Bruchus pisorum (Linnaeus)
Common name: Pea weevil
Taxonomic placing: Insecta, HolometabolaColeoptera, Chrysomelidae.
Geographical distribution: Cosmopolitan.
Host plants: Peas (Pisum spp.)
Morphology: Adults 4-6 mm long, body globular, black with gray pubescence, the elytra punctate, with gray spots, shorter than the abdomen. Larva about 5 mm long, yellow-gray with a dark head, legs reduced.
Life history: In early summer the females lay eggs (about 25/female) on pea pods and the emerging larvae gnaw their way in, where they feed, develop and pupate. The adults develop during summer in the stored seeds, remaining quiescent till the next spring, completing a single annual generation.
Economic importance: The damage caused by this weevil may affect 80% of the crop, due to effect on consumers, receiving a lower price, and to having lower germination rates. Undisturbed large pest populations may reduce a stored pea crop to dust.
Horticultural control: Early pea harvest, before the first weevils reach adulthood. Destruction of pea residues and susceptible volunteer plants by ploughing, in order to bury any remaining pea grains.
Plant Resistance: A gene for resistance to the pea weevil was transferred from the resistant Pisum fulvum Sm. into P. sativum by introgression and with further selection, resulted in several resistant pea lines. Transgenic peas, expressing an enzyme inhibitor, provide complete protection against the weevil.
Chemical control: Pyrethroids were considered the most suitable insecticide against B. pisorum because of their persistence. The extracts of several plants were used to treat peas before egg laying. Fumigation may be used in storage.
Biological control: The braonid Triaspis thoracica attacks the pest within the seed. The egg parasitoid Uscana senex Grese Trichogrammatidae caused 50-80% parasitism rates and reduced seed damage by 70% in the field.
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Hormazabal, R.L. and Gerding, P.N. 1998, Release density of Uscana senex Grese (Hymenoptera: Trichogrammatidae) for control of Bruchus pisorum L. (Coleoptera: Bruchidae). Agro-Ciencia 14: 157-161.
Morton, R.L., Schroeder, H.E., Bateman, K.S., Chrispeels M.J., Armstrong, E. and Higgins, T.J.V. 2000. Bean a-amylase inhibitor 1 in transgenic peas (Pisum sativum) provides complete protection from pea weevil (Bruchus pisorum) under field conditions. Proceedings of the National Academy of Sciences of the USA. 97: 3820–3825.
Pajni, H.R. and Sood, S. 1976. Some observations on the biology of pea-weevil, Bruchus pisorum L. (Coleoptera: Bruchidae). Bulletin of Grain Technology 14: 201-205.
de Sousa-Majer, M.J., Hardie, D.C., Turner, N.C. and Higgins, T.J. 2007. Bean alpha-amylase inhibitors in transgenic peas inhibit development of pea weevil larvae. Journal of Economic Entomology 100:1416-22.