376 
THE TROPICAL AGRICULTURIST. Pecember i, 1887. 
Owing to the impossibility of keeping much stock in 
Bermuda the demand for farmyard manures greatly 
exceeds tne supply. In this connexion it is worth 
drawing the attention of farmers to the compressed 
manure which is now being prepared by the Horse 
Car Companies of New York and Philadelphia, and 
6old by them at a moderate price. 
Another manure which has been highly recom- 
mended for onions is wood ashes, either scattered on 
the surface at the time of sowing or mixed with 
swamp-muck in the proportion of one load of ashes 
to 10 or 12 of muck. This is said to answer well, 
but the large percentage of potash in the ashes 
might, in my opinion, be dangerous where the onion 
disease is prevalent, as it has recently been suggested 
that potash manures foster the development and 
growth of fungoid diseases. 
Guano is a very good manure when used in con- 
junction with others, but it should not be relied 
upon to the exclusion of natural manures. Owing to its 
very variable composition it should always be pur- 
chased on analysis, and samples should be analysed 
from time to time to see that, what is supplied is 
up to the standard. 
There is the old recommendation with which we 
are so familiar to burn all infected plants, but this 
is only likely to be the case if the destruction of 
the refuse is universally practised. It is little use 
for one farmer to burn the diseased plants if his 
neighbour does not. And it must always be borne 
in mind that a small patch of diseased onions, only 
a few square yards in area, will produce enough 
spores to infect every onion plantation in the Islands. 
It has been shown that the onion disease is per- 
petuated from one season to another by means of 
resting spores which lie in the ground during the 
summer and autumn, and which germinate when the 
new crop of onions begins to appear. In northern 
climates it is probable that many of the resting- 
spores are killed by the frost ; unfortunately we cannot 
reckon upon the assistance of this agent in Bermuda. 
Rotating the crops is advised, but mixing arsenic 
with the soil is not mentioned. Mr. Shipley writes: — 
If there is any reason to suspect that the farmyard 
manure is a means of infection, through some refuse 
of a diseased onion crop being mixed with it, or from 
any other cause, it would be advisable to water the 
manure with a week solution of iron sulphate (F2SO4 I 
before putting it on the land. One-tenth of a gramme 
in 100 grammes of water, or a solution of one-tenth 
per cent is sufficiently strong to kill the spores of 
the fungus. Again, if the seed is considered to convey 
the infection, they may be soaked in a solution of the 
same strength. This will effectually kill all the spores 
of the fungus, and leave the seed entirely uninjured. 
We now come to Mr. Morris's cure for coffee fungus, 
effectual if it could have been universally applied : — 
The first of the chemical remedies which may be 
applied to the diseased plants with considerable pros- 
pect of success is a mixture of freshly burnt quick- 
lime and sulphur. 
There can be no difficulty in obtaining plenty of 
quicklime in Bermuda, and for this purpose it most 
always be used when freshly burnt as quicklime loses 
its caustic properties and undergoes chemical change 
when kept any length of time. After burning it 
should be crushed to a powder and mixed with powdered 
sulphur in the proportion of two parts of quicklime 
to one part of sulphur. 
This mixture may be sprinkled on the diseased plants 
by hand or more effectively by means of bellows, such 
as the Kentish hop-growers use for sulphuring the hops. 
The mixture should be applied befor the dew is off 
the plants or after rain whilst the plant is still wet. 
The chemical interaction which is produced by the 
mixture of sulphur and freshly-burnt quicklime leads 
to the forma! ion of sulphurous acid and other allied 
gases. The gases are evolved slowly, and being readily 
diffusible they soon spread over the plant, and being 
easily soluble in water they dissolve in any moisture 
in the leaves, &c. The solution thus formed is strong 
enough to kill the germinating spores without injuring 
the plant, and it does not become concentrated to a 
dangerous degree. The final products are not harmful 
to the plant or soil, and the chief use of 6ulphate of 
lime is a valuable manure, especially in Bermuda, 
where the amount of sulphur in the soil is very slight. 
A second chemical remedy which may be used for 
the onion disease is iron sulphate (F28O4), and this 
has the advantage of being readily soluble in water, 
and hence can be applied in the liquid form. Whea 
in a week solution the iron sulphate will kill the fuugus 
without killing the onion plant. The solution should 
contain one-tenth part FjS0 4 to 100 parts of water. 
It may even be made as strong as three-twentieths 
per cent without injury to the plaut, but anything 
stronger than this is like to prove injurious. 
The diseased onions may be watered with this, or, 
still better, sprayed thoroughly. The ground in the 
vicinity of the affected plants may also be watered 
with advantage with this solution; in this way any 
spores which have fallen off will be destroyed! 
In addition to its antiseptic properties iron sulphate 
forms a very valuable manure. In a paper published 
in the Journal of the Chemical Society, 1886, Mr. 
Griffiths has described many experiments which all 
tend to show the value of this chemical as a 
manure. I will content myself with quoting from 
his paper the results of one experiment. Mr. 
Griffiths sowed three plots of ground the same size 
with potatoes. The first plot of ground was not 
manured ; from this he gathered three tons of pot- 
atoes. The second plot, which was well manured, 
gave six and a half tons; whilst from a third plot, 
which was well manured in the same way as the 
second, but with the addition of iron sulphate, 
he obtained eight and a half tons of potatoes. This 
is only one experiment out of many which all tend to 
show the value of iron sulphate as a manure. 
The iron sulphate should be applied as a top-dress- 
ing after the plants have been transplanted. About 
half a hundredweight should be used to the acre : more 
than this is apt to prove harmful. 
It has been found that wheat crops grown in fields 
manured with iron sulphate do not suffer with the 
wheat mildew, and it is very probable that if the 
land be treated in the manner indicated, potatoe 
and onion crops would also escape the fungus* 
Iron sulphate has the further advantage of being 
very easily obtainable at a very moderate cost. 
There is a second fungus found living upon the onion 
plant. This is known as Macrosporium parasiticum, 
and it is one of the Pleosporous Ascomycetes. 
This fungus is only found upon the onion after it 
has been attacked by the Peronospora, when the 
leaves are already dead or dying. It does not attack 
the healthy plant. 
Macrosporium belongs to that class of fungi which 
are known as Saprophytes ; these are characterised 
by living upon dead or decaying organic matter. 
They are unable to effect a foothold upon the healthy 
plant. Hence if the Peronospora can be exterminated 
the Macrospormm will disappear at the same time. 
The fact that the Macrosporium is, so to speak, 
a sequel to the Peronospora, and that with the ex- 
termination of the former the latter will disappear, 
renders it unnecessary to describe the very complic- 
ated and incompletely known life history of the 
fungus. 
The summary of Mr. Shipley's observation and 
conclusions is as follows: — 
1. The onion disease is caused by a fungus Peronos- 
pora Sciileidcniana, which lives parasitically upon the 
ieaf on the onion plant. 
2. The atmospheric conditions which favour the 
progress of the disease are heavy dews or rains 
followed by warm, moist calm weather, and the ab- 
* All the remedies suggested for the onion disease 
apply with equal force to the potato disease, which 
is caused by a fungus, Peronospora infestans, a species 
distinct from Peronospora Schteideniana, but resembl 
iug it in its life-history. 
