March, 1890. 
AND 
GARDEN 
57 
/ ORCHARD 
objection to this plan is that the beetles are 
not destroyed, but are only driven to new 
pastures. 
Probably the most practical method of 
dealing with these beetles is to destroy the 
adults when feeding upon the foliage. For 
this purpose nothing is cheaper or more 
effective than Paris green and London pur- 
ple. Prof. Cook says, “ I have no doubt 
that a tablespoonful of either one of these 
two insect poisons, mixed with two gallons 
of water, would be quick death to these 
little pests if sprinkled upon the vines.” 
Prof. Forbes states “ that a small bed of 
strawberries upon the University grounds 
was attacked bv the beetles of Paria ater- 
rima, that the vines were dusted with Paris 
green, and that the beetles immediately 
disappeared, no further injury being done 
to the vines. There are thus good reasons 
to believe that the beetles would be de- 
stroyed by this treatment, and thus the 
presence of the grubs in destructive num- 
bers provided against. The t me for apply- 
ing the poisons will of course vary with the 
species to be dealt with. If both species 
are present several applications will be 
necessary. The first spraying should be 
done in April when Paria is feeding upon 
the young leaves. A second application 
will probably be necessary in June when 
Scelodonta is destroying the foliage, and 
perhaps a third will be required in August 
or September when Paria again appears. 
Of course care should be taken not to spray 
just before the fruit is picked. Another 
remedy which it might be well to try is a 
strong decoction of tobacco or tobacco 
stems. Last season we used it upon flea- 
beetles with apparent success. The beetles 
left the vines at once and did not return. 
To make the decoction we steeped a double 
handful of tobacco in twelve or fourteen 
quarts of water, then strained out the leaves 
so that we could apply with a force pump. 
Conducted by Prof. F. Lamson Scribner. 
Botanist, Experiment Station, Knoxville, Tenn 
Bordeaux Mixture for Potato-rot. 
At the Ohio Agricultural Experiment Sta- 
tion during the past season, 1889, Prof. Clar- 
ence M. Weed experimented with the Bor- 
deaux mixture in treating Potato-rot, ap- 
plying it May 28, June 6 and 29, and July 
10. The applications were made to 15 feet 
at the end of each of twenty rows. 
The season proved favorable for the de- 
velopment of the blight which appeared 
jn the experimental field about the middle 
.of June and did serious damage for the next 
six weeks. 
The crop was harvested August 22nd, and 
the product of 12% feet of the sprayed part 
of each row was compared with the pro- 
duct of an equal distance of the un sprayed 
portion of the same row. It was found 
“that the treated portions of the twenty 
rows yielded a grand total of 2,471 potatoes, 
weighing 320 pounds 7 ounces, and that 
1,128 of these were of a marketable size, 
and weighed 244 pounds 2 ounces; while 
the untreated portions of the same rows 
yielded a grand total of 2,771 potatoes, 
weighing 274 pounds 4 ounces, of which 
948 were of marketable size and weighed 
180 pounds 1 ounce. There was, consequent- 
ly, a grand total increase in favor of the 
treated hills of 46 pounds 3 ounces total pro- 
duct, and 64 pounds 1 ounce marketable 
product. 
This 64 pounds 1 ounce increase in mar- 
ketable product was obtained from 250 feet 
of row (20 times 12%). This represents an 
increase of 4.1 ounces to the foot. As there 
are 14,560 feet of row in an acre of potatoes 
as ordinarily planted, an increase of 4.1 
ounces to the foot amounts to 59,696 ounces, 
or 3,731 pounds to the acre. Reducing this 
to bushels and dividing by 60 (the number 
of pounds to the bushel 1 we get an increase 
from the treatment of 62.2 bushels to the 
acre. “ There was in nearly every case a 
marked difference in the amount of scab on 
the treated and untreated tubers, the former 
being much more free from disease.” 
Prof. Weed concludes that so far as a sin- 
pie experiment ^an be relied upon, the re- 
sults he obtained seemed to indicate: 
“(1) That a large proportion of the injury 
done by the potato rot can be prevented by 
spraying the vines with the Bordeaux mix- 
ture. 
(2) That this treatment apparently di- 
minishes the amount of scab affecting the 
tubers. 
(3) That by adding London purple to the 
mixture, the same treatment may be made 
effective in preventing the injuries of both 
the rot and the Colorado potato beetle.” 
Col. Alex. W. Pearson, of Vineland, N. J., 
used the Bordeaux mixture the past season 
(188.i) in treating potato-rot. He states 
briefly in a private communication to us, 
that the yield on the untreated plat was 164 
pounds; the yield on the treated plat, con- 
taining the same number of hills of the same 
variety, was 346 pounds! The diameter of 
the largest tuber on the untreated plat was 
3 inches; the largest tuber on the treated 
plat, was 5 inches in diameter. 
Black-xpot of die Bone. 
One of the most common diseases of the 
rose in out-door culture, both in this coun- 
try and in Europe, is that bearing the de- 
scriptive name of “Black-spot.” Our illus- 
tration (Fig. 267) drawn from a leaf taken 
in December, represents its characteristic 
appearance, although the spots are rathei 
more sharply defined than is usual earlier 
in the season. Every one who has grown 
roses has doubtless noticed these spots com- 
ing on the leaves, sometimes in early sum- 
mer but more often during the later sum- 
mer or early fall months, and has attribut- 
ed their presence to improper culture, to in- 
sects or perhaps to the weather. The true 
cause, however, is a minute parasitic fun- 
gus by whose action the contents of the 
cells of the leaf tissue is disorganized and 
changed to a deep brown color. It is this 
discoloration of the cell contents, particu- 
larly that in the epidermal cells, which im- 
parts to the spots their dark color. The 
fungus itself is white and transparent, a 
fact we can almost determine without the 
aid of a microscope. By carefully examin- 
ing one of the spots we will see very fine, 
white, web-like and much branched threads 
— the mycelium of the fungus — extending 
from the centre to the circumference where 
they are most conspicuous. These threads 
generally extend a little beyond the dark 
portion of the spots, this extension beinc in- 
dicated by the reddish or yellow irregular 
band surrounding the latter. 
The fungus always attacks the upper sur- 
face of the leaf and consequently the upper- 
most cells in the leaf tissue are the first to 
be affected; the disease soon extends to the 
palisade cells, finally reaching the loose tis- 
sue beneath and the spot becomes visible on 
the under surface. This affection of the 
deeper leaf tissues is caused by branches 
of the mycelium which extend through 
them. 
The effect of the fungus growth upon the 
entire leaf, is of course, to weaken its vital- 
ity and we often see spotted leaves with the 
greater part of the remaining portion yel- 
low, like the “sere and yellow leaf” of au- 
tumn. Leaves attacked by the Black-spot 
lose their connection with the stem and fall 
at the slightest jar. We have seen bushes 
completely defoliated from this cause by the 
first of September. 
Like other tungi the Black-spot is propa- 
gated by spores. These are produced in 
great abundance at certain points on the 
spots. They are formed in groups or clus- 
ters and in their development they push up 
the cuticle of the leaf, finally rupturing it. 
By examining the spots v ith a hand glass 
we can see the points where the cuticle has 
been thus raised. Besides their prominence 
they are blacker than the surrounding parts. 
In order to get a good view of the spores and 
the way in which they are borne, we make 
a very thin section of the leaf with a razor 
including in the cut one of the spore clus- 
