First-instar grasshoppers infected withMelanoplus sanguinipesentomopoxvirus consumed 25% less food within 5 d (75 degree-days (DD), base 10°C) after inoculation with 5 × 103virus occlusion bodies. Grasshoppers ate 25 and 40% less food by the end of the second week (200 DD, base 100°C) after being infected as first instars with 5 × 102and 5 × 103occlusion bodies per individual, respectively. When infected as third instars with 1 × l04and 1 × 105occlusion bodies per individual, grasshoppers ate 20 and 35% less food by the second week of the study, respectively. The mean amount of food consumed by infected grasshoppers over the course of the study was 36, 31, 76, and 57% that of noninfected grasshoppers at dosages of 5 × 102or 5 × 103occlusion bodies per first instar, and 1 × 104or 1 × 105occlusion bodies per third instar. This study suggests that an application of entomopoxvirus to first-instar grasshoppers will reduce their damage potential by causing initial mortality, by reducing the amount of plant material consumed by the surviving grasshoppers, and by preventing grasshopper maturation and reproduction (at higher doses). The negative influence of entomopoxvirus on grasshoppers in the interim between infection and death is integral to future evaluations of its potential as a crop protection measure.