Nonlinear models for nondiapause development in the tufted apple budmoth,Platynota idaeusalis(Walker), were developed from estimated parameters obtained from constant-temperature studies under long-day photoperiodic regimes (16:8 [L:D]). Temperature-dependent development was evaluated with laboratory and field strains ofP. idaeusalisreared on semisynthetic diet and excised apple leaves. These data were incorporated into appropriate models to Simulate adult emergence at variable temperatures. Models were validated by laboratory and field strains ofP. idaeusalisreared on semisynthetic diet and apple foliage (either excised leaves or in tree cages) under field conditions and comparing actual percentile adult emergence with predicted percentile adult emergence. Predicted and observed development was faster for the field strain than the laboratory strain and faster for larvae reared on synthetic diet than larvae reared on apple foliage. In most instances, model predictions were within 2 days of actual emergence. All models predicted three generations ofP. idaeusalisper year when temperatures prevalent to the piedmont area of North Carolina were used.