CARTER: ILLINOIS TREES: THEIR DISEASES 85 



growth, as described under "Feeding," may help to combat Cytos- 

 pora canker. Feeding will also stimulate new growth that may 

 till in vacant areas in the contour of trees on which surgery has 

 been performed, 



Diplodia Tip Blight. — This disease of spruce, pine, and 

 Douglas fir is described in the section on pine. 



SYCAMORE AND LONDON PLANE TREE 



The American sycamore and the London plane tree are 

 planted extensively for shade in some Illinois communities, es- 

 pecially those in which the American elm has been killed by 

 phloem necrosis or Dutch elm disease. Anthracnose causes ex- 

 tensive defoliation and twig dieback in the American sycamore 

 in some years (Fig. 82), but it seldom causes conspicuous dam- 

 age to the London plane tree. However, the London plane, an 

 English relative of the sycamore and similar in appearance, is 

 susceptible to canker stain, which has killed many trees in some 

 of the eastern states. 



Anthracnose. — This leaf and twig disease is known also as 

 twig blight. In oak, as well as sycamore and London plane, an- 

 thracnose is caused by the fungus Gnomonia veneta. In sycamore, 

 the fungus produces blight in four distinct stages identified as 

 twig blight, bud blight, shoot blight, and leaf blight. 



Jiki 



Fig. 8.3. — Twig blight of sycamore results in killing the tips of 1 -year- 

 old branches before leaves appear in the spring. 



