WESTERN RED-ROT IN PINUS PONDEROSA. 7 



areas 3 and 4. The older the trees are, the greater the amount of rot 

 present, since such trees have had more opportunities for infection 

 than younger trees. However, taking the area as a whole, probably 

 20 per cent of the yellow-pine trees (exclusive of black jacks) will 

 show western red-rot in some portion of the bole. The areas shown 

 in this table are mainly covered with black jacks intermixed with only 

 a small number of yellow pines. For instance, in the sample strip, 1 

 chain wide and 140 chains long, 195 black jacks were marked for cut- 

 ting and 1,270 left, a total of 1,465 black jacks 4 inches, d. b. h., and 

 over, while 108 yellow pines were marked and 22 left. Of the 1,465 

 black jacks present on this area, there were 605 trees of merchantable 

 size (10 inches, d. b. h., and over) to only 130 yellow pines. This 

 means that on such areas the percentage of western red-rot in the mer- 

 chantable timber will be small compared to similar areas where the 

 proportion of yellow pine is greater than that of black jack. 



WESTERN RED-ROT IN BLACK JACK AND YELLOW PINE. 



The percentage of western red-rot in black jack for all the areas is 

 very small, since only 29 trees out of 1,815 (1.59 per cent) showed this 

 rot, while in yellow pine it was much greater, 77 trees out of 563 (13.6 

 per cent) being infected. Even then, this percentage is not high when 

 compared with some other areas in Arizona and New Mexico. For 

 instance, on certain sale areas on the Upper Pecos Kiver, 70 to 95 per 

 cent of the yellow-pine trees were attacked by western red-rot. Since 

 this rot enters mainly through dead branches it is easily seen why 

 fewer black jacks are attacked by it than yellow pines. The total 

 percentage of trees attacked by western red-rot, both black jack and 

 yellow pine, is only 4.5 per cent for all the areas shown in Table I. 



Of the black jacks infected with western red-rot, nearly all were 

 suppressed or grown under very unfavorable conditions. This indi- 

 cates that all such trees should be marked for cutting when possible, 

 not only on account of their susceptibility to this rot, but also be- 

 cause they will never make strong, thrifty trees. When the soil is 

 deep and capable of producing vigorous growth in the trees, western 

 red-rot is present only in a small degree unless the trees are very 

 old and overmature. Such soil conditions are found on many of 

 the mesas and near the bottoms of small canyons. There is always a 

 marked increase in the amount of western red-rot in yellow pine 

 growing on very steep slopes and on poor, thin soil. 



WESTERN RED-ROT AND THE ROTATION FOR WESTERN YELLOW 



PINE. 



As to the relative efficiency of a long rotation and of a medium or 

 short rotation period in finally eliminating this rot from the forest, 

 the answer is very evident, judging from the viewpoint of the rot 



