290 MANUAL OF TREE DISEASES 



PiNON Buster-Rtjst 



Caused by Cronartium occidentale Hedge, Bethel and Hunt 



For many years a species of Cronartium has been known 

 on currants and gooseberries in Colorado, for which no blister- 

 rust stage on pines could be found. Recently the blister-rust 

 caused by this fungus has been discovered on nut and single- 

 leaf pine. This disease is neither common nor destructive on 

 these trees, so far as observed. • Slight swellings are formed. 

 The blisters which push through the bark in the spring are not 

 prominent. As a result of the formation of the blisters, the 

 bark is broken into irregular flakes and the inner bark dies. 

 The seciospores infect currants and gooseberries and produce 

 symptoms on these hosts which are indistinguis'hable from 

 those on the same plants, produced by Cronartium ribicola 

 (see page 277). The fungus has been named Cronartium occi- 

 dentale. It has not been foimd to infect five-needle pines, 

 although it has been observed for years on gooseberries and 

 currants in close proximity to these pines. 



Basal Canker 



Caused by Phoma sp. ? 



In many localities in northeastern United States, more or 

 less circular areas have been noted in which all the white pine 

 are dead. Around these blanks some trees are often found 

 which have yellowish and scanty foliage. Closer examination 

 usually shows that the base of the tree at the surface of the 

 ground has been girdled. The bark is dead and markedly 

 constricted. Fruiting-bodies of a species of Phoma are gen- 

 erally found on the bark. There is some evidence that this 

 disease occurs only in the vicinity of ant-hills and it is sug- 

 gested that the ants, their burrowings in the ground, or the 

 aphids with which the ants associate, have some connection 



