COLD-HARDINESS OF THE ELM BARK BEETLE SCOLYTUS-LAEVIS CHAPUIS, 1873 (COL, SCOLYTIDAE) AND ITS POTENTIAL AS DUTCH ELM DISEASE VECTOR IN THE NORTHERNMOST ELM FORESTS OF EUROPE
Lo. Hansen et L. Somme, COLD-HARDINESS OF THE ELM BARK BEETLE SCOLYTUS-LAEVIS CHAPUIS, 1873 (COL, SCOLYTIDAE) AND ITS POTENTIAL AS DUTCH ELM DISEASE VECTOR IN THE NORTHERNMOST ELM FORESTS OF EUROPE, Journal of applied entomology, 117(5), 1994, pp. 444-450
Cold hardiness was studied in overwintering larvae of the elm bark bee
tle (Scolytus laevis) which is an important vector of the dutch elm di
sease in northern Europe. Mean SCPs were as low as -29-degrees-C in mi
d-winter and increased to -21-degrees-C in May. Corresponding melting
points varied from -6.5 to -0.7-degrees-C with thermal hysteresis free
zing points 0.2-0.3-degrees-C lower during the winter. Glycerol was th
e main low molecular weight cryoprotectant substance. Frozen larvae be
came active shortly after thawing, but subsequently died or were unabl
e to pupate at 21-degrees-C. In the early part of the winier supercool
ed larvae survived extended periods at -19-degrees-C but were killed a
t this temperature in the s ring. It is concluded that cold hardiness
will not be the limiting factor for the distribution of the elm bark b
eetle within the limits of the elm in Norway.