Supercooling points of Murgantia histrionica (Heteroptera: Pentatomidae) and field mortality in the Mid-Atlantic United States following lethal low temperatures

Authors: DIMEGLIO, ANTHONY - Virginia Tech; WALLINGFORD, ANNA - Cornell University; Weber, Donald; KUHAR, THOMAS - Virginia Tech; MULLINS, DONALD - Virginia Tech

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/28/2016
Publication Date: 8/6/2016
Citation: Dimeglio, A.S., Wallingford, A.K., Weber, D.C., Kuhar, T., Mullins, D. 2016. Supercooling points of Murgantia histrionica (Heteroptera: Pentatomidae) and field mortality in the Mid-Atlantic United States following lethal low temperatures. Environmental Entomology. 45(5): 1294-1299.

Interpretive Summary: Many pests, especially those originating in the subtropics, are sensitive to severe winter cold temperatures, and this limits their invasion of higher latitude temperate regions such as the northern USA. Harlequin bug is a serious pest of cabbage, collards, and other mustard-family crops in North America, which originated in and near Mexico. The limits of its northern range depend on winter temperatures and spread of surviving bugs during the growing season. For many insects including pest species, winter hardiness and their supercooling point, the temperature below 0°C (32°F) at which their body fluids freeze and they die, is not known. This is a very useful number in determining how many insects are expected to survive under winter conditions in different regions and habitats, and how this may change from winter to winter or with other trends such as climate change and urban heat islands. We determined laboratory supercooling points (SCPs) for all harlequin bug life stages, including eggs, nymphs, and male and female adults, and also subjected adults to severe cold naturally occurring under field conditions. SCPs for adults and feeding nymphs were between -11 and -10°C (12-14°F), consistent with field adults in two separate winter cold events experiencing 88% or more mortality in the field at -15°C (5°F) or lower. Our results provide new information on harlequin bug overwintering biology, and severe cold limits to its distribution, which leads to improved ability to forecast pest distribution and severity.

Technical Abstract: 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 (-10.35 ± 2.54 °C (mean ± std.error) and early and late instar (-11.00 ± 4.92°C) and between adult males and females. However, SCPs for 1st instars (-21.56 ± 1.47°C) and eggs (-23.24 ± 1.00°C) 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 sub-freezing soil temperatures in the Mid-Atlantic Region. After the 48h episode in 2014, bug mortality in open field sites averaged 88%, compared to <5% mortality of bugs sheltered in an unheated greenhouse. After the 2015 episode, approximately 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 open 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.