Rapid cold-hardening response in Ophraella communa LeSage (Coleoptera: Chrysomelidae), a biological control agent of Ambrosia artemisiifolia L.

In China, an unintentionally introduced beetle Ophraella communa shows good control efficiency against invasive common ragweed, Ambrosia artemisiifolia. With the aim of understanding the capacity of O. communa to overcome sub-zero low temperature rapidly, the longevity, survival and fecundity of the beetle adults were studied at conditions of different rapid cold-hardening in the laboratory. The results showed that approximately 20% female or male individuals still survive at -12 degrees C for 2 h, thus the discriminating temperature for rapid cold-hardening of both female and male beetles is 12 degrees C. The survival, longevity and fecundity of adult beetles were significantly affected by rapid cold-hardening treatments. Compared to the control, the survival rates of adult beetles experiencing 2 h of rapid cold-hardening at 2, 5 and 8 degrees C prior to exposure to its discriminating temperature (-12 degrees C) were significantly increased. Adult longevity and fecundity were significantly higher after pre-treatment at 2, 5 and 8 degrees C for 2 h than those of the control. Both longest longevity and maximum fecundity of adult beetles were observed at the rapid cold-hardening of 2 degrees C. Our experiment implies that the cold-tolerance ability of O. communa can be rapidly increased after rapid cold-hardening treatments, which reveals an important ecological significance for population establishment and expansion of O. communa in the invaded areas of common ragweed.