Attack preference of Ips pini on Pinus ponderosa in northern Arizona: tree size and bole position
1 The present study investigated the influence of tree size and bole position on selection of ponderosa pines (Pinus ponderosa Dougl. ex Laws.) by Ips pini Say (Coleoptera: Curculionidae: Scolytinae) in a northern Arizona forest. Ips pini were attracted to lower and upper bole positions with pheromone lures, and the number of attacks counted. In addition, tree phloem and bark thickness, resin flow in response to wounding and characteristics of tree water and carbon relations were all measured.
2 Bark thickness was the most strongly related tree characteristic to number of I. pini attacks. Thin bark and a high number of attacks occurred at the lower bole position of 10-cm diameter trees and upper bole positions of 23-, 35-, and 50-cm diameter trees.
3 Phloem thickness increased directly with tree size, was greater at the upper bole compared with the lower bole, but was not associated with number of attacks.
4 Resin flow did not differ strongly over tree sizes or bole positions, and was not related to number of I. pini attacks. Attacks were not related to characteristics of tree carbon and water relations measured during I. pini flights.