One cluster each of balsam fir, Abies balsamea, and white spruce, Picea glauca, trees was chosen from each of five stands of spruce-fir in Michigan's Upper Peninsula. The foliage surface area and the number of new egg masses of the spruce budworm, Choristoneura fumiferana, were determined for each branch and the top of each tree. The effects, in terms of the bias and the variance of the estimator, of sampling in different parts of the tree and with various size branches were determined. Factors that the sampler should consider in developing sampling plans to estimate spruce bud worm egg mass densities in mixed spruce-fir stands were identified. Egg mass density and its per branch variance may be considerably higher in white spruce than in balsam fir. Sampling whole feasible branches at mid-crown yielded, in general, the most precise and accurate estimates of tree egg mass density.
Fowler, Gary W. and Simmons, Gary A.
"Considerations When Sampling Spruce Budworm Egg Masses on Balsam Fir and White Spruce in the Lake States: Low Population Levels,"
The Great Lakes Entomologist: Vol. 17
, Article 8.
Available at: http://scholar.valpo.edu/tgle/vol17/iss2/8