REPRODUCTION" OF WESTERN YELLOW PINE. 



89 



6. In stands containing only black- 

 jacks and intermediate trees, marking 

 will be on an improvement basis, the 

 object being to mark only such trees, 

 the removal of which will release other 

 trees and result in increased growth 

 in the stand left, or will rid the forest 

 of badly diseased or insect-infested 

 specimens. Severe thinnings should 

 be guarded against, particularly in 

 poorly stocked stands. Similarly, the 

 marking of dominant, fast-growing 

 young^ trees, whose removal will open 

 up a bunch of small suppressed trees, 

 which it is clear can never recover 

 from suppression, should be carefully 

 watched. The principle of improve- 

 ment thinnings should always govern. 



7. Mistletoe. — It is felt that mistle- 

 toe can not in all cases be eliminated 

 in one cutting without too great a 

 sacrifice of silvicultural requirements. 

 Mistletoe infections should be classed 

 as heavy, moderate, and light. 



(a) All heavily infected trees 

 should be cut regardless of the con- 

 dition of the stand after cutting. 



( b ) Moderately infected trees should 

 always be marked, except where there 

 are no other trees available to leave 

 as seed trees. 



It is felt that moderately infected 

 trees should be left as seed trees 

 rather than to make clear cuttings 

 because of the infection. This, how- 

 ever, applies to large areas rather 

 than to small openings or small areas 

 which have a chance for reproduction 

 from surrounding tree§ and where the 

 infection might be. completely cut out 

 without opening up the forest too ex- 

 tensively. Moderately infected trees 

 will be left for soil protective pur- 

 poses only on the most adverse sites, 

 where their need for this purpose is 

 clearly evident. 



No comment. 



To rid a stand entirely of mistletoe 

 would in many cases involve clean cut- 

 ting and planting. Until more inten- 

 sive management becomes econom- 

 ically possible this remedy can not be 

 applied. In some cases it might be 

 feasible to practice the scattered 

 seed-tree method of cutting. Only 

 trees which are entirely free of mistle- 

 toe should be left, and infected young 

 growth should be destroyed. As few 

 as two large seed trees per acre might 

 reseed such area,s. 



What data are available indicate 

 that lightly infected young trees will, 

 as a rule, continue to grow and pro- 

 duce seed for 100 years. For moder- 

 ately infected trees this period will 

 be shorter, but comparatively few will 

 die before the next cutting. The chief 

 danger is infection of young growth. 

 Under present conditions, our efforts 

 will of necessity be confined to such 

 control as is possible in connection 

 with logging operations. Forest offi- 

 cers should be on the lookout for 

 newly infected areas, where by cut- 

 ting or pruning a few trees the spread 

 of the parasite may be checked. A 

 great difficulty in such control is that 

 the presence of mistletoe is not readily 

 detected until it has gained consid- 

 erable headway. Thus, even though 

 an elfort were made to cut every in- 

 fected tree, some trees bearing enough 

 mistletoe to perpetuate it and infect 

 reproduction would escape. To be 

 effective, therefore, the control meas- 



