Resistance of Naturally Regenerated and Nursery-Raised Scots Pine Seedlings to the Large Pine Weevil, Hylobius abietis (Coleoptera, Curculionidae)

1990

19 S.

7 Abb., 1 Tab.

Bandaufführung

2628

37271

The susceptibility of naturally regenerated pine seedlings and nursery- grown, planted seedlings to attack by the large pine weevil was compared in a 3-year pairwise field trial. No insecticides were used. The risk of attack and seedling mortality were calculated using a logistic model. Naturally generated plants were generally more successful than their planted counterparts. Plant pairs where the planted seedling alone was attacked or killed were significantly more numerous. However, the planted seedlings were no longer as susceptible during the following years. The risk of weevil attack on natural seedlings ranged from 6.9 to 69.6%, depending on the height of the plants. The corresponding risk for the planted counterparts was 64.5-98.6%. Even the slightly affected, natural plants had a 2.3-10.5% risk of dying, and the planted ones a 5.7-22.8% risk. Although the natural regenerated plants generally performed better than their planted counterparts, the impact of the pine weevil on the natural seedlings was rather high in the freshly cut seed tree stand used as the experimental site. This was especially the case for the smallest seedling height class. Silvicultural methods should be applied to promote the early establishment of an advanced and robust natural seedling stock before the fresh breeding material produced by logging attracts the weevil to the site.