October, 1889. 
193 
ORC HR.R D fepy G R RDEN 
r g yvwN 
Conducted by Prof. F. Lamson Scribner, 
Botanist, Experiment Station, Knoxville, Tenn. 
Black-rot of Hie Apple. 
(Macrnphnma malnrvm.) 
We have frequently observed a rotting of 
apples, the peculiar character of v\ hioh 
leads us to designate it as the Black-rut of 
this fruit. It is not a new disease for the 
fungus causing it has been known to my- 
cologists for many years. We had our at- 
tention called to it this season by its ap- 
pearance on the fruit of an early variety 
growing in our yard, many of the apples 
beginning to rot while yet hanging on the 
tree. Brown, decayed spots, often of con- 
siderable extent, appeared on the sides of 
the apples generally starting near the stem, 
sometimes from the flower end and spread- 
ing gradually over th > surface. After a 
time, usually brief, the central portion of 
the brown spots became darker in color and 
finally quite black. In this blackened area 
there then appeared numerous little elevat- 
ed points or pustules which in their forma- 
tion or growth ruptured the skin. They 
are often disposed in well d .'fined concentric 
circles or zones over the decayed area. These 
little pustules called to mind those which ap- 
pear on the grape when that fruit is affect- 
ed with Black-rot, the color and the more 
or less depressed surrounding surface in- 
creased the resemblance. 
Cutting open an apple through the decay- 
ed part the tissues for a considerable depth 
were found to be rather dry and while the 
mass was for the most part of a dull brown, 
there were scattered through it streaks 
or blotches that were nearly or quite black, 
this was especially marked in the tissues 
immediately underlying the pustules. The 
external characters of this form of rot are 
rot unlike those presented by “Bitter-rot of 
Apples” described on page 348 of the Re- 
port of the U. S. Department of Agriculture 
for 1887; the fruit is affected much in the 
same way and although differences in the 
appearance of the pustules may be detected 
by an expert, only a microscropicel exami- 
nation of the fungus will serve to clearly 
reveal the distinguishing features. Figure 
1606 illustrates the microscopical appear- 
ance of a section cut vertically through one 
of the pustules that occur on the apple; it 
shows the fungus in fruit and if this figure 
be compared with figures 1 and 2, plate III 
of the report of the Chief of the Section of 
Vegetable Pathology in the agricultural re- 
port above referred to, which illustrates a 
similar view of the fungus of Bitter-rot, the 
dissimilarity will appear evident enough. 
Our illustration, as we have said, shows a 
highly magnified view of a vertical section 
through one of the pustules including a 
small portion of the surrounding tissues of 
the apple. The pustule is formed by a 
black and thick walled body w hich has 
pushed its way through the skin of the ap- 
ple and in its interior are produc- 
ed the spores or “seeds” of the fungus. 
These spores are supported on short stalks 
which spring from all parts of the interior 
of the ca\ ity; they are filled with a granu- 
lar contents which is at first colorless but 
becomes a dark divaceous green at matur- 
ity. The ripe spores break away from their 
supports and escape through the opening at 
the top indicated in the figure. The spores 
are oblong in shape, broadly rounded at the 
ends and comparatively large being 30 mi- 
cromillimetres or 1-1181 inches in their 
longest diameter. 
Surrounding each of the fruiting bodies 
of the fungus and abundantly spreading 
everywhere in the diseased tissue of the 
affected apple was the mycelium of the fun- 
gus, nearly colorless and thin walled in the 
tissue that was simply brown but very dark 
or almost black and thick walled in the parts 
immediately surrounding the pustules and 
in the black streaks and blotches conspicuous 
in the decayed parts. It is the growth 
of this mycelium in the tissues of the apples 
which induces the changes termed rotting. 
Black-rot of apples is common to both 
sides of the Atlantic but we have no 
data upon which to base an estimate or even 
to form much of an idea of the extent of 
the injury or losses occasioned by it; nor 
can we at this time propose any method of 
treatment which would be likely to be ef- 
fective and at the same time practical. 
The Potato Kot 
The cause of the disease . — There are sev- 
eral kinds of potato rot, both wet and dry, 
which are due to several causes, but the po- 
tato rot — the disease which the planter al- 
ways has in mind when he says his potatoes 
are being destroyed by the rot — results from 
the growth of a parasitic fungus upon the 
potato plaut, similar in habit and botanical - 
ly related to the Downy Mildew of the Grape 
vine. The growth of this fungus is favored 
by and even dependent upon certain climat- 
ic conditions, so much so that some have 
supposed the disease to be caused by the cli- 
mate or by special conditions of the atmos- 
phere. Some have thought that the disease 
was due to an enfeebled condit’on of the po- 
tato plant itself, the result of many years 
of cultivation, but there is nothing to prove 
that this is the case. The disease has never 
been more destructive than during the years 
1843 to 1845 and the wild potato is as sub- 
ject to the malady as are the cultivated va- 
rieties. It is not the climate, nor the soil, 
nor any vital exhaustion of the potato itself, 
that causes the rot; the disease comes di- 
rectly from the attacks of the minute para- 
sitic plant (the fungus named Phytophthora 
infestans) which infests the potato, penetrat- 
ing in its growth both the tops and the 
tubers. 
The effect of the fungus on the tops of the 
potato is to cause what farmers term 
“blight.” If the tubers are infected they 
wall very soon begin to rot and, unless dug 
within a short time, many of them will be 
found entirely decayed when harvested. 
The potatoes may continue to decay after 
the> are stored, especially if the tempera- 
ture is warm and the atmosphere moist. 
Treatment of the disease . — Briefly. In the 
treatment of potato rot we ought to select 
for planting a light, sandy loam or a soil 
which is well drained; plant perfectly sound 
or disinfected seed; spray the tops with the 
Bordeaux mixture or some preparation con- 
taining sulphate of copper; store in a cool, 
dry place, and keep dry. — Ex. from Vol. II 
No. 2 of Bulletin of Tenn. Aq'l. Ex. Station. 
A iilliracnose of (lie Beau. 
(Collet otri chum lindemuUiranum.) 
We have described and illustrated this 
disease elsewhere (Report U. S. Depart. 
Agriculture, 1887, p. 361, plate VI.) and 
while we have no new facts to present re- 
specting it we believe that an explanation 
of the cause of the malady will interest the 
readers of Orchard and Garden and per- 
haps be new to some of them. The season 
here has been very wet and the effects of 
the Anthracnose of the Bean have been 
brought home to us by the injury done in 
our own garden and it was from our garden 
that the specimens were obtained from which 
the present illustrations were 
'X . drawn. Figure 1607 represents 
^ the appearance of a pod which 
has been attacked by the anthrac- 
nose and those who have ever had 
anything to do with this crop will 
hardly fail to recognize it. 
The disease is wide spread; we 
have seen it in Maine and have 
had specimens of affected pods 
sent us from Alabama, and in F.u- 
rope it is well known. Here it is 
too common. All varieties of 
“string” beans may be attacked, 
those with green pods as well as 
the wax or butter beans, and the 
field varieties are by no means ex- 
empt. The damage to the field 
crop is often very considerable, 
and in small gardens we have se r n 
Fig. 160 ~. the produce completely ruinea by 
it. If the disease is light it may simply 
cause dark reddish well defined but su- 
perficial spots on the pods and go no furth- 
er. In severer cases these spots enlarge 
sometimes by the union or running togeth- 
er of two or more of them, the cuticle of 
the pod is destroyed, the diseased area be- 
comes depressed, the central portion as- 
sumes a dirty grayish tint and the border a 
