412 BULLETIN 371 



The plantings of horse-chestnut in the nurseries of the State are 

 relatively large, owing to the persistent annual demand for this stock. 

 As a rule, however, nurserymen have not been successful in propagating 

 the trees from seed because of the severe injury to the foliage caused by 

 leaf blotch. This failure has resulted in annual importations of horse- 

 chestnut trees from foreign countries. The trees obtained from Europe 

 are three or four years old. They are planted in the nurseries of this 

 country, where they are allowed to grow for one or two years longer 

 before they are placed on the market. This method naturally involves 

 considerable expense, requiring the nurserymen to charge a higher price 

 for their stock than for trees successfully grown from seed in this country. 

 Without question horse-chestnut trees protected from the leaf blotch 

 disease can be propagated from seed at a much lower cost than that paid 

 for imported stock. 



SYMPTOMS 



The leaves, and occasionally the petioles, are affected. The writer 

 has observed lesions also on immature fruits, which were undoubtedly 

 another type of the leaf blotch disease. 



The first indication of the disease on the foliage is a slight discoloration. 

 As the lesion increases in size it becomes more or less irregular in outline 

 and the newly invaded tissues appear water-soaked. Gradually the 

 central part of the lesion becomes from dark red to brown in color, while 

 the margin shows a yellowish discoloration blending into the green of 

 the healthy tissue. The discolored area finally becomes dried and dies. 

 The spots may be small, or they may involve a large part of the leaf 

 surface and thus cause the dead area to curl (see frontispiece). Minute 

 black specks may generally be seen, scattered separately over the lesion, 

 and in some cases these appear before the tissue is completely dried 

 out. In many cases these specks are crowded together in a definite 

 area, which may be slightly lighter in color than the remainder of the 

 affected tissue. 



The lesions on the petioles appear in the form of small reddish brown 

 spots, which are usually somewhat longer than wide and extend up and 

 down the petiole. The effects of the disease on the petiole are never 

 very serious. 



The spots on the fruit are similar to those on the petioles, but there 

 is no decay of the fruit tissue. 



The striking symptom of the leaf blotch disease, however, is the dark 

 red or brown color of the lesions, which often involve large areas or even 

 the entire leaf. When the disease is very prevalent, especially in nursery 

 plantings, the foliage appears as if it had been burned over by fire. 



