Twenty-two fungal species were isolated from surface sterilized water hyacinth parts with
pronounced blight syndrome. The most common species were Alternaria alternata, Drechslera
hawaiiensisand Ulocladium atrum. The patterns of fungal abundance were influenced
positively by changes in conductivity (EC) and negatively by pH and temperature (TE). As a
result of a pathogenicity test, and on the basis ofdisease severity, the pathogenic species were
divided into mildly, low moderately, high moderately and severely damaging species. Of these
species only Al. alternata, (associated with 79% tissue death),D. hawaiiensis(78%) and U.
atrum(70%) showed high disease severity. Because Al. alternata, was reported as a plurivorus
species with several pathotypes, D. hawaiiensisand U. atrumwere selected for further study.
Formulation and daily spraying of water permitted conidial germination and infection by these
species in the field. Both treatments gave similar results. Disease incidence (DI) and disease
severity (DS) increased with increasing incubation period up to 30 days of incubation.
Simultaneously, the chlorophyll content decreased inthe infected leaves compared to healthy
ones. Both DI and DS decreased after 30 days incubation indicating that it is not efficient to
use D. hawaiiensis andU. atrum either separately or in a mixed formulation as biocontrol
agents