The effect of nitrogen and phosphorus on lepidopteran borer attacks and maize yields in the western highlands of Cameroon

Maize is an important staple in Cameroon. Declining soil fertility and the noctuid stalkborer Busseola fusca (Fuller) are the major constraints to crop production. Because of high population pressure in the highlands, the land is not fallowed and synthetic fertilizers are needed for obtaining acceptable yields. Field trials were conducted to investigate the effects of combinations of different rates of nitrogen (N) (0, 60, 120 kg N/ha) and Phosphorus (P) (0, 45, 90/ha) applied to the soil on damage by stemborers and maize yield. B. fusca constituted 89% of the borer species followed by Sesamia calamistis (Lep: Noctuidae). In 2006 and at 56 and 112 days after maize planting, N uptake was 1.2 and P 1.3 times higher in the single nutrient treatments than the control. The combined doses showed the best uptake of both nutrients. Plant vigor, expressed as stem diameter, cob width and length increased with both the single and combined doses. Compared to the control, Percent stem tunneling was 2.9 and 6.3 times lower with the 60N and 120N dosage, respectively, and 1.4 and 2.3 times lower with 45P and 90P dosage, respectively. The 120N/90P combination yielded the lowest stem tunneling. Cob fill was 1.1 and 1.3 times and cob weight 1.4 and 1.6 times higher at the 60N and 120N doses, respectively, while they were 1.6 and 2.2 times and 1.5, 1.8 higher, respectively, at 45P and 90P than the control. Yields were highest with the 120N/45P and 120N/90P combinations. Trends were similar in 2007.