142 DISEASES OF ECONOMIC PLANTS 



The attack is very insidious, and the disease often does 

 much damage before its presence is really known. Defoli- 

 ation is the chief injury, the leaves falling freely after the 

 attack of the fungus. This checks starch production, and 

 thus impairs the tree's general vigor and productiveness, 

 even weakening the tree to such an extent that it cannot 

 withstand the winter. As high as 80 per cent damage has 

 been reported. The loss in Ohio was estimated as $20,000 

 in one year. 



The disease is especially injurious to nursery stock, as it 

 may interfere with successful budding and grafting. The 

 following recommendation in the way of treatment is 

 made : ^ — 



1. Apply the Bordeaux mixture about ten days after 

 the blossoms fall. 



2. About three weeks later repeat this treatment. 



3. About four weeks later repeat again. 

 See also treatment for cherry. 



In one instance, in the New York Station, " The treat- 

 ment resulted in an average increase per tree of twenty- 

 four and one half pounds of marketable fruit, at an 

 estimated cost of less than one cent per pound. The 

 average yield per tree of picked fruit was increased 44 

 per cent, the marketable drops increased 8 per cent, and 

 the waste was decreased 81 per cent. The total yield of 

 marketable fruit, as recorded in pounds, was 45 per cent 

 greater when the trees were sprayed than when they were 

 not sprayed." 



Scab (Cladosporium carpophilum Thuem.). — The plum 

 scab consists of spots on the fruit similar to the scab 



1 Beach, S. A., N.Y. (Geneva) Agr. Exp. Sta. Rpt. 1.5, p. 399, 1896. 



