South Africa and East Africa (EPPO, 2003). However, E. tuberis has never been detected in potato consignments, either nationally or internationally. Nevertheless, international spread could occur if adults were carried on rooted host plants or with eggs or pupae in any accompanying soil. The spread and establishment of E. tuberis into the Old World would lead to a generalized increase in the use of insecticides on potato, rather than the occasional targeted use against existing pests.

Hosts/Species Affected

Top of page E. tuberis is primarily associated with Solanaceae, with adults feeding on foliage and the larvae feeding on underground roots or tubers. Potato is the most significant host. Damage to other solanaceous crop hosts such as aubergine, Chinese lantern, ground cherry (Physalis spp.), tomato and tobacco (Hatch, 1971) is generally less important because adults feed on these only if potatoes are not available. In the spring and autumn, when no solanaceous crops may be available, adults may attack beans, cabbages, chard or cucumbers and various weeds.

Host Plants and Other Plants Affected

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Growth Stages

Top of page Flowering stage, Fruiting stage, Seedling stage, Vegetative growing stage

Symptoms

Top of page Adult feeding damage results in characteristic shot-like holes, 1.0-1.5 mm in diameter, in leaves, usually with 8 to 10 holes per leaf (Bérubé, 2000). The larvae burrow over and into the surface of tubers, causing tiny tunnels reaching up to 15 mm into the tuber. The tuber tissue around tunnels becomes brown and corky. As tubers swell, surface feeding or tunnels, formed early in the season, may become deep cracks in more mature tubers. The surface of tubers can also be rough with scabs and knobs (Campbell et al., 1989).

List of Symptoms/Signs

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Biology and Ecology

Top of page The date at which E. tuberis adults become active and emerge from overwintering sites in the soil varies depending on location but can range from late March or early April in southern locations to early May or July in eastern Washington state (Webster, 1945). Winter survival of adults depends on the depth and quality of the soil. E. tuberis survives well in soils of 20-30 cm (Davis and Landis, 1947) but can overwinter at depths of down to 60 cm (Campbell et al., 1989). It had been thought that adults overwintered exclusively at the margins of fields previously used to grow potatoes (Cusson et al., 1990) although it is now known that a proportion of the population can spend the winter in the middle of potato fields (Vernon and Thomson, 1991). Thus, E. tuberis may be more widely dispersed in a field of second-year potatoes than in a field of first-year potatoes. Adults prefer to feed and mate on the upper surfaces of leaves (Vernon et al., 1990) although, when windy, the beetles will not be as active on the upper surfaces (Bérubé, 2000). Adults tend to move under the leaves at night. Adults will fly considerable distances to find a host plant.

Mating takes place within 24 hours of emergence and there can be repeated copulation for up to 60 days. Vernon and Thomson (1993) measured the female: male ratio as 1: 0.94. After a pre-oviposition period of 5-6 days, eggs are laid over a period of 12-55 days, with an average of 38 days (Neilson and Finlayson, 1953). A number of authors have measured egg production in E. tuberis. Jones (1944) recorded females depositing 106 to 139 eggs over 17 to 30 days. Neilson and Finlayson (1953) recorded a wider variation in the number of eggs laid from 28 to over 200 with a mean of 87. The numbers of eggs laid varies markedly with the food plant of the adult. Females feeding on potato leaves produce the most eggs. In trials where caged adults were fed potato leaves then the diet switched to a less nutritious diet, egg production fell within 2 or 3 days, then increased when potato leaves were returned to the diet (Hill, 1946). Overwintered females will lay about 150 eggs whilst females in the summer generation will lay almost double this number (about 280 eggs). Eggs can be deposited in batches of 11-15 or can be laid singly (Campbell et al., 1989) in the soil or near the base of a host plant.

After incubation of 3-14 days, the eggs hatch and the larvae feed on roots and tubers for 2-4 weeks. The larvae can be found from late May throughout the potato-growing season, depending upon when the adults emerged. Pupation takes place in the soil, and lasts 4-10 days. The time of emergence, or the numbers of adults that emerge from different soil types, does not vary significantly according to the mineral, inorganic or organic nature of the soil in which eggs are deposited (Vernon and Thomson, 1993). Adults of the overwintered generation usually die in July (Kabaluk and Vernon, 2000) when there can be overlap with the next generation of adults that emerge between early July and early September. The second generation develops in 35-85 days, compared with 27-50 for the first. Second pupation starts at the beginning of August and may continue until the beginning of November. The F1 adults then emerge, and later enter diapause to overwinter in the soil. There are usually only two generations per year (Fulton and Banham, 1962) although, depending on the date of adult emergence in the spring or early summer, and larval food availability, there may be a complete or partial third generation in a year (Webster, 1945; Campbell et al., 1989).

In laboratory studies at 21°C, Jones (1944) calculated the average times for egg, larval, pre-pupal and pupal development to be 8.0, 15.3, 6.1 and 8.2 days, respectively.

Notes on Natural Enemies

Top of page No predators or parasites of E. tuberis are reported in British Columbia, Canada (Campbell et al., 1989). Climate is the major factor limiting the distribution and population size of flea beetles (Davidson and Lyon, 1979).

Means of Movement and Dispersal

Top of page Adult beetles can actively fly and will fly considerable distances to find a host plant. There is little flight before midday and there is no flight if the wind speed exceeds 3 m/s (Jones, 1944).

Vector Transmission

E. tuberis can mechanically transmit the pathogens causing potato blight (Phytophthora infestans), potato brown rot (Ralstonia solanacearum), potato scab (Streptomyces scabiei) and potato spindle tuber viroid (Leach, 1940; Hodgson et al., 1974; Davidson and Lyon, 1979). Feeding wounds can also serve as entry points for other potato pathogens.

Movement in Trade

Larvae could be transported in potato tubers, or with soil adhering to tubers. However, the larvae leave tubers when they are harvested (Fulton and Banham, 1962) which explains why E. tuberis have not been detected in potato consignments, either nationally or internationally. Seeno and Andrews (1972) suggested that the spread of E. tuberis into California, USA, in the early 1970s was likely to have been as larvae in the soil around tomato seedlings originating in Oregon.

Plant Trade

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Plant parts not known to carry the pest in trade/transport
Bark
Flowers/Inflorescences/Cones/Calyx
Fruits (inc. pods)
Leaves
Roots
Seedlings/Micropropagated plants
Wood

Wood Packaging

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Impact

Top of page Not surprisingly, most of the literature refers to damage caused to potatoes. E. tuberis is the most destructive of the five Epitrix species that feed on potatoes in North America (Gentner, 1944). The first published account of damage by E. tuberis, which at the time was considered as E. cucumeris, was in 1904 when larvae caused a loss of US $250,000 to potatoes in Colorado (Gentner, 1944). E. tuberis has been a major pest of potatoes in British Columbia since 1940 (Neilson and Finlayson, 1953). Adult leaf feeding damage is relatively insignificant compared to tuber damage caused by larvae (Bérubé, 2000). As overwintered adults lay fewer eggs than the second generation, the tunnelling of early or mid-season potatoes by the progeny of overwintered adults is usually of minor economic importance because the damage they cause can usually be peeled off. More serious economic damage is caused by the second generation of larvae whose population is much greater. Also, later in the season, suberization of tubers causes the larvae to tunnel deeper into the potato causing more serious cosmetic damage and consequent downgrading or rejection. One or two larvae can cause enough damage for a tuber to be rejected (Hill and Tate, 1942; Wallis, 1957). Up to 100 tunnels have been recorded in a single tuber (Gentner, 1944). Damage is greatest during hot, dry summers.

Giles (1987) suggests that overwintered E. tuberis populations should be kept below a density of one per 60 plants to prevent economic damage from occurring. In June or July, five or six adults in a sample of 25 sweeps will cause economic loss.

Adults feeding on tobacco leaves substantially reduce the market value of tobacco grown for cigar wrappers (Davidson and Lyon, 1979).

Diagnosis

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EPPO (2011) describes a diagnostic protocol for adult Epitrix cucumeris, E. similaris and E. tuberis infesting potato.

Similarities to Other Species/Conditions

Top of page E. tuberis is most similar to E. cucumeris and E. subcrinata. A specialist is required to identify specimens to species. Seeno and Andrews (1972) provide a key to Californian species of Epitrix.

Prevention and Control

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Cultural Control

Control measures should focus on controlling the first generation of E. tuberis ensuring only limited treatment is necessary later in the year. In locations where E. tuberis is known to occur, growers may adopt crop rotation to prevent the build-up of E. tuberis populations in the middle of fields (Kabaluk and Vernon, 2000). Growers should also avoid planting early potato varieties. This will cause emerging overwintered adults to have to feed on less nutritious food plants and greatly decrease the number of first-generation larvae available to infest later planted potatoes (Hill, 1946).

Economic Thresholds

To determine whether any chemical control measure should be applied, the number of adult E. tuberis should be monitored within a crop. When potato plants are less than 30 cm tall, a visual examination of plants lasting 5 to 20 seconds per plant is sufficient. Ten plants should be examined per row. The accuracy of monitoring E. tuberis using visual observations can be affected by observer experience and competence, the time spent observing each plant, the time of day, plant height and weather (Vernon et al., 1990). The greatest accuracy is achieved in the morning in calm weather. Plants over 30 cm in height should be sampled by sweep netting. Ten adjacent consecutive circular sweeps should be made enabling a sample to consist of sweeps from around 100 plants. Sweep netting is approximately 1-4% accurate (Bérubé, 2000).

There have been various thresholds suggested when action to control E. tuberis populations is warranted. Cusson et al. (1990) describe a practical action threshold of one beetle per 10 plants. Alternatively treatment may be necessary when a population averages three or four adults per 10 m row of potatoes (Berry, 1998). Bérubé (2000) suggests a threshold of one beetle per 100 plants.

Chemical Control

Insecticides can provide good control of E. tuberis (Antonelli and Davidson, 1991; Vernon and Mackenzie, 1991a, b). Synthetic pyrethroids are particularly effective. Chemicals routinely used against aphids on seed potatoes are also effective against adult E. tuberis and prevent leaf damage due to adult feeding. It is more difficult to control E. tuberis larvae since they are in the soil and insecticides incorporated into the soil may fail to provide adequate protection (Finlayson et al., 1979) although expensive granular formulations can be used. When overwintered populations are kept under control, localized sprays and targeting field edges, from where most overwintered adults will emerge, may be all that is necessary to provide effective control.

E. tuberis developed resistance to a number of organochlorines developed in the 1960s (Campbell and Finlayson, 1976). Organophosphates were used to provide control in the 1970s (Finlayson et al., 1972). Given the history of developing insecticide resistance, there is a possibility that resistance to modern insecticides may develop.

Phytosanitary Methods

Phytosanitary control to prevent the international spread of E. tuberis includes the restriction or prohibition of the importation of soil, or plants with soil, from countries where E. tuberis occurs (OEPP/EPPO, 1989). More specifically, when importing potato tubers from countries where E. tuberis is known to occur, appropriate phytosanitary measures should be used (OEPP/EPPO, 1990).

References

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Antonelli AL, Davidson RM Jr, 1991. Potato flea beetles: biology and control. Extension Bulletin - Cooperative Extension, College of Agriculture & Home Economics, Washington State University, No. EB1198:2 pp.

Arnett RH, 1985. American Insects: A Handbook of the Insects of America North of Mexico. New York, USA: Van Nostrand Reinhold.

Berry RE, 1998. Insects and Mites of Economic Importance in the Northwest, 2nd Edn. Oregon, USA: Oregon State University, 221 pp.

Bérubé C, 2000. Potato IPM: tuber flea beetle. World Wide Web page at http://nanaimo.ark.com/~cberube/tfb.htm.

Bousquet Y, 1991. Checklist of beetles of Canada and Alaska. Ottawa, Canada: Research Branch Agriculture Canada Publication.

CABI/EPPO, 1998. Distribution maps of quarantine pests for Europe (edited by Smith IM, Charles LMF). Wallingford, UK: CAB International, xviii + 768 pp.

Campbell CJ, Finlayson DG, 1976. Comparative efficacy of insecticides against tuber flea beetle and aphids in potatoes in British Columbia. Canadian Journal of Plant Science, 56(4):869-875

Campbell JM, Sarazin MJ, Lyons DB, 1989. Canadian beetles (Coleoptera) injurious to crops, ornamentals, stored products, and buildings. Ottawa, Ontario, Canada; Agricultural Canada, 491 pp.

Cusson M, Vernon RS, Roitberg BD, 1990. A sequential sampling plan for adult tuber flea beetles (Epitrix tuberis Gentner): dealing with "edge effects". Canadian Entomologist, 122(5-6):537-546

Davidson RH, Lyon WF, 1979. Insect pests of farm, garden, and orchard. Insect pests of farm, garden, and orchard. John Wiley & Sons Inc. New York USA, Ed. 7:xi+596 pp.

Davis EW, Landis BJ, 1947. Overwintering of potato flea beetles in the Yakima Valley. Journal of Economic Entomology, 40:821-824.

EPPO, 1990. Specific quarantine requirements. EPPO Technical Documents, No. 1008. Paris, France: European and Mediterranean Plant Protection Organization.

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm

European and Mediterranean Plant Protection Organization, 2011. Epitrix cucumeris, E. similaris and E. tuberis. Bulletin OEPP/EPPO Bulletin, 41(3):369-373. http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2338

Eyre D, Giltrap N, 2013. Epitrix flea beetles: new threats to potato production in Europe. Pest Management Science, 69(1):3-6. http://onlinelibrary.wiley.com/doi/10.1002/ps.3423/full

Finlayson DG, Brown MJ, Campbell CJ, Wilkinson ATS, Williams IH, 1972. Insecticides against tuber flea beetle on potatoes in British Columbia (Chrysomelidae: Coleoptera). Journal of the Entomological Society of British Columbia, 69:9-13.

Finlayson DG, Wilkinson ATS, MacKenzie JR, 1979. Efficacy of insecticides against tuber flea beetles, wireworms and aphids in potatoes. Journal of the Entomological Society of British Columbia, 76:6-9

Fulton HG, Banham FL, 1962. The tuber flea beetle in British Columbia. Canada Department of Agriculture Publication No. 938.

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

Giles KI, 1987. Estimation of an economic threshold for the tuber flea beetle, Epitrix tuberis Gentner (Coleoptera: Chrysomelidae), on potato in British Columbia. Burnaby, British Columbia, Canada: Department of Biological Sciences, Simon Fraser University, Pest Management Professional Paper.

Hatch MH, 1971. The beetles of the Pacific North-west, part V. Rhipiceroidea, Sternoxi, Phytophaga, Rhynchophora, and Lamellicornia. University of Washington Publication in Biology, 16.

Hill RE, 1946. Influence of food plants on fecundity, larval development and abundance of the tuber flea beetle in Nebraska. Research Bulletin of the Nebraska Experimental Station, 143, 1-16.

Hill RE, Tate AD, 1942. Life history and habits of potato flea beetle in Western Nebraska. Journal of Economic Entomology, 35:879-884.

Hodgson WA, Pond DD, Munro J, 1974. Diseases and pests of potatoes. Publication Canada Department of Agriculture, No.1492:70 pp.

Jones EW, 1944. Biological studies of two potato flea beetles in eastern Washington. Journal of Economic Entomology, 37(1):9-12.

Kabaluk JT, Vernon RS, 2000. Effect of crop rotation on populations of Epitrix tuberis (Coleoptera: Chrysomelidae) in potato. Journal of Economic Entomology, 93(2):315-322; 10 ref.

Kirk VM, 1975. A list of beetles of South Dakota. Brookings, USA: Agricultural Experiment Station, Technical Bulletin No. 42, 116.

Leach JG, 1940. Insect Transmission of Plant Diseases. New York, USA: McGraw-Hill.

Neilson CL, Finlayson DG, 1953. Notes on the biology of the tuber flea beetle, Epitrix tuberis Gentner (Coleoptera: Chrysomelidae) in the interior of British Colombia. The Canadian Entomologist, 85:31-32.

Seeno TN, Andrews FG, 1972. Alticinae of California, Part 1: Epitrix spp. (Coleoptera: Chrysomelidae). Coleopterists Bulletin, 26(2):53-61.

UK CAB International, 1987. Entyloma calendulae. [Distribution map]. Distribution Maps of Plant Diseases, April (Edition 1). Wallingford, UK: CAB International, Map 575.

Vernon RS, Mackenzie JR, 1991. Evaluation of foliar sprays against the tuber flea beetle, Epitrix tuberis Gentner (Coleoptera: Chrysomelidae), on potato. Canadian Entomologist, 123(2):321-331

Vernon RS, Mackenzie JR, 1991. Granular insecticides against overwintered tuber flea beetle, Epitrix tuberis Gentner (Coleoptera: Chrysomelidae), on potato. Canadian Entomologist, 123(2):333-343

Vernon RS, Mackenzie JR, Bartel DL, 1990. Monitoring tuber flea beetle, Epitrix tuberis Gentner (Coleoptera: Chrysomelidae) on potato: parameters affecting the accuracy of visual sampling. Canadian Entomologist, 122(5-6):525-535

Vernon RS, Thomson D, 1993. Effects of soil type and moisture on emergence of tuber flea beetles, Epitrix tuberis (Coleoptera: Chrysomelidae) from potato fields. Journal of the Entomological Society of British Columbia, No. 90:3-10

Vernon RS, Thomson DR, 1991. Overwintering of tuber flea beetles, Epitrix tuberis Gentner (Coleoptera: Chrysomelidae), in potato fields. Canadian Entomologist, 123(1):239-240

Wallis RL, 1957. Seasonal abundance and host plants of the tuber flea beetle in the Rocky Mountain region. Journal of Economic Entomology, 50(4):435-437.

Webster RL, 1945. Entomology. Bulletin of the Washington Agricultural Experimental Station, 470:36-40.

Wilcox JA, 1975. Check list of the beetles of Canada, United States, Mexico, Central America and the West Indies. Latham, New York, USA: Biological Research Institute of America, 1(7):116.

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Distribution Maps

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