. Some diseases of Puerto Rican forage crops. Forage plants Diseases and pests Puerto Rico. The conidia (fig. 19, 5) are slender, fainth" three-or-more-septate, and hyaline. Their measurements are 70-80m X 3m. The tufts of conidio- phores are so miuute as to be barely visible with a lens (13, p. 15). West Indies Smutgrass Sooty spike Sooty spike on Sporoholus indicus (L.) R. Br. (West Indies smutgrass, cerrillo) is caused by Hehnintho- sporium rarenelii Curt. This is a disease of the inflorescence and can be found in all seasons since cerrillo blossoms at all times of the year (2, p. 12).
. Some diseases of Puerto Rican forage crops. Forage plants Diseases and pests Puerto Rico. The conidia (fig. 19, 5) are slender, fainth" three-or-more-septate, and hyaline. Their measurements are 70-80m X 3m. The tufts of conidio- phores are so miuute as to be barely visible with a lens (13, p. 15). West Indies Smutgrass Sooty spike Sooty spike on Sporoholus indicus (L.) R. Br. (West Indies smutgrass, cerrillo) is caused by Hehnintho- sporium rarenelii Curt. This is a disease of the inflorescence and can be found in all seasons since cerrillo blossoms at all times of the year (2, p. 12). This disease was observed in Puerto Rico wherever the gTass was growing. Drechsler {12, p. 689) suggests that the dis- tribution of the disease is practi- cally coterminous with S. indicus. \¥hen infection was severe, it was difficult to find specimens enthely free of disease. The extensive infection of Sporo- bolus indicus hy Helminthosporium ravenelii has been recorded else- where {10, p. 352: 18, p. 26). The disease is so much a part of the grass that such misnomers as ^^black seed grass" {10) and '^smut grass" {16) have been assigned to it. The disease is of no importance economically, although Ratera {25) reports that Sporobolus berteroanus Hitchc. & Chase {Sporobolus poi- retii (Roem. & Schult.) Hitchc.) is toxic to animals wheu parasitized b}^ Helminthosporium. The infected inflorescences (fig. 20, A) are most noticeable in the latter stages of infection, when the disease is black and crusty. A noninfected inflorescence is shown in figure 20, B. During the early stages, the disease is present as a brownish-olive velvety or spongy layer that later becomes increasingly dark. The velvety layer is com- posed of crowded sporophores that arise from a mat of h3^phae that occupy the superficial layers of the affected fioral parts. The sporo-. Figure 20.—A, Sooty spike on Sporobolus indicus (West Indies smutgrass) caused by Helminthosporium ravenelii. X 8. B
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