Indexed on: 28 May '08Published on: 28 May '08Published in: Forest Science and Practice
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 (Ct) 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 Ct has a range of 8.90±1.77°C and the value of K lies between 95.19±13.14 degree-day for eggs; the values for larvae are Ct = 13.26±3.06°C and the number of degree-day is K = 2,885.07±187.87 degree-day; for pupae the ranges are Ct = 8.93±2.49°C and K = 131.20±25.63 degree-day. Under the condition of ambient temperatures, the values for eggs are Ct = 17.33±1.24°C 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.