Response of Selected Local Cowpea Vigna unguiculata (Walpers) Grain Varieties to Postharvest Infestation by Callosobruchus maculatus (Fabricius)

Abstract

An assessment of susceptibility of selected predominant local varieties
of Vigna unguiculata in Adamawa State, Nigeria to postharvest cowpea
bruchid (Callosobruchus maculatus) infestation was carried out for a
period of 2 months (56 days). The study was organized in a completely
randomized design (CRD) with 3 replications. Four commonly grown
local cowpea varieties viz; Bakin hanchi, Banjiram, Mai madara and
Jan wake sourced from farmers in Yola town were used. Parameters
measured includes the susceptibility index (SI), grain damage and
weight loss. Data collected were analyzed using Variance analysis and
means were separated using Duncan Multiple Range Test (DMRT) at
5% level of probability. Results showed that SI was significantly
different (p < 0.05) among the cowpea cultivars – range; 4.4 to 6.2.
Based on the Dobie rating; Banjiram and Mai madara were moderately
resistant with lower F1 progeny production of 33.3 and 35.0,
respectively - with Mai madara having the highest median
developmental time of 35 days. However, Bakin hanchi and Jan wake
were moderately susceptible with higher F1 progeny production of 53.3
and 54.0, respectively. Results on grain damage and weight loss
showed that Bakin hanchi and Jan wake recorded the highest grain
damage and weight loss of 58.9% and 54.6%; 44.1% and 39.4%,
respectively. Correlation and linear regression analyses detected
positive and significant relationships between grain damage and
susceptibility index (r = 0.962, R2 = 0.926, p = 0.038) and between
grain weight loss and grain damage (r = 0.995, R2 = 0.991, p = 0.005).
While it is needful to source and screen more local varieties in the
study area, the current study shows that Banjiram and Mai madara
have promising potentials to withstand C. maculatus infestation – an
information which could be helpful for farmer and grain merchants
education and for incorporation into integrated pest management
strategies against the cowpea bruchid.