Callosobruchus maculatus (Fabricius).

Taxonomic placing: Insecta, Holometabola, Coleoptera, Chrysomelidae. {The genus Callosobruchus was formerly in the family Bruchidae}.

Common name: Cowpea weevil.

Geographical distribution: Cosmopolitan, probably of West Africa origin, whence it was distributed around the globe with the trade in legumes.

Host plants: Many stored legumes, such as cowpea, soybean, gram and peas.

Morphology: The body of the adult is 3-4.5 mm long, reddish-brown, with black spots on the prothorax and elytra. The last segment of the abdomen extends out from under the short elytra, and also with black spots. The females are sometimes larger and darker than the males. This pest has two forms, one flightless, the other a flying form. The larva is whitish.

Life cycle: The female cements its eggs (up to 200) on the surfaces of legume seedpods or seeds in the field or in storage. The larvae burrow into the seeds where their entire development (four instars plus pupal stadium) is completed. The larvae cannot move among seeds, thus restricted to the seed that their mother has chosen for them. They pupate there, emerging as reproductively mature adults that are well adapted to storage conditions, requiring neither food nor water to reproduce. The threshold of development is at 14°C and 435 day degrees are required for the completion of a generation. A complete life cycle takes 4-5 weeks and there may be 6-7 overlapping annual generations. The beetles live only for 1-2 weeks.

Copulation in this species copulation is injurious to the female, because the penis bears spines that damage the female‘s reproductive tract. These spines do not increase reproductive success for either sex, and their evolutionary significance is not clear.

Economic importance: Damage to lentils, especially if stored for extended periods, may reduce their germination capacity by up to 80%. Infestations can start in the fields or in storage.

Management

Cultural Control: Good store hygiene, including the removal of any infested residues, will limit infestations, as will intercropping maize with cowpeas, and harvesting crops early. Freezing a storage area for six to 24 hours at -18°C will kills both adults and larvae.

Plant resistance: Legume pods with hairy and thick walls are resistant to infestations. Adzuki beans have been genetically modified to express alpha-amylase inhibitors (alphaAI), making them resistant to the pest.

Chemical control: Various plant extracts, including neem, together called botanical biological pest control agents, are used against the pest.

Biological control: Several hymenopterous parasitoids, such as Anisopteromalus calandrae, Uscana mukerjii and Dinarmus spp. specifically target Callosobruchus species. Dinarmus basalis attacks small larvae and thus limits their damage, although their presence still makes the beans unfit for sowing and human consumption. Uscana mukerjii is an egg parasite which prevents egg hatching.

References

Boeke, S.J., Barnaud, C., van Loon, J.J.A, Kosso, D.K., van Huis, A. and Dicke, M. 2004. Efficacy of plant extracts against the cowpea beetle, Callosobruchus maculatus. International Journal of Pest Management 50: 251-258.

Edvardsson, M. and T. Tregenza. 2005. Why do male Callosobruchus maculatus harm their mates? Behavioral Ecology 16: 788-93.

Ishimoto, M. and Chrispeels, M .J. 1996 Protective mechanism of the Mexican bean weevil against high levels of alpha-amylase inhibitor in the common bean. Plant Physiology 111: 393–401.

Kapila, R. and H. C. Agarwal 1995. Biology of an egg parasite of Callosobruchus maculatus (Fab.) (Coleoptera: Bruchidae). Journal of Stored Products Research 31: 335-41.

Nwanze, K.F. and,Horber, E. 1975. Laboratory techniques for screening cowpeas for resistance to Callosobruchus maculatus F. Environmental Entomology 4: 415–419.

Shaaya, E., Kostjukovsky, M., Berg, J.E.H. and Sukprakarn, C. 1997. Plant oils as fumigants and contact insecticides for the control of stored-product insects. Journal of Stored Products Research 33: 7-15.

Soundarajan, R. P., Chitra, N., Geetha, S. and Poorani, J. 2012. Biological control of bruchid Callosobruchus maculatus (F.) in blackgram. Journal of Biopesticides 5 (Supplementary): 192-95.

Web site: https://www.google.co.il/search?q=callosobruchus+maculatus&noj=1&tbm=isch&tbo=u&source=univ&sa=X&ved=0CBwQsARqFQoTCIuJmfuMv8gCFYpAFAod5hAJpw&biw=1024&bih=695 http://en.wikipedia.org/wiki/Callosobruchus_maculatus