The Colorado potato beetle (Leptinotarsa decemlineata), also known as the Colorado beetle, the ten-striped spearman, the ten-lined potato beetle, or the potato bug, is a major pest of potato crops. It is about long, with a bright yellow/orange body and five bold brown stripes along the length of each of its elytra. Native to the Rocky Mountains, it spread rapidly in potato crops across America and then Europe from 1859 onwards.
Taxonomy
The Colorado potato beetle was first observed in 1811 by Thomas Nuttall and was formally described in 1824 by American entomologist Thomas Say. The beetles were collected in the Rocky Mountains, where they were feeding on the buffalo bur, Solanum rostratum. The genus Leptinotarsa is assigned to the chrysomelid beetle tribe Chrysomelini (in subfamily Chrysomelinae).
Description
Adult beetles typically are in length and in width. They weigh 50-170 mg. The beetles are orange-yellow in colour with 10 characteristic black stripes on their elytra. The specific name decemlineata, meaning 'ten-lined', derives from this feature. Adult beetles may, however, be visually confused with L. juncta, the false potato beetle, which is not an agricultural pest. L. juncta also has alternating black and white strips on its back, but one of the white strips in the center of each wing cover is missing and replaced by a light brown strip.
The orange-pink larvae have a large, 9-segmented abdomen, black head, and prominent spiracles, and may measure up to in length in their final instar stage. The beetle larva has four instar stages. The head remains black throughout these stages, but the pronotum changes colour from black in first- and second-instar larvae to having an orange-brown edge in its third-instar. In fourth-instar larvae, about half the pronotum is coloured light brown. This tribe is characterised within the subfamily by round to oval-shaped convex bodies, which are usually brightly coloured, simple claws which separate at the base, open cavities behind the procoxae, and a variable apical segment of the maxillary palp.
Distribution
The beetle is most likely native to the area between Colorado and northern Mexico, and was discovered in 1824 by Thomas Say in the Rocky Mountains. It is found in North America, and is present in every state and province except Alaska, California, Hawaii, and Nevada. It now has a wide distribution across Europe and Asia, totalling over 16 million km2.
Its first association with the potato plant (Solanum tuberosum) was not made until about 1859, when it began destroying potato crops in the region of Omaha, Nebraska. Its spread eastward was rapid, at an average distance of 140 km per year. By 1874 it had reached the Atlantic Coast. From 1871, American entomologist Charles Valentine Riley warned Europeans about the potential for an accidental infestation caused by the transportation of the beetle from America. From 1875, several Western European countries, including Germany, Belgium, France, and Switzerland, banned imports of American potatoes to avoid infestation by L. decemlineata.
These controls proved ineffective, as the beetle soon reached Europe. In 1877, L. decemlineata reached the United Kingdom and was first recorded from Liverpool docks, but it did not become established. Many further outbreaks have occurred; the species has been eradicated in the UK at least 163 times. The last major outbreak was in 1976. It remains as a notifiable quarantine pest in the United Kingdom and is monitored by DEFRA to prevent it from becoming established. A cost-benefit analysis from 1981 suggested that the cost of the measures used to exclude L. decemlineata from the UK was less than the likely costs of control if it became established.