Pests

Ceutorhynchus obstrictus (Marsham) - Cabbage Seedpod Weevil.

Systematic position.

Class Insecta, order Coleoptera, family Curculionidae, genus Ceutorhynchus Germar. Closely related to Ceutorhynchus gallorhenanus Sol. and C. fallax Boh. Perhaps, some literature records of C. obstrictus are results of misidentification of material and refer to the aforementioned species.

Synonyms.

Ceutorhynchus assimilis Paykull; C. brassicae Focil.; C. floralis Ol., C. floriger Fourcroy, C. subglobosus Gmelin.

Biological group.

Pests of seed crops of cruciferous vegetables and rape.

Morphology and biology.

Body is black with length of 2-2.3 mm. Rostrum is slim and shining, strong and evenly curved. Pronotum is weakly convex, with prominence on each side behind mid length, rounded and narrowed apically. Elytra wide and flattened, slightly rounded laterally. Interstriae flat, densely punctuated, with 2-4 rows of short and narrow, gray or yellowish scales and with small scales along suture. Elytral striae are deep and broad with the same scales as those on interstriae. Legs are long and slender, femora without denticles; 3rd tarsal segment 2 times as wide as the 2n; tarsal claws are free at base and simple.

Distribution.

Europe including Northland, Asia Minor, and Northern America. In the former USSR, it is distributed in the European part from the Caucasus northward to Baltic States and Karelia, presumably in Transcaucasia.

Ecology.

Overwintered beetles appear in April after average daily temperature reaches 7-8°C. At first, the beetles appear on Lepidium sp., Raphanus sp., Barbarea sp.; later they migrate to cruciferous cultures. Adults feed on stems, pedicles, buds, stamens, pistils, gnawing small cavities. Oviposition continues from the 2nd half of May to the end of June. Female gnaws a hole on the young pods and lays 1 (rarely 2) white eggs inside. Fertility is about 40-150 eggs. Egg and larva development takes 7-10 and 30 days, respectively. Larva devours 3 to 7 seeds. In the beginning of June, mature larva gnaws outer hole in the pod and drops to soil. Pupation occurs inside the soil cradle at a depth to 2-3 cm. Young adults emerge until August. Beetles feed on weed cruciferous plants before the fall of autumn temperature. Adults hibernate in the soil or under the litter. Bracon variator Nees, B. fulvipes Nees, Triaspis obscurellus Nees are the larval parasites of C. obstrictus.

Economic significance.

Main damage occurs during larval stage to radish, garden radish, turnip, mustard, rape, garden turnip, and cabbage. Seed crops and quality of the seeds decrease as a result. C. obstrictus is one of the main pests of cruciferous seed crops in Leningrad Region and Belarus Republic. In Finland, 1 adult per 4 plants causes yield losses of spring rape seeds to 5-10%. Rape plant compensates the injury by increasing the number of pods. Control measures include sowing new rape fields a long distance from old cruciferous plantations. Seed harvest is dried out immediately after threshing. Pesticide treatment is necessary in budding stage of culture, before blossoming.

Reference citations:

Arzanov Yu.G. 1989. Ecological and faunistic review of the weevils (Coleoptera, Curculionidae) from the steppe and desert zones of Rostov region and Kalmykia. PhD Thesis. Leningrad: ZIN RAS, 24 p (in Russian)..
Baitenov M.S. 1974. The weevils (Coleoptera: Attelabidae, Curculionidae) of the Middle Asia and Kazakhstan. Alma-Ata: Nauka, 286 p (in Russian)..
Dmoch J. 1965. The dynamics of a population of the cabbage seedpod weevil (Ceutorhynchus assimilis Payk.) and the development of winterrape. Part 1. Ekologia Polska . Seria A. V. 13 (15). Warzawa: 249-287.
Dmoch J. 1965. The dynamics of a population of the cabbage seedpod weevil (Ceutorhynchus assimilis Payk.) and the development of winterrape. Part 2. Ekologia Polska . Seria A. V. 13 (24). Warzawa: 465-489.
Ioannisiani T.G. 1972. The weevils (Coleoptera, Curculionidae) of Byelorussia. Minsk: Nauka i Tekhnika, 352 p (in Russian)..
Ismailova M.Sh. 1993. Ecological and faunistic review of the weevils (Coleoptera: Apionidae, Rhynchophoridae, Curculionidae) from the low-lying and submountain territories of Daghestan. PhD Thesis. St. Petersburg, 23 p (in Russian)..
Korotyaev B.A. 1989. Materials to the knowledge of Ceutorhynchinae (Coleoptera, Curculionidae) of Mongolia and the USSR. In: Scarlato O.A., ed. Insects of Mongolia (7). Leningrad: Nauka. P. 107-282 (in Russian).
Korotyaev B.A. & Cholokava A.O. 1989. A review of the weevil subfamily Ceutorhynchinae (Coleoptera, Curculionidae) of the fauna of Georgia. Entomol. obozr. 68(1): 154-177 (in Russian).
Petrukha O.I., Globova N.D. 1974. Family Curculionidae. In: Vasil.ev, V.P., ed. Pests of agricultural crops and forest plantations. V.2. Arthropods. Kiev: Urozhai, p. 107-177 (in Russian).
Poiras A.A. 1998. Catalogue of the weevils (Coleoptera, Curculionoidea) and their host plants in the Republic of Moldova. Pensoft Series Faunistica N 10. Sofia-Moscow: Pensoft Publishers. 156 p.
Polyakov I.Ya., Kopaneva L.M., Dorokhova G.I. 1981. Number and distribution of pests and entomophages of industrial cultures in different agricultural zones of the USSR. In: Kopaneva L.M., ed. Key to harmful and useful insects and mites of industrial cultures in the USSR. Leningrad: Kolos: 5-26 (in Russian).
Polyakov I.Ya., Kopaneva L.M., Dorokhova G.I. 1982. Number of pests and entomophages of vegetable cultures and potato in different agricultural zones of the USSR. In: Kopaneva L.M., ed. Key to harmful and useful insects and mites of vegetable cultures and potato in the USSR. Leningrad: Kolos: 5-36 (in Russian).
Prasolov V.N. 2005. Weevils (Curculionoidea part.) of the Leningrad Region. http://www.zin.ru/Animalia/Coleoptera/Rus/Prasolov.htm (in Russian).
Silfverberg H. 1992. Enumeratio Coleopterorum Fennoscandiae, Daniae et Baltiae. Helsinki-Helsingfors: Helsingin Hyonteisvaihtoyhdistys, 94 p.

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