428 



Yearbook of Agriculture 1949 



valens Lee. and D. terebrans Oliv.), 

 which attack all species of pines but 

 usually can overcome only weakened 

 and injured trees. 



The engraver beetles (Ips spp.) at- 

 tack all species of pines, breed readily 

 in the tops of recently felled trees and 

 in slash, usually develop large popu- 

 lations, and then move into the tops 

 of living pines, frequently killing trees 

 in large groups. Various species are 

 found in different parts of the coun- 

 try, but they all have similar habits. 



Forestry was young in America 

 when it was discovered that pine bark 

 beetles were forest destroyers of the 

 first magnitude. In the first official 

 report on forestry, submitted to Con- 

 gress in 1877, Franklin B. Hough, the 

 first Government forest officer in the 

 United States, directed attention to 

 the considerable injury done to the 

 pines of South Carolina by bark beetles, 

 and referred to an occurrence of 

 their activity as early as 1802. Again, 

 during the first survey and classifica- 

 tion of lands of the newly created For- 

 est Reserves by the United States 

 Geological Survey in 1898, H. B. Ayres 

 reported serious damage caused by 

 pine beetles to the white pine stands 

 in Montana. In 1900 the first field or- 

 ganization of foresters, working under 

 Gifford Pinchot, found bark beetles 

 killing thousands of trees in the Black 

 Hills. As a result of this epidemic, 

 which killed more than a billion board 

 feet of pine timber, Dr. A. D. Hop- 

 kins, State entomologist of West Vir- 

 ginia, was called on to investigate and 

 recommend measures of control for 

 this and other forest pests. 



So began in the United States a 

 problem in forest protection that ever 

 since has challenged the ingenuity of 

 entomologists and foresters. For it 

 quickly became evident that these 

 were not isolated cases of insect dam- 

 age but typical examples of what a 

 group of insect enemies could do in 

 many forest stands. Over a long pe- 

 riod, the havoc that bark beetles have 

 wrought has resulted in a greater total 

 drain of commercial pine timber than 



has been sustained from any other 

 destructive agency. 



IN PRIMITIVE, UNMANAGED FOR- 



ESTSj pine bark beetles act as nature's 

 forest managers and loggers. Young 

 stands that have become too crowded 

 and suffer from competition and stag- 

 nation are frequently thinned by out- 

 breaks of engraver beetles. In the older 

 stands, the weak, intermediate, and 

 suppressed trees are cut out by pine 

 beetles. And as growing forests reach 

 maturity, the old trees that have es- 

 caped fire and storm are harvested by 

 pine bark beetles, and young trees 

 then come up to replace them. 



In the development of forest succes- 

 sion, pine beetles often have a promi- 

 nent part. When fir-hemlock stands of 

 the Cascade Mountain Range are 

 wiped out by fire, for example, lodge- 

 pole or western white pine come in as 

 temporary species to reestablish a forest 

 cover. When these stands get to be 

 about 100 years old, the more tolerant 

 fir and hemlock again become estab- 

 lished under them. Then the mountain 

 pine beetle appears to act as nature's 

 forester. An epidemic conveniently 

 eliminates about 95 percent of the pine 

 overstory and thus aids the process of 

 reestablishing the fir-hemlock climax. 



On the other hand, the western pine 

 beetle in ponderosa pine makes a selec- 

 tion cutting of certain intermediate, 

 suppressed, and codominant trees that 

 are growing too slowly. In the forest, 

 group killings make holes, which are 

 filled in by young seedlings. This proc- 

 ess tends toward the development and 

 maintenance of uneven-aged stands. 



The trouble is that beetles are crude 

 forest managers. Often they go too far 

 in thinning and eliminating competing 

 trees. They kill and waste much sound 

 lumber. Holes left in the forest stand 

 may take many years to fill. If we are to 

 maintain and utilize our forest re- 

 sources, we cannot afford to allow these 

 natural processes to run their course, 

 and yet we are often responsible for 

 starting and encouraging them through 

 forest mismanagement. 



