Graphs of radial growth since 1950 wero constructed for each crown 

 class. These graphs show a marked decrease in growth during 1953 when 

 defoliation was in progress. An even greater radial growth reduction 

 occurred in 1954 • Growth rate continued down in 1955 but was little 

 reduced from the previous year. Unfortunately, the budwonn outbreak 

 was so widespread in the Juneau area that no undamaged hemlock trees 

 were available for radial growth checks. It is therefore impossible to 

 determine hew much of the loss in increment can be attributed to bud- 

 worm defoliation. 



Two full growing seasons after the budworm epidemic swept through the 

 study area, all of the hemlock trees which suffered top kill still 

 retained the dead top section. On the other hand, 84 percent of those 

 trees had side branches that were assuming the position of leaders. 

 Most of this new leader growth stems fran single side branches at the 

 bases of the dead sections, but a few trees have new leaders developing 

 from bud growth. The average length of this new leader growth is just 

 under twelve inches. 



Biidworm damage to second-growth Sitka spruce 



The investigation of black-headed budworm damage to second-growth 

 Sitka spruce was carried out near Juneau in a stand that was between 

 40 and 45 years old. The dominant spruce averaged 38 feet in height 

 and 8.5 inches in diameter at breast height. The stand was a little 

 more open than normal and as a consequence individual trees suffered 

 more damage than woixLd be found had there been more stems per acre. 

 In sharp contrast to the well-stocked hemlock stand, the spruce area 

 contained only 420 Sitka spruce and 40 western hemlock per acre. As 

 in the case of hemlock, heavy defoliation occurred during only one year. 



Black-headed budworm damage on Sitka spruce was generally concentrated 

 on the current year's growth. The tops were killed in 74 percent of all 

 spruce trees. By crown class this top kill was as follows: Dominant - 

 93 percent; Codcminant - 86 percent; Intermediate - 71 percent; Over- 

 topped - 29 percent. Scxne trees suffered top kill of both 1953 and 



1952 leader growth. Half of the hemlock trees within the spruce stand 

 also suffered top killing. 



While twig killing was chiefly confined to the current growth, heavy 

 defoliation in the tops of the spruce extended back to the 1951 needle 

 growth in 54 percent of the trees. Heavy top defoliation throughout 

 both 1953 and 1952 foliage occurred in 23 percent of the spruce. 

 Twenty-one percent of the spruce suffered only partial top defoliation 

 in the 1953 or ciirrent year's growth. 



Radial growth curves made from spruce trees on the study area and 



from undamaged check trees show a steady decline in diameter growth since 



1953 - the year of budworm defoliation. It is therefore impossible to 

 say how much, if any, growth loss can be attributed to budworm 

 defoliation. 



- 15 



