Some Aspects of the Occurrence, Biology and Cold-Hardiness of Hylobius Weevils : Insects Affecting Reforestation. Biology and Damage

1989

S. 28-33

2 Tab., 13 Lit. Ang.

Unselbständiges Werk

200069368

In Estonia, two species of pine weevils - Hylobius abietis L. (76,8% of the sample) and H. pinastri (23.2%) - are the most dangerous pests in conifer reforestation areas. Hylobius pinastri is more common in forest site types where spruces prevail. In spring, at the beginning of flight, males predominate; later, females are more numerous. In addition to stumps, logging slash not removed from clear-cut areas suitable conditions for the development ofpine weevils. Population density of pine weevils was higher and development was faster in the piles where slash was raked up in spring and mixed with soil and ground litter than on stump roots. By the end of the summer of the first year, 60.8% of the weevils on pine branches and 23.3% of those on spruce branches had pupated or were newly emerged adults, whereas stump roots in the same cut area had only larvae. The mortality of pine weevils in the branch piles was higher than that on stump roots. Cold-hardiness of hibernating larvae averaged -12C, and was sometimes as low as -19C, which guarantees successful hibernation under a deep snow covering.