The Effect of Temperature on Survival of Pityophthorus juglandis (Coleoptera: Curculionidae)

摘要: The walnut twig beetle (Pityophthorus juglandis Blackman) vectors Geosmithia morbida, the causal agent of thousand cankers disease in Juglans, and is particularly damaging to Juglans nigra L. (black walnut). Native hosts P. are distributed southwestern United States where winter temperatures tend be higher than those found within native range black walnut. To better understand temperature effects on survival juglandis, we initiated studies determine: 1) seasonal variations cold tolerance, as measured by supercooling point (SCP), 2) upper lower lethal (LT). In LT study, Xyleborinus saxeseni (Ratzeberg) was tested for comparison. Insects were either exposed increasing or decreasing then checked survival. Upper LTs estimated using a logistic model. For SCP data grouped into seasons. Seasonal mean SCPs highest summer (-15.4°C) lowest fall (-18.1°C). limit estimations required kill 99% population (LT99) adults larvae 52.7 48.1°C, respectively, LT99 -18.1 -18.7°C, respectively. median (LT50) X. -24.7°C. These studies, well infested Colorado trees reached -29°C February 2011, suggest could survive much walnut, but may limited regularly exceed LT.