CORN SMUT 
This is the most common and most noticeable disease of corn. It is 
sometimes known as boil-smut to distinguish it from the head-smut. 
It affects all varieties of field-corn, pop-corn and sweet corn. Some 
varieties of sweet corn suffer severely from this smut. 
SYMPTOMS 
All parts of the plant above ground are subject to the disease. Unlike 
most of the cereal smuts, invasion is local. The lesions are characterized 
by marked hypertrophy. 
On the stalk. Study the specimen provided and oBsERVE:— 
1. At what points on the stem the galls are usually located. 
2. The large size of the boils and the comparatively small area 
from which they arise. Is there.any evidence of injury to the adjacent 
host-tissues? 
3. The texture of the boils. They are more firm in fresh speci- 
on especially when yet immature; the tough fleshy covering of such 
galls. 
4. The color; compare old and young boils. 
5. The dark dusty spore-mass filling the: mature boils. 
A relatively large portion of the hypertrophy is composed of pathogene 
structures (mycelium or spores). 
Make a sKETCH to show stem-boils. 
On the leaves. Lesions are comparatively rare on the leaves. In 
the specimens provided, OBSERVE :— 
6. The small boils arranged in rows parallel with the veins. 
Do they seem to arise from or between the veins; which side of the leaf? 
7. Any effect on the tissues adjacent to the boils; opposite 
the boils. 
SKETCH leaf-lesions. 
On the ear. Affected ears are very common, especially those with 
exposed tips. In the specimens provided, OBSERVE -— 
8. The form, size and location of the boils. 
9. That they are each an enlarged kernel. Find kernels in 
different stages of hypertrophy. 
SKETCH a diseased ear to show healthy kernels and diseased ones, 
hypertrophied in various degrees. 
On the tassel. The boils of this smut are very common on tassels 
but may be confused with those of the head-smut. (See Kansas Bul. 
62:199 and pl. VI, VIII-X.) In the specimens provided, OBSERVE :— 
10. That the boils on the tassels are but hypertrophied parts of 
the flowers. : 
11. That only flowers here and there in the tassel are affected. 
12. That the character and degree of malformation varies in 
different flowers. ; ; 
Carefully dissect a healthy and a diseased flower. Make a series of 
comparative DRAWINGS to show the effect of the disease on different organs 
of the male flower. 
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