OTHER DISEASES 221 



The disease attacks the roots, the stalks and the ears. The specific 

 organism causing the damage has not been determined. The disease 

 is widely distributed throughout Iowa, and in Illinois. As a rule it is 

 ■unnoticed until after the wind has blown over the infected corn, and 

 then the damage is usually charged to the wind or to insects. 



Remedy. The only rational treatment is crop rotation. Corn 

 should not follow corn where the disease exists, since the fungus re- 

 mains on parts of the plants attacked. When corn is planted in the 

 same field the next year the young stalks will be infected. The Iowa 

 Experiment Station recommends the use of formalin in treating the 

 seed from infected plants ; one pint of formalin to forty-five gallons 

 of water for fifteen minutes. This will destroy all of the spores ad- 

 hering to the surface of the corn. This treatment would avail little 

 or nothing if the seed were planted in an affected field. 



EAR ROTS OF CORN.* In a field of matured corn it is not un- 

 common to find ears more or less covered with and penetrated by mold. 

 In many cases, husks and silks are also involved and appear cemented 

 together and to the ear by a mass of white cob-webby filaments. The 

 parts affected have lost their substance, are light in weight and brit- 

 tle in structure. 



This condition is known as ear-rot. Several types of the disease 

 are known. Some of these are so similar though that the casual ob- 

 server would notice no distinction. 



The first indication that ears of corn are diseased is a fading of the 

 bright green of the husks to a pale yellowish green color. With the 

 advance of the disease the outer husks grow darker and darker, fre- 

 quently becoming dirty and sooty in appearance. The inner husks 

 too may be more or less tinged with brown, particularly along the 

 advancing margin of the diseased area. 



The ear rots may be noticed first soon after the fertilization of corn 

 has taken place, the number of infected ears increasing throughout 

 the season. 



The best spore producing periods seem to follow hot, rainy 

 weather preceded by more or less continued dry spells. Since, then, 

 under favorable conditions the spores are produced in such large 

 numbers throughout the season, the matter of little or much infection 

 depends in part at least on these spore producing periods coming at a 

 time when corn is in the most susceptible condition for infection. It 

 is when corn is in the thick milk stage and later that the large per 

 cent of infected ears in the field begins to show. 



•Illinois Bulletin No. 133. 



