White rot disease and epiphytism on Halymenia durvillei Bory de Saint-Vincent (Halymeniaceae, Rhodophyta) in culture

Abstract

We report herein for the first time the occurrence of a white rot disease and heavy infestation of epiphytes on the cultured red seaweed Halymenia durvillei in Bolinao, Pangasinan. White rot disease causes tissues to decay, weakens the affected branches, resulting in the breakage of thalli and loss of biomass. The cause of the white rot disease on H. durvillei remains unknown but may be associated with pathogenic microorganisms similar to other reported cases of diseases among cultured seaweeds. The infestation of the epiphytic alga we identified as Neosiphonia apiculata has detrimental effects on the tank-cultured Halymenia durvillei, where much of the thalli exhibited stunted growth. We hypothesized that the unfavorable environmental conditions preceding the infestation may have triggered the uncontrolled proliferation of the epiphytes on the cultured H. durvillei.