Four Billion Feet of Beetle-Killed Spruce 



417 



the telltale indication of bark beetle 

 infestations. There is still much to be 

 learned concerning the place that the 

 recent developments in aircraft and 

 aerial photography will have in forest- 

 pest surveys of the future. The timing 

 and frequency of the flights will be 

 important. 



CURRENT EXPERIENCE suggests air- 

 craft and aerial photography will prove 

 to be a valuable adjunct to the survey 

 technique and that for certain of the 

 important pests they make it possible 

 to detect the presence and accurately 

 estimate the extent of infestation more 

 promptly. It is reasonable to assume, 

 however, that detailed on-the-ground 

 inspections will still be required to 

 secure exact data needed to appraise 



the potential significance of the 

 infestation. 



Helpful as all known procedures 

 are, it is clear that the practices of 

 detecting infestations and infections 

 of insects and diseases injurious to our 

 forests need to be improved. More 

 than this, we must use to a much 

 greater extent the knowledge we now 

 have if the destructive importance of 

 the pests are detected in stages of in- 

 cipiency. Early discovery of a poten- 

 tially destructive infestation permits 

 action that will prevent important loss 

 and greatly reduce the cost of control. 



S. A. ROHWER is assistant chief of 

 the Bureau of Entomology and Plant 

 Quarantine in the Department of Ag- 

 riculture. 



FOUR BILLION FEET OF BEETLE-KILLED SPRUCE 



N. D. WYGANT, ARTHUR L. NELSON 



Ten years or so ago the Engelmann 

 spruce forests in the higher Rocky 

 Mountains of Colorado were a sight 

 to behold. They were a reservoir of un- 

 exploited virgin timber, the summer 

 homes and playground of thousands of 

 people who love the mountains. Tall, 

 green, silent, majestic, these forests 

 were a gift of God, an important asset 

 to our natural wealth and welfare. 



Today, on much of that ground 

 stand millions of dead trees graceless, 

 lifeless, valueless. They will stand there 

 20 years more, ghost forests and tragic 

 evidence of how fast and silently a tiny 

 insect can do its damage when once a 

 combination of favorable factors brings 

 about a sudden increase in its numbers. 



THE INSECT is the Engelmann spruce 

 beetle, the Dendroctonus engelmanni 

 Hopk. Without the spectacular fea- 

 tures of smoke or fire or explosion, 

 but as devastatingly, the beetle built up 

 its population, mostly in the inner bark 

 of living trees, where it fed and bred. 

 Those trees died; then new beetles 



802062 49 28 



emerged and attacked other trees. No 

 person even suspected what was hap- 

 pening until the outbreak was well 

 under way and approaching its peak. 

 Then it was too late to do much: Be- 

 tween 1942 and 1948, 4 billion board 

 feet of stumpage had been killed. 



Four billion board feet can furnish 

 lumber for 400,000 five-room frame 

 houses. The value in standing trees is 

 estimated at 8 million dollars. It might 

 someday have been made into products 

 valued at 200 million dollars. The in- 

 sects were more destructive than forest 

 fires in the 6 years, 16 times more 

 timber was destroyed than was killed 

 by fire in the past 30 years in the Rocky 

 Mountain region. 



And to those who love the moun- 

 tains and the trees there was another 

 kind of heartbreaking loss: Damaged 

 for a generation were parts of our most 

 beautiful National Forests, the White 

 River, Grand Mesa, Routt, Arapaho, 

 Uncompahgre, San Juan, and Dixie. 

 On a large part of the White River 

 National Forest, nearly all spruce of 



