Pine weevil damage to Norway spruce seedlings: effects of nutrient-loading, soil inversion and physical protection during seedling establishment

Abstract

1 The pine weevil Hylobius abietis (L.) feeds on the bark of young conifer seedlings and is one of the most economically important forest pests in Europe. 2 In a field experiment, we examined the combined effects of the treatments: nutrient-loading of seedlings, planting in scarified plots and protection of seedlings against pine weevil damage for either half a season or a full season. 3 Nutrient loading had no significant effect on the amount of pine weevil feeding. 4 Seedling mortality was significantly reduced when seedlings were protected from pine weevil feeding during establishment. This occurred even though the debarked area of protected seedlings 5 weeks after the shields had been removed was similar to that of the unprotected seedlings. This indicates that initial protection rendered the seedlings more tolerant to later wounding by pine weevil. 5 Planting in soil inversion significantly reduced feeding compared with planting in humus. 6 We conclude that nutrient-loading of seedlings in the autumn before planting would not increase pine weevil feeding after planting. Mortality could be reduced by treatments that postpone the start of pine weevil feeding on seedlings. Such treatments, combined with planting in soil inversion, would result in increased seedling growth, vitality and tolerance to pine weevil attack.