37 



Crown-Gall. 



Crown-gall is a disease of somewhat uncertain origin, characterized 

 by the formation of rough outgrowths, or excrescences, on the vines, 

 usuall}^ near the surface of the soiL Certain forms at least are known 

 to be contagious. 



Treatment. — All plants bearing galls should be burned, and great 

 care should be exercised to avoid planting diseased stock. Fungicides 

 are apparently useless in combating this disease. 



Root-Rot. 



The roots of the grape are known to be attacked by several differ- 

 ent fungi, especially when the root system has beconic weakened or 

 injured by other causes. Two forms of root-rot are of sufficient 

 importance to be mentioned here. 



Vibrissea hypogaea. — The fungus known as Vihrissea hypogsea Ch. 

 Richon & Le Monnier is usually associated with insect injurj^, caused 

 either by Phylloxera or by the grape root-worm. It has been found 

 in New York, Pennsylvania, and Missouri, and appears to hasten the 

 death of plants, especially those on which the root-worm has been 

 at work. 



Treatment. — This root-rot can be prevented only by the destruc- 

 tion of the insects which injure the root system and thus give the 

 fungus opportunity to gain a foothold. 



Ozonium. — There is a root-rot of a more serious nature preva- 

 lent in and chiefly restricted to Texas and New Mexico. This is 

 caused by a fungus known as Ozonium, which also attacks the roots of 

 cotton and a great variety of other plants. It is most destructive in 

 the black wax}^, clay soils, which are very poorly aerated. Plants 

 attacked die suddenh^, the leaves and fruit withering up in a day or 

 two and remaining on the vines. 



Treatment. — No remed}^ is known for this root-rot of the grape. 

 Soil upon which other plants have died with the same disease should 

 be carefully avoided in planting vines. 



Shelling. 



The shelling or dropping of grapes from the bunches before maturity 

 may be due to various causes. In some localities in New York and 

 Pennsylvania this trouble is rather serious. The cases which the 

 Department has had an opportunity to stud}^ have been found to be 

 due mostly to an imperfectly known fungous disease, which appears to 

 be induced chiefly by improper pruning and training. Allowing the 

 vines to produce too heavy crops is also likely to increase this trouble. 

 The subject is at 'present under investigation, and it is hoped to 

 treat it separately in a later publication. 



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