214 GRASSES OP IOWA. 



and Alternaria tenuis Nees. The disease is not limited to corn 

 but also occurs on sorghum {Andropogon sorghum). 



GRAY SPOT DISEASE (PIUICUI.ARIA GRISEA (COOKE) SACC.) 



Crab grass (Panicum sanguinale) is seriously affected at times 

 with the above fungus. It is sometimes difficult to find a 

 healthy plant. The affected leaves at first are pale green in 

 color, then become brown. The mycelium occurs in the interior 

 of the leaf; the hyphae protrude through the openings of the 

 stomata, bearing small pear-shaped spores slightly smoky in 

 color. The spores measure 9 x 18". The affected parts have 

 an ashy gray color.* 



WHEAT SCAB (FUSARIUM ROSEUM, LINK). 



This fungus as an enemy of wheat was first described by 

 Worthington G. Smithf as Fusarium culuiorum. It is probably 

 not common on the continent of Europe, as it is not reported 

 by Loverdo, nor is much said of it by Sorauer. That it is a 

 serious trouble here will be seen from the following estimate 

 in Velvet chaff wheat: Out of a total of 125 heads, 73 were 

 perfect, 24 blighted one-third, 7 entirely blighted, and 24 

 blighted less than one-third. In the variety Johc, Mr. Stewart 

 estimated the loss at about one-fifth. In hybrid Battel, out of 

 120 heads counted, 57 were perfect, while 8 were entirely, 8 

 one-half, 15 one-third and 32 partially destroyed. Weed]; has 

 made this fungus the subject of several papers. He says: "In 

 1890 I saw a field of 100 acres in Madison county, Ohio, consid- 

 ered the finest wheat field in the county, and which was 

 expected, shortly before harvest, to yield 35 to 40 bushels per 

 acre, so severely attacked by the disease that the yield was 

 reduced to 8 bushels per acre. Two other fields, one of 25, the 

 other of 50 acres, were shrunken in yield at least one-third 

 from the same cause. The fungus apparently gains access to 

 the tender, undeveloped kernel, sapping its life and sending 

 down feeders into the main axis of the head on which the ker- 

 nel and enclosed chaff are borne. " 



*3accardo. SyU. Fung. 4: 217. Trichothecium uriseum Cooke Rav. Amer. Fung. 58(1. 



tDiseases of Field and Garden Crops. 308. This fungus is placed with Endoconi- 

 dlum by Prillleux and Delacroix. 



*3oc. Prom. Agrl. Science. 11; 47. f. 1, Fungi and fungicides. 199. See also 

 Pammel. Jour. Mycology. 7: 97. 



