Feeding by the pine weevil Hylobius abietis in relation to sun exposure and distance to forest edges


1Dr Göran Nordlander, Department of Entomology, SLU, Box 7044, SE-750 07 Uppsala, Sweden. Tel: +46 1867 2365; e-mail: goran.nordlander@entom.slu.se


Abstract  1 The intensity of feeding by adult pine weevils Hylobius abietis (L.) on the stem bark of Norway spruce Picea abies (L.) Karst. seedlings planted in rows with a north–south orientation across a clear-cutting, was measured throughout a growth season. The feeding was then correlated to light interception, soil temperature and distance to the nearest forest edge.

2 Feeding was at least twice as intense on seedlings in the central part of the clear-cutting compared to those at the edges. The decline began approximatety 15 m from the edge and was of similar proportions on both the sun-exposed and shaded sides.

3 Measures of global radiation and soil temperature correlated well with consumption on the shaded side. However, on the sun-exposed side, there were no apparent correlations with global radiation or soil temperature that could explain the decline in consumed bark area.

4 We conclude that the decline in feeding towards the forest edges was mainly due to factors other than the microclimate variables we monitored. We suggest that the presence of roots of living trees along the forest edge may reduce damage to seedlings, since they provide an alternative source of food for the weevils. This alternative-food hypothesis may also explain why seedlings in shelterwoods usually suffer less damage from pine weevils than seedlings in clear-cuttings.