Longidorid plant pathogens, specifically Longidorus and Xiphinema, are known to reduce the biomass and seed yields of several monocotyledonous host plants and may serve as vectors for certain plant viruses. The occurrence and densities of species in these genera in the Midwestern United States may be of concern in the production of two biofuel plant species –Miscanthus (Miscanthus×giganteus) and Panicum virgatum. Here we present results from a morphological and molecular survey of plant parasitic nematodes in which two species of Xiphinema (X. americanum and X. rivesi) and one species of Longidorus (L. breviannulatus) were detected. A total of 73 soil samples were collected from 19 sites (nine Miscanthus and 10 P. virgatum) in three states during 2008. Xiphinema spp. was found in 36% of the Miscanthus plots and in 26% of the P. virgatum plots with a population density range of 22–857/100 cm3 soil. L. breviannulatus was detected in association with Miscanthus plot in Havana, IL, in large numbers (54/100 cm3 soil). The occurrence of this species was associated with severe damage to the fibrous root system, including stunting and necrosis. Short notes, measurements, illustrations and molecular data are given to the species level.