Supercooling Points of Murgantia histrionica (Hemiptera: Pentatomidae) and Field Mortality in the Mid-Atlantic United States Following Lethal Low Temperatures.

The harlequin bug, Murgantia histrionica (Hahn), is a serious pest of brassicaceous vegetables in southern North America. While this insect is limited in its northern range of North America, presumably by severe cold winter temperatures, specific information on its cold hardiness remains unknown. We determined the supercooling points (SCPs) for Maryland and Virginia adult populations and found no significant difference among these populations. SCPs were similar for adults ([Formula: see text] = -10.35 °C; [Formula: see text] 2.54) and early and late instar ([Formula: see text] = -11.00 °C; [Formula: see text] 4.92) and between adult males and females. However, SCPs for first instars ([Formula: see text] = -21.56 °C; [Formula: see text]1.47) and eggs ([Formula: see text] = -23.24 °C; [Formula: see text]1.00) were significantly lower. We also evaluated field survival of overwintering harlequin bug adults during extreme cold episodes of January 2014 and January 2015, which produced widespread air temperatures lower than -15 °C and subfreezing soil temperatures in the Mid-Atlantic Region. After the 48-h episode in 2014, bug mortality in exposed field sites averaged 88%, compared to <5% mortality of bugs sheltered in an unheated greenhouse (recorded minimum temperature 4.4 °C). After the 2015 episode, ∼80% of adults that were established in the field the previous November and then sheltered in an unheated garage during the episode, died, in contrast to 96% mortality in exposed field sites. Our results provide new information on M. histrionica overwintering biology, and thermal limitations to its distribution, which leads to improved predictive capabilities to forecast pest severity.