952 
Journal of Agricultural Research v 0 i. xxvii, no. 12: 
maldehyde of 1:240 strength, or four and a half hours in mercuric chlorid 
of 1:1000 strength, were required to kill the free larvae. They endured 
immersion in 0.5 per cent sulphuric acid for three hours, and 5 per cent 
solution of copper sulphate for six and one-half hours. Within the 
protective galls, of course, the larvae can endure a much longer period 
in any of the above chemicals. 
Sommerville (23) tried various strengths of copper sulphate, sulphuric 
acid, and commercial formalin, but found that whatever affected the 
nematodes also reduced the germinating power of the seed. He con¬ 
cludes that seed treatment is impracticable. 
CONTROL MEASURES 
Inasmuch as seed treatment is inadvisable, and completely resistant 
varieties unknown, the control measures are limited mainly to sanitation 
and rotation, in short, clean seed sown in uninfested soil. 
CLEAN SEED 
The best way to insure having suitable clean seed is to obtain a supply 
that has been grown on uninfested land, preferably in the same or a 
near-by locality where the disease does not exist. If this is impossible, 
the gall-infested seed on hand may be cleaned by the salt-brine method 
devised by Johnson and Vaughan (14) for removing ergot from rye. 
This consists of pouring the infested grain into a 20 per cent solution of 
common salt (sodium chlorid), stirring vigorously in the meantime, and 
then skimming off the galls, which float, due to their lower specific 
gravity, while the sound wheat sinks. The grain should then be rinsed 
in fresh water and spread out to dry. It is best to sow it at once. If, 
in addition to this treatment, the grain be soaked in water at 54 0 C. 
for 15 minutes after a preliminary soaking in cold water for several hours, 
any galls that may not have been removed will be rendered harmless, 
and, according to Humphrey and Potter (13), loose smut also will be 
prevented. This latter process, however, is one which demands great 
care, as there is danger of injuring the vitality of the seed by excessive 
temperature or too long an exposure. 
CLEAN SOIL 
In order to free soil from the wheat-nematode infestation it is necessary 
to keep susceptible crops off the land for one year. This was demon¬ 
strated by rotation experiments conducted on infested soil at Morrisville 
and Woodstock, Va., as shown in Table XX. 
Table XX. —Arrangement of rotation plats at Woodstock and Morrisville, Va., showing 
the crops grown on each plat in each season for four years, on land badly infested in 1917, 
and the condition of the wheat following the different rotations* 
Year. 
Plat No. 1. 
Plat No. 2. 
Plat No. 3. 
1917. 
tqtS. . 
Wheat (infected). 
Grass . 
Wheat (infected). 
.do. 
Wheat (infected). 
Do. 
Do. 
Do. 
1010.... .... 
Com. 
Grass. 
1920.'. 
Wheat (uninfected). 
Wheat (uninfected). 
# 
