library 
cereal CROPS ft disease! 
JOMAL OF AMCClTim BESEARd 
Yol. XXXI Washington, D. C., October 15, 1925 No. 8 
LEAFSPOT OF MAIZE CAUSED BY OPHIOBOLUS HETERO- 
STROPHUS, N. SB., THE ASCIGEROUS STAGE OF A HEL- 
MINTHOSPORIUM EXHIBITING BIPOLAR GERMINATION 1 
By Charles Drechsler 
Associate Pathologist i, Office of Cotton, Truck, and Forage Crop Disease Investiga¬ 
tions, formerly with Office of Cereal Investigations, Bureau of Plant Industry 
United States Department of Agriculture 
INTRODUCTION 
For several years the writer has received for identification occa¬ 
sional lots of graminaceous material attacked or suspected of being 
attacked by members of the genus Helminthosporium. Among the 
more noteworthy of these are certain collections of maize (Zea mays 
L.) leaves affected with a foliar disease, which, with the parasite 
responsible for it, this writer has briefly described in an abstract ( 3) 2 
ana which is more adequately treated in this paper. While the 
fungus has evidently not escaped observation by previous writers, 
it has generally been confused with a congeneric form responsible 
for leaf blight of maize. Additional interest attaches to the fungus 
under consideration in that it readily yields an ascigerous stage of 
a type not hitherto recorded as associated with any species of Hel¬ 
minthosporium. The discovery of this association is presumably 
not without significance in relation to the taxonomic position of a 
numerous series of apparently allied forms assigned to the genus, 
including, for example, the parasites causing spotblotch of barley, 
eyespot of sugar cane, and Ieafspot of rice, of which the mode of 
coniaial germination by the production of a polar germ tube from 
one or both end segments represents a common characteristic. 
SYMPTOMS 
Liberal collections of diseased maize leaves made by A. C. Foster 
near Sanford, Fla., on September 22, 1923, and by C. Welles near 
Los Banos, Philippine Islands, in November, 1921, very largely 
provided the material upon which the present studies were based. 
The leaves bore numerous lesions, varying considerably in extent, 
the smaller and evidently incipient ones scarcely discernible and 
measuring approximately 0.5 mm. in each direction, the larger up 
to 15.0 mm. in length and from 1.0 to 3.0 mm. in width (fig. 1, A). 
In the dried condition the interior of the larger spots approximated, 
on the whole, the cinnamon-buff of Ridgeway's color chart, although 
this hue was interrupted by rather delicate transverse reddish-brown 
bands at intervals of 1.0 to 1.5 mm., resulting in a perceptibly zonate 
appearance. Reddish-brown coloration was equally present also at 
the margin of the lesion, setting off the latter from the healthy tissue 
1 Received for publication Nov. 29, 1924; issuedDecember, 1925. 
2 Reference is made by number (italic) to “Literature cited,” p. 726. 
Journal of Agricultural Research, Vol. XXXI, No. 8 
Washington, D. C. Oct. 15,1925 
Key No. G—502 
73704—26f-1 
(701) 
CEREAL INVESTIGATIONS. 
