Articles by Kalervo Salonen

When the seed harvest of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) are low, pine and spruce buds are among the secondary food items of squirrel (Sciurus vulgaris L.) in Finland. In this study, conducted in Nokia in Southern Finland in 1962-1963, eating of pine buds by squirrel is described. The eaten buds in 15-years old Scots pine seedlings were recorded in two seedling stands.

According to the results, the squirrels selected the largest buds of the best seedlings in the studied stands. In over 50% of the cases the squirrels chose only the buds of the leading shoot, especially the terminal bud. In half of the trees, a side bud of the leading shoot continued the growth, which causes form defects in the trees. In 35% of the damaged trees, a lateral branch continued the growth. Well-growing seedling stands may be especially susceptible for damages caused by, for instance, squirrels.

The PDF includes a summary in Finnish.

• Pulliainen, E-mail: ep@mm.unknown
• Salonen, E-mail: ks@mm.unknown

Blastophagus piniperda L. (now Tomicus piniperda) life cycle, especially temperature effects at various stages, has been studied in laboratory, outdoor development experiments and in natural conditions in the field in Finland, 1961–1970.

It was established that when a tree with overwintering beetles in its base is felled during the winter, the overwintered insects can establish an egg gallery into the stump without leaving for swarming flight. The egg gallery can be established in this case already about a month before swarming starts. Swarming starts after temperature in the shade exceeds 10° C. It is at its maximum at a temperature over 12° C and in conditions of no wind. The swarming starts in Southern Finland generally in the latter half of April, and in Lapland two to four weeks later than in Southern Finland, and it lasts from a few days to a few weeks. As the temperature rises, the rate of egg gallery construction and the rate of egg laying increase. The characteristics of the galleries and pupal stage are described in detail.

In Finnish conditions, B. Piniperda does not have a diapause. Movement into overwintering sites starts after the minimum daily temperature goes below 0° C. About 10% of the insects found in the overwintering sites in spring were estimated to have died during the winter. With increasing density, the number of new beetles which developed from each egg gallery decreased.

The PDF includes a summary in Finnish.

• Salonen, E-mail: ks@mm.unknown