FOOT-ROT DISEASES OF WHEAT IN AMERICA o1 
DISEASE SYMPTOMS 
Although wheat seedlings are frequently killed by Helmintho- 
sporium satiwum, this condition has not been observed to any extent 
in the winter-wheat regions. Under conditions favorable for the 
fungus it causes a rotting of the roots. In less severe cases dark- 
brown lesions develop on the roots at points of infection, causing 
but little apparent injury to the plant. ‘The coleoptile, basal leaf 
sheath, and stem may show various degrees of infection from small 
elongated lesions to a complete rotting. In severe cases of root or 
stem rot the seedling leaves show a dark-green coloration or some- 
times a chlorosis, and later the whole seedling usually dies. In the 
case of older plants the type of root and culm injury is much the 
same as that occurring on seedlings, except that there seems to be 
less tendency for a complete rotting of the stem. 
The fungus attacks the leaf blades, sheaths, upper culm, and head. 
The kernels also become infected and develop a dark-brown to 
black tip at the germ end. This condition has been called black- 
point by Bolley (20), Evans (20), Weniger (74), and Henry (30). 
So far as known no part of the wheat plant is immune to infection 
from this parasite at any period during its development. Stem and 
foliage lesions tend to be elliptical in outline. Usually these con- 
sist of a dark-brown margin with a lighter brown center, as illus- 
trated previously (45). On leaves these centers frequently drop 
out, and in some cases lesions may involve the entire width of the 
leaf. This fungus also produces a spot blotch on the leaves of 
barley plants, but on this host the spots tend to be uniformly dark 
brown or almost black in color. They do not incline to the light 
centers which characterize the leaf spots produced on wheat leaves. 
On the roots and stems of wheat seedlings Helminthosporium 
sativum causes the tissues to develop a hght to chocolate brown 
coloration. This color is usually darker than that produced by 
Gibberella saubinetu, and there is no suggestion of pink or red, 
such as that which is frequently associated with the attacks by the 
last-mentioned parasite. In some cases, however, the light-brown 
coloration and rotting produced by these two parasites are so similar 
that they can not be distinguished by ordinary means of superficial 
examination. 
Occasionally observations have shown that Helminthosporium 
satwwum produces a black coloration on the roots and bases of stems 
which may be readily confused with the blackening produced by the 
mycelial plate of Ophiobolus graminis unless the specimens are 
examined very carefully. Microscopic observations on such plants 
show that this blackening may be produced in at least two ways. 
The dark brown to black conidia may develop in a crust on the 
infected parts or the host cells of the infected tissues may contain 
very dark brown to black amorphous masses seemingly of a reac- 
tionary nature. In some cases the cortical cells of the roots thus 
affected slough away and become loosely attached to the roots, thus 
producing an effect resembling a mycelial plate when examined 
macroscopically. 
The blackening caused by nftsses of conidia has been noted a very 
few times under field conditions, but it has never been obtained on 
greenhouse-grown plants. The second type of blackening has been 
