The distribution of a Tomicus piniperda (L.) population in the crown of Yunnan pine during the shoot feeding period.

Abstract

n Kunming, Tomicus piniperda (L.) during the period of shoot feeding distributed mainly around the host trees in which the trunks had been used as the reproduction site. Around all these trees the population density decreased exponentiallyfrom the centre to the periphery. The diameter of dispersion area was about 30m.During shoot feeding, the beetle population dispersed into the new area around progressively. In the crown of host tree, the bark beetles distributed principally to4th-10th whorls. The percentage of the bark beetles in the crown reached thelargest in the 7th whorl. The rate of shoot damaged was the largest in the 6th-7thwhorls, followed in the second place in 2th--5th whorls, and decreased progressively from the 7th to the lowest whorl. At the levels in the crown, the barkbeetles concentrated relatively in the outer portion of the crown, which was aboutthe sum of the numbers in the middle and inner portions of the crown. In the early period of shoot feeding, the population distributed mainly in the outer portionof the crown, and then progressively dispersed to the middle and the inner portionsof the crowns. In the late period of shoot feeding, most of population aggregatedin the crowns of the trees which whould be attacked on the trunks, and distributedmainly in the outer portions of these crowns. On the basis of comprehensive analysis,the spatial distribution of the bark population in the crown is thought to be theresult from the influence of the shoot diameter, the population density, tranferringdamage, landing behavior, and sunlight on the bark beetle behavior.