European corn borer

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European corn borer
European corn borer (Ostrinia nubilalis)

European corn borer ( Ostrinia nubilalis )

Systematics
Class : Insects (Insecta)
Order : Butterflies (Lepidoptera)
Family : Crambidae
Subfamily : Pyraustinae
Genre : Ostrinia
Type : European corn borer
Scientific name
Ostrinia nubilalis
( Huebner , 1796)

The European corn borer ( Ostrinia nubilalis ) is a small butterfly from the Crambidae family . The European corn borer is one of the economically most important pests on corn. According to estimates by the FAO , the European corn borer caterpillars destroy around 4 percent of the annual corn harvest worldwide.

features

The moths show a sexual dimorphism in size and color. The wingspan of the females is around 34 millimeters, that of the males by 30 millimeters (30 millimeters or a forewing length of 13 to 14 millimeters (♂) and 15 to 16 millimeters (♀)). The coloring and drawing of the sexes are also very variable; even in a larger series of butterflies, hardly any individual is the same as another. The females are light yellow, cream-colored to brick-red. The males are yellowish-brown, brown, gray-brown to gray, so on average they are usually much darker in color. There are almost always two transverse lines. Usually they are very clearly drawn, more rarely only weakly. In the male, they are usually yellow or thinly dark with a more or less wide yellow border on the outside. In the female, on the other hand, the transverse lines are darker than the basic color, mostly in shades of brown. The yellow border is almost completely missing. The inner transverse line is roughly jagged, while the outer transverse line is finely indented with a deep medial bulge outwards. In the males, the outer transverse line in the inner edge is often thickened like spots. Other drawing elements are often added in the middle. A short cross vein near the Kostal edge is relatively common. Other specimens have one or two, less concise, mostly darker, occasionally lighter, longitudinal lines. Often the Kostal edge is also a little darker. The lower cross line, longitudinal lines and a short further cross line closer to the inner cross line can even result in a light-core, blemish-like spot. Some specimens develop a darker, indistinctly delimited spot along the edge of the (lower) cross vein. In many butterflies a more or less clearly pronounced wavy line can be seen. The fringe area from the wavy line to the hemline is often markedly alternately light / dark.

The hind wings have a broad, lighter median band, which is often lined with dark. In the male, the hind wings are more gray-brown, in the female more yellow-white or gray-white with a lighter median line. The fringing area is often relatively dark in color in the females. In the male, the head and thorax are yellowish-ocher to brown and the abdomen is brown. The antennae are simple and filiform. In the female, the head and thorax are light ocher to yellowish and the abdomen is light gray-brown. The antennae are simply thread-shaped like in the male.

The round egg is somewhat flattened. It is white at first and later turns brown. It measures 1.0 millimeters in length and 0.75 millimeters in diameter.

The caterpillar is gray-white to brown-white, occasionally pink on the back or with a slight olive tint. It has a broad, only slightly darker, indistinctly limited topline. The stigmata are outlined in gray. The pinacula (small chitin plates on which the bristles sit), the head and anal plates and the thoracic legs are light brown. The headstock has a dark brown pattern. The head is brown with a black-brown pattern. The length of the caterpillars during the six larval stages is: 1.6; 2.6; 4.7; 12.5; 14.5 and 19.9 millimeters.

The pupa is light reddish brown. The abdominal segments have slightly raised striae running across the back. The male pupa is 13 to 14 millimeters long and 2 to 2.5 millimeters in diameter; female pupae are 16 to 17 millimeters long and 3.5 to 4 millimeters in diameter. The cremaster has five to eight (usually six) close together, hook-shaped bristles.

Geographical distribution and habitat

The European corn borer is widespread and common in temperate Europe. In the north, the area extends to southern Norway and the British Isles. It tends to mass reproduce and can thus become a pest. The original area extended to South and Central Europe, North Africa, Asia Minor and West Asia to Turkestan. Due to human deportation, it appears almost cosmopolitan today. However, z. In some cases it has not yet been clarified with certainty whether all populations identified worldwide as "European corn borer" actually belong to Ostrinia nubilalis . In the east joins the distribution area of Ostrinia furnacalis , which is also referred to in the literature as "Asiatic corn borer". Wanner et al. (2003) suggest that it descends from a European corn borer-like ancestor.

The European corn borer was abducted to North America between 1910 and 1920 , which is also indicated by the name European corn borer there .

The species occurs in the open agricultural landscape, on ruderal areas, but also in gardens, where the corresponding host plants are grown.

Way of life

The European corn borer is very flexible in the succession of generations. Until recently, only one generation per year was formed in Central and Northern Europe. In the meantime, however, it has already been observed that in southern Germany and Switzerland two generations are formed per year. In southern Europe it is usually three generations, and in the tropics consecutive (up to six) generations can be formed. In Central Europe, the moths can therefore be found from May to September, depending on the region. They are nocturnal and come to artificial light sources. The female moth lays up to 500 eggs (400 to 600 eggs) in small groups of 15 to 20 eggs (10 to 40 eggs or up to 30 eggs) on the underside of the leaf. the adults are 18 to 24 days old. The egg caterpillars hatch after 7 to 14 days. The main food plants of the caterpillars are maize ( Zea mays ), real hops ( Humulus lupulus ), potatoes ( Solanum tuberosum ), tomatoes ( Lycopersicon ), peppers ( Capsicum ), fennel ( Foeniculum ), millet ( Panicum and Sorgum ), hemp ( Cannabis sativa ), beet ( Beta ), Phaseolus , buckwheat ( Phagopyrum ), celery ( Apium graveolens ), Alante ( Inula ) and mugwort ( Artemisia ), a total of about 20 species of plants are known, which are befressen of the crawler, in which flowers and fruit bunches and the pith of the stalk are eaten. Six larval stages are formed. The development time is 9, 8, 6, 9, 9 and 12 days for the respective larval stages or a little over 50 days in total. However, this time varies considerably depending on the weather and especially the temperature. The caterpillars overwinter in the stems and pupate in a loose cocoon at the beginning of spring. The pupil rest lasts about 12 days under natural conditions. The moths hatch in May.

Harmful effect

Two races - E and Z - are distinguished. While breed E occurs almost exclusively in mugwort, breed Z occurs mainly in the corn and hop growing areas in southern Germany. In recent years, the distribution area has slowly expanded northwards, so that the European corn borer has also been found in Brandenburg since 2004 .

Since the caterpillar of race Z slowly eats its way down in the stem pulp in the course of late summer, especially when it is infested with maize, the regional level of infestation also depends on the type of maize used: If it is used as grain maize , the caterpillars remain after threshing in October until December in the corn stubble in the field and can overwinter there. If, on the other hand, it is used as silage maize , the caterpillars are usually brought into the silo with the maize if the stubble is not cut too high and die when the silage is compacted at the latest , which until around 1990 limited the occurrence of the European corn borer Z to the classic grain maize areas. Due to more intensive maize crop rotation also in the pure fodder-growing regions and (to increase the energy density of the maize silage) large stubble length when chopping the maize silage, it is also In 2006, for example, in southern Vogelsberg there was a very strong infestation of the forage maize areas with the European corn borer, after it had occurred there in isolated cases in previous years from around 1995.

Caterpillar of the European corn borer Ostrinia nubilalis , weakens the stability of the plant through its feeding channels.

The species often occurs as a pest in the maize and hop growing areas in its range.

The stalks occupied by the caterpillars often break off, which reduces the stability of the maize plants and makes harvesting difficult. The development of the respective maize plant is also weakened, since the stem pulp is no longer available in autumn for energy storage in the cob, so that in the case of heavily infested parcels, several 10 percent losses either in grain yield ( grain maize ) or energy yield ( fodder maize ). can adjust. As a result of the European corn borer infestation, there is often an increased susceptibility to disease, for example against molds of the genus Fusarium , which make the corn unusable for any other use other than biogas production.

If sweet corn is grown, the damage caused by the borer eating the ears is an aesthetic problem (similar to worm-like apples, caused by codling moth ), and the affected areas can no longer be sold.

Combat

Either insecticides (e.g. oxadiazines, pyrethroids ), parasitic wasps ( Trichogramma brassicae ) or the soil bacterium Bacillus thuringiensis are used to control the European corn borer .

Two insecticides are approved in Germany. Both Steward (active ingredient indoxacarb , from the class of oxadiazines) and Gladiator (active ingredient methoxyfenozide , from the class of development accelerators) are approved against the European corn borer in maize. In Switzerland, the biologically obtained active ingredient spinosad is also used against the pest. For this active substance there is a listing in Appendix 3 of the list of active substances in the EU. This means that the active ingredient could also be used in "organic" cultivation.

At the time of chemical control, however, the maize is usually more than one meter tall, so that special tractors (gantry tractors or self-propelled vehicles with very high ground clearance) are required if the farmer does not want to have three meter wide tramlines in his inventory.

Genetically modified maize based on the protein from Bacillus thuringiensis ( BT maize ), which is poisonous for the European corn borer, is resistant to the larva , but does not prevent infestation by adult animals. Thus, borer larvae also develop in BT maize, of which, however, only a very small proportion grow to adulthood.

An additional method is the thorough chopping and deep plowing (at least 25 cm and as far as this is not hindered by environmental regulations) the infected parts of the plant, which is all the more effective, the more farmers in a region participate.

In France, the confusion method is being worked on (the pheromone- based attraction mechanism of the moths is disrupted so that males and females cannot find each other). This method can be combined well with control by parasitic wasps.

swell

Individual evidence

  1. ↑ Jens Harnisch: Biology and current distribution status of the European corn borer (Ostrinia nubilalis Hübner, 1796) in Germany. Project work at InnoPlanta e. V., Gatersleben, October 11, 2006 PDF
  2. ^ Kaltenbach & Küppers (1987: p. 222)
  3. ↑ a b c d e f g h Carter (1984: p. 210–12)
  4. ↑ a b c d Featured Creatures - European corn borer Ostrinia nubilalis (Hübner) (Insecta: Lepidoptera: Pyralidae)
  5. ↑ a b Hannemann (1964: p. 346, 348)
  6. ↑ Kevin W. Wanner, Andrew S. Nichols, Jean E. Allen, Peggy L. Bunger, Stephen F. Garczynski, Charles E. Linn Jr., Hugh M. Robertson and Charles W. Luetje: Sex Pheromone Receptor Specificity in the European Corn Borer Moth, Ostrinia nubilalis. PLoS One, 2010. doi : 10.1371 / journal.pone.0008685 .
  7. ↑ Slamka (1997: 22)
  8. ↑ a b transgen.de: European corn borer
  9. ^ Yan Thomas, Marie-Thérèse Berthenod, Laurent Pelozuelo, Brigitte Frérot and Denis Bourguet: Genetic isolation between two sympatric host-plant races of the European corn borer, Ostrinia nubilalis Hübner. I. Sex pheromones, moth emergence timing and parasitism. Evolution, 57 (2): 261-273, 2003. doi : 10.1111 / j.0014-3820.2003.tb00261.x .

literature

  • David J. Carter: Pest Lepidoptera of Europe with special references to the British Isles. 431 S., Dr. W. Junk Publishers, Dordrecht 1984, ISBN 90-6193-504-0 .
  • Karl Eckstein: The butterflies of Germany 5th volume The small butterflies of Germany . 222 p., KG Lutz Verlag, Stuttgart 1933.
  • Hans-Joachim Hannemann: Small butterflies or Microlepidoptera II. The moths (sl) (Cochylidae and Carposinidae) The moths (Pyraloidea). In: Friedrich Dahl: The animal world of Germany and the adjacent parts of the sea according to their characteristics and their way of life. Part 50., VEB Gustav Fischer Verlag, Jena 1964.
  • Thomas Kaltenbach and Peter Victor Küppers: Small butterflies. Verlag J. Neudamm-Neudamm, Melsungen 1987, ISBN 3-7888-0510-2 .
  • František Slamka: The common moth (Pyraloidea) of Central Europe. 2nd Edition. Bratislava 1997, ISBN 80-967540-2-5 .

Web links

Commons : Ostrinia nubilalis  - album with pictures, videos and audio files