CARTER: ILLINOIS TREES: THEIR DISEASES 



79 



Fig. 77. — The orange to yi'll()\^ blisters or fruiting bodies of the white 

 pine blister rust fungus are conspicuous during late spring. 



northeastern, and northwestern parts of the United States. It 

 is known to occur on white pine in several counties in the north- 

 ern half of Illinois. The fungus invades and kills the needles. It 

 grows from the needles into the bark of twigs and branches, 

 where it produces swollen, oval cankers. As these cankers en- 

 large, they girdle and kill infected stems. In late spring, orange 

 to yellow blisters or fruiting bodies of the fungus break through 

 fissures in the diseased bark (Fig. 77). Spores produced in these 

 fruiting bodies infect leaves of currants and gooseberries, plants 

 that serve as alternate hosts. Small orange to yellow pustules are 

 produced on the leaves of these shrubs in summer. The spores 

 produced in these pustules cause new infections on white pine?. 



A common recommendation for protection of white pines 

 from blister rust is the eradication of all currants and goose- 

 berries within one-half mile of the pines. However, in many situa- 

 tions involving ornamental plantings such eradication may not be 

 feasible. Recently, blister rust was controlled on western white 

 pine by the antibiotic fungicide Acti-dione BR. Treatment of 

 diseased trees included removal of dead and dying branches at 

 their points of attachment. The pitch that had accumulated on 

 the surfaces of cankers was removed. Each trunk and branch 

 canker, the surrounding bark area, and branch stubs were then 

 sprayed with Acti-dione BR. Detailed information about Acti- 

 dione for control of blister rust on pines should be obtained from 

 the manufacturer. 



Diplodia Tip Blight. — This stem disease, caused by the 

 fungus Diplodia pinea, occurs frecjuently on Austrian pine, less 

 often on Scotch, red, and mugho pines, and occasionally on Doug- 

 las fir and blue spruce. It causes the needles to turn brown and 

 the twig tips to die (Fig. 78). Development of minute, black 

 fruiting bodies of the fungus at the bases of needles that have 

 turned brown and in the bark of twigs that have died differen- 

 tiates the disease from frost injury and similar twig troubles. 



