Tufted apple budmoth (Lepidoptera: Tortricidae): photoperiodic induction of larval diapause and stages sensitive to induction [Platynota idaeusalis]

A photoperiodically controlled larval diapause of the short-day, long-day type was identified in tufted apple but moth, Platynota idaeusalis (Walker). Pupae obtained from diapause and nondiapause larvae reared at 21 degree C were similar in weight; however, heart rates of diapause larvae were significantly lower than those of nondiapause larvae. Induction of larval diapause was dependent upon both photoperiod and temperature. The critical short-day photoperiod at 21 degree C was between 1 and 3 h for a Pennsylvania strain. The long-day critical photoperiod at 21 degree C was ca. 14 h for both Pennsylvania and North Carolina strains. Diapause at a short daylength was averted entirely at 32 degree C in a Pennsylvania strain. There was no difference in the incidence of diapause in progeny of adults and eggs reared under naturally decreasing short daylengths versus a constant daylength. Sensitivity to a diapause-inducing photoperiod did not occur at any one particular stage in larval development. A maximum of 39% diapause occurred when four of the five larval instars were exposed to a short daylength, and 100% diapause occurred when all five instars were exposed to a short daylength.