936 
Journal of Agricultural Research voi. xxvii, No. i* 
DESCRIPTION 
VEGETATIVE SYMPTOMS 
The first evidence of nematode injury in the seedling plant is the 
appearance of slight elevations on the upper side of the leaf with corre¬ 
sponding indentations on the lower side. These elevations soon become 
more pronounced and the leaf sometimes takes on a somewhat yellowish, 
mottled appearance (PI. i, D). The leaf may become wrinkled, begin¬ 
ning usually at the edge of the blade. This wrinkling, however, often 
is found to a slight extent on healthy plants. As this condition becomes 
aggravated, the leaf margins curl in from the edges toward the midrib 
on the upper side very much as in some cases of aphid injury, and fre¬ 
quently the leaf is split in one or more places. This rolling or curling 
leaf often incloses the emerging blade of a younger leaf, thus retarding its 
normal growth and causing it to become more or less distorted and 
“buckled” (PI. 2, A). As this younger leaf is not free to grow longitu¬ 
dinally, it often grows in a zigzag manner, frequently while within the 
inclosing older leaf sheath, causing the latter to assume a swelled or 
bulged appearance. This hindrance to the growth of the leaf tip often 
causes another deformity, namely, the bending of the culm, as shown in 
Plate 2, C. A similar restriction to the growth of several successive 
leaves may bring about an alternate curving of the stem in opposite 
directions. 
The slight clockwise twist occurring naturally in wheat leaves often 
is so accentuated in the diseased plants that the leaves form a rather tight 
spiral roll, as shown in Plate 2, B. Sometimes only a part and sometimes 
the whole of the leaf is involved. When the plant approaches the heading 
stage, the flag leaf often becomes wound tightly about the stem, thus 
interfering considerably with the emergence of the head from the boot 
(PI. 1, A). The awns frequently are somewhat distorted when they issue 
from the inclosing sheath, but they often assume their normal appearance 
later. 
As the plant approaches maturity, some of the earlier symptoms may 
disappear. This was proved by tagging a large number of infested 
seedlings in April, 1919, and observing them at intervals until maturity. 
Some of the badly distorted leaves were found withered and dead, while 
those formed later showed no pronounced symptoms. This, however, 
is not of general occurrence, especially if the plant is badly deformed 
in the seedling stage, for in the majority of the plants observed symptoms 
on the vegetative parts were evident at maturity. Of the plants examined 
on April 20, 1919, 62 per cent showed symptoms. On May 22 another 
count was made and 58 per cent still showed symptoms. 
It may be well to add that similar symptoms often are caused by other 
agencies, such as aphids, the Hessian fly, drought, and some fungous 
diseases. Neither does the absence of symptons indicate freedom from 
the disease, for often a plant which appears healthy in every respect 
produces an infected head. Wheat with symptoms similar to nematode 
injury, but which probably are due to drought, is shown in Plate 2, F. 
