Articles containing the keyword 'egg galleries'

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

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