Field studies of shell regrowth as a bioindicator of eastern oyster ( Crassostrea virginica Gmelin) response to 2,4-D BEE in Maryland tidewaters

Abstract

New growth was filed from eastern oyster (Crassostrea virginica Gmelin) shells and wire trays holding 25 oysters each were exposed to the butoxyethanol ester of 2,4-dichlorophenoxyacetic acid (2,4-D BEE) at rates of either 22.5, 33.75 or 67.5 kg ae (acid equivalent)/h (20, 30 or 60 Ib ae/acre). Regenerated shell growth was measured to determine the effect of herbicide application on the oyster. Two sites were used; a double-pond area with narrow inlet and outlet, and an open bay. Plant control was noted. Under the conditions of the study, oyster shell regrowth or replacement did not reflect adverse reactions to the level of herbicide applied. It appears that 2,4-D BEE in Maryland probably can be used safely to clear oyster beds of eurasian watermilfoil (Myriophyllum spicatum L.) prior to fall oyster harvest.