50 CIRCULAR 791, U. S. DEPARTMENT OF AGRICULTURE 



CONTROL OF DWARF MISTLETOE 



The dwarf mistletoe of black spruce sometimes causes great damage 

 in open-grown swamp stands. In such instances, trees of all sizes are 

 likely to be parasitized. Probably the only way to accomplish satis- 

 factory control is to cut or burn all the-trees, including small seedlings. 

 Broadcast burning of logging slash in favorable weather would have 

 the desired effect. Prompt planting of the burned area with tamarack 

 would insure continued productivity without the danger of reinfes- 

 tation. 



There is some possibility that dwarf mistletoe may become more 

 widespread and damaging in managed forests where fire is kept out 

 than it has been in wild forests that have burned periodically. Since 

 its rate of spread is slow, a considerable degree of control can be ac- 

 complished by destroying infected trees whenever they are detected. 



Upland Stands 



Most black spruce trees growing on uplands occur in mixture with 

 other species. The black spruce usually is only a minor although valu- 

 able element in such stands. There are two exceptions : the occasional 

 nearly pure stands on well-drained upland soils, and the nearly pure 

 swamp border type which occupies the fringe of poorly drained land 

 around swamps. 



PURE TYPE ON WELL-DRAINED UPLAND 



Pure stands of black spruce on well-drainecl upland soil, although 

 neither common in occurrence nor extensive in area, have been given 

 some special attention because of their high productivity. In rate of 

 growth, they usually correspond to Good Site as shown in table 8. 



Experimental attempts to manage such stands have not yielded 

 wholly conclusive results. They do, however, indicate that there is 

 little possibility of maintaining a pure spruce type on upland soil. 

 Moreover, these stands do not lend themselves to partial cuttings lead- 

 ing to a selection system such as has been recommended as the goal for 

 swamp forests. 



In 1934 a series of experimental plots was established in a 65-year- 

 old even-aged stand on the Kawishiwi Experimental Forest. The 

 stand contained a small admixture of jack pine, quaking aspen, paper 

 birch, red pine (Pinus resinosa) , and white pine. On one plot, 25 per- 

 cent of the volume was removed. The jack pine was cut heavily, the 

 spruce very lightly, and other species were left intact. On another 

 plot alternate 100-foot strips were cleared of all merchantable spruce 

 and jack pine. A third plot was cut clear, and the fourth was left 

 undisturbed as a check. 



After cutting had been completed the duff and humus on parts of 

 the plots were scarified or removed with mattocks to determine the 

 effect of such treatment on reproduction. Seven years later all of the 

 logged areas had considerable tree reproduction, but in most instances 

 the species composition was considerably different from that of the 

 original stand (table 11). Most of the black spruce seedlings were 

 much smaller than the young aspen, jack pine, and paper birch; de- 

 spite the rather generous numbers of black spruce, therefore, this 



