20 MASS. EXPERIMENT STATION BULLETIN 213. 



inch diameter or less, colored white, brown or darker to black, irregular 

 in outline, commonly bordered by indefinite blanching of the immediately 

 surrounding tissue. This border, however, is narrow and inconspicuous 

 and fades away indefinitely into the normal green leaf. It is quite dif- 

 ferent and easily distinguished from the halo about the wildfire spot. 

 The leaf area about the spot is also commonly distorted or puckered into 

 radiating wrinkles. Where excessive amounts of dust are used, whole 

 leaves or entire plants may exhibit this wrinkled, distorted appearance 

 without central dead spots. This results in dwarfing. 



Spray injur}' resulting from the liquid fungicides is indicated by larger 

 dead areas in the leaves on the margins, tips or other places where the 

 liquid stands in drops. 



Injury from either dust or liquid spray has never been serious and at 

 most has resulted only in slightly slower growth of the plants in the beds. 

 The plants immediately recover after being set in the field. The injury- 

 is never of sufficient importance to discourage the application of dust or 

 liquid spray. 



Secondary Benefits. — Practical growers have frequently called attention 

 to the absence of flea beetle in the treated beds. One prominent grower 

 has stated that he would spray whether he had wildfire or not because the 

 beds were free from these insects. Copper-lime fungicides are known to 

 repel flea beetles. 



Frequently when the plants are thick in the bed and kept damp, they 

 rot off at the base of the stem. It has been commonly noticed that this 

 condition does not occur when the beds are properly treated with a fungi- 

 cide. 



Conclusion. — Any groiver who will start when the plants are no larger than 

 a dime and keep the leaves covered at all times with copper-lime dust or any 

 other good copper fungicide can control wildfire in the seed-bed. We agree 

 with Clinton and McCormick (2: 386) in the following quotation except 

 that we would include dusting as well as spraying: — 



We are convinced that spraying of tobacco beds should be made one of the 

 routine practices of tobacco growing as long as there is danger from wildfire. . . . 

 We have evidence that plants thoroughly coated with the spray do not become in- 

 fected anything like unsprayed plants in the same bed. Spraying to be most effec- 

 tive, however, must start before the appearance of wildfire and be continued until 

 the end of the transplanting season. We would start with the young plants that 

 have just taken root and whose largest leaves are about the size of a thumb nail. . . . 

 Spraying, we believe, is the only remedy that prevents spread of the wildfire in a seed-bed 

 no matter what the source of its introduction. 



Destroying Diseased Areas in the Bed. 



It is characteristic of the disease that when it is first found in the beds 

 it does not occur uniformly over the bed, but is usually found in round 

 spots which may be from a few inches to several feet in diameter, de- 

 pending on the length of time during which the spot has been spreading. 

 If only one or a few spots are found in a bed, it is sometimes possible 



