4 DANGEROUS TOBACCO DISEASE APPEARS IN UNITED STATES. 



many of the seed beds was made up for by overhead irrigation. Dur- 

 ing some days immediately preceding the outbreak of the disease 

 and for a few days after the appearance of the disease there was a 

 heavy dew and fog each morning, dissipated before 9 o'clock by the 

 hot, dry sun. During the subsequent period these morning dews and 

 fogs did not occur. Thinly sown seed beds suffered from the disease 

 as badly as those thickly sown. 



The disease appears to be due to Peronospora hyoscyami, originally 

 described by De Bary from the black nightshade (Hyoscyamus niger) 

 in Europe. It does not appear to have done any damage on tobacco 

 in Europe, but it has been known for many years as a destructive 

 parasite of tobacco seed beds in Australia (New South Wales and 

 Victoria), where it is known as the tobacco blue mold. It has also 

 been reported from South Africa. In 1885 it was reported by Dr. 

 W. G. Farlow on a shrubby wild tobacco {Nicotiana glauca) in 

 southern California, which plant was introduced from Argentina. 

 Dr. Farlow, who saw it at San Diego, described it as a bad parasite on 

 this plant, and pointed out at that time the danger of its spreading 

 to cultivated tobacco should it ever migrate into the eastern United 

 States. The disease must occur also in Texas, since the mycological 

 collections of the Department of Agriculture received in 1906 on cul- 

 tivated seedling tobaccos a Peronospora, the examination of dried 

 material of which leads us to think it identical with the Florida 

 fungus. This came from Hallettsville, west of Galveston. 



It is not known how the disease was introduced into Florida. In 

 view of the fact that the Florida-Georgia growers for the most part 

 raise their own seed and that the little seed which has been intro- 

 duced from outside has come from reputable planters in Connecticut, 

 it is not likely that the disease was introduced into this territory on 

 imported seed. No definite statement as to the probable means of 

 introducing the disease into the United States can be made at present. 

 However, it must be borne in mind that the mats used in baling 

 tobacco in this region are imported annually from Sumatra, arriv- 

 ing in Florida in the month of September, about the time the har- 

 vested seed is being cleaned and stored away. It is known that cer- 

 tain insects have been introduced into the United States on such mats, 

 and it is not impossible that this disease may have been introduced 

 into the United States through this agency, especially as many of the 

 mats are second-hand, having been previously used on East Indian 

 tobacco. On the other hand, the disease may have come into Florida 

 by the way of California and Texas, particularly if the species does 

 not produce resting spores and if the fungus on Nicotiana glauca in 

 California is identical, as Dr. Farlow stated ; or in this case it may 

 have come directly from the ballast heaps of the South Atlantic 



