Oyster Mortality Studies in Virginia. II. The Fungus Disease Caused by Dermocystidium marinum in Oysters of Chesapeake Bay

A high death rate of oysters in Virginia waters during the warm months of summer and fall was reported by Hewatt & Andrews (1954b). One of the most important causes of this warm-season mortality is the fungus Dermocystidium marinum, a pathogen discovered in the Gulf of Mexico by Mackin, Owen & Collier (1950). The fungus is found along the coast of the Western Atlantic from Delaware Bay to Florida and on the coast of the Gulf of Mexico from Florida to Texas. Chesapeake Bay the disease was studied for pathogenicity to oysters, seasonal occurrence, distribution, and its effect on the oyster industry. Over 3000 dead or dying oysters and 7000 live oysters were examined. Most of the dead or dying oysters were obtained from trays suspended in the York River at Gloucester Point, Virginia, but the live oysters came from many localities in Chesapeake Bay.