DIEBACK AND MORTALITY IN RED MANGROVE, RHIZOPHORA MANGLE L., IN SOUTHWEST PUERTO RICO

Abstract

Summary Red mangrove (Rhizophora mangle L.) trees in the coastal forests of southwestern Puerto Rico contain small amounts of cankers, limited dieback and exhibited less than one per cent mortality. However, extensive dieback and mortality was detected in the mangrove forests of Bahia Fosforescente. Three canker types were detected: gall cankers, target cankers and canker blights, with the latter type being most often associated with dieback and mortality. The imperfect fungus, Cytospora rhizophorae, was sometimes isolated from gall cankers and canker blights. Challenge inoculation with C. rhizophorae, following wounding, of red mangrove seedlings, resulted in increased dieback around inoculation sites. Inoculations of chlorophyll-deficient mutant seedlings (polyphenol oxidase positive [PPO+] and polyphenol oxidase negative [PPO-], resulted in increased dieback compared to wild-type seedlings, and in the case of PPO- seedlings complete mortality. The causes of the red mangrove dieback and mortality in Bah...