MAINE) AGRICULTURAL EXPERIMENT STATION. I910. 417 



a slight development in the injured tissue at the points of inocu- 

 lation, while inoculations made the same day on the same 

 branches with Sphaeropsis developed well marked cankers. The 

 indications are that the species of Cytospora which is found in 

 Maine is very slightly if at all parasitic. 



Pear blight canker. The canker of apple trees caused by the 

 pear blight organism, Bacillus amylovorits (Burril) DeToni., 

 which has been reported as causing a great amount of damage 

 in apple orchards in other states, has not been found in Maine, 

 though careful search has been made for it. Almost none of 

 the characteristic twig blight or "fire blight" on the pear which 

 is a good indication of the presence of the organism has been 

 seen. If this disease occurs on the apple in this State, it is of 

 very rare occurrence. 



Crozvn Gall. Apple trees, particularly nursery stock, some- 

 times have galls or knots which are usually located near the 

 surface of the soil in the region of the collar. These galls are 

 often covered with many fine roots giving them a hairy appear- 

 ance. Such growths have been reported on a number of plants 

 which are closely related to the apple and also on other plants 

 which are not closely related. 



In the earlier studies of this disease the cause was not under- 

 stood. Injuries to the roots and unfavorable conditions of soil 

 and moisture were advanced as causes of the trouble. Experi- 

 ments were carried on in a number of places, however, which 

 demonstrated that the disease is communicable. 



Recently Smith* and Townsendf have studied crown gall on 

 a number of plants and they have been able to prove quite con- 

 clusively that the crown gall of the apple is of bacterial origin, 

 caused by the organism Pseiidomonas tnmefaciens Erw. Smith 

 and Townsend. 



The organism was first isolated from galls on the Paris daisy 

 and inoculations showed that it could produce the disease. 

 Inoculations of tomato, tobacco, potato, sugar beet, grape, car- 

 nation, raspberry, peach and apple were also followed by the 

 development of galls. This lead to the isolation of organisms 



* Smith, Erwin F. and Townsend, C. O. A Plant Tumor of Bac- 

 terial Origin. Science, N. S. 25 : 671-673. 1907. 



t Townsend, C. O. A Bacterial Gall of the Daisy and Its Relation 

 to Gall Formation in Other Plants. Science, N. S. (Abstract) 29: 27^. 

 1909. \ 



