Impact of foraging byMonochamus titillator [Col.: Cerambycidae] on within-tree populations ofDendroctonus frontalis [Col.: Scolytidae]
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abstract
The impact of foraging by Monochamus titillator (Fab.) on within-tree populations of Dendroctonus frontalisZimm. was described. Total population estimates for D. frontalis and inner bark area foraged by M. titillator were computed for 89 loblolly pine, Pinus taeda L., sampled over a 3 year period. Frequency histograms were prepared for the surface area of habitat infested, area foraged by M. titillator, and within-tree populations of D. frontalis. These data were used to calculate the proportion of area foraged by M. titillator, the proportional D. frontalis mortality for the entire tree, and the proportional mortality occurring in the foraged area. Histograms showing the variation of these components were prepared and described using nonlinear mathematical models. Ca. 20% of the infested surface area was foraged by M. titillator. Mortality to D. frontalis on a per tree basis was ca. 14%. Mortality in the area foraged by M. titillator was ca. 70%. These estimates were highly variable between individual trees and a procedure for predicting the probability of a given level of foraging and mortality was described. Sources of variation influencing foraging by M. titillator and mortality to D. frontalis were investigated. Variation between years and season followed similar trends with both foraging and mortality increasing from the base to the top of the infested bole. Variation between tree size-class was highly significant. Larger size-class trees had substantially greater foraging and mortality than did the smaller size-classes. Mortality within the foraged area was also found to be greater at the extremes of the infested bole. 1980 Le Franois.
