274 MANUAL OF TREE DISEASES 



Swellings of the limb are first formed and later many abnormal 

 branches are sent out and ragged broom-like growths are pro- 

 duced. Burls at the base of the branches and on the side of 

 the trunk also develop where the roots of the parasite find a 

 foothold. The mistletoe plant may die but the stimulus still 

 continues to cause the abnormal growth. The brooms may 

 become so heavy when burdened with ice and snow that the 

 limb breaks. The needles of the old brooms are usually smaller 

 and shorter-lived than on healthy branches. For a general 

 discussion of the mistletoe diseases of trees, see page 54. 



Refebbnce 



Weir, J. R. Mistletoe injury to conifers in the northwest. U. S. 

 Dept. Agr. Bui. 360 : 1-38, pis. 1-4, figs. 1-27. 1916. 



BusTER-RusT OF Five-Nkedle Ptnes 



Caused by Cronarlium ribicola Fischer de Waldheim 



The fungus causing the blister-rust of five-needle pines is 

 native in Europe. With the extensive use of the American 

 white pine in western Europe for forestr-planting, it became 

 widely distributed on this tree and was soon recognized as an 

 important enemy of the white pine. As early as 1890 and 1900, 

 it was prevalent in all the countries of western and northern 

 Europe and was known in Siberia and Japan. The fungus 

 is supposed to have been originally confined to the Swiss stone 

 pine of Eiu-ope, which is not very seriously affected by it. In 

 Germany, France, England and other coimtries of western 

 Europe the blister-rust soon became so prevalent and de- 

 structive that the fmlher use of the American white pine in 

 reforestation was largely abandoned. Previous to this time 

 large numbers of white pine were grown in the forest nurseries, 

 and this disease was found to affect seriously a large percentage 

 of the trees in some regions. 



