t 



Association of Weevil Damage 

 With Precommercial Tliinnings 



There is a positive relationship between the occurrence o£ weevil damage and 

 precommercial thinnings. The presence of weevils is also closely related to when the 

 thinnings are made. Slash resulting from, thinning operations appears to attract the 

 weevils to the area thinned but apparently is not utilized by the insect during any 

 stage of its development. 



During 1965 through 1968, I examined 75 areas on the Lewis ^ Clark National Forest 

 that had regenerated naturally following clearcutting. Forty-five of these had been 

 precommercial ly thinned--the remainder left unthinned. I found no significant weevil 

 damage to foliage on trees in any of the unthinned areas. However, occasional needle 

 punctures often could be found most everywhere because of the vast areas of lodgepole 

 pine regeneration and the abundance of the weevil. 



I devised a numerical system to analytically evaluate damage. Several dozen new 



growth shoots that represented varying amounts of damage were examined and the numbers 



of damaged and undamaged fascicles were counted. Six general categories of damage 

 were arbitrarily chosen as follows: 



Weevil Damage in Thinned Areas 



Damage 

 category 



Percent of 

 fascicles damaged 



[None) 



1 (Occasional! 



2 (Light) 



3 (Light to moderate) 



4 (Moderate to heavy) 



5 (Heavy) 



2-25 

 25-50 

 50-75 





 <1 



>75 



10 



