A study was initiated in Michigan's Upper Peninsula to develop improved foliage sampling methods for spruce budworm, Choristoneura fumiferana (Clemens), egg masses. Four balsam fir, Abies balsamea, trees were chosen from each of four stands in 1979, and four balsam fir trees were chosen from one stand in 1980. The number of new egg masses, foliage surface area, and crown and quadrant classes of each branch were determined for all trees. Egg mass density for each part of the tree was determined by dividing total number of egg masses by total surfaee area. The 20 trees were divided into five groups with forecasted budworm damage varying from low to extreme. On the average the egg mass density (egg mass/lOOO cm2) of the lower-crown was 58% lower than the egg mass density of the entire tree; the mid-crown had 18% higher cgg mass density than the entire tree, the upper-crown had 63% higher density than the entire tree, and the tree top had 69% higher density than the entire tree. There was no strong trend to the small absolute differences in density among the four quadrants. Sampling at mid-crown may lead to over- or underestimation of tree egg mass density. The seriousness of such errors would depend on the bias and where the sample is taken vertically in the mid-crown.
Fowler, Gary W. and Simmons, Gary A.
"Spruce Budworm Egg Mass Density on Balsam Fir: Low to Extreme Population Levels (Lepidoptera: Tortricidae),"
The Great Lakes Entomologist: Vol. 15
, Article 7.
Available at: http://scholar.valpo.edu/tgle/vol15/iss4/7