The data for the prognosis of spring swarming of main species of bark beetles (Coleoptera, Scolytidae) on the spruce (Picea excelsea L.)
Zeitschrift Fuer Angewandte Entomologie 933: 305-320
The release and spring swarming of Ips typographus (L.), I. amitinus Eichh. and Pityogenes chalcographus (L.) was observed in 3 variants of spruce stands (a clearing, sparse and dense spruce stand). The release and spring swarming of the bark beetles was observed using traps and special trap devices placed into spruce logs. Spring swarming was observed beginning with the insects leaving overwintering sites. The effect of maximum day temperature (tmax) of the soil, of the phloem and of air on the release and swarming was demonstrated. On the basis of measured temperature data, release and spring swarming was determined by the sum of effective temperature (.SIGMA.Et). When leaving overwintering sites, the bark beetles appeared 1st from suspended logs in the margin of the stand and from the soil litter in photoelectors in the clearing. Beetles left the phloem of the suspended logs in the margin of the stand 14-16 days soon in comparison to the photoelectors in the clearing and 11-13 days sooner than inside the stand in comparison with photoelectors in the sparse spruce stand. I. typographus spring attack started with the trap logs and landings in the clearing, 1-2 days later in the sparse stand and 3-5 days later in the dense spruce stand in comparison with the clearing. I. amitinus and P. chalcographus spring attack occurred 0-1 day later in the sparse forest and 0-2 days later in the dense spruce forest. The swarming conditions for each of the 3 bark beetle species are discussed.