Spotted cabbage weevil
| Spotted cabbage weevil | ||||||||||||
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Spotted cabbage weevil ( Ceutorhynchus pallidactylus ) |
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| Ceutorhynchus pallidactylus | ||||||||||||
| ( Marsham , 1802) |
The spotted cabbage stem weevil ( Ceutorhynchus pallidactylus ) is a beetle from the family of weevils (Curculionidae).
features
The spotted cabbage weevil is a typical weevil. The eggs have a longitudinal diameter of 0.56 mm and a transverse diameter of 0.38 mm. They are shiny, milky white, and opaque. The larvae go through three stages of development until pupation. In the third larval stage, the larvae are 4 to 6 mm long. The larvae are legless and have a brownish head capsule . The larval body initially appears whitish, later more yellowish. The adult beetle is 2.5 to 3.2 mm in size and appears gray-spotted. There is a white spot on the wing covers , which gives the insect its German name. The beetle has strong scales and looks a bit scruffy. The males are smaller than the females and show a dimple on the last abdominal sternite to make mating easier. The male also has a spike attachment at the end of the rear rail, which enables the female to cling to the female during mating.
Occurrence
The spotted cabbage weevil is common in Central and Northern Europe.
biology
The adult beetles fly from their winter quarters (forest edges) into the young rapeseed stands at temperatures of around 12 ° C in spring (March). In addition to the temperature, the wind strength and the radiation intensity play a role in immigration into the fields. There is no approach at wind speeds of more than 3 meters per second.
The females first go through a ripening process on the young rape leaves because the gonads are not yet mature. After about 10 to 14 days (depending on the weather) the females begin to lay eggs in the petioles of the rape plant. Usually 3 to 5 eggs are laid. The total number of eggs deposited per female can vary greatly.
The larvae develop from the eggs in a few days and go through a total of 3 larval stages. The larvae first eat in the pulp of the leaf stalks, but then migrate into the main shoot of the plant in the course of their development, where they then mine in the pulp. At the end of May / beginning of June the larvae migrate from the plants by eating a borehole in the rapeseed stem. The larvae drop to the ground and then migrate into the ground. The larvae pupate at a depth of about 3 cm. The adult beetles hatch from the ground in early July. The young beetles then continue to eat old rapeseed stocks or weeds from the Brassicaceae family for a while before they migrate to the winter quarters. Overall, the spotted cabbage weevil only goes through one generation per year.
Initial studies assume that climate change will shift the immigration of the Brussels weevil from winter quarters to the rapeseed fields to an earlier date in the year.
Host plants
Infestation is possible on rapeseed ( Brassica napus ), turnip rape ( Brassica rapa ), cabbage ( Brassica oleracea ), black mustard ( Brassica nigra ), Sarepta mustard ( Brassica juncea ), white mustard ( Sinapis alba ), krambe ( Crambe maritima ) and numerous wild plants from the Brassicaceae family, e.g. B. Hederich ( Raphanus raphanistrum ), shepherd's purse ( Capsella bursa-pastoris ).
Harmful effect
The spotted cabbage weevil, which occurs widespread and often appears in larger numbers, usually causes little damage in weak plant populations. To reduce the extent of damage, it is advisable to take all measures to promote growth. Eating damage or puncture sites for laying eggs can represent entry points for diseases (e.g. Phoma ). The possible yield losses in weak stocks are estimated at around 20%.
Combat
The basis for targeted chemical control is choosing the right date by setting up and observing yellow bowls in good time . The first treatment with pyrethroid agents should be carried out three to four days after the currently applicable threshold of 10 to 15 weevils ( large rapeseed weevil and spotted cabbage weevil together) per yellow peel is exceeded in three days . A second treatment may be necessary if the influx is lost.
In addition to chemical control, natural opponents play an important role, e.g. B. the parasitoids . The parasitic wasp Tersilochus obscurator from the order of the Hymenoptera can parasitize the larvae of the spotted cabbage weevil in April / May. The parasitic wasp looks for the host larvae, which mines in the pulp of the leaf style, and sticks with its ovipositor through the plant tissue into the larva of the spotted cabbage weevil to lay an egg. The development of the host larva is initially not disturbed. Only when the larva leaves the plant to pupate in the ground does the larva of the parasitoid hatch and kill the host larva. The larva of the parasitoid then pupates in the ground and hatches in the following spring. In addition to Tersilochus obscurator , the species Tersilochus tripartitus Brischke, Tersilochus exilis Holmgren and Stibeutes curvispina (Thomson) are also listed as parasitoids of the larvae of the Spotted Cabbage Weevil .
The entomophagous species of fly Phaonia trimaculata can lay its eggs in damaged rapeseed stems. The larvae of the fly then feed on the larvae of the spotted cabbage weevil. A reduction in weevil larvae is estimated at up to 55%.
A decimation of the larvae of the spotted cabbage weevil is also possible by predatory ground beetles .
Resistance breeding
Classic plant breeding to achieve insect-resistant rape varieties is still in its infancy. The first results are available from Canada on resistant genotypes of summer oilseed rape that are resistant to the cabbage weevil. Some possible sources of resistance in the resynthesis of oilseed rape have been discovered in Germany for the spotted cabbage weevil . Attempts to cross- breed this material and to breed resistant rape varieties are still pending.
Synonyms
- Ceutorhynchus quadridens carapace, 1795
literature
- David V. Alford: Biocontrol of Oilseed Rape Pests. Blackwell Publishing, Oxford 2003 ISBN 0-632-05427-1
Individual evidence
- ↑ B. Broschewitz: Investigations on the biology and harmful effects of the spotted cabbage weevil (Ceutorhynchus quadridens tank) on winter rape (Brassica napus L. var. Oleifera Metzg.). Dissertation, University of Rostock, 1985
- ^ A. Johnen, H. Meier: A weather-based decision support system for managing oilseed rape pests. Proceedings of the British Crop Protection Council (BCPC). Conference Pests & Diseases 2000, Brighton, UK, pp. 793-800, 2000
- ↑ H. Friesland: A meteorologically justified forecasting method for the cabbage weevil in winter rape. Agricultural Yearbook 67, special issue, 1990
- ↑ A. Körting: About the way of life of the spotted cabbage weevil (Ceutorhynchus quadridens Panz.) And its importance as an oil crop pest. Work on physiological and applied entomology from Berlin Dahlem 9, pp. 207-237, 1942
- ↑ J. Junk, M. Eickermann, K. Görgen, M. Beyer, L. Hoffmann: Ensemble-based analysis of regional climate change effects on the cabbage stem weevil (Ceutorhynchus pallidactylus (Mrsh.)) In winter oilseed rape (Brassica napus L.). The Journal of Agricultural Science. doi : 10.1017 / S0021859611000529
- ^ W. Speyer: Contribution to the biology of the spotted cabbage weevil (Ceutorrynchus quadridens Panz.). Entomologische Blätter 17, pp. 118-124, 1921
- ^ E. Günthart: Contributions to the way of life and control of Ceutorhynchus quadridens PANZ. and Ceutorhynchus napi Gyll. with many observations on other cabbage and rapeseed pests. Communications from the Swiss Entomological Society 23, pp. 441–591, 1949
- ↑ M. Landschreiber: The pre-flower pests are still on the advance. RAPS 23, pp. 4-9, 2005
- ↑ R. Fritzsche: Phaeonia trimaculata Bouché as a parasite of the great cabbage bush Ceutorrhynchus napi Gyll. and Ceutorrhynchus quadridens Panzer of the spotted cabbage bush. Reprint from the newsletter for the German Plant Protection Service 9, pp. 35–36, 1955
- ↑ LM Dosdall, LS Kott: Introgression of resistance to cabbage seedpod weevil to canola from yellow mustard. Crop Science 46, pp. 2437-2445, 2007
- ↑ M. Eickermann, B. Ulber: Screening of oilseed rape and other brassicaceous genotypes for susceptibility to Ceutorhynchus pallidactylus (Mrsh.). Journal of Applied Entomology 134, pp. 542-550, 2009 doi : 10.1111 / j.1439-0418.2009.01449.x