Distribution of Phakopsora pachyrhizi on Lablab purpureus in Puerto Rico. Nader G. Vakili, Research Plant Pathologist, Mayaguez Institute of Tropical Agriculture, Agricultural Research Service, U.S. Department of Agriculture, Mayaguez, Puerto Rico 00708. Plant Dis. 65:817-819. Accepted for publication 5 February 1981. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1981. DOI: 10.1094/PD-65-817.

A survey of soybean rust caused by Phakopsora pachyrhizi in Puerto Rico from 1976 to 1979 indicated that hyacinth bean, Lablab purpureus, is a major reservoir of this pathogen. The uredinial state was the predominant form of the fungus; telial structures were observed on only two occasions. The indeterminate perennial growth of hyacinth bean helped the rust to survive over the seasons. Optimal ranges of ambient temperature and precipitation for development of soybean rust were 17–23 C and 140–260 cm, respectively. In the mountain valleys of the western interior of the island, seasonal rainfall, orographic precipitation, and dew, along with a temperature range of 19–21 C, provided an optimal environment for the continuous growth of hyacinth bean and the development of soybean rust throughout the year.

Keyword(s): epidemiology.