Effect of traditional rice / maize intercropping on population densities, crop damage and parasitism of stem-borers in the Ivory Coast

Early and late cropping season surveys were carried out in the humid forest and derived savanna zones of the Ivory Coast. These surveys assessed pest species composition, infestation levels, crop damage and parasitism in maize fields intercropped or not intercropped with rice, and in rice fields planted along the lowland-hydromorph-upland continuum. The pest species encountered on maize were lepidopterous stem-borers, including Eldana saccharina, Busseola fusca, Sesamia calamistisl/Ig and Sesamia botanephaga , as well as species that attack the cob only such as Mussidia nigrivenellal/Ig and Cryptophlebia leucotreta . On rice, the species comprised lepidopterous stem-borers such as E. saccharina, S. calamistis, S. botanephaga, Chilo zacconius, Chilo aleniellusl/Ig and Maliarpha separatella , as well as the two dipteran species Diopsis thoracical/Ig and Orselia orizivora . During the early season, pest densities were low on maize. The percentage of infested plants and dead hearts were significantly reduced on maize intercropped with rice compared to maize only. Maize yields did not differ significantly with cropping system despite higher inter-plant competition expected in the intercropped fields, indicating that the reduced pest densities positively affected yields. On rice, pest numbers and plant damage increased with altitude in the lowland-upland continuum. On both crops, percentage larval parasitism was low and appeared not to be influenced by the cropping system.