948 
Journal of Agricultural Research voi. xxvn, No. 12 
OVERWINTERING OF THE PARASITE AND THE TIME AND METHOD 
OF INFECTION 
A considerable difference of opinion exists among investigators as to the 
time of year when the larvae leave the galls and invade the host plants* 
Roffredi (21) and Henslow ( 12 ), two of the earlier workers, believed that 
this takes place in the spring only, and that the larvae spend the winter 
within the galls in the soil. Marcinowski (17) likewise maintains, from 
the results of rather extensive experiments, that most of the larvae 
remain in the galls until spring. Some of the nematodes, she admits, 
may escape from the galls and invade the plants in the fall, but most of 
these return to the soil at the approach of cold weather. However, it 
appears that she based her conclusions upon the examination of relatively 
few plants and galls. 
The writer agrees with Davaine (9) that under favorable conditions of 
moisture and temperature most of the larvae leave the galls in the fall within 
a few weeks after sowing and spend the winter between the leaf sheaths 
of the host plants. These conclusions are based upon the examination 
of large numbers of diseased seedlings throughout the fall and winter. 
These seedlings were obtained from plats in which gall-infested seed had 
been sown in the fall. Most of the 30 varieties of wheat sown showed 
abundant symptoms of invasion by the nematodes shortly after sowing, 
so that, in the opinion of the writer, there can remain no doubt of the 
fact that a general invasion of the plants by the nematodes occurs in the 
faff. 
Some of the galls, however, retain their larval content all winter, as 
was shown by the examination of a number of them which had been 
buried in the soil in October and were dug up in the following spring. 
The numbers of full and empty galls and the length of time they were in 
the ground are shown in Table XVIII. 
Table XV III.—Number of full and empty galls found in the ground in spring, in soil 
inoculated the previous fall, Arlington Experiment Farm, IQ20 
Date. 
Days in 
soil. 
Number of galls. 
Sown. 
Examined. 
Exam¬ 
ined. 
Full. 
Partly 
empty. 
Empty. 
Oct. 28, 1919. 
Mar. 17,1920 
140 
22 
17 
3 
2 
Do. 
.do. 
140 
14 
ii 
2 
I 
Do. 
.do. 
X40 
16 
12 
2 
2 
Oct. 20, I9I9. 
Mar. 25,1920 
156 
37 
is 
4 
is 
Do. 
Apr. 9,1920 
171 
39 
s 
7 
27 
Sept. 26, 1919. 
June 2,1920 
268 
16 
0 
0 
16 
Total. 
144 
60 
18 
66 
That more empty galls were not found in the spring was due, un¬ 
doubtedly, to their having disintegrated to such an extent that they were 
no longer distinguishable. The writer repeatedly has found wheat 
seedlings containing immense numbers of larvae from 10 to 15 days after 
gall-infested seed had been sown. From these facts we may conclude that 
the length of time it takes for the galls to disintegrate sufficiently to 
liberate the larvae varies considerably, owing probably to several factors, 
among which are temperature, moisture, and the thickness of the gall 
walls. 
