Cold hardiness and supercooling capacity in the pea leafminer Liriomyza huidobrensis

Pupal SCP (supercooling point) of Liriomyza huidobrensis showed no variation with age, with an average of -20.9degreesC. Low temperature survival of different ages of pupae showed no correlation with their SCP. Nonlinear regression analysis found that the response of L. huidobrensis pupae to exposure time under different low temperature regimes above -5degreesC was best fitted by a logistic equation. Both low temperature and exposure time had significant effects on pupal mortality. Temperatures above 5degreesC do not prevent pupae from emergence. L. huidobrensis was shown to be a freeze susceptible, and at the same time, a chill tolerant insect. It can tolerate subzero temperatures by supercooling. Compared with L. sativae, another dominant leafminer in China (31), L. huidobrensis is more cold tolerant. Our results explain differences between the species in geographic distribution and phenology.