ROLE OF PHOTOPERIOD AND TEMPERATURE IN THE INDUCTION OF OVERWINTERINGPUPAL DIAPAUSE IN THE SPOTTED TENTIFORM LEAFMINER, PHYLLONORYCTER-BLANCARDELLA

The role of photoperiod and temperature in the induction of overwinter ing diapause in Phyllonolycter blancardella (E) (Lepidoptera: Gracilla riidae) was examined in the laboratory and field using leafminers from commercial apple orchards in Ontario, Canada. P. blancardella exhibit ed a long-day response to photoperiod: long daylengths resulted in uni nterrupted development whereas short daylengths induced diapause. The estimated critical photoperiod for diapause induction was L14.25:D9.75 , The larvae of leafminers destined to enter diapause took ca. 3x long er to complete development than the larvae of non-diapausing leafminer s. The development prolonging effect of photoperiod decreased with dec reasing daylength. Temperature modified the diapause inducing effect o f photoperiod. At L14.25:D9.75, diapause incidence was similar at 15 a nd 20 degrees C but was lower at 25 degrees C. Photoperiod also altere d the normal relationship between development rate and temperature. At L14.25:D9.75, the duration of larval development of diapausing leafmi ners was similar at 15, 20 and 25 degrees C. Temperature alone is unli kely to have a role in the induction of diapause because leafminers ex posed to natural late summer and fall temperature regimes and L16:D8 d id not enter diapause.