Colorado potato beetle
The Colorado potato beetle belongs to the family of leaf beetles from the order of Coleoptera, numbering about 35 thousand species in their group. The matured individuals and larvae of the Colorado potato beetle feed on the foliage of plants belonging to the nightshade family, including potato and tomato crops, peppers, eggplants, damaging crops and being insect pests dangerous for the agricultural industry.
Colorado potato beetle
The birthplace of the insect
In Latin, Leptinotarsa decemlineata in nature is also called the potato leaf beetle. The first to learn about his presence among the fauna in 1824 thanks to the research of an American biologist Thomas Say. He collected unknown representatives on nightshade crops and brought them from the Rocky Mountains of the mountain range in North America. Since then, the taxonomy, classification and determination of its place in insect families began.
The potato leaf beetle got its name after destroying potato crops in the fields of the American state called Colorado.
Its true homeland, where the Colorado potato beetle came from and where it takes its origin, is the Mexican northeastern part, where other species of the Leptinotarsa species are found, feeding on nightshade and tobacco vegetation. From the Mexican Sonoran province, the potato leaf beetle migrated to the northern parts of the continent.
Geography of distribution
Primary damage to potato plantings by pests was recorded in the US state of Nebraska. Subsequently, the map of his appearance was stretched across the entire North of America. In the late 70s of the 19th century, individuals moved and crossed the Atlantic Ocean along with cargo on steamers, appearing on the European territory, where it lives to this day. He was able to finally take root in his numerous habitats after the end of the First World War.
The potato leaf beetle is widespread and is found in almost all countries of the European continent with the exception of Britain, where it is still absent or difficult to find today.
In Russia, individuals of the Colorado potato beetle appeared during the Soviet era. Soviet gardeners got acquainted with information about them since the 40s of the last century. The massive spread of the insect, from where the Colorado potato beetle came to Russia, took place together with wagons loaded with straw from the Ukrainian Republic. 1975 was the year of drought.
Features of appearance
Adults
The appearance of the Colorado potato beetle is easy to remember
The description of what the Colorado potato beetle looks like refers to the insect as rather large, reaching a length of 8 to 12 mm, and a width of 6 to 7 mm. The insect has a rather memorable appearance, according to which it is difficult to confuse it with other representatives in the leaf beetle family.The characteristics of the appearance of the insect include its distinctive features, which distinguish the leaf beetle from other pests:
- oval body with a strong convex top and a shiny yellow-orange color,
- the pronotum of the insect is spotty, with black specks,
- both of the two elytra are decorated with five black stripes.
It is believed that the potato leaf beetle owes its name to an extraordinary mask that warns predators because of the five black stripes on each of the elytra.
The belly of the insect consists of 7 segments with black spots arranged in a row. The potato leaf beetle has 3 pairs of paws equipped with hooks that help the insect move along the surface of the leaves and stems of the potato plant.
In nature, there is a so-called false potato beetle (in Latin Leptinotarsa juncta, or Lj), outwardly and in structure looks very similar to the potato leaf beetle. The false representative is widespread in the United States and differs from the true potato in the shape of the elytral stripes and the orange coloration of the paws.
The insect is able to cover long distances thanks to its well-developed wings with a membranous structure.
The weight of an adult potato leaf beetle is about 140-160 mg, young individuals of the Colorado potato beetle are somewhat smaller in size and weight.
Description of the larva
According to the description, the larva of the Colorado potato beetle grows up to 1.5-1.6 cm long, it has a black head and two rows of black dots on the sides. This description of the larva is much similar to the appearance of the ladybug larva, which are often confused with each other. In color, the larva of the potato leaf beetle is initially dark brown, but in the process of its development it turns into bright yellow, sometimes with a pink tint. The color of the larva depends on the presence in its hemolymph (fluid circulating inside the vessels) of a yellow-orange pigment called carotene. When eating the foliage of potatoes and other nightshades, which the Colorado potato beetle eats, it is not processed in the larvae, but accumulates carotene inside, which paints them in the color of carrots.
Life cycle of adults
On average, the duration of the period, how long the Colorado potato beetle lives and all stages of the development of the Colorado potato beetle rarely exceed 1 year. A specific feature of the insect is its ability to stay in diapause. This is a special condition, like the adult Colorado potato beetle hibernates, in which physiological phases of metabolism are inhibited and formative processes are stopped. Some representatives, being in diapause during the cold season, live in such conditions up to 3 years of age.
The number of young generations of the potato leaf beetle directly depends on climatic conditions. In the northern regions, he breeds one generation at a time, in the southern regions, their number reaches 2-3.
The beetle feeds on the vegetable part of the potato
The imago of the potato leaf beetle hibernates in the soil, climbing to a depth. The distance from the surface to the place where the Colorado potato beetle hibernates can be up to half a meter. At the onset of spring heat, it gets out to the surface and starts feeding on plant shoots, while simultaneously starting the mating process.
In the period from the beginning of the spring season until the arrival of autumn, adult females lay oblong eggs of light orange color on the underside of the leaf blades. For one day, each of them can postpone from 5 to 80 pieces. In total, for the entire summer period, a female Colorado potato beetle is able to lay about a thousand eggs.
Life cycle of larvae
Larvae appear 5-17 days after the laying of eggs by the female, and this period depends on the ambient temperature. In the development of the life cycle of the Colorado potato beetle larvae, there are 4 age periods, which are subdivided by molts:
- larva of the 1st instar of dark gray color, reaching a length of 2.5 mm, covered with small hairs, it is able to gnaw the leaf flesh from the bottom,
- individuals of the 2nd larval instar are red and grow up to 45 mm in length, they destroy all the leaf pulp, leaving intact only thickened veins located in the middle of the leaf plate, settling at the top of the shoots,
- 3rd instar larvae are red with yellow up to 9 mm long and 4th instar orange up to 16 mm long spread to neighboring plants, eating foliage and stems.
The larvae are able to feed very intensively, and after two to three weeks they are ready for the development of a new stage and transformation into a pupa, for which they burrow into the soil layer to a depth of 10 cm.
After a two to three week interval, a pupa of the Colorado potato beetle is formed under the layer of earth. Subsequently, the grown insect crawls out of the pupa to the surface or enters a state of diapause until the next spring season arrives.
Life cycle of the young generation
Young insects that have reappeared from under the layer of the earth from pupae stand out from the rest with their bright orange color and softened integuments. However, after a few hours (usually this happens after 3-4 hours), they become darker, brown in color with a slight pinkish tinge, eventually acquiring the color familiar to ordinary adult insects.
When a danger arises, the potato leaf beetle does not leave its place and does not fly away, but freezes, pretending to be dead.
An adult pest begins to feed and accumulate fat reserves, growing in size and gaining weight within 6-20 days, eventually becoming ready for reproduction and movement. They begin to fly in hot summer months or before wintering. Grown insects fly tens of kilometers in summer, forming new settlements in their colonies. Moreover, the speed of their movement can reach up to 8 km per hour.
Harm inflicted and sources of occurrence
Insects can kill crops
The beetle causes the main harm to agriculture and especially to potato varieties.
What is the harm of an insect
The insect feeds on vegetables and is capable of destroying most of the crop in a short period of time. Nicknamed the potato parasite among gardeners, the beetle feeds on all parts of the plant - young stems, foliage and root crops. At the very beginning of the gardening period, juicy young greens of a vegetable bush become its source of food. Towards the middle of summer, he begins to eat the inflorescences of plants, and by the end of the end of the season for growing vegetables, move to the lower tier, damaging the foliage and potato tubers.
Sources of appearance
An insect can appear on a personal plot from various sources:
- at the onset of the first warm days, the beetle flies from neighboring vegetable gardens, where they stopped planting vegetable crops that are favorite for the pest,
- most of it is selected on the soil surface after wintering,
- some insects settle in new places by mass migration due to dramatic climatic changes or with the local use of agrotechnical measures, while flights can occur over rather long distances.
Control methods
Measures to combat the potato leaf beetle involve quarantine measures and the treatment of potatoes and other vegetable crops with insecticidal agents at the stage of 2nd instar larvae and during the mass birth of juveniles of the Colorado potato beetle, which are enormously harmful.
The potato leaf beetle has a high resistance to toxic chemicals, which complicates the fight against the pest. EPV (economic threshold of harmfulness) of the pest reaches 40 individuals per 100 sq. M.
Many gardeners in small sown areas destroy the pest by manually picking it from vegetable bushes, taking into account that it cannot be pressed on the foliage.
Natural enemies
For most birds and many animals, the pest is inedible. This is because in the process of feeding on nightshade crops in its body, the potato leaf beetle accumulates toxic substances alkaloids and solanines contained in the leaf part and stems of plants.
Pheasants are the same feathered bird that eats the Colorado potato beetle. They feed on its larvae of ground beetles and lacewings. A small predator among insects, the ladybug can eat the eggs of the potato leaf beetle, which is useful in the fight against this type of pest. The natural enemy for the Colorado potato beetle is the guinea fowl. Matured individuals can become food not only for guinea fowls, but also for turkeys. For this purpose, from an early age, I add a crushed insect to the feed. Among the natural enemies who eat the Colorado potato beetle, in addition to birds, there are a number of bugs - shield bugs and tahin flies.