Assessment of Yield Loss and Determination of Optimum Planting Date for the Control of Gray Leaf Spot on Maize (Zea mays L.) in South Ethiopia

摘要

Maize (Zea mays L.) is one of the most important strategic crops selected for food security mainly due to its high productivity and wider adaptability in Ethiopia. In recent years, gray leaf spot (GLS) has become a serious disease in different parts of the country. However, no research activity has been carried out to determine the role of planting date on the control of GLS. Therefore, the objectives of this study were to assess the damage and yield loss due to GLS and to identify and determine theoptimum plating date of maize for the control of GLS. The experiment was carried out at Areka and Billito, Southern Ethiopia which are GLS hotspots during the 2004-2006 main cropping seasons. Fungicide treatment as the main plot and planting dates as thesubplot treatment were arranged in a split plot design and replicated four times. The result of this experiment shows that there were significant differences among planting dates, fimgicide spray, years and locations. Analysis of variance carried out across years at Areka and Billito indicated that there were statistically significant differences among planting dates for severity, upper ear leaf infestation, number of cobs harvested, number of diseased cobs, ear length, ear diameter, grain yield and 1000-kernel weight. The highest grain yield (8.12 and 9.09 t ha~(-1)) was recorded from plantings on March 17 and April 18 at Areka and Billito, respectively. Planting on March 27 and April 18 increased yield by 55.5 and 43.0% more than maize planted on April 17 and May 18 at Areka and Billito, respectively. The highest grain yield (8.611 ha~(-1)) was recorded in plots sprayed with fungicide at Billito while the least was recorded in unsprayed plots (6.3 t ha~(-1)) at Areka. The yield loss due to late planting was 29.5% more than early planting.