||Maize is produced primarily in temperate and warm-temperate zones of the world, but its production is increasing in many tropical regions. Some diseases are common to both of these environmental zones, even though their importance may vary greatly. Other diseases are confined to a single zone. The important factors influencing the geographical distribution of maize diseases and some of their vectors are temperature, moisture, cultural practices, and the type and diversity of maize germplasm used. The Sclerospora-incited downy mildew diseases, late wilt, banded leaf and sheath blight, and Rhizoctonia, Botryodiplodia, and gray ear rots occur only in the tropical zone and the warm, temperate areas, while southern rust, Pythium and bacterial stalk rots, Curvularia leaf spot, and ear rot caused by Dilplodia macrospora are much more prevalent there, occurring only occassionally beyond 34°north or south latitude. Conversely, bacterial wilt, eye spot, and yellow leaf blight have been found to occur only in the temperate zones. Ergot has been found only in a few locations at high elevation (2500-2700 meters) in Central Mexico. Northern leaf blight, cemmon rust, and stalk and ear rots caused by Diplodia maydis and Gibberella zeae prevail in the temperate zones and at high elevations and in winter seasons within tropical latitudes.