Cabbage moth
| Cabbage moth | ||||||||||
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Cabbage moth ( Plutella xylostella ) |
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Plutella xylostella | ||||||||||
| ( Linnaeus , 1758) |
The cabbage moth or cabbage moth ( Plutella xylostella ) is a butterfly from the family of the veil and half moths (Plutellidae).
features
The moths reach a wingspan of 12 to 18 millimeters. The forewings are very variable in color, their basic color can range from monochrome brown to gray and dark. In the middle of the wings there is a wavy light line that divides the wings into a lower, dark and an upper, light part. Seen from above, the moths have a distinctively colored back when the wings are closed.
The caterpillars are about 8.5 millimeters long and have a green body color. The head capsule is black in caterpillars in the first two stages, later it is brown.
Occurrence
The species, which presumably originally came from the Mediterranean area , has gradually been carried off by humans to different parts of the world, so that it is now spread around the world, even in remote areas. They are common everywhere and occur en masse in some years.
Way of life
The nocturnal moths are mostly found on or near the host plants. They fly all night, from about an hour after sunset to an hour before sunrise. They are counted among the migratory butterflies and can quickly compensate for weak populations through their flight. During the day the animals rest in the vegetation and, if disturbed, fly around aimlessly for a short time. They suck nectar from the flowers of the cruciferous family (Brassicaceae). They are only moderate fliers and usually only fly short distances when jumping. With the help of the wind, however, they can also cover great distances.
Flight and caterpillar times
The moths fly in Central Europe in two generations from April to October, in the other temperate zones a maximum of six generations occur per year, with the average development time varying from 18 to 51 days. With an annual average temperature of about 26 ° C, the development from egg to butterfly only takes about 11 days, so that up to 30 generations can follow one another in one year. This uninterrupted and at the same time overlapping generation sequence occurs, for example, in Hawaii or in the southern United States . The caterpillars are found in Central Europe from June to July and from August to September.
Food of the caterpillars
The caterpillars feed on cruciferous plants , such as the cabbage ( Brassica ) genus, which is important for agriculture . They mostly feed on the leaves, more rarely on the ovules.
Mating and development
Mating takes about an hour and takes place on the same day after hatching, resting on the vegetation. Eggs are usually laid shortly afterwards, with a female laying an average of 159 eggs over a period of around 10 days. They lay their eggs individually or in groups of two to eight on the top or bottom of the leaves of the food plants. Often they are deposited on the midrib, but also on the petioles and young stems. The eggs are about 0.64 by 0.32 millimeters, oval, flattened, have a fine reticulate structure and have a yellowish sheen. Before hatching, after about two to eight days, they turn dark and you can recognize the caterpillar inside. The caterpillars go through four stages until pupation, which occurs after 6 to 30 days. They eat in a loosely woven web as miners below the epidermis and form whitish mines in the process, later they eat the entire leaf sitting on the underside, but leave the veins untouched. If you disturb them, they wind up quickly and often fall to the ground securely on a thread. This thread can climb up the plant again after a while. The caterpillars are susceptible to rain, with an average of 56% drowning, with heavy rain and low temperatures causing higher failures. Pupation also takes place in a white, loose, net-like web, usually on the underside of the leaves or in other hidden places on the food plant or on the ground in the litter. After an average of eight days, the slip imagines . In Central Europe pupation takes place in July and August in the first generation and in October to April of the following year in the second.
Harmful effect and control
The cabbage moth is one of the most important pests on cruciferous plants, especially cabbage. By eating leaves, but also inflorescences, the species causes so much damage that in some regions it is not economically feasible to grow cabbage without pest control. The animals are very voracious, especially in the last stage of caterpillars.
The species is difficult to control because it often becomes resistant to a wide variety of insecticides. In North America, for example, because of resistance to permethrin and methomyl, other ways of fighting had to be found. Above all, a combination of different control methods is required to minimize resistance to insecticides. The cabbage moth is also the first species to develop resistance to Bt toxins .
About 90 parasites are known worldwide that decimate the populations of the diamond back moth. In agriculture, however, they only play a subordinate role in addition to the other methods of pest control due to the minimal damage tolerance in plants that are suitable for sale. In spite of this, various parasitoids exposed in Hawaii , such as the brackish wasp Cotesia plutellae from Europe, have shown success in combating them.
supporting documents
Individual evidence
- ↑ Tabashnik et al: Diamondback Moth Resistance to Bacillus thuringiensis in Hawaii PDF ( Memento of the original from August 21, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (English)
Web links
literature
- Thomas Kaltenbach, Peter Victor Küppers: Small butterflies . 1st edition. J. Neudamm-Neudamm, Melsungen 1987, ISBN 3-7888-0510-2 .
Web links
- www.lepiforum.de: Taxonomy and photos
- Plutella (Plutella) xylostella at Fauna Europaea