An engraver beetle ( Ips interpunctus Eichh.) working in the white spruce 

 stands north of Fort Yukon has caused widespread losses. A survey in 

 1957 indicates that the outbreak has been in existence over five years, 

 reaching a peak prior to 1956 and returning to an endemic condition in 

 most areas by 1957. The total outbreak area, as determined by aerial 

 mapping surveys, covers 1,800 square miles. The cause of the epidemic 

 is not known; however, observations made in 1957 reveal that this insect 

 will, under favorable conditions, breed to large numbers in weakened or 

 dying trees. This includes primarily fire-weakened trees, windthrown 

 trees, and trees dislodged along river banks by flood waters during 

 spring break-up. It is believed that large-scale outbreaks in green 

 timber may result from !_. interpunctus first breeding to large numbers 

 in these weakened and dying white spruce. 



Table l.-- Age and volume of white spruce loss caused by an Ips 

 interpunctus outbreak in northern interior Alaska 



Currently 

 infested 

 (1957) 



1-year- 

 old loss 

 (1956) 



2-year- 

 old loss 

 (1955) 



3-5-year- 

 old loss . 

 (1952-54)^/ 



Total 

 loss 



Average cubic 

 ft . vol. /acre 



0.3 



2.3 



9.2 



28.5 



40.3 



Percent 



0.7 



5.7 



22.8 



70.7 



100.0 



\^/ Tree losses estimated as over five years old were not tallied 

 because of the uncertainty as to the cause and year of death. 



Defoliator Activity Declines in Southeast- 

 Increases in the Interior 



An eight-year (1948-55) epidemic of the black-headed budworm ( Acleris 

 variana Fern.) throughout Southeast Alaska collapsed by 1956. A closely 

 associated outbreak of the hemlock sawfly ( Neodiprion tsugae Midd.) re- 

 mained active in a few scattered locations within Ernest Sound during 

 1956 and disappeared entirely by 1957. 



For the first time in recent years a defoliator has appeared in the white 

 birch stands of interior Alaska. During the latter part of the summer 

 of 1957 the spear-marked black moth ( Eulype hastata (L.)) caused defolia- 

 tion of white birch over a widespread area surrounding Fairbanks (fig. 5), 

 This defoliation was not serious, occurring but intermittently within the 

 affected area. A large population of this defoliator is overwintering 

 in the pupal stage, but several parasitic insect enemies are known to 

 be present. The overwintering pupal population will be studied in the 

 spring of 1958 to determine winter survival, parasitism, and any other 

 factors responsible for pupal mortality. During the summer of 1958 a 



■8- 



