Pine weevils.. New methods which do not use insecticides are tested against this pest.
Photographer: Erik Viklund, Skogforsk (Forestry Research Institute of Sweden)
The early phases of forest management, i.e. the establishment and young forest phases, are critical for the various qualities and productive capacity of the mature forest. Ever since 2005, work has been carried on in nine projects to produce knowledge that can be used in continuing to improve work on rejuvenation. Part of the results was presented to Formas and invited representatives of the forestry industry in March 2010 at Skogforsk in Uppsala.
One of the results concerned the reason that pine are more difficult to propagate vegetatively than spruce. It is hoped that this problem can be solved so that propagation using somatic embryogenesis can be used in forestry improvement of pine.
The pine weevil’s preferences
The pine weevil does a lot of damage to forest seedlings, and it is important to find methods to limit such damage when insecticides can no longer be used. The pine weevil has certain preferences as regards scents and the environment around the seedling, which is shown, inter alia, by comparisons between seedlings grown in the usual way and miniseedlings that are much smaller.
The degree of maturity of the seedling and its state of stress influence the scent that it emits. The larger seedlings have a more attractive scent and therefore suffer greater damage in the first year. Miniplants are however more susceptible to dehydration and mechanical damage. When the seedlings become larger, damage by pine weevils increases. But if the miniplants have succeeded in becoming well established, they can cope at least as well as the larger seedlings, but at a lower production cost.
Miniplants are highly depenent on access to water and vegetative competition, and the method must therefore be further developed.
Amino acids
Forest seedlings are today fertilised with various preparations that give the seedling nitrogen in the form of nitrate ions, NO3, or ammonium, NH4. The seedling appears to take up both these forms of nitrogen equally well and then distributes it to the whole plant. Recently it has also been found that seedlings can take up organic nitrogen in the form of amino acids. When amino acids were used instead as fertiliser, it was found that, in proportion, more of the amino acid nitrogen was used for root growth. And seedlings that have received fertiliser in the form of amino acids develop a larger root system and appear to have better drought tolerance, which can result in better survival of the seedlings.
One cost in forestry is weeding and creating conditions for growth for selected individuals. This is done at present, to a large extent, through labour intensive motor-manual weeding. Strip weeding may be an alternative method: a strip of two or three metres is weeded through the young forest, and between these strips there is a zone of seven to eight metres in which weeding is performed selectively. Work proceeds more quickly, but some production is lost in the weeded strips where it takes time for the stand to become established.
Author
:
Jan Svensson
Senior Research Officer, Formas