Southern Corn Leaf Blight: A Story Worth Retelling

Abstract

Core Ideas A history of corn leaf blight and its host. A synopsis of southern corn leaf blight. Lessons for the future. The southern corn (Zea mays L.) leaf blight (SCLB) epidemic of 1970–1971 was one of the most costly disease outbreaks to affect North American agriculture, destroying 15% of the crop at a cost of US$1.0 billion (≥$6.0 billion by 2015 standards.). It resulted from an over reliance on cytoplasmic Texas male sterile (cms‐T) lines in hybrid seed production and a natural mutation of a race of SCLB Bipolar maydis that for years was seldom of economic importance. This mutation discovered in the Philippines in 1961 first appeared in the Corn Belt in 1969, damaging not only leaves, but stalks, ears, and developing kernels of hybrids containing cms‐T genetics. A favorable environment, combined with >85% of the hybrids grown being of cms‐T genetics set the stage for an epidemic. The cms‐T was discontinued in 1971 and hybrid seed production returned to using detasseling for the female parent. This serves as warning to the seed production business never to purify the genetics of our crops to such an extent as this again and to preserve genetic diversity.