Citrus mealybug
| Citrus mealybug | ||||||||||||
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Planococcus citri , illustration |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Planococcus citri | ||||||||||||
| ( Risso , 1813) |
The citrus aphid ( Planococcus citri ) is a scale insect from the family of mealybugs (Pseudococcidae).
features
The female lice reach a body length of 3 to 5 millimeters. They have an oval, pink-colored body that is covered with white wax deposits. These form a ring of small threads on the sides of the body. The males are significantly smaller than the females and are winged.
Occurrence
The species is one of the most common mealybugs and occurs in all tropical regions of the world ( pantropical distribution). But you can also find them in the subtropics , especially in almost all countries with coffee plantations . In many other parts of the world they are found on ornamental plants in houses and apartments.
Way of life
Both the nymphs and the adults of the citrus butterflies can move about. There are two forms of the species. One lives on the roots of the plants, the other on their leaves, twigs and fruits. The food crops on which the species is a pest with only little economic relevance include Annona , coffee and cotton . Other food crops are bananas , star fruit , cocoa trees , macadamia , mango and citrus plants . Colonies of citrus bugs are made up of equal parts of males and females. The species produces little honeydew , but is still interesting for some ant species , such as Anoplolepis longipes . By protecting the ants, damage to the host plants is usually increased.
development
The males go through four larval stages. On coffee plants, the four moults take place after an average of 9.9 days to the second stage, after 8.7 days to the third, after 2.5 to the fourth and after 3 days to the adult insect. In the second stage, a dark hue develops around the body and about two days later the animals begin to spin a cocoon around themselves, which becomes denser as they develop until the fully developed nymph sheds its skin into an imago. After hatching, the males only live about 2 to four days, the entire lifespan from hatching from the egg averages 27 days. The females only go through three larval stages. On coffee plants, molting takes place after an average of 11.5 days to the second stage, after 8.2 days to the third and after 8.4 days to the adult insect. Females live significantly longer than the males with an average of 87.6 days (including development 115 days). After 15 to 26 days they begin to lay their yellow-orange eggs. A total of around 200 to 400 pieces are placed in groups and coated with wax. After 2 to 10 days, the nymphs hatch. They are not covered with white wax deposits during the first stage, they wear them from the second stage.
Symbiotes
In 2011, John McCutcheon and Carol von Dohlen published the discovery of symbiotic proteobacteria in citrus smear louse, for which they suggested the names Tremblaya princeps and Moranella endobia . It is a two-stage symbiosis. While T. princeps (a beta proteobacteria ) lives directly in the Planococcus citri, lives M. endobia (a gamma proteobacteria ) in the cytosol of T. princeps .
All three organisms are linked to one another through the synthesis of essential amino acids . The citrus mealybug cannot produce these itself. They are manufactured by T. princeps , which however requires the help of M. endobia for this , since the reaction chains in T. princeps themselves are incomplete. Certain amino acids ( arginine , isoleucine and phenylalanine ) probably even require the help of genes from the citrus smear itself. It is still unclear how the necessary intermediates and enzymes are exchanged between the organisms.
T. princeps has a genome with only 139 kilobases . It is the smallest genome ever found in a cell .
Damage
Citrus bugs cause yellow and then withering leaves and the death of the roots, which, especially in connection with the infestation of fungi of the genus Porlinge ( Polyporus ), can lead to the death of the entire plant. The cocoa swollen shoot virus (CSSV) is also transmitted to cocoa plants .
Natural enemies and combat
The natural enemies are a number of parasites living Hymenoptera and predatory beetles . Fungal attack can also decimate colonies.
In the event of an infestation, plants with leaves that are still green or yellow can be treated; if the leaves are already withered, the plants must be dug up and destroyed. Applied are malathion , diazinon , dimethoate and parathion in particular in connection with a vegetable oil soap solution.
supporting documents
Web links
Individual evidence
- ↑ Nested symbionts share amino acid synthesis. In: Spectrum of Science , October 2011. Spectrum of Science Verlagsgesellschaft mbH , Heidelberg. ISSN 0170-2971
- ^ A b John P. McCutcheon, Carol D. von Dohlen: An Interdependent Metabolic Patchwork in the Nested Symbiosis of Mealybugs. In: Current Biology , Volume 21, Issue 16, 1366-1372, August 11, 2011. ISSN 0960-9822 ( English ), doi : 10.1016 / j.cub.2011.06.051 .