Currutaca: A Pythium Soft Rot of Xanthosoma and Colocasia spp. in Puerto Rico

Abstract

The fungus Pythium ultimum Trow, was found the causal agent of a soft rot disease of taniers [Xanthosoma sagittaefolium (L.) Schott.] and taros [Colocasia esculenta (L.) Schott.]. A yellow pigmented bacterium occasionally associated with the rot turned out to be a saprophyte. Roots of diseased plants became mucilaginous and decayed rapidly. The infected rhizomes were soft and cheesy. The base of infected petioles were water-soaked and the leaves collapsed. The fungus was isolated in pure culture and grew well in most culture agar media, producing abundant sporangia at 20-30° C., but failed to grow at temperatures below 12° C. or above 36° C. Varieties of taniers and taro inoculated with P. ultimum showed differential degrees of susceptibility to infection when kept in an environment of 90-percent relative humidity and a temperature of 20° C. Definitive measures to control the disease effectively are not known. Use of clean "seed", planting in well drained soils, and crop rotation practices, however, have been recommended.