POTATO WILT, LEAF-ROLL, AND RELATED DISEASES. 3 



With the progress of pathological studies, other diseases were 

 recognized m the United States, some of which, like the southern 

 bacterial wilt or brown-rot (Smith, Erwin F., 1896), had doubtless 

 been long prevalent, if not actually endemic, in the United States, 

 while others, like the blackleg {Bacillus phytopJitTiorus Appel and 

 related forms), appear to have been recently introduced into this 

 country from Europe. 



APPEARANCE OF NEW TROUBLES. 



About 1904 there began to come mto prominence a group of potato 

 diseases hitherto not generally recognized as of economic importance. 

 In that year there was published by Smith and Swmgle a bulletin 

 which described a wilt and dry rot due to Fusarium oxysporum, 

 found in the District of Columbia, Michigan, and elsewhere. This 

 was the first important work of the sort m the United States, though 

 a disease that was very likely the same Fusarium wilt was mentioned 

 by Clinton in 1895 as "bundle blackening of tubers." No mention 

 was made of its relation to any disease of the plants, and it was con- 

 sidered "not a very serious malady." The cause was said to be a 

 fungus "quite similar to" the one causing dry end-rot. 



The disease described by Stewart (1896), and thought by Smith 

 and Swingle to be probably the same, was stated by Prof. Stewart 

 at a recent meeting of the American Phytopathological Society to 

 be not due to a Fusarium. 



In the year 1905 there occurred m Europe an outbreak of a disease 

 which was named leaf-roll (BlattroUkrankheit). This recurred in 

 1907 with such virulence as to excite general alarm, and the attention 

 of many pathologists and other agricultural workers was directed 

 toward its study and prevention. Leaf-roU has continued to cause 

 heavy losses in Germany, Austria, and elsewhere, though it has not 

 become as generally destructive as was feared. Its nature remains 

 a subject for debate. In the early years its resemblance to the 

 American disease described by Smith and Swingle led to the general 

 adoption of the theory that it was due to or associated with a Fusa- 

 rium. The evidence on this point was very contradictory, and 

 there have developed nearly as many opinions as there are investi- 

 gators. 



In America little was done after the work of Smith and Swingle 

 untU 1908, when an outbreak in an important potato district in 

 California was studied by the present writer and found to be the 

 same Fusarium wilt (Orton, 1909). 



The writer continued his survey of the country in 1909 and 1910, 

 finding the Fusarium wilt very widespread. In 1911 he studied 

 potato diseases in Europe with the particular purpose of comparing 

 the American Fusarium wilt with the European leaf -roll disease. 



