Deo. 1, 1899.] THE TROPICAL AGRICULTURIST. 
377 
the stems of trees a large paint brush can be need 
in place of the spraying machine, 
McDougal's Insecticide Wash. — This is another very 
useful patent insecticide, also of a soapy natnie. As 
the ingredients are kept secret, the same objection 
applies to its extensive employment upon tea plants. 
It is equally effective against scale insects. The 
two mixtures (Strawson's and McDougall's) were 
tested upon Orlhczia with similar benefical results. 
It is used as a spray. 
The above two insecticides may be safely employed 
'against green bug' 'or mealy bug' on coffee, and 
woold be found very benefical in checking these 
pests tcherethey are confined to a small area. The treat- 
ment would be too expensive over a large acreage, 
and would be useless unless applied very thoroughly. 
Adhatoda. — A decoction made by steeping the leaves 
of Adhatoda vasica (an Indian plantjin water is said 
to have proved benefical against various insect pests 
in India, but I can find no record of its effect upon 
scale insects. Dr. Watt (Eeporter on Economic 
Products to the Indian Government), who first brought 
into notice the properties of the plant as an insecti- 
cide, states that it has a distinctly paralysing effect 
upon many insects. But he appears to have found 
it unsatisfactory and uncertain in general use. The 
plant grows in Ceylon. In Trimen's Handbook cf the 
Flora of Ceylon it is said to occur in the 'low country, 
common in hedges and waste places, especially in 
dry regions, but usually planted , and scarcely a 
native.' I obtained a few leaves and made a strong 
decoction from them, The amount of material was 
insuf&cient for extensive experiment, but leaves affect- 
ed by various insect pests were dipped into the mix- 
ture. I was surprised to find it absolutely ineffectual. 
Even such soft-bodied insects as aphides, when 
thoroughly wetted with the mixture, were as lively 
as ever the next morning. Possibly the Ceylon-grown 
plant does not acquire the insecticidal properties 
noticable in the Indian plant. 
It may here be as well to mention a few other 
supposed remedies for the cure of scale bug, that are 
really quite valueless for the purpose. The benefical 
results that have been attributed to them are pro- 
bably due to some fortuitous circumstance, such as 
the treament having been applied at a time when the 
pest was declining from natural causes. Such errors of 
observation have led to much waste of time and money. 
The application of 'Mana grass' (Andropogon nardi(s), 
was at one time considered a cure for the coffee bug 
(Lec. cqffece). Nietner, in his Enemies of the Coffee tree, 
mentions that it was customary to bind the grass 
round the stems of the trees. I have repeatedly 
tried this plan, at various times of the year. 1 have 
tied the grass round the stems as directed, have 
spread it on the ground, and strewn it over the 
foliage. But in no case have I been able to observe 
the very slightest benefit from its use. 
Soot is another article that has been greatly over- 
rated as an insecticide ; and wood ashes may fall 
under the same category. These substances are, doubt- 
less, useful in dealing with slugs and snaik, their 
astringent and absorptive properties acting upon the 
mucous surface of such animals ; but when applied 
to dry insects, such as caterpillars and scale bugs, 
they fail to adhere, oi', when adhering to act in any 
way prejudicial to the iusect. 
Lime, when applied dry, has little or no effect, un- 
less there happen to be moisture upon the insects. 
Even then its action will be very partial and un- 
satisfactory. 
Powdered sulphur is also quite useless against 
scale insets. 
Many other substances have been made the siibjecta 
of experiment ; but, as they are either far too costly or 
Otherwise impracticable it is useless to enumerate them. 
In the foregoing notes I have endeavoured to gather 
together the most reliable information on the subject 
of insecticides applicable to the treatment of Coccid 
pests. I present it to my subscribers, hoping that from 
amongst the various processes some treatment may be 
found to suit any case that may come under their notice. 
INDIGO-A THREATENED INDUSTRY. 
TO THE EDITOR OF THE "TIMES." 
Sir, — My attention has been drawn to your special 
article on the above subject in your issue of the 4th 
inst., and to a letter in your issue of the 7th inst. from 
Messrs, Mewburn and Ellis, who give some details and 
comparative statements which require correction. 
The indigo industry in India has up to the last few 
years occupied an almost anomalous position in this 
century of scientific progress an invention. Cultivation 
and manufacture have remained practically the same 
as they were at the end of the last century. 
The industry has, on the whole, been a paying one 
until this recent competition of an artificial product, 
and planters as well as agents were content to let 
things remain as they were. There have been chemists 
of an inventing bend of mind who have of late years 
oeoupied themselves with indigo manufacture and 
endeavoured to improve the same and increase the yield 
of dye from the raw material. But the encouragement 
they received has been too limited and was confined 
to a few individual planters. The industry generally, 
as well as the financing agency houses and the buying 
trade discouraged all improved methods of manufac- 
turing processes necessitating the use of chemicals, and 
indigo known to have been made by any such improved 
methods was prejudiced at the indigo sales, if not 
altogether boycotted, so that enterprising planters 
lost courage and dropped all improvements in manu- 
facture, even those of established merits. 
The buying trade had also, up to lately, rested 
upon a most primitive basis of buying, dating also 
from the last century ; valuations were and are still 
being made on comparison with standard samples of 
certain supposed values, and the buying trade was 
therefore suspicious of any alterations in the methods 
of manufacture which might produce an equally good 
looking article but of perhaps less dyeing value. 
All this is now rapidly changing. The indigo 
industry is ripening, sud is now more prepared than 
it was a few years ago to benefit from the scientific 
progress of our century. 
The buying trade is more and more abandoning 
the buying on comparison with standard sarcples, and 
buys now to a great extent on analysis, paying a certain 
amount per unit of indigotine, which varies slightly 
according to the mechanical conditions of the paste. 
Indigo planters have rallied together in face of this 
threatening competition, are now amploying distin- 
guished chemists, and are taking practical steps to 
improve their methods of cultivation and manufacture. 
The financial agency houses are realizing the 
seriousness of the situation, and are taking the lead 
to help their constituents in the only way m which 
they can be helped — viz., to establish experimental 
factories where improvements in manufacture and 
cultivation can be worked out and tested. 
It is not generally known that only about one- 
third of the dye in the plant is obtained by the 
ordinary methods of manufacture, and that, moreover, 
waste to the extent of 20 per cent, of the ultimate 
outturn occurs therein. 
There is, therefore, an ample margin for improve- 
ment in the manufacture alone, besides the progress 
which can be made by improved methods of cultiva- 
tion and drainage and the use of new and selected seed. 
The chemistry of indigo manufacture is till some- 
what obscure ; the dye in the plant is not present 
in a merely extractable state, like theine in tea 
leaves, but has to be developed from certain basic 
products, which is most profitably done by a pro- 
longed fermentation of the plant, the agency being 
then microscopic life. This has made improvements 
in manufacture difficult, for chemists are rare who 
are conversant with and thoroughly understand the 
conditions of low microscopic animal and vegetable 
life, and who in addition possess the necessary per- 
severance, the necessary inventive power and gift, 
to devise experiments, to carry them out, and to 
interpret correctly the results. But such chemista 
will doubtless be found, and the benefits which the 
industry will derive fjrom their work will be more 
