Seriousness of the Problem 



Damage to current year's foliage of lodgepole pine caused by feeding of Magdalis 

 adults will probably continue in young stands as long as thinning operations are 

 continued. However, at least three factors tend to discount the seriousness of the 

 damage, even of heavy damage: (1) Damage is restricted to current year's foliage, 

 and infestations in any thinning area do not persist for more than one growing season; 

 (2) much of the feeding occurs after most of the tree growth has been completed for 

 that season so the effects of defoliation on the tree may be negligible; and (3) there 

 is no damage to newly developing shoots through either feeding or oviposition. Hence, 

 even though defoliation might be reasonably heavy in a given year (fig. 6), a bud will 

 be set and a normal complement of foliage will be produced the following year (fig. 8). 

 Accordingly, I believe that Magdalis infestations in these young lodgepole pine stands 

 should not now be considered as a serious forest insect problem. However, the complete 

 role of this weevil in the lodgepole pine ecosystem cannot be assessed until its 

 biology and ecology are thoroughly studied. 



In the event that damage is ever felt to be intolerable, some preventive or control 

 measures might be applied. Perhaps the most currently acceptable and permanent approach 

 would be through a change in the time of year when thinnings are made. This study 

 indicates that Magdalis damage to crop trees could be substantially reduced if thinning 

 did not begin before late July and that defoliation could be practically eliminated if 

 thinnings were deferred until mid-August. 



15 



