Vol.44 TORREYA July 1944 



Guscuta japonica Ghoisy, an Asiatic Species New to America 



T. G. YUNCKER 



The recent discover}- of Cuscuta japonica in this country is an interesting 

 instance of the distribution of a species of dodder far beyond its natural range. 

 Only a few of the nearly 200 species of Cuscuta now known attack host plants 

 of sufficient economic importance to make these parasites significant. But the 

 wide range of distribution of such species makes the means of dissemination 

 important. 



Although it is conceivable for greenhouse and nursery plants to carry dodder 

 infection, this mode of distribution is not probable because the parasite is suffi- 

 ciently conspicuous to guarantee its elimination. Unusual extension of range 

 is often, perhaps always, caused by the admixture of the dodder seeds with 

 those of its host which are distributed for planting. 



The North American C. campestris Yuncker thrives on leguminous hosts, 

 especially species of Trifolium. Its seeds are often found mixed with those of 

 its host and, consequently, it is found wherever such legumes are cultivated. 

 The South American C. suaveolens Ser., which prefers alfalfa as a host, has 

 been distributed in a like manner. Three European species have been widely 

 disseminated in the same way. C. Epilinum Weihe which rarely occurs on 

 hosts other than Linum, is to be found wherever flax is grown. C. Epithymum 

 Murr. and C. approximata Bab. var. urceolata (Ktze.) Yuncker occur fre- 

 quently on leguminous hosts and are widespread, especially on alfalfa and 

 clovers. 



Until recently, these latter four species — C. suaveolens from South Amer- 

 ica, and C. Epilinum, C. Epithymum and C. approximata var. urceolata from 

 the Old World — have been the only foreign species of economic significance 

 known to have been introduced into the United States. 



In June 1941, R. F. Martin sent me a specimen of dodder, grown on kudzu 

 (Pueraria Tliunbcrgiana Benth.) in a greenhouse in San Antonio, Texas, 

 which proved to be C. japonica. So far as known, this is the first species of 

 Asiatic origin to be found in either of the American continents. Its discovery 

 was reported in Lundell's Flora of Texas (3: 150. 1943). Finding this spe- 

 cies in an American greenhouse was noteworthy but it was thought to be 

 probably just a temporary introduction. The fact it was using an Asiatic host- 

 plant would indicate that the dodder seeds were introduced with those of its 

 host, as is usually the case with the species mentioned before. 



In October, 1943, however, Erdman West of the University of Florida 

 sent me a specimen which had been collected by J. D. Warner on a farm near 

 Ouincy, Gadsden County. Florida. This specimen, also growing on kudzu, 



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