THE WESTERN YELLOW PINE MISTLETOE: 
Effect on Growth and Suggestions for Control. 
Wi December 21, 1922 
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By CLARENCE F. Korstian, Forest Examiner, Appalachian Forest Experiment Station, 
2 Forest Service, and W. H. Lone, Forest Pathologist, Office of lueres in 
Forest Pathology, Bureau of Plant Tndustry, 
CONTENTS. 
1 
ser) aod climatic features of the region... ......--..--.--..------ 2-0-2204 -2cse esses sone eseaeese y 
ame western yellow pine mistletoe... ......-.-..-.--.-.-------------0-2--c--e ee eee mE pl ke 3 
Effect of mistletoe on growth of host...........-..---.-.------.------+---- Jxo 300 St dp ee 4 
I STENT, = a oe ook alin 3 eee! ha ede tbe «=n qqnas done tea oe ae 22 
Effect of mistletoe on merchantibility of timber..............-....---------------------22------ 25 
Effect of mistletoe on seed production of host.............-.2--22-2-2 22-22 eee eee eee eee eee 25 
eres Meneck Of mistletoe infection... ..... .- 2.2.2. 2 eee eee i sores ee eden ans ese ease 29 
Ee ete a ks on Sw ree Soa es oo pe os a ow ome pw a ag Se ee a 30 
34 
INTRODUCTION. 
Western yellow pine (Pinus ponderosa Laws.) occurs naturally 
from southern British Columbia to northern Mexico and from the 
Pacific coast to east of the one hundredth meridian. It is found in 
the forests of every State west of the Great Plains and in many of 
‘them it is one of the most important and valuable forest trees. In 
the Southwest, western yellow pine is by far the most important 
timber tree, constituting over 80 percent of the commercial forests of 
Arizona and New Mexico, approximately 30 billion board feet. 
_ During the past 12 years studies have been in progress to deter- 
‘mine the effect of the mistletoe (Razouwmofskya cryptopoda (Engelm.) 
Coy.) on the growth and seed production of western yellow pine. 
‘This parasite is the most widely distributed and one of the most 
ol _Nore —The author’s names are in alphabetical order. The writers are indebted to Silviculturist G. A. 
‘Pearson, of the Fort Valley Experiment Station, for the permanent sample-plot data contained in Tables 
x and 17, ot =e data on the 1915 seed collection contained in Table 18, and for his general interest in the 
