Bioecology of the cowpea pod weevil Piezotrachelus varius Wagner (Coleoptera: Curculionidae), and cowpea seed damage

Ntonifor, N., Edimengo, P. & Tamo, M. (2006). Bioecology of the cowpea pod weevil Piezotrachelus varius Wagner (Coleoptera: Curculionidae), and cowpea seed damage. African Entomology, 14(1), 185-191.

The bioecology of the cowpea pod weevil, Piezotrachelus varius, and post-harvest seed losses were studied in the laboratory and in cowpea fields in the Western Highlands of Cameroon during the first and second cropping seasons of 1999 and 2000. Adult weevils appeared before flowering and fed on cowpea leaves and flowers before switching to newly formed pods. Pod-feeding produced holes on the pod wall mesocarp through which the female layed a cluster of 2-5 ovoid, semi-translucent eggs; the eggs hatched 3-4 days later. Three larval stages fed on the peas and pupated within the pod, usually near the damaged peas. Juveniles continued to feed in the mature harvested cowpea pods in storage; adults emerged up to two weeks after harvest. Development was completed within 16-17 days and the adults lived for more than five months. Post-harvest cowpea seed damage peaked two weeks after harvest. A number of hymenopterous parasitoids, Anisopteromalus calandrae Howard, Pteromalus sp. (Hymenoptera, Pteromalidae), Pediobius sp., Aprostocetus sp. (Hymenoptera, Eulophidae) and Bracon sp. (Hymenoptera, Braconidae) emerged from the pods. These were collected and appeared to be potential parasitoids of P. varius. During the off-season for cowpea, P. varius adults survived on cowpea haulm residue left in the field and on surrounding cultivated and indigenous alternate hosts. The implication of this bio-ecological information in the management of P. varius populations is discussed.