Assessment of Losses in Yield and Yield Components of Maize Varieties Due to Grey Leaf Spot

Abstract

A study was conducted at Bako Agricultural Research Center for three years (1999 - 2001) to quantify the levels of yield loss in maize (Zea mays L.) incurred by grey leaf spot (GLS) disease caused by Cercospora zeae-maydis. Three commercial varieties with different levels of resistance to GLS, namely, BH-660 (resistant), BH- 140 (moderately resistant) and Phb-3253 (susceptible) and three treatments (inoculated, fungicide sprayed and unsprayed control) were used in factorial combination with three replications. Significant differences were observed among varieties for percent infected plants per plot in all the three years and for percent infected leaves per infected plant in 1999 and 2001. The main effect of treatment was also significant for percent infected plants per plot in 1999 and 2000. Variety and treatment effects were significant for disease severity in all years. Variety x treatment interaction was significant for percent upper ear leaf area infected in 1999, and for AUDPC and upper ear leaf area infected in 2000 and 2001. The main effect of year was significant for thousand-kernel weight and ear diameter. Varietal effect was significant for thousand-kernel weight and grain yield, while treatment effect was significant for ear diameter and grain yield. The interactions among year, variety and treatment were non-significant. Mean kernel and grain yield losses ranged from 1.7 to 10.0% and 7.8 to 29.1%, respectively, on different varieties. Grain yield losses in varieties BH-660, BH-140 and Phb-3253 ranged 0-14.9, 13.7-18.3, and 20.8- 36.9%, respectively, during the three years. The effect of GLS on ear length and diameter, particularly under natural (unsprayed) condition was not significant. The result indicated that GLS could be severe in some favourable seasons causing significant yield losses even on resistant varieties.