44 A PLANT-DISEASE SURVEY IN TEXAS. 



Root-knot {Heterodera radicicola (Greef) Mill.). — This was ob- 

 served in only two localities, but it is probably quite widely dis- 

 tributed. 



Specimens collected: On cymling (Cucurbita pepo L.) — New Braunfels, 1685; 

 San Antonio, 3152. 



SWEET POTATO. 



White-rust {Albugo ipomoeae-pandurmiae (S.) Swingle). — This 

 fungus on the sweet potato {Lpomoea hatatas (L.) Poir.) produces 

 clusters of white pustules on the under surface of the leaves. In 

 young infections the leaves show yellow spots on the upper surface, 

 and as the disease progresses the tissue becomes brown and dead. In 

 severe infections the leaves may show considerable chlorosis in the 

 young stages and in later stages extended brown areas which have 

 been killed. 



Specimens collected: San Antonio, 1781; Llano, 1752; Beeville, 1821; Elgin, 

 2015 ; Uvalde, 1953 ; Nursery, 2562 ; Yoakum, 2765. 



Root-rot. — According to the reports of gardeners, root-rot is very 

 prevalent and destructive in certain localities. All field work was 

 done previous to the harvesting of the crop, and no specimens were 

 obtained, hence it is impossible to say which of the various rot-pro- 

 ducing fungi are prevalent. 



TOMATO. 



Leaf -spot {Septoria lycopersici Speg.). — This trouble on the to-- 

 mato {Lycopersicon esculentum Mill.) was observed to be especially 

 serious in seed beds. The young leaves become thickly covered with 

 small angular spots having a grayish center and a darker colored 

 border. The disease was not so serious on mature plants. 



Specimens collected: Austin, 370, 1307; Llano, 1766; Uvalde, 1952, 1956; 

 Nursery, 2556. 



Rhizoctonia disease {Corticium sp.?). — The symptomatology is 

 very much the same as in diseases of other hosts caused by the same 

 organism. 



Specimens collected : San Antonio, 1380, 3142 ; Austin, 3139. 



Root-knot {Heterodera radicicola (Greef) Mill.). — Probably this is 

 a very general trouble. In several large fields about one-third of the 

 plants had been killed and the others were so stunted that the crop 

 was a complete failure. This is the most serious trouble on tomatoes 

 in the irrigated truck gardens. (PI. IX, fig. 1.) 



Specimens collected: San Antonio, 1328. 3141; Llano, 1769; Beeville, 1842; 

 Elgin, 2011 ; Uvalde, 1949 ; Austin. 3132. 



TURNIP. 



Downy mildew {Peronospora parasitica (P.) De By.). — The oldest 

 leaves of the affected turnip plants {Brassica rapa L.) were dry and 



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