November, 1889. 
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O^RGHRRD 
215 
Our own observations in this direction are 
rather limited but lead us to infer that they 
are of no ava l- We have seen the fungus in 
full development and v ell fruited onleav( s 
| well coated with the Bordeaux mixture. 
The Powdery Jlildrw of the Vine. 
( Uncinula ampelupsidis.) 
In the September number of this journal 
reference was made to the Powdery Mil- 
dews and it was announced that we would 
describe and illustrate some of them, as they 
were of special interest to horticulturists. 
All the species are true parasites attacking 
living plants from which thmy obtain the 
nourishment required for theirown support, 
hence the supporting plants are calle 1 host 
plants. The grape vine is the host plant of 
the fungus which forms the subject of this 
article and which is now generally well 
known as tire Powdery Mildew of the Vine. 
It has been often referred to howevei simply 
as Mildew, but this expression leads to, 
^ confusion for there are two Mildews that 
infest the vine, the Downy ( Peronospora ) 
and the Powdery ( Uncinula), and unless 
some special term is applied to each it be- 
comes uncertain which is meant. Powdery 
is a descriptive term and has been well em- 
ployed to distinguish such fungi (plural of 
fungus) as this Uncinula, for they impart to 
the surfaces upon which they grow a 
marked powdery or mealy appearance 
Much has been said and written about the 
Uncinula ampelopsidis under the name of 
Oi'lium or Oidium Tticfceri, and botanists 
have described it under the names of 
Uncinula spiralis and Uncinula Americana. 
All thees names refer to one and the same 
thing — the Powdery Mildew of the vine 
— a fungus native to the United States and 
found throughout all our grape growing 
regions even to the Pacific coast. In fact, 
it is more injurious in California, on vines 
^■^ithe Vinifera family, than it is in the 
ilastern States. Here it rarely occasions 
serious damage excepting in graperies. The 
European grapes which we grow under 
glass are very apt, unless carefully watched, 
to suffer severely from attacks of this para- 
site. It has been reported to us as being 
very injurious to the same class of vines 
when grown out of doors, as they sometimes 
are in the Gull States. Western New York 
and Northern Ohio is where we have seen 
this fungus most abundant in the open 
vineyard. However, the losses which it 
there occasions are very inconsiderable as 
compared with those caused by the Downy 
Mildew. Here and there on isolated vines, 
we have seen one to several leaves with 
their upper surfaces whitened by the pres- 
ence of this parasite, and also an occasional 
cluster of grapes with its fruit more or less 
^Mamaged by it. The injury done may 
^kmount to a good deal if the clusters are 
attacted when m flower, for fertilization is 
checked or prevented, and doubtless much 
of the disease known as coulure is the result 
of such an attack. 
Unlike the Downy Mildew, Black-rot fun- 
gus, etc., the fungus of Powdery Mildew 
never penetrates the tissues of the host- 
plant but extends its growth on and over 
the surface of the part attacked simply 
sending into the epidermal cells little suck- 
ers through which it imbibes its nourish- 
ment. These suckers are shown in figure 
1616, as small, irregular projections on the 
lower side of the mycelial filaments. The 
plant body of the parasite is, therefore, 
fully exposed to any direct applications 
which may be made to distroy it. 
The Powdery Mildew produces two very 
unlike sets of reproductive bodies — spores. 
During the early part of the season the my- 
celial threads send 
up short, erect 
branches w h i c h 
bear the summer 
or oidium spores. 
These are shown, 
highly magnified, 
in figure 1616. The spores thus produced 
are very numerous and as they are ready 
to germinate as soon as they have fallen 
from their supports, the spread of the fun- 
gus during summer is often very rapid. 
Later in the season the second form of spores 
are produced and as these are carefully pro- 
tected in what may be termed little capsules, 
they serve to carry the fungus over from 
one season to the next, and therefore they 
are sometimes called "winter spores. 
These winter spores are formed in little 
sacs which are enveloped in a hard, globu- 
lar covering from which radiate a num! er 
of delicate appendages which are curled at 
their tips. When mature the globular body 
( termed perithecium ) is black and suf- 
ficiently large to be detected by the unaided 
eye. They are usually abundant by the 
middle of August, especially in the North, 
and appear on the mildewed surfaces as 
minute, black specks. One of these bodies 
with its appendages is shown ; n figure 1617. 
potassium or liver of sulphur, already de- 
scribed in this journal, would doubtless be 
equally efficient and probably more prompt 
in action. 
The Work of ilie Department. 
It is of interest to the readers of Orchard 
and Garden, and to all horticulturists, to 
know how actively the work of the Section 
of Vegetable Pathology in the U. S. Dept, 
of Agriculture is being pushed forward. 
Frank S. Earle, of Mississippi; Prof. E. S. 
Goff, of Madison, Wisconsin, and Prof. L. 
R. Taft, of the Agr. College of Michigan, 
have recently been appointed special agents 
of the Section. Mr. E. F. Smith is contin- 
uing his investigations of Peach Yellows in 
Michigan, and will again visit the peach 
orchards of the East before returning to 
Washington. Newton B. Price has been 
commissioned to investigate the “myster- 
ious” grape disease which appeared in Cal- 
ifornia four years ago, and which already 
has destroyed many hundreds of acres of 
vines in the region south of Los Angeles. 
A number of other special workers have 
been engaged the past season in doing spec- 
ial work in treating the fungous diseases of 
plants, under the supervision of the ener- 
getic chief of the Section, Mr. B. T. Gallo- 
way. Tiie reports of the various workers 
in this important field of research cannot 
fail to be of great practical value and will 
be looked forward to with interest. 
Fig. 1617. 
At the left we have the same with the rad 
iating arms cut off and the spore-contain- 
ing sacs within escaping through a rupture 
in its wall. 
Flowers of sulphur dusted on the vines 
(or. in hot climates, simply spread < ver the 
ground beneath them) serves effectually to 
destroy the Powdery Mildew. No other 
treatment is needed to protect the vines 
from this parasite. In regions where the 
fungus is most injurious it is the custom of 
vineyardists to make at least three applica- 
tions; first, when the young shoots areabout 
four inches long; second, when the vines are 
in bloom; and third, just before the berries 
begin to color. 
Applications of a solution of sulphide of 
Treatment of Apple Scab. 
Prof. E. S. Goff, of Madison, Wis. writes 
us 1 hat, in accordance with our suggestions, 
he has this year employed the ammoniacal 
solution of carbonate of copper for prevent- 
ing the scab in apples. He finds it a much 
more satisfactory and efficient remedy than 
the solutions of hyposulphite of soda and 
sulphide of potassium previously used by 
him. 
Injuries Produced upon Host-plants. 
In a paper published in the American 
Naturalist, (vol. 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 the 
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 
af. er removal while still alive. 
Some valuable plants are liable to injury 
by infection from plants of less value which 
may serye as host-plant to the fungus dur- 
ing a certain period of its development. 
