LOGGING DAMAGE AFFECTS BARK BEETLE RESISTANCE 

 OF RESIDUAL PONDEROSA PINE STANDS 



Philip C. Johnson, Entomologist 

 Intermountain Forest and Range Experiment Station 



Ogden, Utah 



Increasing use of sanitation-salvage cuttings—'^ is being made 

 in old-growth pondorosa pine stands in the northern Rocky Mountains 

 to minimize tree mortality from bark beetles while the stands await 

 final harvest or utilization, often as much as 30 years later. The 

 degree of beetle control achieved by sanitation-salvage cuttings 

 depends somewhat upon the severity of damage to residual trees during 

 logging . 



Several types of residual tree damage can occur from various 

 phases of logging involved in sanitation-salvage cuttings (table l). 

 Some damage is inevitable and a reasonable amount may not materially 

 reduce the beetle control benefits of these relatively light cuts. 

 It is the damage in excess of this amount that substantially reduces 

 cutting benefits. Regardless of its cause, the effect of the damage 

 renders the residual trees more susceptible to beetle attack despite 

 their original low risk rating. This effect is more immediate when 

 bark scuffing, top breakage, or fire scorching has occurred because 

 these injuries cause the release of oleoresinic odors from the trees. 

 Bark beetles are readily attracted to these trees and the chance is 

 good that some of them will be attacked and killed within a year or 

 two following the cuttings. Other types of damage cause more gradual 

 increase in the beetle risk rating or susceptibility of trees and 

 several years may elapse before some of them are attacked and killed. 



A recent observation illustrates how logging damage may contrib- 

 ute to reduced beetle control benefits of sanitation-salvage cuttings , 

 Continuous cuttings of this nature were made during the period 1949- 

 1951 over most of a large tract of pine in western Montana to lessen 

 the possibility of subsequent beetle-caused tree mortality as well as 

 to achieve certain silvicultural objectives. Timber markers received 

 special training and supervision in the use of the risk rating system 



1/ Cuttings designed to remove from 15 to 35 percent of the pine 

 stand made up of Risk 3 and Risk 4 trees of the Ponderosa Pine 

 Risk Rating System. These are trees currently susceptible to 

 attack by the western pine beetle, Dendroctonus brevicomis Leo. 

 Their cutting and utilization removes the normally favored breed- 

 ing place of the beetles, thus helping to prevent the buildup of 

 epidemic beetle populations for a period of years . In addition 

 a few trees are cut for silvicultural or management objectives or 

 because they will not survive from causes other than beetles. 



