INJURIOUS INSECTS, FUNGOUS DISEASES, ETC. 197 



The leaf spot can be controlled by spraying in winter 

 with copper sulfate solution to destroy the spores lodged in 

 the bark. This should be followed by applications of Bor- 

 deaux mixture once before the flowers appear and two or 

 three times thereafter at intervals of about two weeks. 



The sycamore leaf blight (Glceosporeum nervisequum 

 Sacc. ) needs particular mention. It attacks both the Euro- 

 pean and the American species, but the native variety, Pla- 

 tanns occidentalis, seems to be more susceptible. It develops 

 with great rapidity at the time of the development of the 

 foliage in the spring, and causes the leaves to hang lifeless 

 upon the stems. In severe cases the leaves are dropped pre- 

 maturely, and if the attacks are continued for several years 

 the trees become seriously weakened. 



This trouble can be controlled by raking up and burning 

 loose bark, dead branches and leaves, and spraying with 

 Bordeaux mixture. The spraying should be done during the 

 resting period of the trees, as the leaves begin to develop, 

 ten days later and within three weeks of the time of the 

 unfolding of the buds. 



DISEASES DUE TO CONDITIONS OF SOIL AND CLIMATE 



Diseases due to insects and fungi are more easy of diag- 

 nosis than those due to unfavorable surroundings. Some- 

 times, however, no sharp line can be drawn between the two 

 classes of diseases. As long as the conditions for obtaining 

 food and water from the soil and for conducting these to 

 every part of the tree are favorable and the effects of cli- 

 mate are not detrimental to growth, the tree will continue to 

 be in full vigor. If, on the contrary, there be a continual 

 drain on the supply of soil-foods with no addition, and there 

 be long periods of drought, severe cold or other unfavorable 



