Changes of cryoprotectants in overwintering larvae of beet armyworm, Spodoptera exigua (Lep.: Noctuidae)

The beet armyworm، Spodoptera exigua (Hübner)، is a polyphagous pest that causes serious damages to a wide range of agricultural crops including beet، potato and cotton. In order to deepen our understanding of the biology of the pest during the winter، overwintering larvae of beet armyworm were collected from the fields from November 2008 through March 2009. Using HPLC technique، the level of cryoprotectants (antifreeze compounds) inside the body of larvae was measured and the following five compounds were detected: trehalose، glucose، myo-inositol، glycerol and sorbitol. It is found that the amount of polyols and trehalose is always higher than the other compounds and during the coldest days of the winter their level sharply increases from 0. 99 mg/g fresh weight in November to 3. 9 mg/g fresh weight in January. The results suggest that trehalose is the key cryoprotectant that helps overwintering larvae of beet armyworms survives during the harsh winter days.