Hessian fly (Mayetiola destructor (Say)) is a relative newcomer to northeastern Oregon with the first reports of Hessian fly in 1980, although it was reported in western Oregon in the late 19th century. Yield losses as great as 60% have been reported in susceptible varieties in severe infestations. Hessian fly tends to be more severe under minimum tillage or no-till (direct-seeding) systems. Hessian fly management is based on sowing resistant varieties and using insecticide seed treatments. Hessian fly regularly causes yield reductions in susceptible varieties of spring wheat (Triticum aestivum L.) at the Columbia Basin Agricultural Research Center. The objective of this research was to determine if seed-placed P fertilizer had an effect on Hessian fly infestation in spring wheat. We seeded resistant, moderately resistant and susceptible varieties of spring wheat in 2003 and resistant and susceptible varieties in 2006. Phosphorus was applied as 0-45-0 with the seed at planting at 0 or 20 kg P ha-1. Soil test levels of P were greater than the critical level in all trials. Plants from 1 m of row were collected at jointing and the number of fly pupae counted. The plots were harvested using a plot combine and the grain yield estimated. In 2003, banding P with the seed reduced the number of pupae per tiller and increased grain yield of a susceptible variety but not a resistant variety; moderately susceptible varieties exhibited an intermediate response. A similar trial was conducted in 2006. P fertilization reduced number of pupae per meter of row, reduced the percentage of tillers that were infested, reduced the number of pupae per plant and pupae per tiller and increased grain yield. The possible mechanism(s) of the effect are unclear.