58 
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March, 1889. 
/orchard 
fjUkVUM^ 
GARDEN 
CONDVCTED BT PROF. F. LAMSON SCRIBNER, 
Botanist Experiment Station, Knoxville, Tenn, 
Potato Rot. 
We know that potato rot is due to the at- 
tacks of a fungus. 
We know that this fungus is a true para- 
site and that all kinds and varieties of pota- 
toes may be attacked by it. 
We know that a high degree of humidity 
is necessary for the development of the fun- 
gus and that its attacks are most virulent 
during wet, sultry weather. 
We know that heavy undrained land and 
clayey soils favor the disease. 
We know the appearance of the disease on 
the tops and how quickly these may become 
affected and destroyed. 
We know how seriously the tubers may 
become affected and how the loss from rot 
may amount sometimes to more than one 
half of the crop. 
All do not know that these tubers are 
generally infected by spores from the tops 
washed into the soil by rains. 
We know that the fungus in germinating 
usually produces zoospores, that these zoo- 
spores are exceedingly minute particles of 
naked protoplasm, and that they are ex- 
tremely sensitive to circumstances unfavor- 
able to their further development. 
We know that these zoospores rest for a 
short time upon the surfaces of the plants 
they are destined to enter by further de- 
velopment. 
We know that it is by the penetration of 
these zoospores into the potato plants that 
the latter become infected with blight and 
rot. 
We know that every minute quantities of 
sulphate of copper will destroy these zoo- 
spores. 
We know that the fungus enters the 
tubers and that if these are placed where it 
is warm and damp that they will quickly 
rot. 
We know that by keeping the tubers dry 
and in a cool place they are not likely to rot 
although the fungus may already have at- 
tained some growth in them. 
We know that the fungus lives through 
the winter in the tubers and that the plant- 
ing of such potatoes serves to carry infection 
to a new crop. 
We know that the fungus in the tubers 
may generally be detected by a discoloration 
or browning of the flesh underlying the skin. 
We know, from what has just been said, 
that such potatoes should never be used for 
seed. 
It is said that the seed may be disinfected, 
that is, the fungus in the tubers used des- 
troyed, by soaking the whole potatoes for 24 
hours in a solution of sulphate of copper — 
four ounces in water enough to cover one 
bushel. 
R is said that the tubers may be disinfect- 
ed by keeping them for a few hours at a 
temperature of from 105 to 110 degrees. 
This degree of heat is said to kill the fungus 
without destroying the value of the tubers 
for seed. 
It appears from the above that: 
We ought to disinfect the seed potatoes by 
heat or by soaking in blue vitriol solution, if 
there is any question as to their containing 
the parasite, remembering that this cannot 
always be told by the eye. 
We ought to select for planting a light 
sandy loam, or certainly a soil well drained. 
We ought to spray the tops with some solu- 
tion of sulphate of copper that will adhere 
well in order to effect the destruction of the 
zoospores that may come upon them. After 
these spores have penetrated the plants and 
the disease appeared, the applications will 
have comparatively little effect. 
We ought to store our potatoes where no 
dampness will collect about them, and 
where the temperature is low, say 35 to 45 
degrees. 
Downy Mildew of file Vine. 
Peronospora Viticola. 
According to Sig. G. Cuboni, this parasite 
of the vine occurs in two forms: (1) “ forma 
palese ” on the flower-stalks either before or 
after flowering, numerous conidiophores ap- 
pearing through the stomata, and causing 
the flower or young fruit to perish ; and (2) 
“ forma larvata” on the fruit when nearly 
ripe, bringing about discoloration and decay 
(brown rot) ; in this form no conidia appear 
on the surface, but the pulp is permeated by 
the characteristic mycelium with its globu- 
la haustoria, as illustrated in the last vol- 
ume of Orchard & Garden (page 80, figure 
1489). Infection takes place on the flower- 
stalks by the conidia formed on the leaves ; 
the fungus spreads from them to the berries, 
and not from the berries backwards on to 
the axis. The mycelium appears to retain 
its vitality for a long time in the dead fruits. 
The remedy recommended is the copper 
sulphate, which applied in season, prevents 
the germination of the conidia on the flower- 
stalks. 
■ 
Experiments In Combating the Pero 
nospora of the Vine In Italy. 
Through the kindness of Dr. Cavara, of 
the Royal University of Pavia, Italy, we 
have received the report of the director, 
Giovanni Briosi, to the Italian Minister of 
Agriculture, on the experiments in that 
country made in 1888 in combating the 
Downy Mildew of the vine. The remedies 
experimented with were solutions of sul- 
phate of copper, sulphate of nickel and boric 
acid. After detailing the manner of prepa- 
ration and way in which the solutions were 
used the results or conclusions are presented 
as follows : — *• From our own experiments 
and from that of others in the regions north 
of the Po, it is clear that the remedy which 
has been most generally successful is the 
sulphate of copper whether used in simple 
solution or mixed with lime. In a very 
rainy season, like that of 1888, the sulphate 
of copper and lime mixture manifests 
greater efficiency on account of its greater 
adhesiveness to the foliage ; in the simple 
solution the small amount of copper remain- 
ing on the leaves is very easily washed off 
or carried away by heavy rains. 
“ It is known also that the simple solution 
is more likely to injure the vines, by burn- 
ing the leaves, than the mixture with lime, 
especially in the early part of the season 
when the foliage and shoots are young and 
tender. The numerous samples of leaves 
thus injured received at the laboratory 
show that this injury is greater and more 
frequent than is usually supposed. 
“ It is well, therefore, to add to the solu- 
tion of sulphate of copper a small amount 
of lime, enough at least to neutralize the 
sulphate. Eight to ten kilograms (1 kilo- 
gram=2 1-5 lbs.) of sulphate of copper and 
four or five kilograms of lime in one thous- 
and litres of water (1 litre=l% pints') ought 
to give the best results. 
“ The boric acid preparation has not been 
efficient, and the results obtained with sul- 
phate of nickel are inferior to those with 
sulphate of copper. 
“ No case of poisoning in consequence of 
the applications of the copper mixtures, the 
treated grapes are eaten by everyone with 
impunity. 
“ It will be noted that purchasers and 
dealers in grapes will favor those proprie- 
tors who have treated their vineyards with 
the solutions of copper, because their fruit 
will be larger and more beautiful and much 
richer in saccharine matter.” 
Injuries produced by Parasitic Fungi 
upon tlieir Host-plant*. 
In a paper published in the American 
Naturalist, (yol. xxi. p. 1114.), Prof. A. B. 
Seymour discusses the various ways in 
which parasitic fungi injure their host- 
plants. (1) They deprive them of nourish- 
ment; this is by far the most important and 
general injury which is produced upon 
plants by parasitic fungi. (2) While the 
food supply of the plant is reduced, its 
power to replenish it is at the same time im- 
paired, i. e., in case the fungus grows upon 
the green parts, as it does most frequently. 
(3) Growth may be abnormally accelerated 
or retarded, and both these effects may be 
produced in different cases by the same 
fungus, thus causing distortion; (4) Not 
only the green parts are affected, but roots, 
stems, inflorescence, flowers and fruit. (5) 
Leaves and fruit when diseased fall prema- 
turely. (6) Many fungi cause decay of 
ripe fruit both while attached to the plant 
and after removal while still alive. 
Some valuable plants are liable to injury 
by infection from plants- of less value which 
may serve as host-plant to the fungus dur- 
ing a certain period of its development. 
Certain groups of flowering plants are 
liable to be attacked by certain species of 
fungi. 
