Clavigralla tomentosicollis (African pod bug)

The main damage on Phaseolus vulgaris (common bean) caused by C. tomentosicollis is dimpling and wrinkling of the seed coat and browning and shrivelling of seeds. These symptoms are caused by transmission of the fungus Nematospora phaseoli. C. tomentosicollis also causes a reduction in the weight, number and quality of seed beans.

Insecticides, particularly those with some systemic action such as dimethoate are usually effective in controlling the spiny brown bug (Hill and Waller, 1988; Singh, 1990; Allen et al., 1996). Synthetic pyrethroids such as alpha-cypermethrin, bifenthrin and cypermethrin are also effective (Amatobi, 1994).

In East Africa, some Cajanus cajan genotypes have been reported as being resistant to spiny brown bugs. TVu 1, TVu 1890, TVu 3164, TVu 3198 and TVu 3199 at the International Institute of Tropical Agriculture (IITA), Nigeria, have been found with low or moderate resistance. Hadronotus gridus is an effective parasite against low populations of C. tomentosicollis (Materu, 1971). Intercropping cowpea with sorghum reduces C. tomentosicollis in the field (Alghali, 1993).

In parts of Africa, C. tomentosicollis causes damage to more than 50% of bean (Phaseolus species) seeds (Jones, 1953) and over 50% of pigeon pea (Cajanus cajan) seeds (Materu, 1970). With an infestation of only two bugs per plant, the expected weight of pigeon pea seeds was reduced by 40-60%, the number of seeds reduced by 25-36%, and the seed quality by 94-98% (Hill and Waller, 1988). Ogunwolu (1992) has also noted damage to soyabean (Glycine max) and cowpea (Vigna species) by C. tomentosicollis.