34 BULLETOT 1112, U. S. DEPARTMENT OF AGEICULTTJRE. 



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 in 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 sjiow 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 

 obtusaY^ 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 

 (Razoumofslcya 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. 



n Hopping, Ralph. Insect Infestation in Relation to Injury, Fungi, and Mistletoe. Manuscript report. 

 February 2t, 1915. 



15 Determined by E. H. Gibson, Scientific Assistant, Bureau of Entomology, U. S. Department of 

 Agriculture. 



