Colorado potato beetle
- "Potato beetle" redirects here. This may also refer to the Chrysomelid beetle Lema trilineata (the three-lined potato beetle).
|Colorado potato beetle|
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 approximately 10 millimetres (0.39 in) long, with a bright yellow/orange body and five bold brown stripes along the length of each of its elytra.
They vary somewhat in size but adult beetles average 6-11 mm in length and 3 mm in width. The beetles are orange-yellow in colour with black markings, the size and number of which vary in different individuals. The elytra on the dorsum of the thorax and abdomen display ten characteristic black stripes. The species name decemlineata, meaning 'ten lines' derives from this feature. The posterior end of the last ventral abdominal segment is depressed in the male, whereas in the female this depression is absent. Adult L. decemlineata are easily differentiated from other chrysomelid adults, because only they have the head inserted deep in the thorax. 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 beetle larvae has four instar stages, characterized by their large abdomen and arched back. The orange-pink larvae have black spots and measure up to 15 mm in length in their final instar stage. The larval head is small and black. This pronotum is entirely black in first- and second-instar larvae. In third-instar larvae, the anterior margin of the pronotum appears orange-brown. In fourth-instar larvae, about half the pronotum is light brown anteriorly. The abdomen has nine segments. At its posterior end is a tubelike structure that has some adhesive properties.
The beetle is native to America and Mexico and is present in all States of American except Alaska, California, Hawaii, and Nevada. It now has a wide distribution across Europe and Asia. Its first association with the potato plant, Solanum tuberosum, was not known until about 1859 when it began destroying potato crops in the region of Omaha, Nebraska. It had spread east and reached the Atlantic Coast by 1874.
In 1877, the Colorado beetle reached the United Kingdom and was first recorded from Liverpool docks. There have been many further outbreaks but the species has been eradicated in the UK at least 163 times. The last major outbreak was in 1976.
During or immediately following World War I, it became established near USA military bases in Bordeaux and had proceeded to spread by the beginning of World War II to Belgium, the Netherlands and Spain. The population increased dramatically during and immediately following World War II and spread eastward, and the beetle is now found over much of the continent. After World War II, in the Soviet occupation zone of Germany, almost half of all potato fields were infested by the beetle by 1950. The GDR government made the claim that the beetles were dropped by American planes. In East Germany they were known as Amikäfer (Yankee beetles). In the EU it remains a regulated (quarantine) pest for the UK, Republic of Ireland, Balearic Islands, Cyprus, Malta and southern parts of Sweden and Finland. It is not established in any of these Member States, but occasional infestations can occur when wind blows adults from Russia to Finland.
Adults of the genus Leptinotarsa measure about 3/8 inch long and are yellowish-orange with multiple black stripes down the back with five per elytron. They are robust and oval in shape when viewed from above. The head has a triangular black spot and the thorax has irregular dark markings.
Colorado potato beetle females are very prolific; they can lay as many as 800 eggs. The eggs are yellow to orange, and are about 1 mm long. They are usually deposited in batches of about 30 on the underside of host leaves. Development of all life stages depends on temperature. After 4–15 days, the eggs hatch into reddish-brown larvae with humped backs and two rows of dark brown spots on either side. They feed on the leaves. Larvae progress through four distinct growth stages (instars). First instars are about 1.5 mm long; the fourth is about 8 millimetres (0.31 in) long. The larvae in the accompanying picture are third instars. The first through third instars each last about 2–3 days; the fourth, 4–7 days. Upon reaching full size, each fourth instar spends an additional several days as a non-feeding prepupa, which can be recognized by its inactivity and lighter coloration. The prepupae drop to the soil and burrow to a depth of several inches, then pupate. Depending on temperature, light-regime and host quality, the adults may emerge in a few weeks to continue the life cycle, or enter diapause and delay emergence until spring. They then return to their host plant to mate and feed. In some locations, three or more generations may occur each growing season.
Behaviour and Ecology
As an agricultural pest
In about 1840, the species adopted the cultivated potato into its host range and it rapidly became a most destructive pest of potato crops. The large scale use of insecticides in agricultural crops effectively controlled the pest until it became resistant to DDT in the 1950s. Other pesticides have since been used but the insect has, over time, developed resistance to them all. The Arthropod Resistance Database records that the species as a whole has evolved resistance to 56 chemical insecticides. There is even reports from Ukraine in the 1970s of a strain resistant to hydrogen cyanide.
Insecticides are currently the main method of beetle control on commercial farms. However, many chemicals are often unsuccessful when used against this pest because of the beetle's ability to rapidly develop insecticide resistance. The Colorado potato beetle has developed resistance to all major insecticide classes, although not every population is resistant to every chemical.
High fecundity usually allows Colorado potato beetle populations to withstand natural enemy pressure. Still, in the absence of insecticides natural enemies can sometimes reach densities capable of reducing Colorado potato beetle numbers below economically damaging levels. A ground beetle, Lebia grandis, is a predator of the eggs and larvae, and its larvae are parasitoids of the Colorado beetle's pupae.
Beauveria bassiana (Hyphomycetes) is a pathogenic fungus that infects a wide range of insect species, including the Colorado potato beetle. It is probably the most widely used natural enemy of the Colorado potato beetle, with readily available commercial formulations that can be applied using a regular pesticide sprayer.
Relationship to humans
During the Cold War the Warsaw Pact countries, fearing a food shortage, decried the beetle as a CIA plot to destroy the agriculture of the Soviet Union. Officials launched a Warsaw Pact-wide campaign to wipe out the beetle, villainizing them in propaganda posters and pulling schoolchildren from class to gather the bugs and drown them in buckets of benzene or spirit.
2014 pro-Russian conflict in Ukraine
During the 2014 pro-Russian unrest in Ukraine, the word kolorady, from the Ukrainian and Russian term for Colorado beetle, (Ukrainian: жук колорадський, Russian: колорадский жук) gained popularity among Ukrainians as a derogatory term to describe pro-Russian separatists in the Donetsk and Luhansk Oblasts (provinces) of Eastern Ukraine. The nickname was a reference to the black and gold so called St. George's ribbons worn by many of the separatists as a symbol of their identity.
The Austrian postal authority featured the beetle on a 1967 stamp. The beetle also appeared on stamps issued in Benin, Tanzania, the United Arab Emirates, and Mozambique. The Belgian postal authority featured a drawing of the Colorado beetle and larvae on a 1934 and 1935 propaganda postcard.
In 1956, Romania issued a set of four stamps calling attention to the campaign against insect pests. The 55 Bani stamp features the Colorado potato beetle.
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- Sindelar, Daisy. "What's Orange and Black and Bugging Ukraine?". Radio Free Europe / Radio Liberty. Retrieved 18 May 2014.
Ukraine’s Reins Weaken as Chaos Spreads, The New York Times (4 May 2014)
(Ukrainian) Lyashko in Lviv poured green, Ukrayinska Pravda (18 June 2014)
- A guide to Ukrainian and Russian flags, The Economist (7 May 2014)
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|Wikisource has the text of the 1921 Collier's Encyclopedia article Colorado Beetle.|