NEMATODE DISEASE OF WHEAT. 35 
been adopted. Kiihirs (21) catch-crop method, once thought to be 
a practicable means of controlling the sugar-beet nematode (Hetero- 
clera schachtii) has been proposed. It consists of growing a suscep- 
tible plant, in this case wheat, on the land, allowing it to become well 
infected, and then destroying the young plants at the proper time 
to catch the largest number of nematodes. Then by removing the 
crop from the land many of the parasites are eliminated. The 
method is ineffective because only a portion of the nematodes free 
in the soil enter the seedlings, and it is also impracticable because 
of the cost involved. Deep plowing is a more successful means of 
reducing the disease, but this by itself is not adequate to eliminate 
the nematodes. The deeper the larvse are turned under the soil be- 
low a depth of a few centimeters, the less opportunity they have for 
reaching and infecting plants. Marcinowski (22) obtained a higher 
percentage of infection when the nematodes were placed 3 centi- 
meters below the surface of the soil than at any other depth, and 
only a small number were able to reach the wheat seedlings buried at 
a depth of 30 centimeters. 
SUMMARY. 
A serious disease of wheat known in Europe since 1713 and due 
to the nematode Tylenchm tritici (Steinbuch) Bastian has been re- 
cently found causing considerable damage in certain parts of the 
United States, particularly in Virginia. 
Reports in the literature and an examination of specimens re- 
ceived from various foreign countries show that the malady is almost 
world-wide in distribution, having been discovered in all continents 
except Africa. Within the United States it is known to occur at 
present in California, Virginia, West Virginia, Maryland, and Geor- 
gia, and other States also may be found to be infested. 
Samples of harvested wheat collected in Virginia contained from 
less than 1 per cent to more than 50 per cent of diseased kernels by 
count, and as much as 40 per cent damage by it to some fields of 
wheat in the same State has been observed. 
On seedlings the disease usually causes a decided wrinkling and 
rolling or distortion of the young leaves, which, if severely attacked, 
turn yellow, wilt, and die. Occasionally such leaves have one or 
more small light-colored galls, which may be located on any portion 
of the leaf and contain the causal organism. Roots are not directly 
affected, nor do the stems of infected plants near the surface of the 
ground become swollen, as in the case of tulip-root, another disease 
of wheat, caused by the nematode Tylenchus dipsaci, which infects 
stems and crowns. It is on the maturing spikes that the malady 
produces the most conspicuous symptoms. As a rule, infected heads 
