Lee says extreme cold is critical for achieving high insect mortality rates. The cold is good news for ash trees who are under attack from the emerald ash borer.
Fig. 1. Location of United States and Canada weather stations used in this study,and ranges of green,white,and black ash in North America according to Little (1971). R.D. DeSantisetal./Agricultural and Forest Meteorology 178–179(2013)120–128
When temperatures hit minus 36 to minus 40 in Minnesota, up to 99 percent of ash borer larvae can die.
Coldest temperatures recorded in largest and smallest diameter logs used in larval COLD HARDINESS OF EMERALD ASH BORER, AGRILUS PLANIPENNIS: A NEW PERSPECTIVE Robert C. Venette1 & Mark Abrahamson2
Paul Huttner is chief meteorologist for Minnesota Public Radio. Huttner has worked TV and radio stations in Minneapolis, Tucson and Chicago. Paul is a graduate of Macalester College in St. Paul and holds a bachelor’s degree in geography with an emphasis in meteorology.