Abstract:

The super cooling point (SCP) and mortality of the pine scale insect (Hemiberlesia pitysophila) that hosted on four different pines of Pinus massoniana, P. elliottii, P. taeda and P. thunbergii were investigated when being exposed to a designated and regulated low temperature. Results showed that a significant effect of pines on SCP of female adults was observed, and the SCPs on P. massoniana and P. thunbergii were 0.9～2.3 ℃ higher than that on the other two pines. The mean SCP of the second instar female nymph on P. massoniana after sex differentiation was 2.08 ℃ higher than that on P. elliottii. However, a separate experiment showed no remarkable difference in the SCPs of the second instar male nymph after sex differentiation between on the two pines. Relations between low temperature and mortality of all insect developing stages and the populations on P. massoniana and P. elliottii all exhibited a revised double-variable Logistic model. Nevertheless, the incipient sensitively low lethal temperature and mortality of these developing stages and the population exposed at -20 ℃ were all lower on P. massoniana than that on P. elliottii. The semi-lethal sum of injurious temperature of the population was lower on P. massoniana than on P. elliottii. The results suggested that the SCP and mortality of Hemiberlesia pitysophila exposed to low temperature were significantly affected by host pines, and its cold tolerance on P. elliottii was lower than that on P. massoniana.

Key words: Hemiberlesia pitysophila, cold tolerance, host plant, supercooling point, exposure to low temperature