Seasonal changes in supercooling capacity and main polyols in overwintering adults of Acrosternum millierei (Hemiptera: Pentatomidae)

Abstract

Acrosternum millierei (Hemiptera: Pentatomidae) is a major pest of pistachio because it attacks nuts from early spring to the time of harvest. In this research, the physiological adaptations of non-diapausing and overwintering adults, including changes in the supercooling point (SCP), in the survival at low temperatures, and in the accumulation of polyols were studied. The results showed that the SCP decreased significantly from a mean value of −11.8 °C in July 2018 (non-diapause adult) to −17.6 °C in February 2018 (overwintering adult). Survival at low temperatures was well correlated with SCP capacity. Survival at −10 and −15 °C/24 h was 0% in mid-summer, whereas it increased to approximately 100% (at −10 °C) and 50% (at −15 °C) in winter. The major polyols in overwintering adults were trehalose, myoinositol, sorbitol and glycerol, respectively. The results of the present study suggest that A. millidegree adults accumulate polyols to improve their SCP capacity, and enrich cold hardiness by decreasing the SCP with respect to a reduction in ambient temperature. A. millirem adults seem to be freeze intolerant.