Figure 6. — Standing or fallen dead 

 pine trees often are indisputable 

 evidence of the severity of tree 

 killing by the western pine 

 beetle in past years throughout 

 many old-growth ponderosa pine 

 forests in western Montana. 

 Loss of merohantable trees from 

 even endemic populations of the 

 pine beetle can be a significant 

 cost factor in commercially 

 managed ponderosa pine forests. 

 It can be greater if ncnpine 

 tree species — such as Douglas- 

 fir ^ shewn here — swiftly usurp 

 the ground surface under the 

 former crown shadow of the dead 

 pine treesj thus preventing 

 establishment of often-desired 

 seedlings of ponderosa pine. 



Figure 7. — This mature ponderosa 

 pine tree dying on a risk rating 

 plot in the Bitterroot National 

 Forest, Montana, was struck by 

 lightning during the spring of 

 1964 and heavily infested soon 

 after by two successive generations 

 of the western pine beetle. While 

 the tree might have survived the 

 lightning strike, it could not 

 have survived the excessively 

 numerous attacks of the pine 

 beetle. Ponderosa pine trees 

 occasionally struck by lightning 

 in western Montana are usually 

 dominant, vigorous , low-risk trees 

 presumably resistant to attackc of 

 the pine beetle. Once they are 

 struck by lightning , however, they 

 become highly attractive for a year 

 or two as a breeding habitat for 

 the beetle. 



