Cold hardiness of three aphid species, Acyrthosiphon pisum, Megoura crassicauda and Aulacorthum solani (Hemiptera: Aphididae).

Abstract

The cold hardiness of three aphid species, Acyrthosiphon pisum, Aulacorthum solani and Megoura crassicauda, was investigated using the active stages of holocyclic and anholocyclic clones. Although a progressive increase of supercooling points (SCPs) was exhibited with increasing age in the three aphid species, little variation in the SCPs was observed among the species at the same developmental stages. However, the survival rate at a prefreeze temperature of −10°C differed among the three aphid species. The survival rate of both nymphs and adults of M. crassicauda was the lowest and that of A. pisum the highest. At −10°C, the survival rate of fourth-stadium nymphs of A. pisum reared at 15°C under a short photoperiod (10L : 14D) was higher than that of the same stadium nymphs reared at 20°C under a long photoperiod (16L : 8D), but there was no significant difference in the survival rate between the holocyclic and anholocyclic clones reared under the same conditions. These results indicate that nymphs and adults of both holocyclic and anholocyclic clones have insufficient cold hardiness to survive the severe winter in the northern parts of Japan. Furthermore, the distribution of the two life cycle clones of M. crassicauda in Japan was estimated from the different levels of cold hardiness among the three aphid species.