2009 Volume 57 Issue 3 Pages 475-482
The aim of the current study was to investigate the effects of Thai herbs as anti-fungal agents in Nile tilapia Oreochromis niloticus eggs in Thai hatcheries. The fungistatic and fungicidal effects of 5 herbs including guava, tamarind, salapeepa, betel pepper and red rose against the fungal species Saprolegnia diclina, Achlya sp. and Aphanomyces invadans were evaluated in vitro. The effects of guava and betel pepper against fungal hyphae were greater than those of the remaining 3 herbs when the fungi were exposed to each herb for 7 days. At 24 h exposure, guava and betel pepper exhibited fungicidal activity against zoospores of S. diclina and Achlya sp. at concentrations of 125 to 250μg/ml. However, when fertilized and eyed eggs of Nile tilapia were exposed to 125μg/ml of guava or betel pepper solution, the observed mortality was significantly higher than that of the control group. We conclude that these herbs are not suitable for the control of fungal infection in tilapia eggs at the established fungicidal concentration. However, if zoospore germination can be inhibited at lower concentrations, the herbs may still prove useful as a potential anti-fungal agent.
