Effective accumulated temperature and developmental threshold temperature for Semanotus bifasciatus(Motschulsky) in Beijing

In order to understand the occurrence and development of Semanotus bifasciatus (Motschulsky), a borer insect of Platycladus orientalis in parts of northern and eastern China and to improve its prediction, the developmental threshold temperature (C_t) and effective accumulated temperature (K) of S. bifasciatus were determined under conditions of constant and variable temperatures. The results show that under constant temperatures the value of C_t has a range of 8.90±1.77℃ and the value of K lies between 95.19±13.14 degree-day for eggs; the values for larvae are C_t=13.26±3.06℃ and the number of degree-day is K=2,885.07±187.87 degree-day; for pupae the ranges are C_t=8.93±2.49℃ and K=131.20±25.63 degree-day. Under the condition of ambient temperatures, the values for eggs are C_t=17.33±1.24℃ and K=70.79±8.99 degree-day. It is suggested that S. bifasciatus adults over-winter in a state of dormancy, not at a diapause. Warm winter may accelerate the life cycle of S. bifasciatus. Equations can be used to predict an early occurrence of S. bifasciatus.