Effects of intercropping tomato (Lycopersicon esculentum) at different times with cowpea (Vigna unguiculata) or okra (Abelmoschus esculentus) on crop damage by major insect pests

Abstract

Two 2-year field trials were conducted in Nigeria to investigate the effectiveness of tomato intercropped at different times with cowpea or okra in controlling the field densities of cowpea pod-sucking bugs and okra flea beetles. The two experiments were arranged as split-plots within a randomized complete block design. The main plots were 4-week-old tomato seedlings transplanted into a field, with cowpea or okra intercropped at 0, 2 or 4 weeks after transplanting tomatoes, while the two sub-plots were cowpea or okra sole crop and tomato/cowpea or tomato/okra intercrop. The densities of the pod-sucking bugs Clavigralla tomentosicollis, Riptortus dentipes, Anoplocnemis curvipes and Nezara viridula were significantly lower (P<0·05) on cowpea intercropped at 2 weeks after transplanting tomatoes than those obtained in the sole crop. Similarly, cowpea seed damage was significantly lower (P<0·05) on cowpea planted at 2 and 4 weeks after transplanting tomatoes than in the monocrop and when cowpea and tomato were planted simultaneously. Cowpea yields were influenced by both time of intercropping and cropping system; in the intercrop, the highest yield was obtained at 2 weeks after transplanting tomatoes. In the tomato/okra intercrop, the numbers of flea beetles (Podagrica spp.) were significantly influenced (P<0·05) by cropping system alone; their density was significantly lower (P<0·05) in the intercrop than in the sole crop irrespective of time of intercropping. Similarly, damage was significantly higher (P<0·05) in the sole crop than in the intercrop while yield comparable to that of the monocrop was obtained at 2 WAT. The highest land equivalent ratio (LER) for cowpea (1·8 and 1·6) or okra (0·7 and 0·8) was obtained at 2 weeks after transplanting tomatoes in both years. Two weeks after tomato establishment appeared to be the best time to introduce either cowpea or okra into the cropping system.