Another management practice--clearcutting followed by prescribed burning--is 

 necessary in many forest types to provide suitable site conditions for regeneration and 

 to control species composition. Also, clearcutting is the only practical way to manage 

 certain forests troubled with serious insect or disease problems. 



Management of Engelmann spruce, Viaea eng eVmanni Parry, forests in the northern 

 Rockies during the last 20 years provides an excellent example of a change in forest 

 insect problems that can occur as old-growth forests are converted to stands of young 

 trees. During the fall of 1949, hurricane- force winds swept through northern Idaho 

 and northwestern Montana laying large volumes of Engelmann spruce on the ground. 

 Severe epidemics of the spruce beetle, Dendroatonus rufipennis (Kirby) (= obesus 

 (Mannerheim) ) , developed in much of this downed timber during 1950 and 1951, spreading 

 in 1952 to standing spruce throughout most of the spruce type in the northern Rockies. 

 As a result, approximately 2.5 billion board feet of spruce timber was attacked by 

 this beetle between 1952 and 1956 (Tunnock 1959). During this same period, thousands 

 of acres of spruce forests were clearcut in northern Idaho and western Montana to 

 salvage damaged and/or beetle-killed trees, both standing and windthrown. The outbreak 

 steadily declined following its peak in 1953; by the late 1950' s, no infestations were 

 reported in many forest compartments. 



As spruce beetle problems diminished with the logging of progressively more acres 

 of mature and overmature spruce during the past two decades, an increasing number of 

 clearcuts have been planted or have naturally regenerated with Engelmann spruce. 

 Damage to these young trees by the Engelmann spruce weevil, Pissodes strohi (Peck) 

 (= engeZmanni Hopkins) steadily increased. These small weevils attack and kill or 

 seriously injure terminal shoots of young trees, causing crooks in the trunk or a 

 stunted, forked, and worthless tree (Keen 1952). By 1966, terminals destroyed by 

 weevils were noticeable in almost all stands of spruce reproduction in the northern 

 Rockies; some stands were recurrently damaged (Tunnock 1966). By 1971, the weevil 

 was distributed throughout spruce stands in this region (McGregor and Ouarles 1971) , 

 and terminal killing was prevalent throughout many areas. In some young trees, 

 repeated attacks to live portions of the main bole killed the trees outright, or 

 predisposed them to death by secondary insects. "In some areas" according to McGregor 

 and Ouarles (1971) "large blocks of young even-aged spruce offer ideal conditions for 

 buildup and maintenance of weevil populations." No doubt this weevil will continue 

 to be a serious problem in the management of Engelmann spruce in the northern Rockies. 

 In British Columbia, the weevil has become generally recognized as an important pest, 

 notably of spruce plantations (Molnar and others 1970) . 



We are experiencing some, and we can expect more, changes in our forest insect 

 problems as increasing acreages of mature forests are being converted to stands of 

 young trees. In some young stands, problems will develop from forest insects, such as 

 the Engelmann spruce weevil, which characteristically and historically are pests only 

 of young trees. In other young stands, ubiquitous forest insects, such as the western 

 spruce budworm and the larch casebearer, will be responsible. At the present time, 

 for example, western spruce budworm larvae (by severing stems of terminal shoots) are 

 causing disfigurement and as much as a 30-percent reduction in height growth of young 

 western larch (Schmidt and Fellin, in press). 



We know very little, and sometimes nothing, of the role forest insects play in the 

 management of young forests of seedlings, saplings, and pole-size trees in the northern 

 Rocky Mountains. If we wish to minimize damage and losses caused by insects in these 

 young coniferous stands, where much of our forest management effort is directed, more 

 research effort must be devoted to the study of the biology, ecology, and impact of 

 insects that affect forest regeneration. 



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