As part of a study to develop improved foliage sampling methods for spruce budworm, Choristoneura fumiferana (Clemens), egg masses, two balsam fir (four in one stand), Abies balsamea, and two white spruce, Picea glauca, trees were chosen from each of five spruce- fir stands in Michigan's Upper Peninsula in 1980. All stands had very low to low population densities. Each tree was completely enumerated so that the number of new egg masses, foliage surface area, and egg mass density could be determined for the entire tree, three crown classes, four quadrants, and the tree top. Results indicated (1) considerable tree-to- tree and stand-to-stand variation; (2) no meaningful or consistent differences among quad- rants within or between species; (3) the average density in white spruce trees was 3.2 times larger than that in balsam fir trees; (4) the tree-la-tree variation of density in white spruce trees was 8.4 times larger than that in balsam fir trees; (5) densities in the mid-crown, upper-crown, and tree top are considerably higher than that in the lower-crown for both species; the relative differences for balsam fir are about twice that of white spruce; and (6) on the average, density at mid-crown was close to that of the entire tree for balsam fir, but density at mid-crown was 17.9% lower than that of the entire tree for white spruce. These results have important implications to the development of sampling plans for estimating egg mass density in spruce-fir stands.
Simmons, Gary A. and Fowler, Gary W.
"Spruce Budworm Egg Mass Density on Balsam Fir and White Spruce: Low Population Levels (Lepidoptera: Tortricidae),"
The Great Lakes Entomologist, vol 15
Available at: https://scholar.valpo.edu/tgle/vol15/iss4/8