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Title: Endemic pathogen biocontrol research on submersed macrophytes : status report 1996
Authors: Aquatic Plant Control Research Program (U.S.)
Shearer, Judy F. (Judy Fredrickson)
Keywords: Biological control
Mycoleptodiscus terrestris
Hydrilla verticillata
Eurasian Milfoil
Pathogenic fungi
Aquatic plants
Publisher: Environmental Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Technical Report
Abstract: This report documents development of endemic pathogens as potential inundative biological control agents for Hydrilla verticillata and Myriophyllum spicatum. Prototype formulations of Mycoleptodiscus terrestris were tested on rooted plants of H. verticillata. The ability to adhere to hydrilla under submersed conditions was met by each of the formulations tested. For ease of application the granular formulation was superior to both the suspension concentrate and the two invert emulsions. Maintenance of fungal viability through formulation processes of drying and milling continues to be a formidable problem. Control of a target plant may be enhanced by timing an application that optimizes fungal growth and development with certain weak points in the host. Preliminary results indicate that hydrilla may be more susceptible to pathogen ingress early in a growing season, a period when temperatures are more conducive to fungal growth. Hydrilla plants stressed by an initial application of inoculum are little affected by a second dose applied when plant regrowth commences. The second application of inoculum was shown to yield only an additional 5 percent reduction to the standing biomass of above-ground hydrilla. Efforts continue to find an endemic pathogen of M. spicatum that is effective in the field. Thirty pathogens, isolated from milfoil collected from different geographic regions in the United States, were screened for pathogenicity. Isolates that produced disease symptoms in the host during the initial laboratory screening were further evaluated in greenhouse and field tests. Three isolates reduced aboveground milfoil biomass behveen 95 and 100 percent in greenhouse studies but were ineffective in the field.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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