264 
Journal of Agricultural Research 
Vol. XXI, No. 4 
soil was inoculated with virulent tap water suspensions of the wilt 
bacteria; in other instances pieces of diseased stalks were thickly strewn 
in furrows, and the seed of susceptible varieties was planted among and 
directly over them. No evidence whatever of infection from the soil or 
from proximity to diseased stalks has thus far been obtained. However, 
the organism has been isolated from the endosperm of seeds developed 
on diseased plants. Furthermore, seed collected from known diseased 
plants gave a higher percentage of wilt than seed of the same varieties 
purchased in the open market. 
Infection of the young corn plant from the seed was found to be 
largely dependent upon the growth condition of the seedling during 
the first week or two after planting, as influenced by soil moisture, 
soil texture and fertility, and temperature. Data relative to seven 
different plantings during three seasons (1918-1920) in our experimental 
fields in Maryland and two plantings during 1920 in Maine have shown 
that the most important single factor predisposing to infection from the 
seed is soil moisture. Whenever rains have been plentiful about the 
time of sowing the seed, wilt has later developed in abundance, whereas 
the same lots of seed planted during a dry period have invariably given 
much less infection. With moisture conditions approximately the same, 
the later plantings at higher temperatures have given a greater amount of 
wilt. Similar relations to temperature were found with inoculations in 
greenhouse compartments held at different temperatures.. Both plant¬ 
ings in Maine, under conditions of drouth and low temperature, gave no 
wilt at all. On the other hand, the same lots of seed planted at three 
different dates in Maryland under more favorable conditions of both 
moisture and temperature gave an abundance of the disease. One 
planting in Maryland during the same season, although at more favorable 
temperatures, was sown during a period of drouth, and in this case only 
2 per cent of infection occurred. At the same place during 1918 in a 
4-acre variety test planted in light sandy soil during an exceptionally 
dry period only 10 cases of wilt occurred during the whole season. It was 
further noted that when seed from a single lot was planted simultane¬ 
ously in light soil, in fertile sandy soil, and in rich sandy loam a consider¬ 
ably higher percentage of infected plants developed in the richer soil. It 
thus seems apparent that anything which retards the germination and 
early development of the seedling lessens the chances of infection from 
the seed. Of these environmental factors soil moisture and temperature 
seem to be of greatest importance. 
Control methods are still in the experimental stage. However, these 
preliminary results seem to indicate that northern-grown seed is less 
likely to carry infection than that grown farther south, and that infected 
seed may be rendered safe for planting by a dry heat “pasteurization” 
at 6o° to 70° C. for one hour. 
