Effect of plant age conidial germination and survival on development of northern leaf blight [Exserohilum turcicum Pass KJ Leonard and EG Suggs] of maize in Tanzania

Epidemiological studies are important tools in forecasting models and prediction of disease progress. In 2013, screen-house experiments were conducted in Morogoro to determine the crop growth stage at which severity of northern leaf blight caused by E. turcicum was most strongly related to 20 maize varieties. Studies on conidial germination and survival of the pathogen were also undertaken for proper and timely management of the disease. Percent disease index (PDI) assessed at 20 days after each inoculation indicated very high significant (p ? 0.05) effect on the extent of susceptibility within variety, age of maize plant and interaction between variety and age. Maize plants at all age groups from 25 to 85 days were susceptible to E. turcicum, however, disease intensity varied significantly within varieties and among plant age groups. Results indicated that the most vulnerable stages to infection were between 65- 75 days (78.6-81.4 %) which coincided with silking/grain filling depending on variety. Disease pressure was proportional to PDI and ranged from 2763 in H308 to 5023 in Kito varieties. It was also observed that within 24 hour of incubation, 87.9 % conidial germination was achieved. Under different storage conditions, E. turcicum survived for 20 months, 16 months and when stored in laboratory and open field conditions. Results of this study therefore revealed that northern leaf blight is a significant foliar fungal disease of maize and infected maize plant debris may be source(s) for the disease epidemic in Tanzania.