Overwintering in the cotton leaf roller Syllepte derogata F. (Lepidoptera: Pyralidae)

Abstract

Using the release and collection method, it is confirmed that cotton leaf roller, Syllepte derogata overwinters as mature diapausing larvae. To elucidate the species’ cold resistance mechanism, body water content, biochemical substance levels and the supercooling point of diapausing and non-diapausing larvae were evaluated during the winter. The maximum and minimum supercooling points of diapausing larvae were –18.23°C and −22.33°C, respectively, which were significantly lower. The free body water content of diapausing and non-diapausing larvae was 74.72% and 78.00%, respectively. However, the combined water, glycogen and fat contents were significantly higher in diapausing larvae. In the early overwintering stage, the supercooling point and body free water content steadily declined while glycogen content decreased rapidly. On the other hand, the fat and combined water contents increased slightly. In the late overwintering stage, glycogen content changed minimally, fat content declined rapidly and free water content increased slightly. These demonstrate that S. derogata utilises glycogen in the early stage and fat in the late stage of its overwintering.