THE WESTERN YELLOW FIFE MISTLETOE. 31 



cutting and proriding more favorable conditions for the optimum 

 development of the parasite, every effort should be made to free the 

 stand entirely of mistletoe infection, although it is doubtful whether 

 in certain cases the removal of lightly infected trees would be war- 

 ranted because of silvicultural reasons. The increased activity of 

 the mistletoe following the opening of the stand militates against 

 leaving for a future cutting operation any but lightly infected trees, 

 the infection of which is confined to the lower portion of the crown. 

 Old and heavily infected trees should be cut for two reasons: (1) To 

 improve the hygienic condition of the forests of the future through 

 the removal of the mistletoe, and (2) to secure the maximum reali- 

 zation on a rapidly diminishing growing stock or forest capital. 

 Since the future productivity of the forests depends to a great extent 

 upon the proper choice of seed trees or of the seed itseK in the case of 

 artificial regeneration, those trees used for reproductive purposes 

 should be sound, healthy, and of an intermediate age class. 



As heavy a stand of healthy trees as possible should be left in order 

 to compensate for the removal of diseased trees, and to maintain 

 better forest conditions, reduce wind damage, and insure a denser 

 stand of reproduction. Exceptional care should be taken to leave 

 every healthy black jack which is free from infection. Wherever 

 possible, trees should be freed from light infections by cutting off 

 lower branches within reach. Transition trees and vigorous yellow 

 pines, suitable for seed trees, should be left in greater numbers to 

 take the place of diseased black jacks removed, to maintain better 

 forest conditions, and to furnish abundant seed for the restoration 

 of the stand. Small heavily infected black jacks should be marked 

 wherever it is possible to have them cut under the sanitation clause 

 of the timber-sale contract, or where there is a market for small 

 material, such as stulls, mine props, ties, poles, posts, and pickets. 



Forest officers in charge of marking on mistletoe-infected timber- 

 sale areas should study carefully the possibilities of increasing the 

 number of healthy trees in the remaining stand. The pruning of 

 infected limbs from small trees at the time of marking presents a 

 practical means of eliminating light limb infections and at the same 

 time increasing the number of healthy trees. Occasionally there are 

 trees in a stand that are lightly infected on a low branch within 

 reach of the ground. Mistletoe-infected reproduction and young 

 timber below merchantable size should also be freed from the disease 

 either through cutting the seedlings and saplings or by lopping off 

 the infected branches. Such measures may be impracticable except 

 on timber sale areas and in some cases the ex'tra labor and expense 

 involved may prove prohibitive. 



The areas of mistletoe infection should be located and mapped as a 

 prerequisite to an efficient control campaign. The degree of injury 



