Changes of low molecular weight compounds of cryoprotectants in overwintering adults of Eurygaster integriceps (Hem.: Scutelleridae)

The Sunn pest, Eurygaster integriceps Puton, is a univoltine insect and considered as one of the most important pests of wheat and barley. The adults of E. integriceps migrate to higher altitude in mountains for about nine months to complete their aestivation and hibernation period. To measure the cryoprotectants compounds, the insects were collected monthly between August 2009 and May 2010 in an altitude of 2000 meters and from wheat fields on the outskirts of Kabudarahang in the province of Hamadan. The level of cryoprotectants was determined using high performance liquid chromatography (HPLC). The identified compounds were trehalose, glycerol, glucose, myo-inositol, ribitol and sorbitol. It appears that trehalose and glycerol are the major cryoprotectants. The amount of trehalose significantly increased from 1.36 µmol/g fresh weight (f. w.) in September to 8.26 µmol/g f. w. in December. The amount of glycerol (22.36 µmol/g f. w.) and glucose (8.97 µmol/g f. w.) were at their highest levels in February and December, respectively. The amount of total cryoprotectants significantly increased from 12.28 µmol/g f. w. in September to 44.07 µmol/g f. w. in February. Results show that the Sunn pest has a great capacity to synthesize various cryoprotectants.