28 BULLETIN 1256, IT. S. DEPARTMENT OF AGRICULTURE. 



Control. — The control measures recommended are largely con- 

 cerned with the production of disease-free plants in the seed beds. 

 Failing in this, healthy plants should be sought elsewhere in pref- 

 erence to taking the chance of introducing even a seemingly small 

 amount of infection into the field. 



The principles of plant-bed sanitation previously stated (p. 4) 

 apply particularly to wild-fire prevention. In addition to this, it 

 may be necessary to resort to other methods. In districts where wild- 

 fire is almost certain to be of general occurrence and the probability 

 of obtaining completely disease-free plants seems small, it may be ad- 

 visable to spray or dust the seed beds with Bordeaux mixture once or 

 twice a week to hold down the amount of infection. 



Where wild-fire infection is found in isolated spots in the seed 

 beds, destroy the plants in such areas, together with surrounding 

 plants, by burying or applying formaldehyde (1 part to 25 parts of 

 water) and covering the treated area to hold the fumes. The covers 

 should not be replaced on the treated beds until most of the formalde- 

 hyde fumes have escaped into the air: otherwise the healthy plants 

 may be damaged. The disease may be easily spread throughout the 

 bed from such infected areas during the process of weeding beds or 

 pulling plants for transplanting. 



If wild-fire develops in the field on only a few isolated plants 

 early in the season it is well to destroy them and replant with 

 healthy plants. In case of a high percentage of infection, it is often 

 advisable to plow up and replant the entire field if the season is 

 not too far advanced. If such a procedure can not be profitably at- 

 tempted owing to lateness of the season, serious effort should be 

 made to remove all the infected leaves as thoroughly as possible 

 early in the season with the hope that such reduction of infective 

 material, together with the chances of an unfavorable season for 

 the disease, may hold its spread down to a minimum. 



With persistent effort on the part of the grower to hold down the 

 disease and to destroy or otherwise dispose of all infected material 

 on the farm, including the plowing down of sucker growth in the 

 fall before it becomes infected, much headway will be made toward 

 reducing the chances of wild-fire in the crop the following year. 



BLACK-FIRE. 



Description. — A tobacco leaf-spot which has probably been existent 

 for many decades, especially in Virginia and other southern dis- 

 tricts, but which has not been carefully studied until recently, is 

 the disease now properly referred to as black-fire (angular leaf- 

 spot). The disease is in many respects similar to wild-fire, occurring 

 in the same districts, and doubtless the two are often confused by 

 growers. Since these diseases are caused by different parasites, 

 though similar, and as the symptoms of the two are fairly dis- 

 tinct, they must be considered separately, although the control 

 measures for both diseases are much the same. It may likely de- 

 velop that from a practical standpoint the chief reason for the 

 grower recognizing the difference between these and other leaf spots 

 lies in the fact that one or the other of such diseases will prove 

 much more dangerous in some sections than others, which will in- 

 fluence the control measures undertaken. So far as known, black- 



