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Title: Supercooling points of Lysiphlebus testaceipes and its host Schizaphis graminum

Author
item JONES, DOUGLAS - University Of Illinois
item GILES, KRISTOPHER - Oklahoma State University
item Elliott, Norman - Norm

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2008
Publication Date: 12/15/2008
Citation: Jones, D.B., Giles, K.L., Elliott, N.C. 2008. Supercooling points of Lysiphlebus testaceipes and its host Schizaphis graminum. Environmental Entomology. 37(5):1063-1068.

Interpretive Summary: Knowledge of supercooling points for the parasitoid Lysiphlebus testaceipes and its host Schizaphis graminum help provide insight about their ability to successfully function throughout the winter in the southern Great Plains. Supercooling points were measured for various life stages of male and female Lysiphlebus testaceipes, along with mummies, and its aphid host the greenbug. Some parasitoids were acclimated to low winter time temperatures before cooling down to the supercooling point to determine whether acclimation lowered the supercooling point. Acclimation did not lower the supercooling point for L. testaceipes. An inverse relationship between age of the adult parasitoid and its supercooling point was detected. Younger female adult parasitoids and mummies had mean SCPs less than -26°C. Non-acclimated male and female parasitoids older than 12 h after emergence spontaneously froze at the warmest mean temperatures. The SCP for the greenbug host was -25.98°C. From the viewpoint of the ecology of L. testaceipes and the greenbug in the southern Great Plains, the low supercooling points suggest that low temperature by itself is rarely a factor contributing to high mortality of the greenbug or the parasitoid.

Technical Abstract: Supercooling points (SCPs) were measured for various life stages of male and female Lysiphlebus testaceipes (Cresson) parasitoids, along with mummies and its aphid host, Schizaphis graminum (Rondani). Some parasitoids were acclimated (4 h at 10°C before cooling down to the SCP) to determine whether this could significantly lower the SCP. Acclimation did not improve SCPs for L. testaceipes. An inverse relationship between age of the adult parasitoid and its SCP was detected. Non-acclimated male and female parasitoids older than 12 h after emergence spontaneously froze at the warmest mean temperatures (-20.32 ± 1.32 and -22.55 ± 0.62°C [SE], respectively). Younger female adult parasitoids (<6 h after emergence) and mummies had mean SCPs less than -26°C. The SCP for the greenbug host was slightly warmer at -25.98 ± 0.10°C.