Chiekahominy Reservoir, Virginia, was treated with a mixture of herbicides diquat and endothall to control obnoxious growths of Egeria densa Planchon. Herbicides were undetectable in water by the 16th day after treatment. Herbicides accumulated in plant tissue at levels higher than those in the water. Only diquat accumulated in hydrosoils. Diquat levels in hydrosoils increased as levels in plants and water decreased. All diquat had dissipated from hydrosoils after two years. Neither herbicide concentrated in edible fish flesh. Aerial photographic monitoring revealed the amount of surface acreage and fishable shoreline was increased substantially following treatment. Weed regrowth was greater in shallow areas than in deeper areas after one year. Seventy-two percent of the anglers polled to determine the sportsmen's opinion of the weed control project believed that the treatment alleviated the weed problem and increased fishing and boating enjoyment.
