APPLE DISEASES 



447 



From these cankers the spores 

 are washed by the rains over the young 

 fruits, causing their infection. The 

 spread of the disease may often be 

 traced to its source by the conelil^e in- 

 fected area, with the canker at the apex. 

 Alwood, of the Virginia Station, claims 

 that infection sometimes takes place 

 without the presence of cankers, and he 

 thinks that mummy fruits are the prin- 

 cipal source of primary infection. In 

 the publications, both of the Illinois Sta- 

 tion and the Bureau of Plant Industry, 

 the authors recommend cutting out the 

 cankers and thorough spraying of the 

 trees with Bordeaux mixture, but Al- 

 wood advises caution in pruning, unless 

 it can be done without material injury 

 to the tree. 



Marked differences in susceptibility of 

 varieties to bitter rot have been noted. 

 While no list can be given that will 

 apply to all regions, yet in general the 

 Yellow Newtown or Albemarle Pippin, 

 Rhode Island. Willow, Huntsman. North- 

 ern Spy, Ben Davis, York Imperial, 

 Grimes, and Winesap are subject to the 

 disease almost in the order of enumera- 

 tion, the Yellow Newtown seeming to be 

 most liable to serious loss. 



Certain conditions of weather influ- 

 ence the spread of the disease. It is 

 favored by a hot, moist temperature, the 

 fungus being very dependent upon the 

 combination of high temperature .ind 

 moisture for its development. During 

 cool, dry summers little of the disease 

 may be expected, and an outbreak may 

 be checked If the mean temperature falls 

 to and remains at or below 70 degrees 

 Fahrenheit for a few days. 



W. M. Scott, of the Bureau of Plant 

 Industry. * gives an account of spraying 

 experiments for the control of the bitter 

 rot on apples. These experiments were 

 carried on in 1905 on an orchard of 

 Yellow Newtown or Albemarle Pippin 

 trees in Virginia, and the conditions 

 that season were so favorable for the 

 development of bitter rot, as was shown 

 by the large number of decayed fruits 



*U. S. Department of Agriculture. Bureau of 

 Plant Industr.v Bulletin 93. 



on unsprayed trees, that the conclusions 

 are believed to be of general applica- 

 tion. The Bordeaux mixture used in 

 the experiments was composed of five 

 pounds of copper sulphate, five pounds 

 of lime, and 50 gallons of water. It is 

 shown that bitter rot can be controlled 

 by four applications of Bordeaux mix- 

 ture if applied at the proper times and 

 in a thorough manner. The first appli- 

 cation should be made about five or six 

 weeks after the trees bloom, followed by 

 others at intervals of about two weeks. 

 By this method the experimenter was 

 able to save from 93 to 98 per cent of 

 sound fruit on the trees, while on ad- 

 joining trees that were not sprayed the 

 fruit was a total loss. In dry, cool sea- 

 sons the intervals between the later 

 sprayings may be increased, while in 

 hot, moist summers the intervals should 

 be shortened and the number of appli- 

 cations increased. If for any reason the 

 spraying is not begun until after the 

 bitter rot has made its appearance on 

 the young fruit, the trees should be 

 given at intervals of only a few days 

 two thorough sprayings, to be followed 

 by applications as described above. 



By beginning the spraying with the 

 swelling of the buds and following at 

 intervals of about two weeks until about 

 eight applications have been given the 

 trees, attacks of apple scab, leaf blotch, 

 and sooty mold may also be prevented. 



tCompiled from Illinois Station Bulletin 77. 

 Circulars 58. 67 : Virginia Station Bulletin 

 142: U. S. Department of Agriculture, Bureau 

 of Plant Industry Bulletins 44, 93 and B^rm 

 Bulletin LMiT. 



Black Heart 



The cause of this disease of the trunk 

 is obscure. It may be due to too low a 

 winter temperature, and again it may 

 be the effect of the earliest invasion of 

 fungal filaments. Possibly it is the re- 

 sult of some other general causes. 



Black Rot, Canker, and Leaf Spot 



Sphaeropsis Malorum Berk. 



The three diseases given above have 



been found to be due to a single fungus, 



"Sphaeropsis Malorum." The black rot 



of the apple is very common in New 



