Distribution and association of common leaf rust (Puccinia sorghi Schwein) and turcicum leaf blight [Exserohilum turcicum (Pass.)] of Maize (Zea mays L.) with biophysical factors in Eastern Ethiopia

Abstract

AbstractCommon leaf rust (CLR) and turcicum leaf blight (TLB) are the key foliar diseases of maize in Ethiopia. However, in Eastern Ethiopia, information related to the distribution and abundance of CLR and TLB and the relationship of the diseases with independent variables are lacking. Therefore, this study was initiated with the objectives of assessing the distribution of CLR and TLB and their association with biophysical factors and cropping systems. A survey was conducted in the 2019 cropping season in different agroecological zones of East and West Hararghe zones and a total of 120 fields were surveyed. For each field assessed, disease parameters and information on cropping system were recorded. Data were analyzed by using the SAS GENEMODE procedure. Result showed that CLR incidence ranged from 16.84% to 100% in Kombolcha and Kuni districts, respectively. The severity level ranged from 6.0% for Kombolcha to 58.2% for Kuni and Chelenko districts. However, the TLB incidence ranged from 13.4% to 100% at Kobo and Haramaya districts, respectively. Similarly the severity level ranged from 6.0% to 58.0% at Kombolcha and Kuni districts, respectively. Result also showed the presence of higher values of CLR incidence, and severity (>61.7% and >32.1%, respectively) and higher level of TLB incidence and severity (>58.1% and >30.2%, respectively) were highly associated with the West Hararghe Zone, Altitude >2000 m.a.s.l., Kuni and Haramaya districts, fields without any type of fertilizer, un weeded fields, intercroped with sorghum, maize verities sown in June, and seeds collected from previous yield resulted in the highest disease incidence and severity. Among the independent variables, district was the most important variable in its association with CLR incidence (χ2 = 647.93 and 341.18, 7 df) and severity (χ2 = 219.56 and 112.83, 7 df) and with TLB incidence (χ2 = 758.91 and 350.03, 7 df) and severity (χ2 = 330.92 and 124.04, 7 df) when entered first and last into the logistic regression model, respectively. Hence, it is concluded that CLR and TLB are the most widely distributed and important foliar diseases of maize in the Hararghe highlands. Information from this study is very useful to maize growers to device an ecologically sound, and effective management options against these diseases in the study are and elsewhere where the diseases are common and prevalent.