A comparative study of the bionomics of Clavigralla tomentosicollis Stäl (Hemiptera: Coreidae) on three varieties of cowpea (Vigna unguiculata (L.) Walp)

Clavigralla tomentosicollis Stal, is a notorious pod-sucking bug of cowpea in tropical agro - ecosystems. The improvement of cowpea grain yields by screening of cowpea lines for resistance to pod-sucking bugs has not been undertaken in South Africa. In this study, C. tomentosicollis populations were reared on fresh pods of two local cowpea varieties (Glenda and Bechuana White) and one improved variety (IT03K-396-3). Pre-oviposition periods of mated females fed on Glenda, Bechuana White and IT03K-396-3 were 2.5, 7 and 3.8 days, respectively. A longer oviposition period of 56 days was recorded on IT03K – 369 - 3 compared to 51.75 days and 54.75 days on Glenda and Bechuana White, respectively. A significantly (F=8.3, P < 0.05) higher number of eggs were laid by mated females fed on fresh pods of Glenda and Bechuana White than on IT03K-369-3, and lived for a significantly longer period on Glenda (F= 4.4; P < 0.05) than IT03K-369-3. Nymphal survival rate was also significantly higher, at 76.7% (F = 9.16, P < 0.05) on Bechuana white as well as nymphal weight gain (F = 8.11; P < 0.05). Results obtained from this study have significant implications for future research pertaining to cowpea varietal resistance against insect pests in general, and the integrated control of pod-sucking bug infestations on grain legumes in particular.