16 



BULLETIN 562, U. S. DEPARTMENT OF AGRICULTURE. 



Table V. — Condition of tobacco on plats of icilt-infested land at Creed-moor, 

 N. C. which had been planted to crops not affected by the wilt for three, four, 

 and five years, respectively. 





Period of crop- 

 ping with im- 

 mune crops. 



Number of plants. 



Percentage of wilt. 



No. of plat and year of test. 



Healthy. 



Wilted. 



In rota- 

 tion plat. 



In check 



plat 

 cropped 

 to tobacco 

 continu- 

 ously. 



Plat 2-A, 1914. . .'... 





359 

 680 

 871 



52 

 159 



107 



12.6 

 18.9 

 10.9 



53 



Plat 3-A, 1915 





72 



Plat 4-A, 1916 . . . 





81 











111 these tests, the check plat on which tobacco was grown every 

 year indicates that the wilt was not so destructive in 1914 as in the 

 following two years. In the rotation plat for 1915 it should be stated 

 that on August 3 only 3 per cent of the plants showed the wilt, while 

 only a week later, when the final count was made, 18.9 per cent of the 

 plants were affected. It is evident that the effectiveness of the rota- 

 tion will depend to some extent on the seasonal conditions, but the 

 growing of immune crops for four or five years probably will re- 

 duce the loss from wilt to a minimum even on very badly infested 

 fields. On such fields it is believed that three years of such cropping 

 will not be sufficient to bring the wilt under satisfactory control. 



P2066T 



Fig. o. — Tobacco growing after peanuts and tomatoes, Creednioor, N. C. All of this 

 plat was cropped to peanuts in 1911 and 1912 ; in the three following years a portion 

 of the plat was cropped to peanuts and a portion was planted in tomatoes. On the 

 plat as a whole 5S per cent of the plants showed wilt on July 27. 1916. There was 

 somewhat more wilt after tomatoes than after peanuts. (Plat C.) 



