The cold-hardiness of Dendroctonus valens (Coleoptera, Scolytidae) and Rhizophagus grandis (Coleoptera, Rhizophagidae)

Dendroctonus valens LeConte ( Red turpentine beetle, RTB) was recently found in outbreak in China. Its elder instars and mature larvae mainly over-winter under the roots of the pine stumps and standing trees in China. The cold tolerant capabilities of the pest was estimated in the laboratory by super-cooling points (SCP) and short-term lower lethal temperatures (LIT). The results show that the lowest mean super-cooling point of the RTB over-wintering larvae is - 11. 98[plus or minus] [plus or minus] 2. 55[degree]C and it is a species of r tolerant-freezing insect. The SCP of RTB is significantly different between different geographical populations, the elder stage larvae have lower cold-hardiness than younger ones, but no significantly different between the larvae in early winter and later winter. The RTB larvae could spend its life in winter below s the atmospheric temperature which being lower more than -23.5[degree]C at least. In contrast, Rhizophagus grandis Gyll., as a predator of Dendroctonus micans, was introduced to China against RTB since 2001. The mean SCP of Rhizophagus grandis larva is -18.05[plus or minus] [plus or minus] 2. 76 [degree]C which being lower temperature more than ones of any stage of RTB.