Introduction 



There are approximately 25 million acres of stocked commercial forest land in the 

 northern Rocky Mountains:^ 51 percent is in sawtimber; 37 percent, pole-size trees; 

 and 12 percent, seedlings and saplings. Land supporting mature sawtimber stands is 

 rapidly being converted to growing young trees; each year, about 2.8 billion board 

 feet of sawtimber is harvested. These cutover lands are restocked either artificially 

 by the land manager using direct seeding and planting, or by natural seeding. Artifi- 

 cial methods often are desirable because they assure well distributed trees over the 

 area, as well as giving strong species control. However, cutover areas that regenerate 

 naturally are often overstocked, particularly in forests of western larch, Larix 

 oooidentalis Nutt., and lodgepole pine, Pinus aontovta var. latifolia Engelm. These 

 dense young stands are often thinned to minimize competition and to provide optimum 

 growing conditions for crop trees (fig. 1). 



This paper describes the association of a tiny defoliating weevil, Magdalis 

 gentilis LeC. , with young^ precommercially thinned stands of lodgepole pine. It is 

 based on 4 years of observations (1965-1968) and describes the development of the 

 problem and assesses the (a) nature of the weevil feeding; (b) damage caused by the 

 weevil; (c) relationship between the occurrence of the weevil and si Ivicultural thin- 

 ning operations; (d) role of slash in weevil infestations; and (e) seriousness of the 

 problem. The paper also discusses some other forest insect problems associated with 

 forest management practices. 



Encompassing western Montana, northern Idaho, and northeastern Washington. 



