G. Orlander et U. Nilsson, Effect of reforestation methods on pine weevil (Hylobius abietis) damage and seedling survival, SC J FOR R, 14(4), 1999, pp. 341-354
Damage to Norway spruce (Picea abies (L.) Karst.) seedlings by the large pi
ne weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae), was monitored
in relation to clear-cutting age and silvicultural treatments in southern
Sweden. New clear-cuttings were established on four sites during five conse
cutive years, and seedlings were planted on them from 1989 through 1993. In
total, 31 774 seedlings were planted on 20 clear-cuttings. The measures ev
aluated were seedling insecticide treatment, application of herbicide to gr
ound vegetation, scarification (mound) and planting late in the season. In
addition, the effects of slash removal and seedling type were studied.
The pine weevil was, by far, the dominant damaging agent. Planting without
insecticide or soil treatment on fresh, one- or two-year-old clear-cuttings
resulted in a mean level of weevil-caused mortality exceeding 60%. The res
ults indicate that the risk of serious damage by pine weevils remains high
until the clear-cuttings reach four or five years of age. Killing the veget
ation with herbicide had no effect on pine weevil damage. Slash removal dec
reased damage on older clear-cuttings, but the effect was small. Scarificat
ion (mounding) strongly reduced damage. On fresh clear-cuttings the mean mo
rtality caused by pine weevils in mounded plots was 13%, whereas it was 77%
in the controls. The mounding effect varied between sites and clear-cuttin
gs of different ages. Late planting (10 June instead of I May) reduced dama
ge on two- and three-year-old clear-cuttings. Three-year-old, bare-rooted s
eedlings were not damaged as seriously as two-year-old, containerized ones,
but the effect was probably due to the larger size of the bare-rooted seed
lings. Non-lethal injury resulted in reduced seedling growth. Damage by pin
e weevils varied between years and within growing seasons. However, on fres
h, one- and two-year-old clear-cuttings, damage was severe enough to cause
high mortality during all studied years.