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Maize (Zea mays L.) is widely cultivated across regions in Tanzania. To understand the relationship
between maize and epidemics of northern leaf blight, surveys were conducted in 2012 and 2013.
Disease incidence and percent severity were determined in 280 farmers’ field. Each sampled point
measuring about one acre at intervals of 500 meters was marked with global positioning system and
used to construct the disease map. Data was subjected to ANOVA and means separated with
Turkey’s-kramer simultaneous test at P≤ 0.05. Northern leaf blight (NLB) disease was found in all
the fields studied, however the level of virulence differed. The disease incidence (57.5 - 96 %) and
percent severity (33.4 – 62.2 %) were significantly more severe in humid highlands of Mbeya and
Arusha districts compared to incidence (11.8 - 61.3 %) and severity (3.9 – 34.5 %) in the lowland
dry Coastal and Morogoro districts. Significant correlation coefficients (p ≤ 0.05) and coefficient of
determination (R² = 0.36 and R² = 0.38) between disease incidence, percent severity and
environmental factors confirmed that NLB spread in maize was proportional to high altitude, low
temperature, high relative humidity and rainfall.The results from this study suggested that (i) Mbeya
was a hotspot area for NLB and therefore can be used to screen germplasms for resistance to NLB,
(ii) host resistance and susceptibility was influenced by location and environmental factors and (iii)
frequent surveys in the studied areas and beyond will be imperative to identify source(s) of
resistance and pathotypes/races of the pathogen in Tanzania.
Key words: Maize, northern leaf blight, Exserohilum turcicum, distribution, environment, Tanzania