Abstract
Stem borers are major insect pests of maize worldwide. In Nigeria, maize yields are threatened by stem borers such as Busseola fusca, Sesamia calamistis, Eldana saccharina, Coniesta ignefusalis, and Chilo partellus. Field experiments were conducted in the early and late seasons of 2009 and 2010 in the Guinea Agro-ecological zone of Cross River State, Nigeria, to assess the effects of borer damage and population dynamics. Treatments consisted of seasonal differences (early and late) and synthetic (carbofuran 1.0 at 1.5 kg a.i/ha) and botanical (Azadirachta indica and Gmelina arborea seed powders at 20 and 30 kg/ha) insecticides. The treatments were laid out in a randomized complete block design (RCBD) with three replications. Data collected included percentages of dead heart, lodged stem, bored stem, tunnel length, larval population, and grain yield. Results showed that damage variables and population dynamics were significantly (P<0.05) lower in early-planted maize as compared to late-planted maize. The lowest incidence of dead heart between the botanicals in the late season was recorded in A. indica (30 kg/ha) treated plots (4.81% and 5.13% in 2009 and 2010, respectively). The same was observed for tunnel length (6.27 cm and 9.00 cm) and lodged stem (4.40% and 8.89%) in 2009 and 2010, respectively. Yield was higher in early season maize than in late season maize. The highest yield (2.23 and 2.95 ton/ha) was obtained from carbofuran (1.5 kg a.i/ha), followed by A. indica (30 kg/ha) (2.20 and 2.90 ton/ha) treated plots in early plantings of 2009 and 2010, respectively. The results indicated that stem borer population and yield varied by season, which was determined by climate.
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