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Title: Evaluation of fungi for biological control of Hydrilla Verticillata (L.f.) Royle
Authors: Aquatic Plant Control Research Program (U.S.)
Joye, Gary F.
Theriot, Edwin A.
Hennington, M. Susan.
Keywords: Biological control
Hydrilla verticillata
Aquatic plants
Fungal pathogens
Plant pathogens
Publisher: Environmental Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Technical Report
Abstract: Fungal isolates collected from the microsphere of hydrilla were evaluated for their use as potential biological control agents of this weed. Test-tube and aquaria pathogenicity tests were conducted with each isolate alone and in combination. Fungal isolates were also tested in conjunction with commercially produced enzymes to determine if pathogenicity could be enhanced. Environmental parameters including pH, temperature, and light were evaluated for their effect on the growth and sporulation of 16 fungal isolates that exhibited an impact on hydrilla. Preliminary host range and acute fish toxicity tests were performed on the fungal isolate Cladosporium cladosporioides (number 224), which exhibited the greatest potential as a biological control agent of hydrilla. Preliminary test-tube studies of individual isolates indicated that several fungi may impact hydrilla. Although C. cladosporioides did not impact hydrilla in the test-tube assay, it did impact this weed in an aquarium assay, with plants being killed within 2 weeks after inoculation. In the combination studies, isolates 170/249 and 170/59 significantly damaged hydrilla. In this same study, tests were also·performed to determine if there was any inhibitory growth action between fungal combinations. No such activity was found to occur between the fungal isolates used. Studies using commercial enzymes were performed in Petri dishes. Results indicated that enhanced biocontrol capabilities may be possible for fungi with the addition of pectinolytic enzymes. The environmental parameters of pH, temperature, and light all affected growth of fungal biocontrol agents to varying degrees, with temperature exhibiting the most pronounced effect. In preliminary host range studies, isolate 224 did not cause symptoms of disease on any of the test plant species, including hydrilla. In repeated experiments, isolate 224 was unable to impact hydrilla. This fungus apparently lost its pathogenic ability through continuous reculturing on artificial media. Isolate 224 did not cause any significant detrimental effects to test fish in acute toxicity tests. Although none of the fungi in these studies could be considered a serious candidate for use as a biocontrol agent, other fungi have been found to cause disease of hydrilla.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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