Efficacy of host plant resistance, sowing date modification and intercropping as methods for the control of Pachnoda interrupta (Olivier) in pearl millet in the Nigerian Sudan savanna

Three experiments were conducted in 1997 and repeated in 1998 cropping seasons in Maiduguri, Nigeria to assess damage caused by the scarab beetle, Pachnoda interrupta (Olivier) (Coleoptera: Scarabaeidae), in six varieties (Exborno, Wame, Zongori, Gargasori, Mboderi and GB8735) of pearl millet sown as sole crops on 14, 21, 28 July and 5 August and as mixed crops with cowpea (var. Borno brown) or sorghum (var. Gooseneck). Damage in the local variety (Ex-borno) of pearl millet sown as a mixed crop with cowpea or sorghum in cropping patterns of 3:1, 2:1, 1:1 and 1:0 was also assessed. Damage and grain yield loss were significantly higher in millet sown on or before 21 July than in those sown later in both 1997 and 1998 cropping seasons; grain yields were, however, significantly higher in millet sown on 14 July or 5 August in 1997 and in millet sown on or before 28 July 1998. Damage and grain yield loss were significantly higher in GB8735 but lower in Gargasori in both years while grain yields were significantly higher in Wame in 1997 and in Gargasori in 1998 than in GB8735. The highest grain yields were obtained from Zongori sown on or before 21 July in 1997 and 1998. Damage and grain yield loss were significantly lower in the millet-sorghum intercrop than in the other cropping systems in 1998; grain yields were significantly higher in sole millet intercrop but lower in millet-sorghum than in the other systems in 1997. Damage and grain yield loss were significantly higher in GB8735 in both years and lower in Gargasori in 1998. The highest grain yields were obtained from sole Zongori in 1997 and Zongori-sorghum intercrop in 1998. Damage was significantly lower in the 1:1 cropping pattern than in the other patterns in 1998. Grain yields were significantly higher in the 1:0 cropping pattern but lower in the 1:1 pattern than in the other patterns in 1997. Similarly, grain yields were higher in the millet-cowpea than in the millet-sorghum intercrop in 1997.