Articles by Bo Långström

Shoot losses due to maturation feeding by pine shoot beetles (Tomicus piniperda (L.) and T. minor (Hart.), Col., Scolytidae) and subsequent growth losses were studied in Scots pine (Pinus sylvestris L.) stands growing at different distances from a timber yard, where pine timber was stored during the years 1982–84. In autumn 1985, pine trees were felled at 20, 40, 80, 500 and 1,500 m distance from the timber yard, five trees in each distance class. Trees were analysed for beetle attack, needle biomass and growth. In autumn 1988, increment cores were taken from 20 trees in each distance class.

In 1985, different damage estimates showed that beetle damage was more than 10-fold in the crowns of pine trees growing close to the timber yard as compared to less damaged trees in greater distance. Crude needle biomass estimates indicated that the trees attacked most had lost more than half of the total foliage. Following three years of attack, basal area growth decreased for 2–3 years and recovered during the subsequent 3 years, the total period of loss thus being 5–6 years. The loss in volume growth during 1983–85 was ca. 70, 40, 20 and 10% at 20, 40, 80 and 500 m distance from the beetle source, respectively, compared to the stand at 1,500. Growth losses did not occur until the number of beetle-attacks, ”pegs”, exceeded ca. 200 per tree. The highest observed growth losses occurred in trees with more than 1,000 pegs per tree.

The PDF includes an abstract in Finnish

• Långström, E-mail: bl@mm.unknown
• Hellqvist, E-mail: ch@mm.unknown

In the 1980 and 1981, windthrown and felled Scots pine (Pinus sylvestris L.) were examined at 8 localities in Sweden. The number and length of egg galleries as well as the number of exit holes of Tomicus piniperda (L.) and T. minor (Hart.) were recorded on sample sections (30 m in length) distributed at 3 m intervals on the 37 fallen pine stems, which were successfully colonized by the beetles. In addition, 78 uprooted pines were surveyed in 6 localities. Most trees were attacked by T. piniperda, but only a few by T. minor. Successful colonization often resulted in the production of several thousand beetles per tree, the maximum being approximately 1,800. The attack density of T. piniperda seldom exceeded 200 egg galleries/m³ bark area, and the brood production usually remained below 1,000 beetles/m³. Much higher figures were obtained or T. minor. In T. piniperda, the rate of reproduction (i.e. the number of exit holes /egg gallery) decreased rapidly with increasing attack density, whereas T. minor seemed to be less sensitive to intraspecific competition.

The PDF includes a summary in Finnish.

• Långström, E-mail: bl@mm.unknown

The aim of this study was to investigate how the weight loss and water content of cold stored plants depend on the storage conditions, and if there is a clear connection between these factors and the field survival of the planting stock. The experiments were carried out in a climate chamber at about +2°C and at three moisture levels (about 70, 85, and 95%) from November 1968 to May 1969. Three-year-old seedlings of Scots pine (Pinus sylvestris L.) average length 127 mm, diameter 3.5 mm and the top/root-ratio of fresh weight 1.93, were stored in open and sealed plastic bags. In addition, a transpiration retardant (Silvaplast) was used. The plastic bags (10 plants each) were weighted every 4. week. The remaining 270 seedlings were planted out and inspected after one growing season.

Although the experiment was made in a small scale, the results showed clearly that plant mortality, varying between 3 and 97%, was due to the storage conditions. The weight loss ranged between 2 and 50%, and the correlation between the weight loss and the mortality in the field was high. The water content of the seedlings was about 61%. The correlation between water content and survival was very high. Thus, the determination of weight loss or water content could be a useful method in observing the changes of water balance of the seedling stock during winter-storage. Further investigations are needed to show the tolerable rate of drying out for different sorts of plants. The Silvaplast-treatment had no visible effect either on the drying out or on the field survival.

The PDF includes a summary in English.

• Långström, E-mail: bl@mm.unknown

The aim of the study was to investigate the effect of four packing methods on the field survival and growth of seedlings and transplants of Scots pine (Pinus sylvestris L.) stored over the winter in a cold-storage cellar. The following sorts of plants were used: one-year-old seedlings (1+0) grown in a plastic greenhouse, two-year-old (2+0) open grown seedlings and three-year-old open grown transplants. These plants were stored in open wooden boxes, in sealed plastic bags, in boxes with wet peat on the bottom and in plastic-laminated paper bags.

The control plants were of the same types and were kept in a nursery over the winter. The storage was carried out in a mantle-chilled cold-storage from October 1966 to May 1967. The temperature in the cold-storage was kept around -2 °C and the relative humidity of the air over 90%. The water content of a randomly selected sample plants showed no increase in water deficit after the storing. Part of the seedlings were transplanted in the nursery and the rest were planted in a clear-cut area. A number of the latter plants were treated with an insecticide (1% Intaktol, which contains DDT, Lindane and dieldrin) before planting. All the experiments were examined after one growing season and the planting experiments the next fall.

The transplants (2+1) in the nursery, and in the forest had survived and grown better than the seedlings. In the nursery the 1+0 seedlings survived and grew better than the 2+0 seedlings. There was no difference in mortality between the seedlings. After the first growing season occasional significant differences between the packing methods were observed, but they disappeared during the second growing season. Thus, all packing methods proved to be as successful as the control method without winter storage.

Transplants were more often attacked by the large pine weevil (Hylobius abietis L.) than the smaller seedlings. The damage, however, was considerably greater on the seedlings because of their lower resistance. No significant differences in the Hylobius-attack between the packing methods could be observed. The Intaktol-treated plants were as often attacked as the untreated ones, but the damage was slighter on the treated ones.

The PDF includes a summary in English.

• Långström, E-mail: bl@mm.unknown

• Långström, SLU, Dept. of Entomology, P.O.Box 7044, S-750 07 Uppsala, Sweden. Fax +46 18 672 890 E-mail: bo.langstrom@entom.slu.se
• Hellqvist, SLU, Dept. of Entomology, P.O.Box 7044, S-750 07 Uppsala, Sweden. Fax +46 18 672 890 E-mail: ch@nn.se
• Cedervind, SLU, Dept. of Entomology, P.O.Box 7044, S-750 07 Uppsala, Sweden. Fax +46 18 672 890 E-mail: jc@nn.se

• Annila, Finnish Forest Research Institute, P.O. Box 18, FIN-01301 Vantaa, Finland E-mail: erkki.annila@metla.fi
• Långström, Swedish University of Agricultural Sciences, Dept of Entomology, P. O. Box 7044, S-750 07 Uppsala, Sweden E-mail: bl@nn.fi
• Varama, Finnish Forest Research Institute, P.O. Box 18, FIN-01301 Vantaa, Finland E-mail: mv@nn.fi
• Hiukka, Finnish Forest Research Institute, P.O. Box 18, FIN-01301 Vantaa, Finland E-mail: rh@nn.fi
• Niemelä, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: pn@nn.fi