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The Colorado potato beetle ( Leptinotarsa decemlineata; also known as the Colorado beetle, the ten-striped spearman, the ten-lined potato beetle, and the potato bug) is a beetle known for being 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 elytron. Native to the Rocky Mountains, it spread rapidly in potato crops across the United States and then Europe from 1859 onwards.; see pp. 453–454: "Doryphora, Illig.: D. 10-lineata".
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.
Adult beetles may be visually confused with L. juncta, which is the false potato beetle. Unlike the Colorado potato beetle, it 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 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 Pedipalp. (1988). 9780916846404, Brill. ISBN 9780916846404
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. The beetle has the potential to spread to temperate areas of East Asia, India, South America, Africa, New Zealand and Australia.
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 1977. It remains as a notifiable quarantine pest in the United Kingdom and is monitored by the Plant Health and Seeds Inspectorate of the Animal and Plant Health Agency (APHA) 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.
In July 2023 Colorado beetles were officially confirmed in a potato field in Kent, England. Farmers and growers, gardeners and members of the public are being encouraged to remain vigilant for signs of the pest and to report potential sightings to APHA.
Elsewhere in Europe the beetle became established near USA military bases in Bordeaux during or immediately following World War I 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. In East Germany they were known as Amikäfer ('Yankee beetles') following a governmental claim that the beetles were dropped by American planes. In the European Union it remains a regulated (quarantine) pest for the 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, for example, wind blows adults from Russia to Finland.
After 4–15 days, the eggs hatch into reddish-brown with humped backs and two rows of dark brown spots, one row on each side. They feed on the leaves of their host plants. Larvae progress through four distinct growth stages (). First instars measure about long, and the last (fourth) instars about long. The first through third instars each last about 2–3 days; the fourth lasts 4–7 days.
Upon reaching full size, each fourth instar spends several days as a nonfeeding 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 . In 5 to 10 days, the adult beetle emerges to feed and mate. This beetle can thus go from egg to adult in as little as 21 days. Depending on temperature, light conditions, and host quality, the adults may enter diapause and delay emergence until spring. They then return to their host plants to mate and feed; overwintering adults may begin mating within 24 hours of spring emergence. In some locations, three or more generations may occur each growing season.
Colorado potato beetles are also attracted to the volatiles potato plants emit. In the article Sexual contact influences orientation to plant attractant in Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) by Joseph Dickens, the beetles were attracted to kairomone substance but after mating, their attraction to it reduced. Within 24 hours of mating, there was no difference between levels of attraction to kairomone and control solvent. Lack of attraction occurred for two days but resumed three days after mating. Male beetles produce a pheromone that is further enhanced by plant host volatiles like the kairomone. After a beetle is attracted to the host, mating occurs and the female lays her eggs on the plant. The beetles' attraction to kairomone decreases until 72 hours later once oviposition occurs and the probability of re-mating increases.
The predatory ground beetle L. grandis is a predator of both the eggs and larvae of L. decemlineata, and its larvae are of the pupae. An adult L. grandis may consume up to 23 eggs or 3.3 larvae in a single day.
In a laboratory experiment, Podisus maculiventris was used as a predatory threat to female L. decemlineata specimens, resulting in the production of unviable alongside viable ones; this response to a predator ensured that additional food was available for newly hatched offspring to increase their survival rate. The same experiment also demonstrated the cannibalism of unhatched eggs by newly hatched L. decemlineata larvae as an antipredator response.
| + Examples of parasitoids, predators, and pathogens of different life stages of Leptinotarsa decemlineata ! Type !! Species !! Order !! Predates !! Location !! Reference |
Three current setae are known: simple pointed with an asymmetric narrowing at the tip (males and females), spatula-like with a pin on its dorsal surface (males and females), setae with an adhesive terminal disc (males only). Male setae are better designed for smooth surfaces; male Colorado potato beetles have been observed attaching onto smooth glass and plastic surfaces and also attach to the smooth female elytra.
Microscopy of the tarsal reveals five articulated Arthropod leg and paired curved claws. Males and females have an adhesive setae covering the first three tarsomeres. The fourth is hidden and the fifth bears sensory setae with no adhesive function. Both males and females have filamentous with a tapered terminal part, lanceolate with a flattened tapered terminal part, and spatula-shaped with an enlarged tape-like terminal part. Males have a discoidal terminal part with a bulge around the disc. Female elytra appears smooth on the surface, but further magnification shows irregular lines. This indicates fluid on the elytra.
Reasoning behind the genetic diversity is the landscapes of the regions: shrub-land and grains in the Columbia Basin versus the forest, corn, and beans in the Central Sands. In the same study, potatoes covered 3.5% in the Columbia Basin and 1.8% in the Central Sands. Landscape resistance can be characterized by how the land responds to the spread of beetles. Its overall effect on allele frequency covariance was low, and the Central Sands had a higher rate of decay in allele frequency. Potatoes' relative effect sizes of land cover variables on genetic differentiation was the highest in the Columbia Basin. However, when comparing all the land types, no particular land cover displayed any significant difference from the others.
Genetic differentiation in the Colorado potato beetle can be impacted by agricultural practices such as crop rotation. The same study mentioned earlier examines crop rotation's effects on genetic differentiation in Colorado potato beetles that were not found in the Central Sands. On the other hand, genetic diversity decreased with increased crop rotation in the Columbia Basin. This difference could be attributed to larger rotation differences in the Columbia Basin or differences in the landscape itself that affect the spread of the beetles. Genetic diversity is not directly impacted by the land cover type. Instead, other factors such as climate could be responsible for the differences between the Colorado potato beetle in these two regions.
Polymorphism was highest in Colorado potato beetles in Colorado and the lowest was in France. Polymorphism and Zygosity was higher in North America than in Europe. Heterozygosity ranged from 0.25 in New Brunswick to 0.14 in France. Further analysis revealed population differentiations between North America and Europe. There were two separate groups of European beetles, one formed by western European beetles and the second being eastern European beetles. 13% of total variation is from variation among the two continent groups, and 17% of variation is from population variance within groups. Beetles from North American and Europe formed clusters. With the exception of New Brunswick and Kentucky beetles, most beetles from the same population cluster together. In Europe, there were more complex relations between the beetles. Estonian and Spanish beetles clustered, French and Italian beetles formed separate groups, and Russian and Finnish beetles were closely related to Estonian ones. European beetles could be categorized by East and West except for Polish beetles which had relations to multiple countries.
Visual cues are also important for the beetles. Colorado potato beetles respond to light, and intensity is proportional to rest period. Beetles exhibit phototactic orientation in which they align themselves with a cone of light and move with it. Compass orientation is when large amounts of beetles walk in a single direction and have memory of their angle to the sun.
The rate of linear displacement is important for the probability of the beetle finding a plant, mate, or habitat. This is important for the success of orientation mechanisms.
New beetles disperse for crops once they emerge. The crops affect colonization: crop rotation prolongs colonization, and neighboring crops are colonized rapidly and by walking. Overwintered beetles fly to find crops and once a host plant is found, flight frequency decreases. The strategy behind this is thought to be minimizing reproductive risk because female beetles that emerge in the spring are already mated. Dispersal continues after finding a host. Moving helps beetles find better resources, mates, and progeny distribution. When moving, flight is less frequent than walking in cultivated fields than in the wild.
Researchers have also evaluated how flight frequency is related to the beetle's diet. In a beetle population that had returned from diapause and been exposed to poor food conditions, mean flight frequency was decreased. This is because beetles required better food conditions to regenerate their flight muscles. Prior to diapause, beetles increased their flight frequency to compensate for poor food conditions.
The economic cost of insecticide resistance is significant, but published data on the subject are minimal. In 1994, total costs of the insecticide and crop losses in the US state of Michigan were $13.3 million, representing 13.7% of the total value of the crop. The estimate of the cost implication of insecticides and crop losses per hectare is $138–368. Long-term increased cost to the Michigan potato industry caused by insecticide resistance in Colorado potato beetle was estimated at $0.9 to $1.4 million each year.
Following the introduction of the gene, Russet Burbank potato plants with the gene were tested for kanamycin resistance and Colorado potato beetle resistance. In 308 plants that were tested, 18% (55) displayed complete resistance to the beetle. Later larval stages and adult beetles are more sensitive to cryIIIA protein. Controlling adults is important because they produce the next larvae generation. Colorado potato beetles overwinter as adults in the soil and feed immediately after emerging in the spring. In cryIIIA expression levels above 0.005%, adult feeding was negligible. Oviposition was also affected. In non-Transgene leafs, mean number of eggs per cage were 117 and 143 in two separate trials. On the other hand, transgenic leafs displayed a mean of 1.7 and 0 eggs per cage in two trials. The female beetles were also studied, and the beetles put in the cage with transgenic plants displayed reduced size with ova that were partially or totally reabsorbed. They absorbed body fat and reproductive tissue as a result of ceasing consumption of transgenic plants.
The potatoes showed benefits of the gene treatment; potatoes expressing the cryIIIA gene had protection from Colorado potato beetles in the laboratory and the field. Furthermore, these potato plants displayed agronomic and tuber characteristics that aligned with healthy Russet Burbank Potatoes.
| + Examples of insecticides available for the control of Colorado potato beetle on different crops in Kentucky, USA. ! Insecticide class !! Common examples !! Potato !! Eggplant !! Tomato !! Notes |
CPBs have evolved widespread insecticide resistance. No cases without fitness cost or of negative cost are known.
Beauveria bassiana (Hyphomycetes) is a fungus that infects a wide range of insect species, including the Colorado potato beetle. It has shown to be particularly effective as a biological pesticide for L. decemlineata when used in combination with B. thuringiensis.
Crop rotation is, however, the most important cultural control of L. decemlineata. Rotation may delay the infestation of potatoes and can reduce the build-up of early-season beetle populations because the adults emerging from diapause can only disperse to new food sources by walking. One 1984 study showed that rotating potatoes with nonhost plants reduced the density of early-season adults by 95.8%.
Other cultural controls may be used in combination with crop rotation: the potato crop with straw early in the growing season may reduce the beetle's ability to locate potato fields, and the mulch creates an environment that favours beetle's predators; Plastic-lined trenches have been used as to catch the beetles as they move toward a field of potatoes in the spring, exploiting their inability to fly immediately after emergence; may also be used to kill the beetles when they are visible at the top of the plant's foliage.
Another enemy/potential control method is a fungal pathogen called Beuveria bassiana. This fungus has implications in population control of the beetles. It cannot be used to quickly contain large populations of beetles. Additionally, the pre-existing use of fungicide in disease management of crops presents an obstacle for the effectiveness of the fungus. Other reasons as to why this fungal treatment has not been utilized heavily include costs of production and longevity of formulations.
The fans of Alemannia Aachen carry the nickname "Kartoffelkäfer", from the German name for the Colorado beetle, because of striped yellow-black jerseys of the team.
During the 2014 pro-Russian unrest in Ukraine, the word , from the Ukrainian and Russian term for Colorado beetle (, ), gained popularity among Ukrainians as a derogatory term to describe pro-Russian separatists in the Donetsk Oblast and Luhansk Oblast Oblasts (provinces) of Eastern Ukraine. The nickname reflects the similarity of black and orange stripes on St. George's ribbons worn by many of the separatists.
In some European cultures, the Colorado potato beetle is known as the 'gourd beetle' due to the likeness of the beetle to various gourds of the Cucurbitaceae family.
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