Physical protection of conifer seedlings against pine weevil feeding

Protection of seedlings afforded by two types of coated barriers (CB) against pine weevil (Hylobius species) feeding was evaluated in field experiments in Sweden. The CB is an upright sheath surrounding a seedling and covered on the outside with a coating of polytetrafluoroethylene that hinders insects from crawling up. In experiments during 1992-1993 on four sites, protective treatments by CB applied after planting greatly reduced seedling mortality due to pine weevil feeding and increased survival over two growing seasons. Seedlings with correctly positioned CB were rarely attacked. In a large-scale experiment during 1993-1994 on nine forest sites, protection by CB applied before planting reduced the risk of seedling mortality caused by pine weevil feeding by 93% in the first year and by 83% for both years. Seedling mortality due to Hylobius feeding in plots with CB protected seedlings was largely independent of the mortality in plots with unprotected seedlings. Pine weevil damage was less frequent on scarified sites than on unscarified sites. Differences in damage levels between years were partly attributed to differences in weather conditions.