Spartina alterniflora Loisel. and Haliaspis spartinae (Comstock) (Hemiptera: Diaspididae), with its parasitoid, were surveyed in Ellisville Marsh, Massachusetts. Average scale density on the damaged leaves was equal to 265 individuals per 10 cm2. Parasitization of H. spartinae was recorded for the first time; however, the percentage was very low at 2.67%. The parasitoid is a new species for science and is described as Encarsia ellisvillensis Japoshvili & Russell sp. nov.