Spring and fall field trials were conducted to determine the efficacy of two species of entomopathogenic nematodes for the control of larvae of Diaprepes abbreviatus in a citrus grove with alfisol type soil (sandy clay loam). Both Steinernema riobrave (Bio Vector 355) as a water-dispersible granule and Heterorhabditis indica (Grubstake™ 100) as a paste on sponge at rates from 22-108 IJ’s/cm² failed to reduce larval populations in the tree rhizosphere at 25 d post-treatment. Larval parasitism by entomopathogenic nematodes in baited screen cages was sporadic over time, with the only significant treatment effect occurring at the highest rate (108 IJ’s/cm²) of S. riobrave in the fall at 7 d post-treatment. Possible constraints to nematode efficacy are discussed.