Evaluation of microfungi for the biological control of water hyacinth in Egypt

Twenty-two fungal species were isolated from surface sterilized water hyacinth parts with pronounced blight syndrome. The most common species were Alternaria alternata, Drechslera hawaiiensis and 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 of disease 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. hawaiiensis and U atrum were 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 in the 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 and U. atrum either separately or in a mixed formulation as biocontrol agents.