A Field Test Of Selected Insects And Pathogens For Control Of Waterhyacinths PDF Download

During the 1975 growing season a field experiment was begun on Lake Concordia, La., to test the potential effectiveness of selected organisms as control agents against waterhyacinths, Eichhornia crassipes (Mart.) Solms. Floating frames, each approximately 2 m square, were anchored on the lake in open water and planted with locally growing waterhyacinths. Sixty of these frames (plots) were selected for treatment with various combinations of two insects (Arzama densa Walker and Neochetina eichhorniae Warner) and two fungi (Acremonium zonatum (Sawada) Gams and Cercospora rodmanii Conway) in a random block factorial arrangement with four replications per treatment, and four frames were designated as control (no-treatment) plots. All plots were weighed at 2-week intervals throughout the growing season, flowering stalks were counted, and plant heights were measured at each weighing date. Observations were also made on insect and pathogen populations on the plots during the season. Preliminary indications are that significant reductions in the growth rate or total accumulation of waterhyacinth mass in the test plots were not achieved by any of the treatment combinations during the first season's tests, but the potential for some of the treatments to effect the desired control began to emerge during the second year.