ABSTRACT
The sycamore lace bug, Corythucha ciliata is a new, invasive pest of Platanus trees in China. Although C. ciliata is often subjected to acute low temperatures in early winter and spring in northern and eastern China, the cold tolerance of C. ciliata has not been well studied. The objectives of this study were to determine whether adults of C. ciliata are capable of rapid cold hardening (RCH), and to compare the benefits of RCH vs. cold acclimation (ACC) in the laboratory. When the adult females incubated at 26°C were transferred directly to the discriminating temperature (-12°C) for 2 h, survival was only 22%. However, exposure to 0°C for 4 h before transfer to -12°C for 2 h induced RCH, i.e., increased survival to 68%. RCH could also be induced by gradual cooling of the insects at rates between 0.1 and 0.25°C min(-1). The protection against cold shock obtained through RCH at 0°C for 4 h was lost within 1h if the adults were returned to 26°C before exposure to -12°C. Survival at both -12 and -5°C was greater for RCH-treated than for ACC-treated adults (for ACC, adults were kept at 15°C for 5 days), and the lethal temperature (2 h exposure) was lower for RCH-treated than for ACC-treated adults. The results suggest that RCH may help C. ciliata survive the acute low temperatures that often occur in early winter and early spring in northern and eastern China.
Subject(s)
Acclimatization , Cold Temperature , Heteroptera/physiology , Animals , Female , Time FactorsABSTRACT
Supercooling point (SCP) of female adults of Corythucha ciliata was significantly lower than that of male adults, with an average being -11.49 degrees C and -9.54 degrees C, respectively. Low temperature survival of adults of different ages indicated that there were differences in cold survival ability among age groups of adults. Nonlinear regression analysis found that the response of C. ciliata adults to exposure time under different low temperature regimes (above -5 degrees C) was best fitted by a logistic equation. Both low temperature and exposure time had significant effects on mortality of adults. Temperatures above 5 degrees C did not prevent C. ciliata adults from surviving. C. ciliata was shown to be a freeze-intolerant but chill-tolerant insect. C. ciliata could tolerate subzero temperatures by supercooling. Temperature around -8 degres C is a critical point for successful overwintering of C. ciliata adults, which can establish in the whole areas where Platanus trees are planted in China.
