104 
May, 1890. 
/ ORCHRRD GAR DEN 
lated to the smut of wheat aud oats but its 
spores which constitute the so called “smut” 
possess special characters which serve at 
once to distinguish it. These spores con- 
sist of a central, dark, thick-walled and 
nearly spherical "resting" spore which is 
surrounded by a variable number of thin- 
walled bladder-like bodies named pseudo- 
spores. Together (the resting spore and 
pseudospores) they are called spore balls. 
The enormous number's of these spore balls 
that are produced in a single spot of smut 
may be imagined when we consider that 
the diameter of each spore ball does not ex- 
ceed 75-100000 of an inch. 
The disease tirst appears as a dark area in 
the leaf, which 
finally bursts let- 
ting out the black 
powdery mass of 
spores. Un less 
the onion is killed 
when young the 
same dark areas 
soon begin to ap- 
pear on the bulbs 
between the veins 
and extend up 
through all but 
perhaps the inner 
leaf as shown in 
figure 265, and if 
the onion is cut 
in two horizontal- 
ly, it will be found 
that the outer lay- 
ers are smutted to 
a greater or less 
depth the inner- 
most layers being 
often quite sound. 
As a rule onions 
Fig. 265. Onion attacked by the 
thus affected al- 
Smut Fungus, showing appear 
ance in Midsummer (Redrawn ^vays die, either 
after Thaxter.) drying up or rot- 
ting soon after they are pulled. 
The severity of the disease in different lo- 
calities is variable. It appears at first in 
isolated spots here and there in a field and 
from these it spreads in all directions until 
the whole piece becomes affected and the 
cultivation of onions upon it has to be dis- 
continued. This period from the first ap- 
pearance of the smut to the enforced dis- 
continuance of the onion crop, appears to 
be, on new ground, never less than five 
years, which is the shortest ascertained in- 
terval. 
In considering the conditions favoring 
the development of smut little account is 
made of the general weather conditions and 
the influence of the soil is regarded as in- 
considerable. The notion that potash ferti- 
lizers form smut is doubtless wholly un- 
founded; but whether those fertilizers 
which are rich in xiitrogen favor the growth 
of smut is a question which may be exam- 
ined with profit. 
As to the liability of different varieties of 
onions to smut it appears that the yellow 
and especially the red kinds are less sus- 
ceptible than the white. 
The dissemination of smut may occur 
through the transportation of soil contain- 
ing the spores or on farming tools, or on the 
feet of man or animals; the spores may be 
washed with the surface earth from higher 
to lower ground, or they may be blown by 
the wind about the same field or into ad- 
joining fields. Insects may assist in scat- 
tering the spores from place to place and 
they may be carried on seeds grown in 
smutted districts, the spores adhering to the 
surface of the seeds as any small particles 
of dust might do. 
The germinating power of onion smut 
spores is retained for a long period ; state- 
ments which place this period at twenty or 
twenty-five years may not be greatly exag- 
gerated. The endurance of smut is so pro- 
tracted that discontinuance of the crop can- 
not be considered a remedy of any consider- 
able value. 
It may be assumed with tolerable safety 
that the smut makes its entrance into the 
onion seedling in the ground. That infec- 
tion ever occurs in the portions of older 
plants above ground has not been definitely 
proven. It is evident, then, that in consid- 
ering any means of treatment by fungi- 
cides, the usual external applications would 
be quite useless. The fungicides must evi- 
dently be employed so as to act under- 
ground during the period of germination 
of the seed. This is best accomplished by 
applying the material, or sowing it, in the 
drills with the seed. 
In his experiments Dr. Thaxter applied 
in this way a number of substances includ- 
ing sulphate of iron, sulphate of copper 
and lime, sulphide of sodium, hyposul- 
phite of scdium, and flowers of sulphur 
with air slaked lime. The onions came up, 
for the most part, during the first week of 
May and showed abundant evidences of 
smut by May 10 while still in the first leaf. 
A considerable number were killed in the 
second leaf, a few even before this. By 
May 18, when the onions were examined, 
the different appearance of the treated and 
untreated rows in some of the plots began 
to be apparent, and by the first of June was 
very marked. Those treated with sulphur 
and lime and with sulphide of potassium 
were not only visibly thicker, but much 
taller and healthier in appearance than the 
alternate untreated rows. There was also 
a visible, though not so striking, difference 
in the sets treated with hyposulphite of 
soda. The sets treated with iron showed 
no appreciable differences between the 
treated and untreated rows, while the cop- 
per application was evidently injurious, the 
detrimental effect upon the onions them- 
selves not being compensated for by any 
appreciable action on the smut. 
Of the substances used to prevent the dis- 
ease sulphur alone merits consideration 
from a practical standpoint, sulphide of so 
diura yielding no better results, being ex- 
cluded because of the trouble and expense 
involved in its application. Referring to 
the results of his experiments, Dr. Thaxter 
remarks that it is manifestly unsafe to gen- 
eralize from a single experiment and it can 
merely be said now that flowers of sulphur 
cffer a promising substance for the desired 
purpose. 
Precautionary measures against smut : All 
refuse of whatever kind that is left on the 
field should be burned as soon as prac- 
ticable, and although onion land is us- 
ually kept so clean that it cannot be burned 
over in the fall, this practice will be found 
very advantageous when it is possible. 
At the second and subsequent hand weed- 
ings all onions which show smut in the sec- 
ond or third leaf should be pulled, collected 
in a basket or other convenient receptacle, 
and burned at once. A single large onion 
may mature during the season something 
like a cubic inch of smut, which means be- 
tween one and two thousand millions of 
spores, each capable of producing a smutty 
smut, any more 
than it would be a 
remedy to stop 
raising onions alto- 
gether in affected 
sections. 
Fig. 2. a. Spore ball of the 
Onion Smut Fungus: b. Opti- 
cal section of same. x= pseu- 
dospores, x'= resting spore; 
c. Spore germinating in a 
moist chamber, producing 
sporidia x. (Redrawn after 
Thaxter.) 
Black-rot Treatment. 
As verifying statements already publish- 
ed by us, we quote here the conclusions 
reached by Mr. Galloway, chief of the Sec- 
tion of Vegetable Pathology, from exper- 
iments made under his dii'ection at East- 
ham, Virginia, last season: 
(1) It pays to treat vines for Black-rot. 
(2) The best preventive, all things con- 
sidered, is the Bordeaux mixture, contain- 
ing 6 pounds of copper sulphate, 4 pounds 
of lime to 22 gallons of water. 
(3) As the amount of copper in the Bor- 
deaux mixture is decreased its value as a 
preventive is lessened. 
(4) The application of the Bordeaux mix- 
ture should in all cases begin early, i. e., 
about the time the flowers are open. 
(5) Spraying the vines before the leaves 
start with a simple solution of sulphate of 
copper is decidedly beneficial. 
We have usually recommended, on ac- 
count of its cheapness, sulphate of iron for 
the winter treatment; but undoubtedly sul- 
phate of copper will serve equally well and, 
as a much less quantity of this substance 
would be required, there need be little if 
any difference in the expense. 
O 
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