Versuche über den Verlauf des Schwärmens von Borkenkäfern und des Insektenbefalls an Kieferenholz in Mittelschweden
Studies on bark beetle flight periods and the course of insect attack on pine logs in Central Sweden. The flight periods of bark beetles and the insect attack on pine logs, felled at intervals of 20 days from January to June, were studied by using window traps and by marking fresh entrance holes in the logs followed by autumn inspection. The periods of flight and attack had similar patterns. Blastophagus piniperda and B. minor, as well as several other bark beetle species, had relatively short periods of flight and attack, while especially Pityogenes chalcographus had a long flight period with less accentuated peak. Trypodendron lineatum had a flight pattern with one early and one late peak. The Blastophagus species attacked all groups of logs felled before the flight period with similar high intensity. They attacked logs felled during the flight period within short time but in small numbers. The upper side of the logs was more often attacked in the earlier part of the flight period than in the later one. Dates for felling and of attack had no greater influence on success and length of the Blastophagus galleries. The mean production of one square metre surface area attacked by 82 galleries (mostly B. piniperda) was 933 young bark beetles leaving the logs, a population increase of about six times. The earliest exit holes of B. piniperda appeared on the logs 57-77 days after entrance of the females, for B. minor 90 days after entrance. The damage by tunneling of pine shoots began in July and amounted up to the following spring to 95 broken shoots per tree in close vicinity to the attacked logs, corresponding to 30 % of Blastophagus leaving the logs.
Borkenkäfern; Insektenbefalls; Kiefernholz
Studia Forestalia Suecica
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