Significance We explore mechanisms by which stress caused by acute injury affects blood cell development and inflammatory response in Drosophila . Similar to their mammalian myeloid counterparts, these cells are predisposed to sense and react to sterile injury at distant sites. Upon sterile injury, a breach of epidermis sets up a reactive oxygen species-based signal that bypasses the pathogen-sensing apparatus of septic immune challenge, but merges downstream to activate Toll. A number of autonomous and nonautonomous signaling pathways follow in a sequence and are mapped temporally by the appearance of their corresponding molecular phenotypes. A cell-type that fights deposited parasitic wasp eggs appears with sterile injury without the immune challenge, perhaps in anticipation, because in nature injury is usually followed by infection.