The diversity of A.alternatawithin these clusters
was affected by pH, TE and chemical oxygen demand. Pathogenicity testing revealed that A.
alternata strain A, was the most destructive. Host-range testing determined that the majority of
Waterhyacinth plants tested are not highly susceptible to the pathogen and thus may show
some resistant. Observation over three years indicated that with the exception of P.stratiotes
and C.alopecuroides, the major economic crops, weeds and ornamental plants surrounding
water courses with diseased Waterhyacinth showed no signs of infection by A.alternata.
Application of the fungus crude toxins to tested plants increased the host range to include
Ipomoea tricolor, Nymphaea lotusand Lemna gibbain addition to Waterhyacinth. We also
found that a toxin plus fungal combination applied to tested plants, enhanced the degree of
susceptibility but not the hosts range. Formulation of spores of A.alternatastrain A in oil
emulsion significantly improved the effectiveness of the pathogenon Waterhyacinth. Greater
values of disease incidence (80), disease severity (95) and necrotic leaf area (98.5) were
observed at the end of the experiment. Waterhyacinth was susceptible to the fungus at all
growth stages tested. Susceptibility range decreased in sequence: leaf stages 11-14> leaf stages
5–9 > leaf stages 2–4. Thus, A.alternatahas potential as a biocontrol agent of Waterhyacinth
and its toxins may be used as a herbicide.