.Mar. 22, 1924 
Nematode Disease Caused by Tylenchus tritici 
953 
Soil on which badly diseased wheat had been grown in 1917 was divided 
into three separate portions, each of which was given a different 
rotation. The first part was in grass in 1918, corn in 1919, and wheat in 
1920. The second part was in wheat in 1918, grass in 1919, and wheat 
in 1920. The third part was used for wheat in all three years. In each 
case the wheat grown in 1920 on the rotated fields was entirely free from 
the disease, while that grown on the second plat in 1918 and on the third 
plat in all three years was badly infected, although clean seed had been 
used. Similar results have been obtained on small plats at Arlington 
Experiment Farm and on the Agricultural Experiment Station Farm at 
Madison, Wis. 
Marcinowski (17) advises the “catch crop’’ method suggested by 
ICtihn (16). This consists in growing a susceptible cereal on die infested 
soil, allowing the plants to become thoroughly infested with the nema¬ 
todes and then destroying the plants. This plan is both ineffective and 
impractical, because all the nematodes do not enter the seedlings and 
the cost involved is prohibitive. Inasmuch as rotation and clean seed 
offer such a simple remedy it would be manifestly unwise and unprofitable 
to attempt any uncertain method. 
RESISTANT VARIETIES 
Among the many varieties of wheat tried in experiments covering three 
years, none showed sufficient resistance to nematode infection to be of 
any value in controlling the disease. Kanred showed marked resistance, 
but, nevertheless, enough galls were produced to perpetuate the disease. 
A wheat variety, to be effective in nematode disease control, would have 
to be practically immune. 
SUMMARY 
The nematode disease of wheat has been reported from all continents. 
In the United States it appears to be confined to Virginia, West Virginia, 
North Carolina, South Carolina, and Georgia. 
Severe losses occur where the disease is prevalent, some fields being 
damaged as much as 50 per cent. Preliminary field data indicate that 
spring wheat is severely injured if infested seed is sown. Fortunately, 
the disease does not occur in any spring-wheat district in this country. 
The disease attacks wheat, rye, emmer, and spelt with almost equal 
virulence. Oats and barley, while capable of being parasitized to some 
extent, are practically immune, as are also the various grasses. 
In the seedling stage the disease causes wrinkling, twisting, or various 
other distortions of the leaves. The emerging leaf often is held by the 
older one, thus causing a “buckling” of the former while still in the 
inclosing sheath. Infected plants are usually shorter and thicker than 
normal ones. Badly infested seedlings often wilt and die. 
In the mature heads the disease is characterized by the presence of 
hard, dark galls in place of normal kernels. These galls are somewhat 
thicker than wheat kernels and cause the glumes to stand out as in bunt- 
infected heads. 
Several galls of varying size may be produced in one head. Galls in 
rye generally are smaller and lighter colored than those in wheat. They 
also are less conspicuous in the head and do not shatter out as easily. 
