Temperature-dependent development of Macrocentrus iridescens (Hymenoptera: Braconidae) as a parasitoid of the obliquebanded leafroller (Lepidoptera: Tortricidae): Implications for field synchrony of parasitoid and host

Obliquebanded leafroller (OBLR), Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), is widely distributed in North America where it causes damage to several fruit and nut crops. Macrocentrus iridescens (French) (Hymenoptera: Braconidae) parasitizes OBLR in California pistachio orchards, but to date there is little published information on its biology or effectiveness. To determine its potential as a biological control agent, development of M. iridescens was evaluated at eight constant temperatures, ranging from 12.6 to 36.8 °C. Results show development times, from egg to adult eclosion, ranged from 115.8 to 36.5 days at 13.9 and 31.0 °C, respectively, the lowest and highest temperatures tested that permitted complete development. Fitting the data to a nonlinear model provided estimates of M. iridescens lower (9.8 °C), upper (34.3 °C), and optimal (23.7 °C) development temperatures. M. iridescens requires 625 degree-days to develop from egg to adult stage. To complement laboratory studies, OBLR and M. iridescens season-long field population dynamics were monitored in pistachio orchards, including overwintering behaviors. M. iridescens overwinters in the OBLR larva and produces one generation for each generation of the host.