Colorado potato beetle - enemy number 1
More recently, about 50 years ago, the Colorado potato beetle was not in our fauna. "History with geography»Colorado potato beetle for convenience can be represented in the form of a list:
- 1824 The American entomologist Thomas Sey first described a new species of insect for science, which later became known as Leptinotarsa decemlineata;
- 1842 European immigrants reached the Rocky Mountains, everywhere on their way planting captured plants, including cultivated potatoes;
- 1844 Potato plantations appeared in Colorado;
- 1855 The first significant potato damage by a beetle in Nebraska was noted;
- 1859 The first significant damage to potatoes in Colorado. The beetle received the name Colorado (although, logically, at that time it should have been called "non-Brasque");
- 1864 The beetle overcame the river. Mississippi;
- 1870 Beetle infiltrated New York State;
- 1874 The beetle reached the shores of the Atlantic Ocean;
- 1876 On a busy sea route with cargoes on steamboats, a beetle overcomes the Atlantic Ocean and for the first time “lands” in Europe;
- 1877 The first hearth in the vicinity of the German cities of Mülheim and Leipzig. Destroyed
- 1878 The first outbreak in the vicinity of the town of Suwalki in northeastern Poland. Destroyed
- 1887 Hearth in the vicinity of Hanover. Destroyed
- 1918 "Landing" in Bordeaux. Justification in France.
During the First World War, Europeans had no time to protect plants, and a dangerous potato pest quickly "fixed on the bridgehead" of the French coast. Then, despite the opposition of agricultural workers, he quickly settled one after another all the countries of Central Europe, except England with its cold fogs and a well-established plant quarantine service. (By the way, she still keeps the country's border “locked” for him).
Moving east along the prevailing winds in the summer months, overcoming all obstacles and withstanding the total processing of potato fields with pesticides, by the end of the 40s, the bug, driven by the wind and the thirst for conquering new habitable spaces, approached the state borders of the USSR. I must say that the beetles themselves are beautiful flyers. True, in order to take off, they need hot weather - in the mornings and evenings and on cloudy and cool days, beetles prefer walking crossings.
The first foci of a harmful insect on our territory were discovered in the Lviv region of Ukraine in 1949. Then in 1953 it appeared simultaneously in the Kaliningrad, Volyn, Brest and Grodno regions.
Finally, in the hot, windy days of May 1958, a Colorado potato beetle flew into the Transcarpathian region from Hungary and Czechoslovakia. At the same time, the multimillion-strong “landing” of beetles that incredibly reproduced that summer on the vast potato fields of Poland was thrown out onto the Lithuanian and Kaliningrad coast of the Baltic Sea.
Then most of the desperate flyers died in the stormy waters of the Baltic; survivors and creeping ashore were immediately destroyed by vigilant collective farmers. But the "landing" was so numerous that it was not possible to cope with it and "dump into the sea". Many individuals, only "stepping" on the coastal sand, and barely having time to dry out, flew into the nearest fields. From that time, in fact, began a massive settlement, literally, by an overseas guest of the territory of Russia.
But we will interrupt the story of the alien conquering a new continent and describe it. Although, it seems that this beetle is well known to everyone. Its length ranges from 9 to 12 mm, a width of 6-7 mm. The body is short-oval, strongly convex, brilliant, reddish-yellow with light elytra, each of them has five black stripes (there are therefore ten in total, hence the Latin species name decemlineata - ten-fold). The webbed wings of the beetle are well developed; with their help, on hot summer days, beetles make long flights.
Body color of the larva in the first and second age of dark brown; from the third age, the larva becomes bright orange, pinkish or yellow-orange. During this period, they easily differ in their color and “humpbacked" form from the larvae of our other leaf beetles. And the bugs and larvae of the Colorado potato beetle feed on the leaves of nightshade crops: potatoes, tomatoes, eggplant, much less often - tobacco. Some wild plants of the same family also readily eat.
The lifestyle of the Colorado potato beetle is very complicated. Many foreign and Russian scientists have devoted many years to studying it.
Beetles winter in adulthood. In spring, they emerge from the soil and soon begin to feed on seedlings of potatoes and mate. If, as often happens, mating occurred in the fall, before the onset of deep winter dormancy, called diapause, then in the spring, after several days of feeding, females can begin to lay eggs without additional mating. Thus, only one female can be the founder of a new outbreak.
Overwintered females from spring to autumn lay bright orange eggs on the lower surface of the leaves. Within one day, the female lays from 5 to 80 eggs. In total, it can postpone them to 1000, although the average fecundity is much less - 350. The number of generations during the summer depends on the climate of the area and the weather. In the north of the European range, the beetle develops in one generation, in the south manages to form three successive generations (in Central Asia up to four on irrigated lands!).
At the larval stage, the Colorado potato beetle distinguishes four ages, separated by molts. In the first and second age, the larvae feed and remain on the tops of the potato shoots with “broods”. In the 3rd and 4th they disperse, often moving to neighboring plants. For pupation, the bulk of the larvae burrow into the soil within a radius of 10-20 cm from the bush on which they fed. The depth to which the larvae thus leave depends on the structure and soil moisture; but usually does not exceed 10 cm. A chrysalis forms in an earthen cradle in 10-20 days.
Young, newly hatched beetles differ at first in a bright orange color and have soft integuments. But after only a few hours, they darken, turn brown with a pink tint, and soon acquire their usual color. The life expectancy of adult beetles varies and averages one year. However, some bugs can live 2 or even 3 years.
The most remarkable physiological feature of the Colorado potato beetle is the variety of resting forms. Insects usually have one form of dormancy. The Colorado potato beetle has six! We list them. The first is winter diapause. The second is winter oligopause. The third is a summer dream, in which they leave in the middle of summer for a period of 1 to 10 days to half of all overwintered individuals. Fourth - long-term diapause in summer. Fifth - repeated diapause, which manifests itself at the end of summer once or twice (rarely three) times of wintering and in the growing season of potatoes of breeding beetles that survived until the fall.
And finally, the sixth is a long-term diapause (superpause), which can last 2-3 years. There is no way to describe in detail each of these states. We will only say that such physiological plasticity allows the beetle to successfully overcome all the hardships of life. And for farmers - it is extremely difficult to combat the pest.
Take at least many years of diapause. Planting potatoes on a field where it has not been for 3 years, and knowing that no one is cultivating this culture this year, the farmer suddenly finds in despair that this time the field is full of Colorado potato beetle. These are individuals who were in the diapause for two years and, having “decided” that it was time to “go out”, they went out of their stupor and it turned out to be not in vain.
Concluding the description of the biology of this North American guest, we only say that such a complex organization of life largely contributes to the invulnerability of the pest for any means of control.
And their development has been in fact since the appearance of the pest on the European continent. At first it was a purely chemical struggle with terrible pesticides such as DDT and hexachloran. Then pesticides of more and more generations began to apply against the pest. The beetle quickly got used to some of them, some had to be abandoned due to the negative consequences of their use for nature.
If there are few larvae, then it is easier to collect them in containers with kerosene or with saturated salt solution and destroy them, if there are many, then it is necessary to treat them with chemical preparations. Plants are usually treated when more than 15 young larvae per plant are planted. For the first treatments, it is better to use systemic insecticides (for example, Aktara or Regent) - they provide protection for 14-20 days.
Further processing should be carried out with contact preparations that kill beetles and larvae on the surface of the leaves. However, do not forget that after treatment with chemicals, tubers should not be eaten for 21 days. During this time, the drug in the plant decomposes into harmless components.
List of drugs used against Colorado potato beetle:
- Agravertine dose per hundredth - 20 ml, number of treatments - 1-3 (interval - 7-10 days)
- Aktara dose per hundredth - 0.6 ml, number of treatments -1
- Arrivo, Citkor, Tsimbush, Sherpa dose per hundredth - 1.5 ml, number of treatments -2
- Bankol dose per hundredth - 2.5 g, number of treatments -2
- Decis dose per hundredth -2 ml, number of treatments -2
- Spark dose per hundredth -1 tab., the number of treatments -2
- Karate dose per hundredth -2 ml, number of treatments -1
- Kinmix dose per hundredth -2.5 ml, number of treatments -2
- Mospilan dose per hundredth -0.3 g, number of treatments -1
- Regent dose per hundredth -6 ml, number of treatments -2
- Sonnet dose per hundredth -2 ml, number of treatments -1
- Sumi — alpha dose per hundredth -2.5 ml, number of treatments -2
- Fastak dose per hundredth -1 ml, number of treatments -1
- Fitoverm dose per hundredth -5 ml, number of treatments -1-3 (interval 20 days)
- Fosbezid dose per hundredth -30 ml, number of treatments -2
- Fury dose per hundredth -1.5 ml, number of treatments -2
Meanwhile, a less dangerous method of suppressing the number of foreign pests has long been known. By the time the Colorado potato beetle appeared in Europe, entomologists had already developed the so-called classical biological method for controlling the number of harmful insects. It was applicable precisely to species-aliens, just to those who broke through the borders from the places of their usual existence. At the same time, leaving far behind their natural enemies - parasitic and predatory invertebrates.
The essence of this method consisted precisely in the search in the homeland of the "stranger" of his natural enemies and their delivery to him after. In our case, they had to find them on the American continent, and then release them on European fields, so that they acclimatize here and begin to naturally destroy their usual food - the Colorado potato beetle.
By the time of the “conquest” of Europe by the beetle in scientific entomological circles, the opinion was firmly established that his homeland was the United States, and even more precisely - the state of Colorado (it was not for nothing that it got its name!). It remained to quickly find parasites or beetle predators in the United States, bring them to Europe, release them to the fields and observe how the “natural mechanisms of regulation of numbers” begin to work. Work began to boil. Scientists of many European countries became its participants. Birds of prey and bugs brought to Europe, parasitic flies were bred and released into the fields, waiting for purification from the "overseas guest".
Scientists have learned to breed some American Colorado potato beetle predators in large numbers. Thousands of predatory bugs were released: perillus and podizus not only on potato fields, but also on eggplant and tomatoes, which by that time the beetle had included in its diet. But as soon as mass releases ceased, the malicious pest quickly regained its strength and continued to “repair robbery,” and our predatory helpers disappeared without a trace from the fields. The work resembled Sisyphus labor.
The Colorado potato beetle is eaten with pleasure by ordinary chickens (and their relatives - pheasants and guinea fowls), as well as cuckoos, starlings and some other birds.
But now, in the late 60s, the Americans themselves began to suffer from a bug. Until that time, they successfully defended themselves with pesticides. But here, the chemical struggle became less and less effective. Finally, there came a time when none of the pesticides allowed in the USA for use on potatoes exerted a harmful effect on the bug: it was used to all of them. American scientists faced the same problem as European ones - they had to look for an alternative to the chemical method. That is, look for its effective entomophages.
By this time, it had already become clear that all the natural enemies of the Colorado potato beetle, which European entomologists had been engaged in for many years, and after them the American ones, were multi-species. The Colorado potato beetle for them is just one of many possible exotic dishes. As for us Russians, for example, the fruits of avocado or papaya.
Specialists in biological plant protection were already well aware that the most effective regulators of the number of harmful insects are not polyphagous beneficial species, but those for which this pest is the main food specializing in feeding them.
It turned out another curious circumstance, which was of fundamental importance. Faunistic research allowed by that time to reconsider the history of the "travels" of the Colorado potato beetle and, moreover, to determine its true homeland. The American scientist W. Tower convincingly proved that the center of origin of the genus Leptinotarsa, to which our hero belongs, is not Colorado at all. The homeland of these beetles is located much further south - in the so-called Sonora zoogeographic province.
Here, in northeast Mexico, there are about 50 species of insects of this genus. It is from here that “our” beetle relatively recently penetrated north, up to the eastern slopes of the Rocky Mountains, which are bordered by Colorado valleys from the west. And he eked out a miserable existence there, “pinching” rare wild plants from the nightshade family.
And only when desperate American pioneers got here almost across the continent and planted potato tubers brought with them, did the beetle “understand” that it was not for nothing that it was making its way through the hot deserts of Mexico, Arizona and Texas. Of his many relatives, he alone quickly adapted to eating on potatoes. And he began to devour the hard-growing valuable crop. Here, immigrants - immigrants from Europe, first encountered this beetle and called it Colorado.
So, it finally became clear where the true homeland of the pest is. And this, in itself, is an extremely important fact. After all, it was here, and not anywhere else, that his main natural enemies should have evolved and inhabited. And, therefore, here it was necessary to look for them in the first place. It is in the exotic cactus forests of the Sonor province that wild nightshade grows - distant and close relatives of cultivated potatoes, tomatoes, and tobacco. Numerous relatives of the “Colorado potato beetle,” which, as we now understand, would be more correct to call a sonor beetle, are used to eating them.
Over the past decade, the joint efforts of scientists from several countries have found parasitic insects specializing in feeding the Colorado potato beetle (in particular, the parasite of eggs Edovum puttleri grissell) However, alas, this species does not suit either the Americans or us. He is a southerner, and in areas of intensive cultivation of cultivated potatoes, he simply does not winter. And to breed this one-man for mass production is possible, of course, only on the eggs of the same Colorado potato beetle. Again a vicious circle.
- Zhukov. B. Indestructible // Around the World No. 9, September 2008