SB

818 .
C576
ENT No. 52, SECOND EDITION.

ited States Department of Agriculture,
DIVISION OF ENTOMOLOGY,

L. O. HOWARD, Entomologist.

THE LIME, SULPHUR, AND SALT WASH.

By C. L. MARLATT,
Entomologist in Charge of Experimental Field Work.

JSE AGAINST THE SAN JOSE SCALE IN THE EAST.

The experiences of the last two years with the use of the California,
or lime, sulphur, and salt wash in the East have been in many cases
of so satisfactory a nature as to cause numerous letters of inquiry, and
indicate the need of a special circular of information. This wash is
described and recommended in Circular 42 (second series) of this office,
relating to treatment for the San Jose scale, and also in Farmers’ Bul-
letin 127 on insecticides. But in these publications the information is
very concisely given and none of the experiments on which are based
the recommendations for the East are described. It is proposed in this
circular to give a brief history of the employment of this wash in the
East and to make such recommendations as the results justify.

EARLY TESTS IN MARYLAND.

With the discovery of the San Jose scale in Eastern nurseries and
orchards the first thought naturally was to employ against it the washes
which were very commonly used for its control in California and other
Pacific coast regions. The results of the preliminary tests are recorded
in the first general publication of this office on the San Jose scale,
namely, Bulletin 3 (new series), pp. 57-71. Among many other tests
made the lime, sulphur, and salt wash as used in California, and the
Oregon wash, a slight variation of the latter, were the subject of careful
experiments. This work was done by the writer, assisted by Mr.
Coquillett, who, while the California agent of this Division, had employed
the lime, sulphur, and salt wash in many combinations and was
thoroughly familiar with its use on the Pacific coast.

HOW THE WASHES WERE PREPARED.

The washes referred to were made after the following formulas:

California wash.—Lime, unslaked, 40 pounds; sulphur, 20 pounds;
coarse salt, 15 pounds. Add 40 gallons of water to the above ma-
terials, stirring thoroughly while the lime is slaking. Boil fully three

2

hours, then add enough water to make 80 gallons of the solution.
Strain through burlaps and apply milk warm, using only on deciduous
trees and when the said trees are dormant. This formula is that given
by Mr. H. B. Muscott, then chairman of the San Bernardino County
Board of Horticultural Commissioners, who reported that the wash was
prepared by a practical chemist employed by the commissioners and
furnished at cost in concentrated form, and was extremely successful.
A description furnished by H. P. Stabler, of Yuba City, Cal., of the
method of making the California wash by means of a twelve-horsepower
boiler and attached pipes and hot water tank was also given, an appa-
ratus by means of which 800 gallons of the wash could be prepared at
one time.

Oregon wash.—Sulphur, 15 pounds; slaked lime, 15 pounds; blue-
stone, 14 pounds; water to make 100 gallons. Prepared in the same
way as the California wash. This mixture is interesting as representing
a distinct variation in ingredients. It has little if any excess of hme,
and the bluestone, which takes the place of the salt, probably does not
add to the value as an insecticide and increases the difficulty of prepa-
ration. It is little employed.

RESULTS OF THESE TESTS.

The trial with these two washes was made November 17, 1894.
They were used on peach and other fruit trees at the strength recom-
mended in California and Oregon, and also at double this strength.
The treated trees were carefully examined a month later, December 15,
and only a very small percentage of the scales were found affected, not
more than on untreated trees. The same results were seen with both
strengths; in other words, the double strength was no more effective
than the ordinary strength used on the Pacific coast. The trees were
still whitened with the wash. These conditions had not changed at
the time the orchard was given the general spraying with soap toward
the end of April, 1895, which prevented following the action of these
washes further.

INEFFECTIVENESS BELIEVED TO BE DUE TO CLIMATE.

The explanation which naturally suggested itself for the apparent
failure of these Pacific coast washes to be effective in the East was in
the difference in the climate between the two regions, and especially as
earlier experiments (January-March, 1894) with the lime, sulphur, and
salt wash conducted by the writer against the so-called West Indian
peach scale (Diaspis pentagona) had shown similar unsatisfactory
results.t In California these washes are applied in the dry season, and
a long period may follow without rain. Inthe East a period more than

1Insect Life, Vol. III, pp. 118-119.

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a few days without rain can not safely be counted on. So poor were
the results, in fact, that the writer felt inclined to doubt the effective-
ness of these washes even in California. But subsequent trips to Cali-
fornia and careful investigation of conditions there, demonstrated to his
complete satisfaction that the effectiveness of these washes on the Pacific
coast had not been overstated.

CALIFORNIA WASH AGAIN TESTED.

The confirmation thus gained of the value of the California wash as
an insecticide led the writer in the spring of 1900 to again institute
some experiments with it against the San Jose scale and the Diaspis.
These experiments are recorded in detail in Bulletin 30 (new series) of
this Office, pp. 33-39. They include also parallel experiments with
kerosene emulsified in the Bordeaux mixture and kerosene-lime emul-
sion, both suggested by Professor Galloway; and also a test with white-
wash made at the suggestion of Doctor Howard. A special steam plant
was prepared, so that the lime, sulphur, and salt wash could be made
after the most approved methods and thoroughly boiled. An account
of these experiments, so far as they apply to the lime, sulphur, and salt
wash, is transcribed below from the publication cited. The report of
the chemist on this mixture is of especial value and seems to confirm
the view previously expressed on the relative effect of a moist and of a
dry climate on the behavior of the wash.

RECORDS OF EXPERIMENTS IN 1900.1

Lime, sulphur, and salt wash.—A mixture of this substance was prepared,
differing slightly from the formula given in Farmers’ Bulletin No. 19 in that the
amount of lime was somewhat reduced, namely, from 40 to 30 pounds. This
reduction in the amount of lime was made simply because in the ordinary for-
mula the lime is very greatly in excess and remains as a pure lime sediment in
the wash and has to be kept in suspension by agitation. Even as thus reduced
there is still a considerable excess of lime. ‘The formula followed was:

WAT) ERE ee ae soe pounds__ 30
all) id es Do ee ee 2002 == 20
Set) te cee TU Ee AL Le doze Lb
\iV ler = oe 2 es ae SN Sy es eee Se SEM ovate S50)

The mixture was steam boiled all together in barrels about four hours and
applied March 23 and repeated March 24. The hot liquid was taken immedi-
ately from the barrels at almost a boiling temperature and sprayed at once on
the trees. A series of experiments was also made with the preparation of this
wash on a smaller scale, following practically the same formula. The products
obtained were submitted to the Chemist of this Department for analysis, and the
assistant chemist charged with the work was especially advised just what fea-
tures were supposed to be desirable and what points the analysis should bring
out. The result of this analysis, made by Mr. J. K. Haywood, of the Bureau of
Chemistry, as reported by Dr. H. W. Wiley, Chief Chemist, is given in a foot-

' Bul. 30 (new series), Div. of Entomology, pp. 34-37.

4

note.! It is very interesting and valuable as showing the probable exact chem-
ical nature of the wash in a dry climate and correspondingly also in a wet clim-
ate, in these respects practically substantiating the theory which the writer had
announced several years ago. The practical application of this wash, as
described above, was made to pear and plum trees, both infested with the San
Jose scale, the plum'trees being very thickly covered with the scale from top to
bottom and the pear trees scaly from the butts upward three or four feet, scat-
tered more or less over the whole tree. The plum trees had also more or less of
Diaspis pentagona.

The question naturally arose, in view of the extreme heat at which the liquid
was applied, whether any results gained might not be due to the high tempera-
ture of the liquid rather than from any insecticidal action. To test this matter
some plum and peach trees covered with Diaspis pentagona were sprayed on
March 27 with water at boiling temperature, or nearly so, the nozzle being held
within 3 or 4 inches of the bark and the spraying being very thoroughiy done.
At a distance of 18 inches, as tested by spraying one’s hand, the mist or spray
was barely warm; ata distance of 12 inches, fairly hot; and very hot from 4
to 6 inches. The bark of the trees sprayed was cold to the hand as soon as
spraying stopped. This hot-water spray, brought to bear closely on the scale
insects, it was thought would kill them, although it would of course be imprac-
ticable to make such close-range application in general practice. On the
contrary, however, the scales remained in a vigorous, healthy condition, and
apparently did not suffer in the least from the warm douche.

The results, therefore, gained by the lime, sulphur, and salt wash may be
properly ascribed, it is believed, to a true insecticidal value of the substance
rather than to the temperature of the application. The trees treated with this
wash remained nearly snow-white, little, if any, of the mixture being taken off
by the light snow and rain of the 25th and 26th instant. Discoloration of the
Diaspis began to be noticed on the 27th instant. On April 18 the Diaspis scale
insects killed ranged between 20 and 50 per cent on the young, vigorous limbs.
All were dead on the old trunk, where the wood was in a very unhealthy con-
dition owing to the completeness of the infestation, both by the Diaspis and the
Aspidiotus. The San Jose scale, so far as investigation could determine, seemed

1'The lime, salt, and sulphur wash, as finally prepared, contains the following
substances in solution: A large amount of (CaS) calcium sulphid, some of the
higher sulphids of Ca (as CaS3 and CaS;), small amounts of (CaSO,) calcium
sulphate, and traces of (CaSO;) calcium sulphite, and a large amount of (CaS.QO3)
calcium thiosulphate; also some of the excess of Ca (OH), lime is in solution.
The residue is composed of lime.

On evaporating down a portion of the wash, with blast and at a gentle heat,
no decided change takes place. Calcium sulphid still remains, as does calcium
thiosulphate. A small amount of sulphur is deposited (doubtless from the poly-
sulphids of calcium), and the amount of calcium sulphate is increased to a small
degree.

If such a wash were applied to trees in a dry climate, the various compounds
formed would remain for a long time and only gradually decompose. Event-
ually, however, the calcium sulphid would decompose, most likely forming cal-
cium sulphate and some hydrogen sulphid (H.2S), and the calcium thiosulphate
would decompose, first setting free sulphur and calcium sulphite, which last
would oxidize to calcium sulphate. The lime would change to calcium carbonate
(CaCO;) and the polysulphids would break down, yielding sulphur and calcium
sulphid, which would in turn change as above.

In a wet climate the calcium sulphid and the calcium thiosulphate would soon
leach out, leaving behind small amounts of calcium sulphate and a large amount
of lime, which would in turn form insoluble calcium carbonate. In this latter
case the tree would still remain white and appear to still have the wash upon it,
but, in fact, very little other than the calcium carbonate would be left.

5

to be killed completely ; no insects were found on the young, vigorous shoots or
older wood. The trees were still whitened with the wash, which had not been
carried off to any great extent by the heavy rains of April 11 and 12. The
infested trees, especially those that had been pruned back, made a very vigorous
growth, and the fruiting and growth of the others were entirely satisfactory.

In this experiment, which differed so remarkably in results from other experi-
ments made in the East with this substance, it must be noticed that the weather
conditions were exceptionally favorable. The application was made on March 23,
and no washing rains followed until April 11 or 12, the light rain and snow of
the 25th and 26th of March being not enough to vitiate the wash particularly, as
very little of the snow rested on the trees, and much that did gain lodgment fell
or was blown off subsequently. A very light shower occurred on April 4, but
the first heavy downpour and long rain occurred on the night of April 11.

This experiment would seem to indicate that if one could count on a week or
two of good weather following an application, the lime, sulphur, and salt wash
might be as beneficial in the East as on the Pacific coast. Its cost is inconsider-
able compared with the other treatments for the San Jose scale.

During the summer of 1900 the writer spent considerable time in California
and saw a great many deciduous orchards that had been treated with the lime,
sulphur, and salt wash. This treatment had been made in the winter or early
in the spring, before the trees had begun to leaf out, and at the end of August
the trees were still distinctly whitened by the application, there having been no
rains in the interim to remove it from the bark. Under such circumstances it is
plainly to be seen that this wash has the maximum chance of effectiveness, and
that it is thoroughly effective under these conditions, is beyond question. Its
effectiveness is undoubtedly, in the first instance, chiefly due to the direct insec-
ticidal action of the mixture; and possibly, secondarily, in protecting the tree
by the limy and sulphurous coating, which remains for months and is undoubt-
edly distasteful to the young scales coming from old individuals which may have
escaped, and perhaps retains enough of its insecticidal value to destroy many of
them.

RECOMMENDATIONS BASED ON THESE EXPERIMENTS.

On the strength of these experiments the lime, sulphur, and salt
wash has been since recommended by us, as already stated, as a remedy
for San Jose scale in the East, with the understanding that unfavorable
weather conditions, that is, heavy rains, immediately following treat-
ment, may very probably decrease the benefits to be derived from it.
That under favorable conditions its use may be thoroughly satisfactory,
as much so as kerosene or crude petroleum, was fully demonstrated.

WORK DONE BY OTHER EXPERIMENTERS.

In the winter of 1901-02 Prof. S. A. Forbes instituted certain experi-
ments with the California and Oregon washes, and his results of a
highly satisfactory nature are given in Bulletins 71, 72, and 80 of the
Illinois Agricultural Experiment Station. In brief, these seem to indi-
cate that either the California wash or the Oregon wash, the preference
in the later publications being given to the former, can be used under
Eastern conditions with the probability of satisfactory results irrespec-
tive of weather conditions; in other words, Professor Forbes’ experi-
ments were directed particularly to determine whether washing with

6

rain or artificial washings of sprayed trees would affect the efficiency of
the wash, and, rather surprisingly, such washings seemed to have had
no prejudicial effect.

From the experience up to the present time it does not seem reason-
able to assert from Professor Forbes’ results alone that the California
wash is not affected by hard washing rains, especially in view of the
tests made by the Department Chemist, and the less favorable or con-
tradictory results obtained by other experimenters, nevertheless the
evidence is sufficient, on the whole, to warrant the placing of this wash
among the best of the remedies in the East against the San Jose scale.

The work in Illinois has been supplemented by independent experi-
ments in New Jersey, New York, Maryland, Georgia, and other States,
and while all tests have not been successful, they seem to indicate that
the lime, sulphur, and salt wash will, in the majority of instances, give
decidedly good results, often destroying the scale as effectively as an
oil or a soap application.

HOW THE WASH AFFECTS THE SCALE INSECT.

The action of this wash on the scale is very slow and, judging from
Professor Forbes’ experience, it is possible that in the case of our pre-
liminary work in Maryland in 1894, if the trees had been left for the
summer without other treatment, the lime wash might have continued
its effect and exterminated the scale in a much greater percentage than
was the case in April. This wash coats the tree thoroughly, has a
decided caustic insecticidal effect, and dissolves, to some extent, and
loosens the scale covering, so that a large number of scales perish during
the winter and early spring, and this action continues until the emerg-
ing of the first brood of young. As indicated above in the quotation
from Bulletin 30, the weakened wash remaining on the trees through
early summer may still be strong enough to kill some of the delicate
‘ larvee and act as a deterrent to the settling of others until they perish.
In fact, the chief benefit seems often to come at this season.

CAUTION IN ESTIMATING RESULTS.

It should be remembered that the sudden increase in the percentage
of dead San Jose scales on trees in April may not necessarily be due to
the wash, but rather to the fact that the male insects transform to the
winged stage in April long before the females reach full growth, and
hence there is an appearance of a sudden increase of dead scales, the
abandoned scale covering of the male insect still adhering to the bark.
This may often amount to 95 per cent of the scales. In the spring of
1902 the male scales in the Department orchard represented fully 95 to
98 per cent of the living insects on the trees in early April. The hatch-
ing of these, of course, gave an immediate appearance of an almost
complete extermination of the San Jose scale on these trees. This

6

point is an important one and should not be overlooked in making esti-
mates of the effectiveness of washes.

THE WASH AN AVAILABLE REMEDY FOR THE EAST.

The advantages of the California wash are notable. It is inexpensive,
costing but little above one cent per gallon for materials, and does not
entail any danger to the plant treated. It is furthermore a very valu-
able fungicide and is notably useful against the peach leaf curl, sprayed
trees being practically immune from this disease. In its general fungi-
cidal action, it 1s noted that trees to which it has been applied are
much cleaner and freer from disease and more fruitful, so that the cost
of treatment is often more than made good by the fungicidal benefit
alone. Its disadvantages are the difficulty of preparation and heavy
wear which it entails on apparatus, objections, however, which do not
offset its advantages if future experience confirms the more recent
results. The danger in careless hands in the use of petroleum oils,
also their expense, and the great expense of soap washes, bring this
lime, sulphur, and salt wash into especial prominence and recommend
it to all who are so situated as to prepare it easily. This does not,
however, discredit in the least the other washes mentioned.

COMPOSITION AND PREPARATION OF THE WASH.

The report of the Department Chemist (given in footnote on page 4)
indicates sufficiently clearly the compounds entering into this wash and
the behavior of these, respectively, in dry and moist climates. It is
evident that in all the formulas, both those recommended above and
others (practically every experimenter making a formula of his own),
there is a great excess of lime which adds to the lime coating on the
tree, and doubtless has its benefit as a deterrent. The composition of
the wash is a matter of some indifference. I believe the formula fol-
lowed in the experiments just described and recommended in Circular
42 is a good one to follow. This wash gave perfectly satisfactory results
against the San Jose scale and is less wasteful in ingredients than many
others, although still containing a considerable excess of lime, but per-
haps not more than is desirable. The action of the salt is not very well
understood, and it is possible that this element could be eliminated, as
indicated by some recent tests, without affecting the results of the treat-
ment. Salt is, however, used in whitewash to give adhesiveness, and
it may act in the same way in this wash, causing it to adhere longer
and better than would be the case without it.

The wash is practically a sheep dip imported into California, I
believe, from Australia, and with the advent of the San Jose scale
employed with little change against this insect, and by a lucky chance
proving effective.

Prolonged and hard boiling increases the percentage of the higher

HSONIAN INSTITUTION LIBRARIES

WOM A

8 3 9088
sulphids, although in the main the liquid will consist of the simpler
compounds of lime and sulphur; and from this fact it is to be inferred
that these latter are by themselves effective, although a slight increase
in efficiency may be gained by increasing the higher sulphids.

When making this wash in quantities of 50 gallons and upwards, it
is necessary to boil for three to five hours, and especially at the start it
should be stirred up thoroughly to prevent caking. In the process of
making, the color changes from a yellow to the clear brown of sulphid of
lime except for the excess of lime floating in it. It may be prepared
by boiling in an ordinary iron kettle or vat, but is much more satis-
factorily made by boiling in hogsheads or barrels with steam. Where
the wash can be prepared in the latter manner, its use is to be strongly
recommended. It may then be made up at once with the full amount
of water, and taken hot from the boiling tank and promptly applied so
as to get the advantage of the higher sulphids and the full strength of
the mixture. In transferring to the spray tank, pass it through an iron
screen or strainer. The spray tank must be provided with an effective
agitator. The experiments of 1900, quoted above, discuss the matter
of temperature fully. In important fruit districts it would be well
worth while to adopt the plan followed very commonly in California—
of organizing spraying companies to undertake at a reasonable charge

the preparation of the wash and the spraying of orchards. In California
the wash is furnished and put on the trees, everything included, at a
charge of five cents per gallon.

PRECAUTIONS TO BE NOTED.

This wash is a winter application and can not be apphed to trees in
leaf. The best season is February or March. The fact that this wash
is destructive to pumps and nozzles has already been indicated. The
iujury in this direction can be reduced to a minimum by carefully clean-
ing the pump each night with water. The Vermorel nozzle is the best
one for the wash, and additional caps may be secured to replace worn
ones. The use of an air pump instead of a liquid pump would save the
wear of the lime onthe pump; and doubtless our Eastern manufacturers
could be induced to make a suitable apparatus of this sort. In spray-
ing with this wash clothing is ruined, and only the oldest garments should
be worn, and care should also be taken to protect the eyes to avoid
unnecessary inflammation. There is, however, no special danger.

Approved:
JAMES WILSON,
Secretary of Agriculture,

WASHINGTON, D. C., March 18, 1904.

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