Mar. 22,1924 Nematode Disease Caused by Tylenchus tritici 
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They usually are dark, almost black, in color, but the proximal ends 
invariably show a light-brown coloration. The distal ends often have 
one or more characteristic beaklike projections. The galls, like the 
wheat kernels, generally are furrowed on one side, but they usually are 
shorter and proportionately thicker (PI. 5, G). They are without 
pubescence of any kind. 
Galls in rye, as a rule, are longer in proportion to their width than 
those in wheat and are more irregular in form. In length they vary from 
2 to 4.5 and even 5 mm., and in width from 1 to 2.5 mm. They are 
decidedly lighter in color than galls in wheat, being of a buff shade, 
much like rye kernels. The difference between galls in rye and wheat and 
the variation in the size of galls in rye are shown in Plate 5, G and H. 
In addition to the galls formed in the flower, galls sometimes are formed 
on the leaves (PI. 1, B and C). How these galls originate has not been 
determined, but they probably begin to form before the leaf emerges 
from the sheath. They bear no resemblance to flower galls in appear¬ 
ance, being very much wrinkled and irregular in shape. They contain 
mature nematodes when still green and at a later stage are full of larvae. 
As these galls are relatively rare they are of minor importance. 
Nematode galls in wheat often are mistaken for smut balls, cockle 
seeds, vetch seeds, bin-burnt kernels, ergot sclerotia, or other material 
commonly found in threshed grain. Galls are readily distinguished from 
smut balls by the fact that the latter are easily crushed between the 
fingers into a mass of black powder, whereas the galls are hard and firm. 
Cockle seeds should be recognized at once by their characteristic spiny 
seed coat and vetch seeds by their smoothness, rotundity, and uniform 
color. The ergot sclerotia formed in wheat heads by Claviceps purpurea 
(Fr.) Tul. can be identified by their color, shape, and cross section. 
Some of the differences between galls and other material commonly 
found in wheat are shown in Plate 5. 
THE CAUSAE ORGANISM 
The nematode disease often is called the eelworm disease of wheat on 
account of the eellike appearance and movements o£ the causal organ¬ 
ism, Tylenchus tritici , as seen under the microscope. The mature gall 
contains a white fibrous mass of these microscopic worms. Their life 
history, according to Byars ( 6 ), is quite simple. Escaping into the soil 
from the disintegrating galls after the latter have been sown with the 
wheat, the nematodes reach the wheat seedlings, climb up the stem 
presumably, get in between the leaf sheaths, and finally reach the apical 
growing point of the culm, with which they are elevated when the culm 
elongates. Here they remain until the wheat head begins to develop, 
when in some manner they enter the floral organs which are stimulated 
to the formation of galls instead of some of the normal flower parts, such 
as the ovary and stamens. It is uncertain whether they enter the tissues 
by penetration or by inclusion. Within the newly formed galls they 
develop rapidly into mature males and females. Copulation and egg 
laying follow, and by the time the galls are mature they are filled with 
masses of newly hatched, partly dried larvae. Galls opened just before 
maturity are found to contain thousands of eggs from which these larvae 
develop. At a somewhat earlier stage are seen only the adult males and 
females. 
