TOBACCO WILDFIRE. 75 



common plants, j'et it may occur rather commonly in a semi-parasitic 

 inconspicuous condition, and this fact may prove to be of some importance 

 in the dissemination or overwintering of the organism, and thus indirectly, 

 also, in the control of wildfire. 



CONTROL. 



Necessity of starting with the Seed-bed. 

 It has been shown that nearly every field infection originates in the 

 seed-bed, and that as yet there is no positive evidence that the disease 

 has originated in the field, at least in Massachusetts. In every case that 

 came to our attention where healthy seedlings were set, no infection was 

 found except that brought in afterward by partial resetting. Therefore 

 it is evident that if the seed-beds can be kept free from disease, the fields 

 will be free from it also. All control measures should start in the seed-bed. 



Sterilization of Soil. 

 It is the practice of many growers to steam sterihze the seed-beds in 

 order to destroy disease-producing organisms and also to kill weed seeds. 

 With regard to liability of wildfire infection, our observations have been 

 that it has made little or no difference whether or not the seed-beds have 

 been sterilized. It is, however, a good practice, and will minimize the 

 chances of infection from material containing the organisms which may 

 have remained in the beds. No precautionary measures should be over- 

 looked; therefore, where it can advantageously be done, it is well to 

 change the location of the seed-beds, particularly if sterilization is not 

 practiced. 



Seed Disinfection. 

 Fromme (2) has found that the organism overwinters on the seed, and 

 has devised a method for the sterilization of seed which is apparently 

 satisfactory, and, if carried out exactly according to the recommendations, 

 will not injure the seed. We have steriUzed several lots of seed this year, 

 and in none of them has germination been injured. Some bad results have 

 been reported, but these have resulted from faulty technique. Two of the 

 most important points in seed sterilization are thorough washing out of 

 the formaldehyde and rapid drying of the seed. Fromme in principle 

 recommends for sterilization of seed the following procedure: Soak the 

 seed for fifteen minutes in a solution made by adding one fluid ounce of 

 formaldelyde (commercial strength) to a pint of water. Stir the seed all 

 the time that they are in the solution. At the end of the time cover the 

 pail or jar with cheesecloth and wash in running water, or wash in several 

 changes of water until all trace of formaldehyde odor has disappeared. 

 Spread the seed in a thin layer and dry as rapidly as possible at room 

 temperature. Do not heat during the drying. 



