CONTROL OF TOBACCO WILT IN THE FLUE-CURED DISTRICT. 15 



Fig. 4. — Tobacco growing after corn, Creedmoor, N. C. This plat was cropped to corn 

 for five years, 1911 to 1915, inclusive, with crimson clover as a winter cover crop. 

 Less than 3 per cent of the plants showed wilt on July 27, 1916, but it should be 

 noted that the tobacco is decidedly smaller in size than that after grass and clover 

 (plat E). (Plat D.) 



Another important lesson from the experiments is that, other 

 things being equal, injury from wilt is likely to be much greater on 

 poorly drained spots ; hence, crop rotation may be less effective under 

 these conditions. 



LENGTH OF ROTATION REQUIRED TO RECLAIM INFESTED SOILS. 



In the preceding pages it has been demonstrated that under proper 

 conditions the growing for a period of five years of crops not at- 

 tacked by the wilt organism will make it possible, even on the worst 

 infested fields, to produce a crop of tobacco with only a very small 

 loss from wilt. This would mean a 6-year rotation, or 1 acre of to- 

 bacco every year for each 6 acres of tobacco land on the farm. In 

 most cases the farmer will want to grow a larger acreage of tobacco ; 

 hence, it is important to know the shortest practicable rotation for 

 controlling the wilt. As was explained on page 11, the rotation plats 

 at Creedmoor were so arranged that after the third year half of one 

 plat came into tobacco each year, and the system of cropping was 

 that shown for rotation plats 2, 3, and 4 in figure 1 (p. 11). These 

 experiments furnish data on the comparative effects of cropping 

 three, four, and five years, respectively, with crops not attacked by 

 wilt. The results are brought together in Table V. 



