Acanthoscelides obtectus Say - Bean Weevil

Systematic position.

Class Insecta, order Coleoptera, family Bruchidae, genus Acanthoscelides.

Biological group.

Oligophagous pest of leguminous.

Morphology and biology.

The beetle body is ovoid, slightly convex, light or dark brown, with yellow-green golden hairs and longitudinal spots from above, light gray hairs from below. Its length varies from 2 to 5 mm. Dark brown short elytra do not cover abdominal end. Pronotum is wider than it is long; quadrangular scutellum is large. The insect has clavate antenna (first 4-5 segments are red-brown) and yellow-red legs. Oblong egg is white, about 0.6-0.7 mm in length. Young cylindrical white larvae have bristles and 3 pairs of legs. White pupa is about 4 mm in length. Overwintering of the Bean Weevil takes place at the stages of beetle or larva (other stages can also winter),usually in storehouses. In southern part of the species area, the overwintering can be observed in plant residues. The beetles appear at the temperature 12.5°C, but they are inactive at the temperature below 16°C. The insects migrate to fields at 20°C. At first they feed on vetch, peavine, lupin, alfalfa, and other leguminous cultures; they then move on to haricot bean, bean, soybean, lentils. The pest also migrates to grain fields. In some days after coupling, female lay eggs into or on ripening pods by groups (5-20), piercing the pod sutures or gnawing holes. Fecundity of one female reaches 200 eggs. The eggs develop during 30-45 days. Larvae penetrate into the grains, eating the contents completely. Several larvae can develop in one grain (to 56). Larval period lasts 3-3.5 weeks. Pupation also takes place in grain (9-29 days). Life cycle of one generation takes 100-110 days. The pest arrives in the storehouse with grain where it develops until cold.


The native land of this species is Central America. It was transferred with grain to Europe in the end of Nineteenth century; in the 1920s it was brought to Crimea. Now the Bean Weevil is spread in Europe, Asia, North and South America, Africa, Australia, Hawaiian Islands, and others territories. Within the territory of the Former Soviet Union, the insect is marked with spotted distribution. The northern border of its area goes along northern borders of Lithuania, Byelorussia, Tula and Ryazan' Regions, Bashkortostan, Tatarstan. Sometimes it is observed in the southern part of West Siberia. In storehouses, the pest occurs in more northern territory. High harming activity is reported in Transcaucasia, Krasnodar Territory, in some regions of Ukraine.


The most favorable conditions for the insect are the temperatures 27-29°C (beetles), 24-27°C (larvae), and 22-26°C (pupa). Higher and lower temperatures cause a decrease of fecundity. The species is very sensitive to temperatures below zero. The Bean Weevil prefers high humidity, 80-88%. It gives 2-5 (2 in fields) generations in conditions of Transcaucasia and Middle Asia; 3-4 (1 in field) in Krasnodar Territory, Ukraine, Moldova, Byelorussia, Kazakhstan. The largest number and harming activity are observed at the end of June and in July. Most important predators are Eupelmus degeeri Dalm., E. maculipes Walk., E. cyaniceps Ashm., Bruchobius laticollis Ashm., Lathromeris senex Grese., Bruchocida orientalis Cwfd., Aplastomorpha sp. Lar., Eupteromalus leguminis Gahan., Sigalphus thoracius C., Microdontomerus anthonomi Cwfd., Triaspis thoracicus Curt., Trichogramma evanescens West., Pediculoides ventricosus Newp., Staphylinus nigrellus Horn.

Economic significance.

The Bean Weevil causes significant damage to haricot-bean and bean. Larvae usually eat the pod contents completely, decreasing the yield by 50-60%. Partially damaged grains lose their germinating power and taste quality. The pest damages grain in both field and storehouses, becoming rather harmful. Control measures include keeping the temperature below zero in storehouses, fumigation, insecticide treatments in fields.

Reference citations:

Chelidze I.A. 1966. To studying bean weevil in Georgia and its control. In: Kanchaveli L.A., ed. Proceedings of Georgian plant protection institute, N 18. Tbilisi: Georgian NIIZR. 89-91 p. (in Russian).
Egorov A.B. 1989. Review of weevil-beetles (Coleoptera, Bruchidae) of the genus Acanthoscelides Schilsky in "Fauna of the USSR" (Lukyanovich & Ter-Minasyan, 1957). Entomologicheskoe obozrenie 68: 748-758 (in Russian).
Karapetyan A.P. 1983. About ecology and harming activity of bean weevil Acanthoscelides obtectus (Say) in Armenian conditions. Biologicheskii zhurnal Armenii 36(8): 647-651 (in Russian).
Medvedeva V.I. 1953. Bean weevil and its control. Moscow: Publishing house of agricultural department. 16 p. (in Russian).
Medvedeva V.I. 1956. Bean weevil. Zashchita rastenii ot vreditelei i boleznei 2: 48-50 (in Russian).
Ovodov I. 1964. Bean weevil. Zernobobovye kul'tury 1: 35-36 (in Russian).
Pavlyushin V.A., Lazarev A.M. 2005. Bean weevil. Zashchita i karantin rastenii 12: 34-35 (in Russian).
Ragimov K.B. 1973. Bean weevil . dangerous pest of leguminous cultures in Azerbaijan. In: Mzhavanadze A.V., ed. Proceedings of Sixth Session of Transcaucasian Board to coordination research works on plant protection (12-15 November, 1973). Tbilisi. 67-68 p (in Russian).
Rachvelishvili E.V. 1972. The influence of air humidity on bean weevil (Acanthoscelides obtectus Say). In: Kanchaveli L.A., ed. Proceedings of Georgian plant protection institute, 23. Tbilisi: Georgian NIIZR. 57-59 p. (in Russian).
Rachvelishvili E.V. 1975. Biological features of bean weevil (Acanthoscelides obtectus Say) in Georgia. In: Kanchaveli L.A., ed. Proceedings of Georgian plant protection institute, 27. Tbilisi: Georgian NIIZR. 44-47 p. (in Russian).
Sai Mpu Fregat. 1992. Biological basis for control measures improvement on haricot-bean seeds against bean weevil. PhD Thesis. Moscow: TSKhA, 24 p. (in Russian).
Sindyashina N.G. 1958. New pest of haricot-bean Acanthoscelides obtectus Say in Stavropol' area. In: Salmin I.G., ed. Proceedings of Stavropol' agricultural institute. 8. Stavropol': Stavropol' publishing house. 161-166 (in Russian).
Shavrina E.A. 1988. About temperature and humidity influence on bean weevil number and damaging haricot-bean seeds at keeping conditions. In: Novozhilov K.V., ed. Proceedings of VIZR, N 71. Leningrad: VIZR. 34-56 p. (in Russian).
Shevchenko M.I. 1970. Ecological features of bean weevil and basis for control measures. In: Zakolodina-Mitina L.A., ed. Plant protection against agricultural pests, diseases, weeds in Pskov region (Proc. of Velikie Luki agricultural institute). 11. Velikie Luki: SKhI. 24-28 p. (24-28).
Vasil'ev I.V. 1934. Bean weevil. Sukhumi: Quarantine station of Narkozem of Abkhazian ASSR. 12 p. (in Russian).
Vasil.ev V.P., ed. 1973. Pests of agricultural crops and forest plantations. 2. Kiev: Urozhai. 95-96 p. (in Russian).

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