The Desert of Wheat | Page 8

arise
and penetrate the shoot of a young seedling and reach the growing
point. Here the fungus threads keep pace with the growth of the plant
and reach maturity at or slightly before harvest-time.
"Since this disease is caused by an internal parasite, it is natural to
expect certain responses to its presence. It should be noted first that the
smut fungus is living at the expense of its host plant, the wheat, and its
effect on the host may be summarized as follows: The consumption of
food, the destruction of food in the sporulating process, and the
stimulating or retarding effect on normal physiological processes.
"Badly smutted plants remain in many cases under-size and produce
fewer and smaller heads. In the Fife and Bluestem varieties the infected

heads previous to maturity exhibit a darker green color, and remain
green longer than the normal heads. In some varieties the infected
heads stand erect, when normal ones begin to droop as a result of the
increasing weight of the ripening grain.
"A crop may become infected with smut in a number of different ways.
Smut was originally introduced with the seed, and many farmers are
still planting it every season with their seed wheat. Wheat taken from a
smutty crop will have countless numbers of loose spores adhering to
the grains, also a certain number of unbroken smut balls. These are
always a source of danger, even when the seed is treated with
fungicides before sowing.
"There are also chances for the infection of a crop if absolutely
smut-free seed is employed. First, soil infection from a previous smutty
crop; second, soil infection from wind-blown spores. Experiments have
shown that separated spores from crushed smut balls lose their effective
power in from two to three months, provided the soil is moist and loose,
and in no case do they survive a winter.
"It does not seem probable that wheat smut will be controlled by any
single practice, but rather by the combined use of various methods:
crop rotation; the use of clean seed; seed treatment with fungicides;
cultural practices and breeding; and selection of varieties.
"Failure to practise crop rotation is undoubtedly one of the main
explanations for the general prevalence of smut in the wheat-fields of
eastern Washington. Even with an intervening summer fallow, the smut
from a previous crop may be a source of infection. Experience shows
that a fall stubble crop is less liable to smut infection than a crop
following summer fallow. The apparent explanation for this condition
is the fact that the summer fallow becomes infected with wind-blown
spores, while in a stubble crop the wind-blown spores, as well as those
originating from the previous crop, are buried in plowing.
"If clean seed or properly treated seed had been used by all farmers we
should never have had a smut problem. High per cents. of smut indicate
either soil infection or imperfect treatment. The principle of the

chemical treatment is to use a poison which will kill the superficial
spores of the smut and not materially injure the germinating power of
the seed. The hot-water treatment is only recommended when one of
the chemical 'steeps' is not effective.
"Certain cultural practices are beneficial in reducing the amount of
smut in all cases, while the value of others depends to some extent
upon the source of the smut spores. The factors which always influence
the amount of smut are the temperature of the soil during the
germinating period, the amount of soil moisture, and the depth of
seeding. Where seed-borne spores are the only sources of infection,
attention to the three factors mentioned will give the only cultural
practices for reducing the amount of smut.
"Early seeding has been practised by various farmers, and they report a
marked reduction in smut.
"The replowing of the summer fallow after the first fall rains is
generally effective in reducing the amount of smut.
"Very late planting--that is, four or five weeks after the first good fall
rains--is also an effective practice. Fall tillage of summer fallow, other
than plowing, seems to be beneficial.
"No smut-immune varieties of wheat are known, but the standard
varieties show varying degrees of resistance. Spring wheats generally
suffer less from smut than winter varieties. This is not due to any
superior resistance, but rather to the fact that they escape infection. If
only spring wheats were grown our smut problem would largely
disappear; but a return to this practice is not suggested, since the winter
wheats are much more desirable. It seems probable that the conditions
which prevail during the growing season may have considerable
influence on the per cent of smut in any given variety."
* * * * *
When Dorn finished his discourse, to receive the thanks of his listeners,
they walked back