Scale insects
| Scale insects | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Australian woolly scale louse ( Icerya purchasi ) |
||||||||||
| Systematics | ||||||||||
|
||||||||||
| Scientific name | ||||||||||
| Coccoidea | ||||||||||
| Handlirsch , 1903 |
The scale insects or Coccoidea are a superfamily of insects and belong to the plant lice (Sternorrhyncha). About 90 of the known 3000 species live in Central Europe. The body length of the animals is between 0.8 and 6 mm, the largest species Aspidoproxus maximus can be up to 38 mm long. All scale insects feed on sap and are often considered pests for this reason. A typical example of the malicious behavior is the Buchenwollschildlaus .
The male scale insects are usually winged. The hind wings are transformed into swinging bulbs, they also have no mouthparts and accordingly do not take in any food.
The females usually live in large colonies on different parts of the plant. Their bodies are shield-shaped and often enclosed in a capsule; in many species the females are completely immobile. The long proboscis is inserted into the plant. Often the female scale insects are coated with a wax secretion . Parthenogenesis occurs in scale insects, the first larva is mobile and settles very quickly. The females lay huge amounts of eggs under their shield.
The young larvae hatch from around July and then migrate to leaves and young shoots. The sucking activity leads to the formation of honey dew during the summer .
The pigment carmine can be obtained from scale insects .
Systematics of scale insects
Scale insects are also represented in Central Europe by a number of family-ranked taxa .
- Scale insects
- Lid scale insects - Diaspididae
- Smallpox Lice - Asterolecaniidae
- Tube scale insects - Ortheziidae
- Cave scale insects - Margarodidae
- Cup scale insects - Coccidae
- Oak Nape Lice - Kermesidae
- Mealybugs and mealybugs - Pseudococcidae
distribution
Especially in winter and spring. On various houseplants, mostly on the undersides of the leaves, the leaf veins and the branches. Often found on: palms , oleanders , ficus , orchids , aralia. They like to attack ferns and hard-leaved plants such as citrus plants or laurel .
Since an adult scale insect usually maintains its location, it depends on good camouflage . Therefore, it usually lives on the underside of leaves or on branches and is color-matched to its surroundings. The presence of scale insects can often only be recognized by their sticky excretions as drops on leaves and on the ground or by the appearance of ants.
nutrition
Scale insects feed mainly on proteins present in the sap . Since plant sap - apart from water - mainly contains sugar, some species of bowl louse excrete the excess as sticky, clear honeydew drops . So that the louse does not stick together, it flings the drops away from itself.
Scale insects as pests
Some scale insect species are among the economically most important pests in agriculture. For example, the pineapple marmoset ( Dysmicoccus brevipes ) and Dysmicoccus neobrevipes are two of the main pests on pineapple plants, Asterolecanium coffeae is one on coffee, and the Australian scale louse ( Icerya purchasi ) is it on citrus fruits.
In addition to aphids and whiteflies , scale insects are among the most common pests on indoor plants. They remove nutrients from the plant. By the honeydew excreted some Napfschildlausarten and the subsequent formation of Rußtaupilz is the photosynthesis affected. Lid scale lice emit toxic substances into the plants. All of this inhibits the growth of the plant and, in extreme cases, contributes to the death of the host.
Honeydew can be a nuisance for people: in apartments it sticks together floors, furniture and windows, and outside car windows. In viticulture, it can affect the taste of the wine.
Cause of an infestation
The cause of a scale insect infestation usually lies in the unfavorable framework conditions of the plant. The scale insects are usually only the symptom. Scale insects like to attack weakened plants that are over-fertilized with nitrogen . In winter, many indoor plants get too little light and are very warm. This changes the composition of the sap and offers favorable conditions for the animals to multiply quickly.
Prevention and control
As an improvement measure, the site conditions of the plant and thus the health of the plant are primarily to be improved: Brighter, cooler site. The soil should be loosened, mulched and loosened with compost .
Suitable aromatic herbs: savory with beans, lavender with roses, nasturtiums in tree slices.
In the case of weak infestation on individual plants, it is sufficient to wipe the animals off the plants with a damp cloth or a brush, possibly with soapy water. Showering with a strong water jet is particularly gentle and efficient. In the spring, crush the parent mothers. Spray mixtures made from onion or potato peels , rhubarb leaves , garlic , nettle , tansy , wormwood or algae preparations are also suitable .
Oil-based pesticides can be used in the case of more severe infestation and in area crops. In area crops, crop rotation and mixed crops should be observed. In extreme circumstances, dimethoate (preparations such as Bi 58, Perfection, Rogor, etc.) can be used as a systemic pesticide.
There are also various beneficial insects against scale insects , each specializing in one type of louse. For example, Australian ladybirds can be used against mealybugs and mealybugs in the greenhouse and winter garden . Other natural enemies of the mealybug include lacewings , hoverflies , parasitic wasps , predatory bugs , earwigs and gall midges . It is therefore recommended that a specialist determine the exact species of the scale insects.
Scale insects as beneficial insects or symbionts
It is often overlooked that scale insects are not only pests but also beneficials. Sometimes they enter into symbioses with other animals or even with humans.
Scale insects as a dye
The production of the intense red dye kermes from scale insects has been known since ancient times and was at times of great economic importance. In the Mediterranean area, the species Kermes vermilio, which lives on the roots of evergreen oaks, was used for this . Porphyrophora polonica served as a cheaper substitute for carmine red in Eastern Europe in the Middle Ages . Since the discovery of America were both largely on cochineal ( real Carmine ), the dye of the US, only on the prickly pear cactus Opuntia ficus-indica living Dactylopius coccus repressed, she was already the Aztecs known. The dye was at times (after the precious metals gold and silver) the third most important import good from the New World; Instead, the species Protortonia cacti (under its old synonym Coccus cacti ) is often mistakenly given as the producer. The Porphyrophora hamelii, which lives in the Caucasus region, or the East Asian lacquer scale louse Kerria lacca (→ dye lacquer ) were also used less frequently . As a food coloring agent E 120, carmine / Koschenille is mainly used in colored candies, and also in jams, confectionery and alcoholic beverages. However , it has not been included in Campari available in Germany for some time.
Use as paint
The lacquer scale louse ( Kerria lacca ), which is native to South and Southeast Asia, supplies the shellac . The most famous applications are shellac records in the first half of the 20th century and hairspray . Today it is used in furniture care and furniture construction , in musical instrument construction especially for violins and in the food industry as a coating agent E 904, for example for chocolate dragees .
Use of wax
The male larvae of the Chinese wax scale insects Ericerus pela produce china or pela wax . A similar wax is also secreted by the larvae of the Indian wax scale louse Ceroplastes ceriferus ( Syn .: Coccus ceriferus ) (Indian wax scale louse). As well as from other Ceroplastes species (e.g. Ceroplastes irregularis ). This is where both male and female larvae separate the wax. Axin wax also supplies Llaveiella taenechina (Syn .: Coccus Axin ) from South America .
Use of the honeydew
- Ants: They use the honeydew as food. They literally milk the lice, protect them and contribute to the local spread of the young lice.
- Wasps: They use the carbohydrate-rich honeydew as food. They contribute to the pollination of the host plant.
- Bees: They collect honeydew and use it to make forest honey , also known as honeydew honey.
- People: As early as biblical times, the Bedouins processed the honeydew of the Sinai scale insect living on tamarisk trees into manna and sold it as sugar.
- Plants: Some host plants benefit from the mold that grows on the honeydew in that it can protect them from parasitic growth, such as lianas .
Scale insects as food
Birds and insects: Different bird and insect species have scale insects on their diet. They therefore play a role in the control of scale insects, see above. Some scale insect species, on the other hand, have found protection: their enemies avoid them because of their bitter body fluids.
Use in homeopathy
In classical homeopathy , the scale insect Coccus cacti is used to produce globules . The remedy is used against spastic cough, whooping cough and asthma . An effect beyond the placebo effect has not been proven - as is generally the case with homeopathic preparations.
Fossil evidence
Scale insects are particularly rich in species as inclusions in Baltic amber , but have also been found in Cretaceous and Tertiary amber from other deposits. Otherwise, fossils of this group of insects are extremely rare. The oldest evidence is a find from the Upper Triassic ( Rhaetian ) or the Lower Jurassic Kyrgyzstan (Mesococcidae family). The oldest evidence of brood care of a scale insect ( Wathondara kotejai ) is a find in the Cretaceous Birit .
literature
- Bernhard Klausnitzer : Coccina, scale insects. In Wilfried Westheide , Reinhard Rieger (Hrsg.): Special zoology part 1: single-celled and invertebrate animals. Gustav Fischer Verlag, Stuttgart / Jena 1997, ISBN 978-3-437-20515-6 , pp. 654-655.
Web links
Individual evidence
- ↑ CK Chávez-Moreno, A. Tecante, A. Casas (2009): The Opuntia (Cactaceae) and Dactylopius (Hemiptera: Dactylopiidae) in Mexico: a historical perspective of use, interaction and distribution. In: Biodiversity and conservation. Vol. 18, No.13: 3337-3355.
- ^ Wilhelm Halden, Adolf Grün: Analysis of fats and waxes. Volume 2, Springer, 1929, ISBN 978-3-642-89318-6 , p. 578.
- ↑ W. Weitschat, W. Wichard: Atlas of plants and animals in Baltic amber. Pfeil, Munich 1998, ISBN 978-3-931516-45-1 .
- ^ Arno Hermann Müller: Textbook of Palaeozoology. Volume II, part 3, 2nd edition, Jena 1978, DNB 790161656 .
- ↑ 100 million year old scale insects were brood care. In: labo.de , accessed June 9, 2017.