Physiological strategy in overwintering larvae of pistachio white leaf borer, Ocneria terebinthina Strg. (Lepidoptera: Lymantriidae) in Rafsanjan, Iran

Abstract

The pistachio white leaf borer, Ocneria terebinthina Strg., is a minor pest of pistachio trees in the pistachio-producing zone of Rafsanjan, Iran, where it overwinters as fourth larval instar. In this study, the quantities of several metabolites including trehalose, glycogen and lipids were measured each month from October 2009 to March 2010. Physiological changes in relation to ambient temperature were also investigated in field-collected overwintering larvae. The glycogen content decreased as ambient temperature decreased; this decline was proportional to increases in trehalose content. In January, which has a mean ambient temperature of 8.0°C, the glycogen content of the larvae was at its lowest level (17.98 mg/g fresh body weight) whereas trehalose was at its highest level (23.99 mg/g fresh body weight). Total body lipids decreased during overwintering and reached the lowest level at the onset of spring. In conclusion, trehalose may be involved in winter survival and the adaptation of the pistachio white leaf borer to cold, by providing cryoprotection. Larvae of the pistachio white leaf borer may have the ability to reserve energy in the form of lipids and utilize it during overwintering.