Occurrence of Rust of Pangola Grass in Puerto Rico

Abstract

Pangola grass (Digitaria decurribens Stent) rust was first observed in Puerto Rico at the Corozal Substation and then in the Soils farm at the Río Piedras Station. A study of the urediospore and teliospore morphology revealed that this Pangolagrass rust resembles Puccinia oahuensis Ell. & Ev., except that the urediospores are shorter and the teliospores are longer. In view of this size variation, and considering the fact that the general appearance of the rust resembles that of P. oahuensis, the Pangola grass rust has tentatively been identified as a variant of P. oahuensis. Results of pathogenicity tests indicate that a great number of species or clones of Digitaria are resistant to the rust. Among the chemicals tested, Dithane M-45 seemed to be the most promising for delaying the appearance and development of pustules.