26 FIELD STUDIES OF THE CROWN-GALL OF THE GRAPE. 



the soil was removed around the base of the plants, the galls removed 

 by excision with a sharp knife, and the wound washed with a fungi- 

 cide. The galls were cut from the vines in an adjacent row, but no 

 chemicals were applied. This row served as a wound control. On 

 a fifth row of vines the galls were undisturbed, as a further control 

 to treatment by excision and by the use of fungicides. This block of 

 five rows made an experiment. 



Several such blocks were similarly prepared and three rows treated 

 in each, using the following water solutions of chemicals, a different 

 one in each block: (1) A 2 per cent solution of copper sulphate; (2) 

 a 5 per cent solution of iron sulphate; (3) a 2 per cent solution of 

 formalin. In a fourth block the wound was covered with powdered 

 sulphur. Four more blocks were given the foregoing treatments 

 except that each plant received in addition an application of a fer- 

 tilizer containing bone phosphates and nitrate of soda. 



During the winter which followed many vines in all of the rows 

 died, and of those that lived none certainly recovered. The rows 

 treated showed no improvement over the others. The experiment 

 resulted so badly that the vines were removed and replaced with 

 other varieties in an attempt to secure resistant varieties. Although 

 these experiments failed to accomplish the cure of the diseased vines 

 they can be considered only as indicative of the probable futility of 

 curing the disease by excision of the galls followed by the application 

 of a fungicide. They do not prove the impossibility of a cure by 

 some other method of surgical or chemical treatment. 



THE PREVENTION OF CROWN-GALL. 



The results of the studies and experiments with the disease indicate 

 the necessity for prevention rather than cure. This can be accom- 

 plished either by the use of resistant vines or by grafting nonresistant 

 vines on resistant stocks. 



RESISTANT VINES SHOULD BE PLANTED ON THEIR OWN ROOTS. 



In the experiment previously described, where 24 of the best vari- 

 eties were grown in infected soil to test their resistance to attacks 

 by the disease, it was found that a number of varieties were quite 

 resistant to crown-gall, as follows: Rupestris St. George, Feher Sza- 

 gos, Sweetwater, Golden Chasselas, Seedless Sultana, Carignane, 

 Grenache, Gros Colman, and Mataro. These varieties will succeed 

 well on their own roots. More than a hundred varieties are being 

 tested by Prof. Fabian Garcia, of the New Mexico Agricultural 

 Experiment Station, in an experiment begun in 1904 in coopera- 

 tion with this Bureau but now being completed by the station. An 



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