26 MASS. EXPERIMENT STATION BULLETIN 213. 



relation to weather conditions and (2) its behavior in States where it has 

 been present longest. 



We know that the disease can spread only when the rains are long 

 continued or follow each other in close succession, i.e., Avhen the water 

 remains for long periods on the leaves. The summers of 1921 and 1922 

 were for the most part ideal in this respect for the spread of the disease. 

 They have not been average summers for the Connecticut Valley. The 

 disease will not be as destructive during an average growing season. We 

 do not believe that wuldfire will soon disappear from the valley, but during 

 a dry summer it might not cause any damage. After a succession of 

 unfavorable seasons the sources of infection might be so reduced that it 

 would cause little trouble even with the return of a summer favorable 

 for its spread. The above opinion is supported by the course which the 

 disease has taken in the South. Five years ago it was destructive there. 

 In 1921 the season was very dry and the injurj^ from wildfire was slight. 

 The season of 1922 is said to have been not unusually drj^, but the disease 

 has not returned to any extent. Our advice to the Connecticut Valley 

 grower is to plant as usual, take a chance on the weather, but to omit no 

 precaution recommended against wildfire. 



CONDENSED RECOMMENDATIONS FOR CONTROL. 



There is no one measure by the use of which a tol^acco grower may be 

 assured of raising a clean crop. As long as wildfire is in the valley, he must 

 start before the seed is planted, be ever on the alert and ready to put into 

 practice any part or all of the season's program which may now be briefly 

 summarized: — 



1. Select seed only from plants knowai to be free from the disease. If 

 possible, go a step farther and take onlj' from fields known to be disease- 

 free. Protecting the flower heads with bags niay be useful. Old seed is 

 less likely to be contaminated. 



2. If there is doubt about the seed being sterile, soak it in a cheesecloth 

 bag for fifteen minutes in Viooo corrosive sublimate, wash and spread 

 out to dry. 



3. If possible, locate seed-beds only on land where there was no wildfire 

 during the previous year and where there has been no opportunity for 

 contamination. 



4. Sterilize soil with steam at 100 pounds pressure for thirty minutes, 

 or with formaldehj^de Vso at the rate of one-half gallon to the square 

 foot. It is safer to sterilize walks also. Spring sterilization is safer than 

 fall sterilization. 



5. Drench boards and sash with formaldehyde Voo. If cloth is used, 

 it should either be new or should be boiled in water or treated like the 

 boards and sash. If sash and plank are new or have never been used for 

 tobacco beds, they need not be sterilized. 



6. Keep the plants covered with copper-lime dust or a copper spray such 



