TOBACCO DISEASES AND THEIR CONTROL. 49 



which are not serious in their native country may be much more so 

 when introduced into other countries with. different climatic condi- 

 tions prevailing. 



Tobacco diseases have been reported on in most detail from the 

 Dutch East Indies, Italy, India, Dalmatia, Russia, France, and 

 Germany. In general, foreign countries have most of the common 

 diseases of tobacco which occur in the United States, although their 

 occurrence as a serious problem is naturally very variable, as it is in 

 the tobacco districts of the United States. It does not appear from 

 the literature that the recently described bacterial leaf-spots of 

 tobacco in this country exist elsewhere, with the exception of the 

 possible occurrence of wild-fire in South Africa. 



The diseases of tobacco are naturally described in foreign litera- 

 ture under a wide variety of names, and with the unsatisfactory de- 

 scription and diagnosis presented in many cases it is difficult to 

 ascertain the relationship between the diseases as described from 

 different districts. In the Dutch East Indies the bacterial wilt 

 disease due to Bacterium solanacearum and the lanasziekte caused 

 by Phytophthora nicotianae (our black-shank) seem to have been 

 given most consideration. In Italy root-rot due to Thielavia oasicola 

 is said to be serious. Leaf-spot diseases are world-wide and have 

 been attributed to a number of different parasites, many of which are 

 not known in this country. Mosaic and frenching are common, as 

 are a number of minor diseases attributed to nonparasitic agents or 

 of unknown cause. Broom rape due to various species of Orobanche 

 are common in southeastern Europe, as are also species of Cuscuta 

 (dodders). 



Among the more common fungous diseases not yet known to occur 

 in this country is the powdery mildew due to Erysiphe to which 

 at least five specific names have been given, though all probably are 

 identical. Two species of Cercospora are reported, at least one of 

 which is probably our American species. Alternaria tenuis Nees 

 is frequently reported on tobacco in Europe, causing various types of 

 troubles from seed bed to curing house, as are also various species 

 of Sclerotinia. Parasitic species of Phyllosticta, Ascochyta, and 

 Septoria on tobacco are apparently more common in Europe than in 

 America, but none are probably of much economic importance. 

 Ascochyta and Septoria have not been reported on tobacco in this 

 country. A species of Olpiclium is reported as causing a root disease 

 of tobacco in Dalmatia. and two new species of Pythium are re- 

 ported elsewhere as causing seed-bed troubles. On curing and fer- 

 menting tobacco, species of Botrytis, Penicillium, Aspergillus, Alter- 

 naria, Cladisporium, Sporidesmium, Pleospora, Sclerotinia, and 

 Mucor are reported, but in most cases association of these with any 

 of the damage occurring in these processes has not been definitely 

 established. Oospora nicotianae is described as causing " must " 

 in Italy. 



Several diseases due to bacterial parasites have been described, 

 particularly in France, but the relation of the organisms described 

 to these diseases is still open to question. In the East Indies a 

 bacterial leaf-spot (black rust) due to a bacterium (B. pseudozool- 

 loeae Hon.) has been shown to exist. Bacillus amylobacter Van 

 Teigh. is said to cause a bed rot in Italy. 



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