December i, 1887.] THE TROPICAL 
AGRICULTURIST, 
375 
ROYAL GARDENS, KEW. 
(Bulletin of Miscellaneous Information.) 
ONION DISBAsK AT DKRMUDA. 
( Peronospora ScMeideniana, Dc Bary.) 
It seems as if pests were sure to attack any 
product largely grown, from potatoes up to coffee ; 
the latest victim is tlie ouion in Bermuda, regard- 
ing which we get information from Kcw, as follows : — 
The current Bullet in is occupied with the re- 
sults of an inquiry conducted under the auspices 
of the Royal (iardens, into a disease prevalent at 
the Bermudas affecting the onion crop, which is a 
staple industry of these small islands. Owing to 
climate and geographical position these islands are 
enabled to raise large quantities of early vegetables, 
Which are shipped and sold at New York at a time 
when the corresponding American produce has as 
yet scarcely shown itself above ground. The onion 
crop, amongst others, raised from seed obtained 
from Teneriffe, has hitherto proved most productive ; 
but owing to causes which are discussed in the 
following pages, this crop has latterly proved less 
remunerative. An inquiry was desired in the in- 
terest of cultivators, and this inquiry was undertaken 
by Mr. Arthur Shipley, B. A., Fellow of Christ's 
College, Cambridge. Mr. Shipley's reports deal 
with the circumstances connected with raising and 
harvesting of onion seed at Teneriffe, and with an 
exhaustive inquiry carried on at Bermuda, while the 
usual crop of onions was being raised for the American 
market, The results of the inquiry are given with 
great clearness by Mr. Shipley, and remedial and 
other measures are suggested which deserve the at- 
tention which no doubt they will receive from the 
persons directly interested. 
We quoto some interesting information on the onion 
cultivation of the Canary Islauds : — 
There are two varioties of onion grown in the 
Canary Islands, the white and the red. These 
varieties are not permanent, but pass into one 
another under altered conditions of the soil, &c. 
The whito variety is chiefly grown in the Island 
of Palma and on the south side of Teneriffe, in 
the neighbourhood of Santa Cruz. Those grown 
in Teueritfe gradually lose their character, become 
reddish in colour, and after three years' cultivation 
are indistinguishable from the red variety. Those, 
however, grown "in the Island of Palma niaiutain 
their character unchanged, heuce the seed for ex- 
port is obtained from the latter island. The red 
variety is grown on the north side of Teneriffe, 
chiefly iu the neighbourhood of Tejina. 
The strain of onions is preserved from deterior- 
ation by alternating the onion crop with Indian corn, 
or more usually with potatoes, or by planting the 
onions in newly cleared ground. Thus the same field 
does not bear onions iu two successive years. 
The shipping prices for the onions themselves this 
year ( lHSl) were from 3-. to 4s. 6d. a quintal (100 lb), 
for the white, and 2.<. (id. to is. a quintal for the 
red< Tho white variety comes into tho market rather 
earlier than the red, and thus commands a rather 
higher price. 
On the disease iu Bermuda, Mr. Shipley reported 
fully, and he writes : — 
I had tho advantage of the assistance of Professor 
Marshall Ward of tho Indian Civil Engineering 
College, a Well-known authority upon fungoid diseases. 
This, of course, is the mycologist who reported on ou r 
cotfoo fungus. Mr. Shipley states : — 
The disease amongst the onions in Bermuda is caused 
by the presence of a microscopic fungus which lives 
pnrasiticnlly upon the leaves of the onion plant. This 
fungus is known to botanists under the name of 
PiwfltjWfB SelUtUtmant. De Bary, (B"trytis Dmtructor, 
Berkeley,! an ! amongst the onion farmers of the 
Old World as the Onion Mildew. 
It belongs tt the sumo order of fungi as the well- 
know n potato fungus. Its geographical distribution is 
tot wJI falOWU, hut it occurs iu England, Otruiauy, 
and has, I believe, been found in the United States. 
Tho symptoms are thou described, and it is observed 
that : — 
The conditions of the atmosphere which are 
favourable to the development aud growth of the 
fungus, and heuce to the progress of the disease, 
are heavy dews or rains followed by warm, moist, 
calm weather, aud the absence of direct sunlight aud 
strong winds. Shady and sheltered spots are ubually 
the most liable to be attacked. 
The land along the south side of Hermuda usually 
keeps free from the disease, and this freedom from 
attack is attributed by the planters to the fact that 
there the onion plants are exposed to the early 
morning sun and to the prevalent northerly winds, 
which rapidly cause the dew to evaporate. 
The progress of the disease is sometimes arrested, 
after it has appeared in a field, by cold windy weather 
aud strong sunshine, but this is rarely the case; as 
a rule, when it has once appeared it spreads with 
great rapidity, large fields becoming affected in the 
course of a single night. 
The Structure and Life-History of tho Fungus 
Peronospora ScMeideniana, is very fully given, but 
we need not quote the technical details. 
The power of reproduction of the fungus like that 
of the coffee pest is great : — 
If we take 20 as the average number of spores 
upon one stem, and that is rather below than above 
the average, we fiud that a single square inch of a 
diseased onion leaf may have the enormous number 
of (20 x 7,000) 140,000 spores, each capable of repro- 
ducing tho fungus, and hence the disease. 
Some of our planters were inclined to trace the 
development of HeniiUia vastatrix to the application 
of artificial manures, but no evidence supporting this 
view was obtained. Mr. Shipley, however, writes :— 
There seems to be some connexion between tho 
extensive use of artificial manures and the origin and 
spread of fungoid diseases. The potato is frequently 
attacked aud largo crops destroyed by fungus which 
is nearly related to that causing the ouion disease. 
The potato was introduced into Eugland MOO years 
ago, and for about 250 years it flourished without, as 
far as is known, auy disease appearing among the 
cultivated varieties. But about 50 years ago, the Potato 
Fungus, Peronospora infestans (Phytophthora infestans, 
De Bary) made its appearance, and has never siucc 
disappeared. Its appearance was roughly coiucidout 
with the first general use of artificial mauures. A 
similar couuexion might be shown to exist betweeu 
the origin aud spread of the onion disease fungus, 
which did not make its ap2>o.»ranco till eight or 10 
years ago, aud the recent extensive use of artificial 
manures iu the Bermudas. 
Remedial measures are then treated of. We quote 
as follows : — 
It is important to emphasise the fact that manures 
must not be looked upon as a means of curing the 
disease, but simply as a means of strengthening the 
crop of onions. 
With regard to the kind of manure it is the uni- 
versal opinion amongst the onion-cultivators of Europe 
and America that natural mauures are preferable 
to artificial. Of these that from tho hog-pen is 
perhaps the best, aud an excellent manure for onion 
is made by putting seaweed under the hogs. Stable 
manure is also very valuable, but it cannot bo too 
strongly stated that the liquid parts of the natural 
manures are the most valuable, hence cire nm-t be 
taken to prevent their draining away. The manure 
should be well rotted ; during the fermentation 
wbieh then goes on it loses little of its valuable con- 
stituents whilst it becomes more concentrated. At 
the samo time some of its constituents ire rendered 
more soluble, aud hence aro more easily washes! into 
tho soil and more readily taken up by the plant. 
If kept in heaps it should be turned once or twice, as 
by this mcanuiauy of the s lids of weeds arc dietrojeJ 
