390 JOURNAL OF FORESTRY 



and other material accumulate in such quantities that when a fire oc- 

 curs it is much more intense and usually covers a larger area before it 

 can be controlled than is the case where the land is grazed. Trampling 

 by stock in the fall and early spring aids germination by covering the 

 seed. Overgrazing to the extent of exterminating perennial grasses 

 just before the reproduction period begins would undoubtedly assist in 

 the establishment of pine seedlings by reducing competition for soil 

 moisture. These facts, however, constitute no argument in favor of 

 unregulated grazing, since it is possible to secure practically all the 

 benefits of grazing without subjecting the forest to serious damage. 



One of the worst enemies to reproduction is the tip moth (Evetra 

 bushnelli and B. neo-mexicana). The larvae of these insects destroy 

 the growing shoots and thus deform the young tree. Attacks begin 

 when seedlings are 3 or 4 years old and continue until they are about 6 

 feet in height. Usually the plants recover after being held back for 

 several years. If, however, the attacks are repeated year after year 

 new foliage is prevented from forming and the plant is starved. Pres- 

 ent knowledge suggests no remedy for this pest, aside from the action 

 of natural enemies. 



Another insect pest is the common May-beetle or June-bug, the larvae 

 of which feed on the roots of seedlings. This insect is most injurious 

 to planted stock, since it prefers loose soil for Qgg deposition, but it also 

 attacks natural reproduction. 



On the whole, studies of western yellow-pine reproduction have 

 given much information in regard to conditions under which seedlings 

 die, but comparatively little definite knowledge regarding conditions 

 under which they survive. The present silvicultural system has been 

 in practice on the Coconino and Tusayan for 10 years, but, aside from 

 the development of advance growth already present at the time of log- 

 ging, there has been little progress in reproduction. This does not prove 

 the system a failure, because during the same period results under 

 other methods of cutting and in virgin stands appear to have been no 

 better. The experience does, however, cause us to reflect and ask if 

 we have not expected too much of silviculture. One idea has begun to 

 stand out clearly, and that is that reproduction is controlled by some- 

 thing far more potent than silvicultural practice. The one dominant 

 factor or complex of factors is climate. This so far overshadows all 

 human efforts that the latter become relatively insignificant. This fact 

 has been recognized in a general way, but nevertheless the idea persists 

 that somehow a method of cutting or brush disposal may be evolved 



