34 BULLETIN 1112, U. S. DEPARTMENT OF AGRICULTURE. 
When a proposed timber-sale area contains a considerable amount — 
of mistletoe, a special mistletoe sanitation clause should be inserted 
in the contract, containing the stipulation that all heavily infected 
trees, whether merchantable or unmerchantable, and certain other 
moderately infected trees will be marked for cutting. If the amount 
of unmerchantable infected timber is sufficient to affect the stumpage 
price materially, this factor should be fully taken into consideration 
and due allowance made for it m the stumpage appraisal. 
In control work on those areas where both mistletoe and insects 
are present, it would be advisable to combine the eradication of 
both pests where the commercial value of the stand justifies such 
‘measures. Infestations of secondary bark borers have occasionally 
been found and reported with or immediately following mistletoe 
infection.** It is believed that certain of these insects even show a 
-slight preference for trees infected with mistletoe. The attack of 
trees weakened by the mistletoe often hastens their death, or in the 
case of dead trees the work of the borers hastens deterioration. The 
control of such combined infection and infestations by eliminating 
the weakened trees would tend to control both mistletoe and insects, 
and thus hasten the realization of the ideal—a productive, thrifty, 
and healthy forest. 
The western yellow pine mistletoe probably has few natural enemies 
which can contribute toward its control. During the course of the 
studies reported in the preceding pages, a spittle insect (Clastoptera 
obtusa) was very frequently found within masses of spittle on the 
mistletoe plants. The work of the insect in controlling the mistletoe 
is probably of little practical importance. However, since the 
insect subsists on the juices of the mistletoe, it must tend to weaken 
the mistletoe to a certain extent, especially in cases of severe infes- 
tations. 
Through a proper realization and appreciation of the necessity 
for adequate control measures and their adoption on all cutting 
areas where the amount of mistletoe infection is relatively great,-a 
very good beginning can be made toward the eradication of the 
pest through the more or less gradual process of elimination. 
SUMMARY. 
Western yellow pine is subject to severe injury by mistletoe 
(Razoumofskya cryptopoda). The injury to the forest caused by the 
insidious and destructive action of this pest results in serious losses 
of western yellow pine and presents one of the most important 
silvicultural problems in the Southwest. 
14 Hopping, Ralph. Insect Infestation in Relation to Injury, Fungi, and Mistletoe. Manuscript report. 
February 24, 1915. ; 
1s Determined by E. H. Gibson, Scientific Assistant, Bureau of Entomology, U. S. Department of 
Agriculture. 
