73 Bulletin No. 34. 



the deciduous fruit industry in practically all of the great fruit 

 centers of the United States. 



For the past six years I have had the crown gall under obser- 

 vation, and five years ago published a preliminary report regard- 

 ing it, as Bulletin No. 12, of the Arizona Experiment Station. 

 This report was based almost entirely upon observations in the 

 field. Two years ago extensive experiments were begun to ascer- 

 tain the communicability of the gall. It is sufficient at this time 

 to state that I have repeatedly produced the disease by inocula- 

 tion of young seedlings with small bits of the gall, in some in- 

 stances the gall beginning to develop twenty days after the inocu- 

 lation. 



Again, I have repeatedly produced the gall on almond seed- 

 lings by planting the seeds in sterile soil, and at the time of plant- 

 ing, placing a few pieces of minced gall in the soil. 



There is no question regarding the communicability of this 

 disease; it is contagious. The disease is probably caused by a 

 micro-organism known as a "slime fungus;" the plasmodia of the 

 organism, through irritation, causing the galls to develop. Under 

 certain conditions the plasmodia creep to the surface of the gall 

 and form minute amoeba-like bodies which slowly make their way 

 through the damp soil to other plants. 



No details are here given, the reader being referred to Bul- 

 letin 33 of the Arizona Experiment Station, which is a detailed 

 report of the investigations, including the cause and nature of the 

 disease, and how best to deal with it. Knowing the nature of the 

 disease, the question with the fruit grower is how to eliminate it 

 from the infested orchards. The best advice that I can give to those 

 intending to plant trees is to get trees from a nursery that is absolute- 

 ly free from the crown gall. It is not sufficient to cast aside as worth- 

 less only those trees with galls upon their roots. Every tree that 

 comes from an infested nursery is dangerous, and when such trees 

 are planted, great chances are taken. If your orchard is already 

 infested with crown gall, you cannot entirely get rid of it. All 

 that you can do is to hold it in check and keep the galls as much 

 as possible from the crowns of the trees. When it appears on the 

 main stem of the tree a few inches below the ground, that is, at 

 the crown, as it frequently does, particularly on young trees, it is 



