74 MASS. EXPERIMENT STATION BULLETIN 203. 



could also be found on the lower leaves of the same plant which were 

 present when the plant was set out. If not on the same plant, then they 

 could be found on a plant which was very close by. In all the field obser- 

 vations we have seen nothing to indicate any other independent source 

 of the inoculum. 



OTHER HOSTS. 



Up to the present the causal organism of wildfire has been found activeh' 

 parasitic only on tobacco. The possibility is not excluded, however, that 

 it may occur on other hosts. Wolf and Foster (5) isolated the organism 

 from spots on cow peas, and were able to produce the typical disease on 

 tobacco with the strain taken from cow peas. Only occasional small spots 

 developed on inoculated cow peas, and they are of the opinion that the 

 organism is not parasitic on this host, but developed only in the weakened 

 tissues about injuries produced by leaf hoppers. They also inoculated 

 bell peppers, potatoes, tomatoes, eggplants, horse nettle and jimson weed 

 but were unable to produce the disease. 



The writers have inoculated petunia, eggplant and pokeweed {Phy- 

 tolacca decandra) by spraying them with suspensions of bacteria in water 

 in the same way in which tobacco plants were usually inoculated. Some 

 of the leaves in each case were wounded by punctures with a sterile needle. 



Petunia. — Within four days after inoculation typical wildfire lesions 

 appeared about all the punctures and on some of the leaves where no 

 punctures were made. These increased to the usual size and the centers 

 died. Reisolations gave the organism in pure culture, and, when tobacco 

 plants were inoculated from these cultures, wildfire resulted. The tobacco 

 wildfire organism is thus parasitic on the closelj' related genus Petunia. 



Eggplant. — These plants were kept under humid conditions in bell 

 jars. After six days necrotic lesions developed about all the punctures, 

 but none where punctures had not been made. The lesions were 5 to 10 

 millimeters in diameter. Thus, although the bacteria are able to spread 

 from wounds, apparently they are not actively parasitic on eggplant. 



Pokeicced. ■ — After a week a few lesions developed about the punctures 

 and showed the typical broad halo. Parasitism is thus about the same as 

 on eggplant. 



Tomato. — While examining a seed-bed of infected tobacco plants at 

 Southwick, the writers found lesions of the same type on some tomato 

 plants which were growing among the diseased tobacco seedlings. Micro- 

 scopic examination showed bacteria of the same kind in the lesions, and 

 pure cultures were obtained. Tobacco plants inoculated from these cul- 

 tures developed typical wildfire lesions. The spots on the tomato leaves 

 appeared to have started around injuries of some kind. Undoubtedly, 

 however, the bacteria were able under natural conditions to spread from 

 these wounds into healthy tissue. 



Further investigations of host relationships are in progress. Probably 

 the same species of bacteria does not cause a serious disease of any of our 



