Hemlock Sawfly 



The hemlock sawfly is again epidemic, for the most part in areas un- 

 related to those in which the budworm is active. It is estimated that 

 the sawfly is presently epidemic throughout 1,2 million acres in the 

 southern portion of the Tongass National Forest, The actual area of 

 defoliation is only a fraction of this acreage as the epidemic is in 

 widely scattered pockets, and within pockets not all hemlock trees are 

 being defoliated. Defoliation was first noticed by the district 

 ranger in the George Inlet area, A subsequent ground examination 

 revealed scattered sawfly feeding, which on some trees had removed a 

 very high percentage of the hemlock needles, Sawfly cocoons were col- 

 lected and placed in rearing for parasite emergence. To date only 

 5 parasites have emerged from a collection of 100 cocoons. 



The areas mapped from the air in the vicinity of Craig were marked as 

 "possible sawfly*'. Foliage conditions indicating very light sawfly 

 feeding were scattered high on the slopes and were visible only at 

 close range. 



The sawfly is again active in Excursion Inlet but defoliation is less 

 severe than in the southern epidemic area. The sawfly is not n\jmerous 

 enough to make combined budworm-sawfly feeding fatal to the hemlock. 



Recommendations 



1, An aerial survey no less extensive than the 1955 survey should be 

 conducted in the fall of 1956, It should concentrate on the northern 

 budwoiTO areas and the southern budworm epidemic pockets. The outer 

 limits of the hemlock sawfly areas should be re-determined, 



2, Tree mortality plots should be established to determine the long- 

 term effect of budworm defoliation. Plots should be established 

 at Thayer Lake, Orchard Lake, and perhaps Frederick Point near 

 Petersbxirg, These are areas of heavy top kill and some ccxnplete 

 tree kill. Mortality cruises should also be run in these areas 

 to determine the percent of trees killed, the volume so affected, 

 and the rate of stand deterioration, 



3, As a long-term endeavor, economical methods of determining budworm 

 populations in terms of expected destruction must be developed. 

 Should the tree mortality and stand deterioration studies sub- 

 stantiate it, perhaps the correct approach to the black-headed 

 budworm problem in Alaska is to spray those stands of adequate 

 volume which harbour budworm populations capable of causing 

 extensive top kill and complete tree kill. While the outbreak of 

 recent years has swept across mill i ons of acres, the areas of 

 serious top and tree kill are relatively small and expenditures to 

 treat such areas by aerial spray might not be excessive, 



4« A sawfly egg suivey shoiJ-d be conducted in the spring of 1956 to 

 determine the extent and severity of sawfly populations, 



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