Bruchus pisorum Linnaeus - Pea Weevil.
Systematic position.Class Insecta, order Coleoptera, family Bruchidae, genus Bruchus.
Biological group.Monophagous pest of pea.
Morphology and biology.Body of the beetle is black, covered with reddish-gray hairs dorsally. Its length varies from 4 to 5 mm. Elytra are short, not covering the last two abdominal segments. White cruciform pattern is located at the end of abdomen. Thoracic scutellum has a big excavation. First segments of antenna, tarsi and front legs are red. Cream-colored larvae have brown heads, varying from 5 to 6 mm in length. Eggs are oval, yellow. Overwintering takes place during the adult phase within pea grain in granaries and in fields, as well as in nature (under fallen leaves, mosses and lichens, in dumps, in fences, under the bark of trees). In the southern regions of its distribution, the pest overwinters mainly outside pea grains. In the northern regions, the species overwinters during the pupal phase or as IV-instar larva. In the zone of high damage, the beetles appear in April, when the average daily air temperature reaches 18-21°C. Additional feeding is necessary for the maturing of gametes, which takes several weeks. The insects feed on pollen and corolla of flowers of alfalfa, clover, dandelion, bittercress, shepherd's purse, lotus, chamomile, and common plantain. Feeding on pea flowers promotes rapid development of gametes. Colonization of pea fields by beetles takes place during plant budding, but the maximum number of insects is recorded during blossoming. Extensive migration (up to several kilometers) is observed during this period. After coupling, the beetles begin to lay eggs on the surface of bean pods (from the beginning of their formation until the beginning of ripening). The period of oviposition lasts 55-60 days. Fecundity reaches 220 eggs (up to 45 eggs on one pod). Embryonic development lasts 7-11 days. Hatching larvae penetrate into the pod and under the husk of pea grain through a hole. As many as 5 larvae can get into one grain. One of them develops, while the other larvae perish. All four larval and pupal phases occur inside the grain. The larval period lasts 30-45 days. The pupal period lasts 16-29 days. Young beetles appear at the end of August until the middle of September.
Distribution.The insect is widespread in Europe, Asia, North Africa; North, Central, and South America; and Southwestern Australia. Within the territory of the Former Soviet Union, the species occurs widely, i.e., in the European part of Russia and in Byelorussia north to 54°N (farther north it only appears during years with favorable conditions), in Middle Asia, North Kazakhstan, Transcaucasia, Caucasus, Moldova, and Ukraine. The eastern border of the area reaches Chelyabinsk. High harm is reported in the southern part of the Central Black Earth zone, in Southwestern Ukraine, and the Caucasus.
Ecology.The insect development depends on weather conditions. Mass oviposition is recorded during the middle of June; maximum number of beetles on pea fields is observed during this period. The oviposition is inhibited by average daily temperatures below 18°C and by heavy rains. Larvae are observed at the end of June and the beginning of July. The most favorable conditions for insects are temperatures of 25-30°C and relative humidity levels of 50-60%. If the temperature is above 35°C and humidity is 20-30%, then 50% of larvae die. Excess moisture levels during the period of grain ripening is unfavorable for the insects. The grains swell and the larvae die. The pest is cold-resistant. Beetles outside the grains die if the temperature falls to or below -9.5°C; however, the insects inside the grain survive at temperatures as low as -20°C. Insects successfully winter at temperatures below -18°C if snow is abundant. Mass perishing of bruchids is recorded during mild and warm winters. The species is monovoltine. Life span from egg to adult lasts 55-66 days. The number of pests in the current year depends on the insect numbers in the previous year. Most important predators are Bruchobius lacticollis Ash., Bruchocida orientalis Cwfd., Aplastomorpha sp. Lar., Eupteromalus leguminis Gahan., Eupelmus cyaniceps var. amicus, Sigalphus thoracius C., Microdontomerus anthonomi Cwfd., Triaspis thoracicus Curt., Trichogramma evanescens West., Pediculoides ventricosus Newp., and Staphylinus nigrellus Horn.
Economic significance.The species causes damage to pea plants. Weight of grains decreases. These grains are not suitable for sowing. High damage is found in the south of the pest distribution area every year. Intensive colonization of field edges by beetles is observed during the period of mass oviposition. Control measures include early harvesting of grain, stubbling, under-winter plowing, fumigation of grain in granaries, and insecticide treatments in fields during the period of budding and blossoming.
Related references:Brudnaya A.A. 1940. Natural enemies of pea weevil (Bruchus pisorum L.). In: Vavilov N.I., ed. Reports of All-Union Agricultural Academy, N 12. Moscow: Sel'khozgiz. P. 6-10 (in Russian).
Burov V.N. 1967. Significance of population density for Bruchus pisorum L. population dynamics (Coleoptera, Bruchidae). Zoologicheskii zhurnal 46(9): 1357-61 (in Russian).
Burov V.N. & Karpunina N.N. 1967. Physiological characters of pea weevil (Bruchus pisorum L.) during the autumn-summer period. Zoologicheskii zhurnal 46(6): 883-90 (in Russian).
Chmyr' P.G. 1970. Some control methods of agricultural engineering with pea weevil (Bruchus pisorum L.). In: Kolychev N.O. Science for plant protection. Voronezh: Central Black Earth Publishing House. P. 101-5 (in Russian).
Ivanova Z.V. 1959. Pea weevil. Moscow: Publishing house of agricultural literature. 47 p. (in Russian).
Kadamshoev M. 1985. To biology and damage of pea weevil (Bruchus pisorum L., Coleoptera, Bruchidae) in conditions of West Pamir. Izvestiya Akademii Nauk Tadzhikskoi SSR 2: 73- 6 (in Russian).
Karpunina N. 1966. Weeds and pea weevil. Zashchita rastenii 10: 54 (in Russian).
Karpunina N.N. 1971. Significance of weed plants in blossoming phase for pea weevil biology (Bruchus pisorum L.). In: Novozhilov K.V., ed. Bulletin of VIZR, N 17, Leningrad. P. 24-8 (in Russian).
Karpunina N.N. 1971. Features of pea weevil reproduction. In: Novozhilov K.V., ed. Bulletin of VIZR, N 22, Leningrad. P. 15-8 (in Russian).
Khimera E.I. 1988. Pea weevil in conditions of forest-steppe zone. In: Lesovoi M.P., ed. Republican inter-institutional scientific collection of papers, N 35. Kiev: Urozhai. P. 30-1 (in Russian).
Kirichek Yu.F. Damage of pea by pea weevil. Zashchita rastenii 11: 56-7 (in Russian).
Kolesnichenko L.I. 1972. Character of pea resistance (of different varieties) to pea weevil. Ph.D. Thesis. Leningrad: VIZR. 12p (in Russian).
Korab I.I. 1923. Pea agriculture in relation to damage by pea weevil. In: Bulletin of sort-seed production department of sugar-trust, N 7, Kiev. P.111-8 (in Russian).
Korab I.I. 1923. Additional information on pea weevil Laria (Bruchus) pisi L. observation in 1923. In: Bulletin of sort-seed production department of sugar-trust, N 7, Kiev. P.118-20 (in Russian).
Malakhanov Yu.A. 1988. Characteristics of pea resistance to pea weevil. In: Novozhilov K.V., ed. Bulletin of VIZR, N 70, Leningrad. P. 27-9 (in Russian).
Malakhanov Yu.A. 1989. Damaging of pea plants by pea weevil in dependence on vegetation conditions. In: Novozhilov K.V., ed. Bulletin of VIZR, N 74, Leningrad. P. 60-7 (in Russian).
Mazarakii V.V. 1903. About pea weevil (Bruchus pisi L.). In: Semenov A.P., ed. Proceedings of Russian entomological society, Saint-Petersburg. V. 36. P. 101 (in Russian).
Nikiforov A. 1962. Pea weevil and its control. Kolkhoznoe proizvodstvo 3: 25 (in Russian).
Posylaeva G.A., Malakhanov Yu. A. 1989. Pea weevil in Ukraine. Zashchita rastenii 3: 18-19 (in Russian).
Selivanova S.I. 1964. Detection of pea weevil. Zashchita rastenii 12: 31-3 (in Russian).
Vasil'ev I.V. 1939. Origin and world distribution of pea weevil (Bruchus pisorum L.). Vestnik zashchity rastenii 1. P. 44-5 (in Russian).
Vasil'ev I.V. 1941. Pea weevil (Bruchus pisorum L.). Vestnik zashchity rastenii 1. P.27-36 (in Russian).
Zatyamina V.V. 1967. Sources of colonization of fields by pea weevil and their influence on pest spreading in crops. In: Proceedings of Voronezh station of plant protection, V. 17. Voronezh: Central Black Earth Publishing House. P. 97-103 (in Russian).
Zatyamina V.V. 1976. Pea weevil. In: Lakhidov A.I., ed. Calculation and forecasting methods of pests and diseases development on field cultures in Central Black Earth Zone. Voronezh: Central Black Earth Publishing House. P. 83-5 (in Russian).