Mar. 22,1924 
Nematode Disease Caused by Tylenchus tritici 
941 
Table XII .—Number of adult nematodes found in immature galls from spelt , wheat , 
and emmer grown at the Arlington Experiment Farm in igig 
Source of galls. 
Number 
of galls. 
Highest number 
of— 
Lowest number 
of— 
Average number 
of— 
Males. 
Eemales. 
Males. 
Females. 
Males. 
Females. 
Spelt. 
36 
6 
8 
0 
1 
3 
4.4 
Wheat. 
40 
18 
14 
2 
3 
7 
8.0 
Do. 
20 
42 
37 
1 
3 
17 
16.0 
Emmer. 
94 
40 
45 
2 
3 
20 
22.0 
These figures are larger than those of Marcinowski (17), who found 
that none of the nine galls examined contained more than 16 adults. 
Byars ( 6) states that a gall contains an average of six or seven females. 
According to the figures given in Table XII his estimates also are rather 
low. 
SPREAD OF THE DISEASE 
IN GRAIN, STRAW, AND MANURE 
The most common and only important method of spreading this dis¬ 
ease is by means of galls in the seed wheat from infested areas. It is 
likely to be spread from farm to farm by means of threshing machines. 
This was illustrated in Jackson County, Ga., where the disease occurred 
.for many years only on those farms in a certain “threshing ring.” 
As many galls are blown into the straw at threshing time, this also 
may serve to distribute the disease, provided the straw is not allowed 
to decay in the barnyard or in the manure pit. 
At Madison, Wis. (1921-22), the writer thoroughly mixed a quantity 
of barnyard manure with a generous sprinkling of whole galls. An 
equal quantity of manure was mixed with a like quantity of ground 
galls. This manure was stored in a manure pit for six weeks and then 
applied to two separate plats of land which later were sown to wheat. 
No infection of the wheat followed. Two adjacent plats of soil received 
an application of manure which was mixed with galls, both whole and 
ground, immediately before being spread on the land. Wheat sown on 
these plats showed abundant evidence of nematode injury in the fall 
and although badly winterkilled produced a number of infected heads 
the following summer. These results with others are shown later in 
Table XVII. 
IN THE son. 
The organisms may be spread in the soil to a limited extent by sur¬ 
face water, by infested soil on farm implements, or by the feet of farm 
animals going from infested to uninfested fields. In such instances the 
larvae may be within the galls or in a free-living condition in the soil. As 
they can endure long periods of desiccation they even may be blown about 
by the wind. However, dissemination by these means is so relatively 
unimportant that it is quite safe to grow wheat on clean soil adjacent to 
very badly infested soil. The writer has grown wheat repeatedly on 
plats a few feet away from badly infested soil, and where no heavy wash¬ 
ing occurred was unable to find any infected heads in the plats on clean 
soil. 
85607—24-4 
