8 BULLETIN 580, U. S. DEPARTMENT OF AGRICULTURE. 
TABLE III.—Periodic. damage. 
Period. Per cent | Average | Average 
oftrees | per cent | Por ver 
Total | found | oftrees | so mnced 
on Nee Year. es demaped damaged Se ree 
F egin- umber observed.| at eac eac 
No. of period. | “jing | Ending. | of weeks, exami- | grazing rs ee 
nation. | season. Reson 
RT et Me 8,945| 0.3 
yt ee oe Apr. 15 | May 20 5 [J1918...-.------ ope 2 0.35 0.07 
Average. 8,945 35 
1912 te 8,945 | 14.0 
Second........- May 21| July 8 7 os seeeeeeeeee BED | zee 17.6 2.5 
Average. 8,945 18.0 
1912. cobs. ae 8,945 | 35.0 
Third.......... July 9 | Sept. 12 g ls. ---- == 2 ee) 17.5 1.9 
Average. 8, 945 35.5 
191 eek 8,945 | 46.0 
Hourth sees. se Sept.13 | Nov. 6 8 1913 potas sia we ne BD 7.5 5) 
Average. 8,945 43.0 | 
The observations indicate that the greatest amount of damage 
occurs during the latter half of June and early in July, or during 
the severest portion of the early summer dry period, and that the 
least damage occurs during the first few weeks of the grazing period, 
or before June 1. A considerable amount of damage occurs during 
the main growing season and a smaller amount during the fall drying 
period. 
The fact that a relatively small amount of damage occurred during 
1914, which was unusually favorable for the growth of forage, gave 
support to the theory that the severity of damage varies inversely as: 
the amount of succulent feed available. The record of periodic 
damage, however, indicates that there is an important factor besides: 
the amount of available succulent forage which determines the 
severity of damage. This is believed to be the condition of the cur- 
rent year’s growth of pine shoots. All observations substantiate the 
belief that, except in unusual cases, stock will not injure coniferous 
shoots of a previous year’s growth. It has been noted particularly 
that during the early summer practically no damage occurs until new 
shoots appear, and that damage in any year is confined largely to 
that year’s growth. Yellow-pine vegetative buds start active growth 
on the Coconino Forest about May 15, and by June 20: have formed 
succulent shoots with well-developed needles. From that time until 
about the middle of August the shoots are tender and more palatable 
than at other periods. Thus the season of best forage growth is also 
the period when yellow-pine shoots are most palatable. This and 
the probability that during the severe spring dry period stock develop 
a taste for the pine shoots which continues during the early portion 
of, the summer growing period may explain the rather severe dam- 
