Bacterial Leaf Spot of Bougainvillea in Florida Caused by Pseudomonas andropogonis. S. E. Walker, Bureau of Plant Pathology, Florida Department of Agriculture and Consumer Services, Gainesville 32602, and N. C. Hodge, Department of Plant Pathology, University of Florida, Gainesville 32611. Plant Dis. 75:968. Accepted for publication 17 April 1991. DOI: 10.1094/PD-75-0968B.
A leaf spot disease of Bougainvillea Commerson & Juss. was first
observed in Zimbabwe in 1956 (2), was reported in Australia in 1980
(1), and was present in numerous locations throughout Florida and
other southeastern states in 1990. A nonfluorescent bacterium was
isolated from foliar lesions on interspecific hybrids of bougainvillea
and confirmed as the causal agent by Koch's postulates. Leaf spots
were characterized by circular to irregular necrotic lesions with tan
centers, dark red-brown margins, and sometimes chlorotic halos.
Reddish brown leaf margin necrosis was frequently the main symptom.
Under conditions of abundant rainfall or high relative humidity, foliar
lesions were black and vein-delimited and colored bracts became
infected. Infection of developing foliage and bracts resulted in puckered,
distorted growth (2). Differences in cultivar susceptibility were
apparent in field observations, with cv. Barbara Karst being the most
severely affected. Overhead irrigation accelerated disease progression,
frequently resulting in defoliation. The oxidative, gram-negative bacterium
caused a hypersensitive reaction on tomato and was negative
for oxidase and arginine dihydrolase. Strains were catalase-positive,
produced poly-J3-hydroxybutyrate, but did not liquefy gelatin or reduce
nitrate. Cellular fatty acid analyses closely matched the pathogen to
well-characterized reference strains of Pseudomonas andropogonis (E.
F. Smith) Stapp.