222 CORN 



These diseases occur with more or less severity over a wide area. 

 In Illinois alone the State Department of Agriculture estimated the 

 loss from ear rot at $5,620,147 for a single year. 



Corn grown on the rich, black land of our corn belt, however, is' 

 more subject to the disease than on higher, thinner soils. 



The greater the number of old stalks and the greater the supply of 

 moisture, the better the opportunity for a continual and rapid propaga- 

 tion of the most destructive of these fungi. 



The ear rots are undoubtedly more prevalent where corn is grown 

 continuously for some time than on land where a careful system of 

 rotation is practiced. 



Causes of Ear Rots. These diseases of corn are due to definite 

 species of mold like parasites. So far as is known these grow on 

 nothing but the corn plant. These molds belong to the great group 

 of plants called fungi. These fungi develop upon the growing stalks 

 and dead stalks, as well. They are both parasitic and saphrophitic. 



The spores are produced during the summer upon old stalks, even 

 from those lying on the ground the second year, and these spores are 

 readily carried by the wind. Lodging upon the developing ear, they 

 germinate under favorable conditions of moisture and temperature. 

 The rot does not occur without the infection of these spores. 



There are several kinds of these ear rots. Careful observation is 

 necessary however, to differentiate these. The four types commonly 

 discussed are as follows : 



(1) Diplodia. 



(2) Fusarium I. 



(3) Fusarium II. 



(4) Fusarium III. 



The greater amount of damage seems to be done by the "Diplodia 

 Zeae." The manner of infection, character of growth and the nature 

 of the damage does not seem to vary materially, however, between the 

 different species. 



In the Diplodia, the germinating spore sends out a slender thread- 

 like structure called a mycelium. These slender threads penetrate the 

 plant tissues. After the ear has become entirely involved or the 

 growth of the parasite somewhat checked, the fungus begins to form 

 its reproductive stage. This consists of small black bodies which 

 develop in husks, cobs, and more rarely in grains, and which contain 

 large numbers of purplish brown rather slender two celled spores. 

 These spores are scattered by such natural agencies as the wind. 



