16 APPLE BLOTCH IN SOUTHERN ORCHARDS. 



INOCULATION EXPERIMENTS. 



To show that the fungus which causes the twig cankers is also the 

 cause of the fruit blotch, a series of cross-inoculations was under- 

 taken during the season of 1907. Owing to the press of other work 

 the writers were unable to devote much time to these experiments, 

 so that the results are not all that could be desired. The first inocu- 

 lations were made on June 26, after the main natural infection period 

 had passed and dry weather had set in. 



As spores could not be obtained in sufficient quantities from the 

 pure cultures then on hand, fertile pycnidia were carefully picked 

 from thoroughly washed young cankers on the twigs and crushed in 

 sterile water, thus liberating the spores. An examination of drops of 

 this liquid showed that it was rich in spores of the canker fungus. 

 and cultures made from it proved to be free from other fungi, but, as 

 might be expected, were slightly contaminated with bacteria. This 

 fluid, containing spores from young cankers, was applied with an 

 atomizer to the fruit and foliage of a Ben Davis tree in a young 

 orchard just beginning to bear, in which the disease had not yet 

 gained a foothold. The fruit and foliage of another tree in the same 

 orchard were sprayed with sterilized water containing spores obtained 

 in a similar manner from pycnidia on the fruit. A third tree was 

 sprayed with sterile water as a check. Although this experiment was 

 made in a period of dry weather, the effects of the inoculation began 

 to show in about a month. On July 24 numerous small blotches 

 were found on the fruits which had been inoculated with the canker 

 spores, as well as on those inoculated with the fruit-blotch spores. 

 The characteristic spots on leaf blade and petiole were also found on 

 both trees. A careful examination of the check tree, as well as of a 

 number of others in the same orchard, revealed no such blotches or 

 leaf spots. As the season advanced the blotches increased in size, 

 and when the crop was picked on September 3, the following data 

 were obtained: 



Tree 1, inoculated with canker spores, gave 34 apples affected with 

 a total of 114 blotches and 52 sound apples. Many of these latter 

 were not inoculated because they were in the top of the tree and could 

 not be reached with the atomizer. (See PI. IV, figs. 1 and 2.) 



Tree 2, inoculated with spores from the fruit blotches, gave 14 

 apples affected with a total of 97 blotches and 4 sound apples. 



Tree 3, check, gave a total of 59 apples, only one of which was 

 affected, and that with only one blotch. Another adjacent tree bore 61 

 apples, none of which were affected. 



No cankers were found on the twigs of either inoculated tree, owing 

 perhaps to the hardened condition of the bark brought about by the 



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