Effects of planting time on pine weevil (Hylobius abietis) damage to Norway spruce seedlings

ABSTRACT

Feeding by pine weevil (Hylobius abietis L.) causes severe damage to newly planted conifer seedlings in most parts of Scandinavia. We investigated the effect of planting time and insecticide treatment on pine weevil damage and seedling growth. The main objective was to study if planting in early autumn on fresh clear-cuts would promote seedling establishment and reduce the amount of damage caused by pine weevil the following season. The experiment was conducted in southern Sweden and in south-eastern Norway with an identical experimental design at three sites in each country. On each site, Norway spruce seedlings with or without insecticide treatment were planted at four different planting times: August, September, November and May the following year. In Sweden, the proportion of untreated seedlings that were killed by pine weevils was reduced when seedlings were planted at the earliest time (August/September) compared to late planting in November, or May the following year. This pattern was not found in Norway. The average length of leading shoot, diameter growth and biomass were clearly benefited by planting in August in both countries. Insecticide treatment decreased the number of seedlings killed or severely damaged in both Norway and Sweden.

KEYWORDS:

• Autumn planting
• establishment
• seedling growth

Acknowledgements

We would like to thank the staff at Asa Research Station, SLU, Sweden and Roald Brean, Norway for scrupulous fieldwork. Thanks also to Sveaskog, Sweden and Mjøsen Skog SA, Norway for excellent cooperation and help. We would also like to thank the anonymous referees for constructive comments on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The Swedish part was included in the Swedish Hylobius Research Program funded by the Swedish forestry sector. The Norwegian part of the study was financed by the Development Fund for Forestry, the County Forest Officers of Hedmark and Oppland, and the Norwegian Forest and Landscape Institute.