First Report of Sorghum Ergot Caused by Sphacelia sorghi in Mexico.

Abstract

In the winter of 1996-1997 ergot was observed in sorghum (Sorghum bicolor) plants growing in several locations of Tamaulipas, Mexico, including San Fernando, Soto La Marina, Manuel, Cuahutemoc, and Altamira. The disease in sorghum plants was associated with high humidity and low temperatures during the blooming stage in February, 1997. The most obvious symptom was the exudation of honeydew from the infected flowers. Microscopic analysis of the honeydew revealed the presence of the asexual conidia of a Claviceps sp. The abundance, size, and shape of conidia were characteristic of Sphacelia sorghi (1). Honeydew was also observed in plants of Sorghum halepense, forage sorghum and volunteer plants of sorghum, which are also hosts. The first report of ergot in the Americas was made in 1995 in Brazil (2), where it was probably introduced via contaminated seed from Africa. The disease spread rapidly from Brazil to Argentina, Bolivia, Colombia, Paraguay, and Venezuela. The pathogen was probably dispersed and introduced to Mexico by contaminated seed, wind, or insects from South America. The disease represents a serious threat to the 800,000 ha of sorghum grown in Tamaulipas. Due to its confirmed extraordinary capacity to spread rapidly, ergot could affect sorghum growing in regions adjacent to Tamauli-pas, including Nuevo Leon in Mexico, and Texas in the U.S.