SUSCEPTIBILITY OF COWPEA (VIGNA UNGUICULATA (L.) WALPERS.) VARIETIES TO THE PULSE BEETLE (CALLOSOBRUCHUS MACULATUS FAB.)

Abstract

The pulse beetle, Callosobruchus maculatus (F.) is a key pest to stored cowpea. There is limited information on host plant resistance management of this pest on cowpea in Northern Ghana. A laboratory experiment was conducted to test for varietal resistance of some improved varieties against this pest in cowpea. The experiment was laid out in a Completely Randomized Design (CRD). Seven varieties of cowpea namely; Padi-tuya, Songotra, Apagbaala, Zaayura, Bawutawuta, Marfo-tuya and a local variety obtained from farmers’ stores in Nyankpala were tested. Data were collected on level of oviposition, developmental period, adult emergence, grain damage, grain weight loss, and seed viability. The results showed that the number of eggs laid on the seeds was significantly (p < 0.05) different among the varieties tested. More eggs were laid on seeds of the local variety, Apagbaala, Padi-tuya and Marfo-tuya, while Zaayura, Songotra and Bawutawuta recorded the least egg load. The mean developmental period was also significantly (p < 0.05) higher on Zaayura, Songotra and Bawutawuta, and lower on the local variety, Apagbaala, Padi-tuya and Marfo-tuya. A significantly (p < 0.05) higher number of adults emerged from the local variety, Apagbaala, Padi-tuya and Marfo-tuya, while Zaayura, Songotra and Bawutawuta recorded the least. Moreover, the local variety, Apagbaala and Padi-tuya recorded the highest percentage weight loss while Zaayura, Songotra and Bawutawuta recorded the least. Overall, susceptibility correlated positively with oviposition, emergence, grain damage, and grain weight loss. Zaayura, Songotra and Bawutawuta varieties consistently demonstrated high tolerance to infestation by C. maculatus and therefore, should be promoted for incorporation into further management/breeding programs to help minimize the high grain losses incurred by farmers during storage.