CONTROL OF TOBACCO WILT IN THE FLUE-CURED DISTRICT. 19 



in varying quantities. Tests were made with a large number of 

 germicides, including standard copper and mercury compounds, 

 formalin, carbolic acid, and other well-known organic and inorganic 

 germicides, in addition to numerous proprietary products. Finally, 

 subsoiling with the plow and by the use of dynamite' was tried as a 

 possible remedy for the wilt. In none of these tests were the results 

 sufficiently encouraging to hold out hope of controlling the disease 

 by any of the treatments employed. 



Crop rotation was the only method tested which gave satisfactory 

 results in controlling tobacco wilt. By cropping badly infested land 

 for five years with crops not affected by wilt the injury to the to- 

 bacco from the disease was reduced from 80 to less than 10 per cent. 



The wilt germ attacks a number of plants other than tobacco, and 

 these plants must be kept off the land if the rotation is to be effective. 

 For this reason tomatoes, Irish potatoes, and peanuts should not be 

 grown on tobacco lands ; and since ragweed, which is a very common 

 weed in the flue-cured district, is attacked, it is important that this 

 weed be kept down. 



The crops tested which gave satisfactory results for the practical 

 control of the wilt are corn, wheat, rye (as a cover crop), sweet pota- 

 toes ; cowpeas, grasses, red clover, and crimson clover. There is good 

 evidence tending to show that cotton 1 also is not affected by tobacco 

 wilt, and there is no reason for supposing that oats are affected. 



From the tests conducted at Creedmoor, N. C, when taking into 

 account the differences in the amount of wilt due to varying weather 

 conditions, it appears that on badly infested land the growing of 

 crops not attacked by wilt for four or five years will give better re- 

 sults than only three years of such cropping, although the 3-year 

 period greatly reduced the amount of wilt. It is believed that on 

 badly infested soils a crop of tobacco should not be grown oftener 

 than once in every five years, but after the disease has been brought 

 under control tobacco probably may be grown safely every fourth 

 year. Under no circumstances should two crops of tobacco be grown 

 in succession on infested soil. 



To keep the wilt off farms not already infested, it is recommended 

 that seed beds be thoroughly burned to insure complete sterilization 

 and that care be taken not to allow surface drainage from infested 

 farms to reach the seed bed or the tobacco land. Great caution 

 should be used in securing plants or farming implements from 

 farms on which the wilt is present. Tobacco stalks or stems from in- 

 fested farms should not be used as a fertilizer on healthy soils. 

 Every effort should be made to prevent infested soil or diseased 

 plant material in any form from reaching the farm. 



1 Results obtained since the text of this bulletin was written have shown that cotton 

 is immune to the tobacco wilt. 



