76 MASS. EXPERIMENT STATION BULLETIN 203. 



This treatment will not eliminate the possibility of the occurrence of the 

 disease in the seed-bed, for some of our seed-bed infection this past season 

 occurred after the plants were well developed, but it wdll eliminate one 

 source of infection, and if the other recommendations are followed will 

 reduce the chances of infection. 



Sterilization of Sash, Cloth Covers, etc. 

 In the South it has been shown that the covers used on the beds are 

 sometimes a source of infection, and it is recommended as an additional 

 precaution that the sash, covers and side plank be washed or sprayed 

 with a solution of formaldehyde, 1 part to 50 by measure, and dried 

 before being used. So far, in Massachusetts, we have no positive proof 

 that the disease is carried over in this way, but possibly it may be. 



Spraying or dusting Plants in the Seed-bed. 



Although the bacteria when once inside the tissues of the leaf cannot 

 be destroyed by application of any substance to the surface, the possi- 

 bility of preventing them from entering in the first place is not precluded. 

 Spraying and dusting experiments were therefore undertaken with the 

 object of covering the leaves with a poisonous coat which would kill the 

 bacteria while on the surface and before they had an opportunity to pass 

 through the epidermis. 



A cloth-covered seed-bed 40 feet long and 6 feet wide was divided into 

 18 equal plots, and the fungicides applied for the first time when the plants 

 were about 1 inch high and again a week later. The substances applied, 

 rates of application and results are indicated in the table below. Four 

 of the plots received no applications and were used as checks for com- 

 parison. No infection was present at the time of the first application, 

 but on the following day the entire bed was sprinkled equally with a 

 gallon of water suspension of the bacteria. Five days later infection was 

 noted in abundance on the checks. The beds were inoculated again after 

 the second appUcation of the fungicides, although frequent rains in the 

 meantime were causing satisfactory spread. One week after the second 

 appHcation the plants were all pulled, examined one at a time, and data 

 recorded as to number of infections. At that time the plants were of 

 about the right size for setting in the field. The amount of control is 

 probably indicated more nearly by the number of spots than by the per- 

 centage of infected plants. A hand-operated 2-gallon compressed air 

 sprayer was used for applying the liquids, and a D and B No. 100 powder 

 blower, manufactured by the Dust Sprayer Manufacturing Company of 

 Kansas City, Mo., was used for dusting. 



