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Historic, archived document

Do not assume content reflects current
scientific knowledge, policies, or practices.

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CIRCULAR NO. 33, SECOND SERIES.—(Supplementary to Circulars 18 and 27.)

United States Department of Agriculture,

DIVISION OF ENTOMOLOGY.

REMEDIAL WORK AGAINST THE MEXICAN COTTON-BOLL WEEVIL.

In the course of the investigations of the boll-weevil problem in
southern Texas in the spring of 1896 by my first assistant, Mr.
C. L. Marlatt, it was early discovered that the overwintered weevils
were not only collecting on the volunteer cotton but were feeding to
a noticeable extent on the expanding leaves and soft green stems of
the new shoots. The possibility of destroying the beetles by wetting
this new growth by an arsenical poison at once suggested itself, and
experiments which were promptly instituted with confined beetles on
small plants demonstrated conclusively that not only do the beetles
feed on the leaves and tender shoots voraciously, but that by poisoning
such shoots the beetles subjected to experiments could all be killed
in the course of 8 to 12 hours.

A more general experiment to test the value of poisoning was
instituted in a field containing much volunteer cotton which had
already (April 26) made considerable growth, forming rather dense
bushes. This experiment was carried out on the farm of Judge
Borden, of Sharpsburg, the plants being sprayed from an ordinary
wagon cart. Great difficulty was experienced in wetting more than
the outer leaves, which were now of large size and protected much
of the inner growth, especially the squares. The outcome of this
work demonstrated that while the poisoning of the cotton plant was
thoroughly feasible and practicable when done at the right season
and would result in the killing of the overwintered weevils, if delayed
too long it was very unsatisfactory and promised very little of value.
In other words, it is much more difficult to poison plants successfully
as a means of destroying the weevil than to poison them for the
cotton-leaf worm, which feeds very often if not generally on the outer
leaves and can be reached by powder dusted over the plant in the
most careless and general way. The weevil, on the other hand, feed-
ing as it does on the tender growing tips and on the flower buds,
which are very often concealed and covered up by the larger leaves
of older growth, requires for its destruction very careful and thorough
spraying, such as would be impossible after either volunteer or planted
cotton has reached any considerable size.

2

As a means, however, of destroying the overwintered weevils on
volunteer cotton, a spraying of poison in April promised very valu-
able results, and a recommendation for such treatment was inserted
in the last edition of the boll-weevil circular (Circular No. 18, second
series), as follows:

The beetles which have survived the winter collect in the early spring on the
first sprouts which appear on old cotton and eat the partially expanded leaves
and the tender leaf stems, and at this stage can be poisoned by the application
of anarsenical to thisnew growth. To do this it will be necessary to thoroughly
spray the growing tips, and this should be done when volunteer cotton is very
small, preferably mere sprouts or bunches of leaves an inch or two in length;
later on the growing parts can not be easily reached. With an ordinary knap-
sack pump a field may be gone over rapidly and the volunteer cotton thoroughly
treated, the nozzle being directed at each growing tip. The first application should
be made as soon as the volunteer plants sprout, and perhaps repeated two or three
times within as many weeks. As ordinarily cultivated, the number of volun-
teers is small and the time required for the thorough spraying of such plants will
not be great. A strong solution should be applied, viz, 1 pound of the poison to
50 gallons of water, because no harm will be done if the volunteer plants are
ultimately killed by the poison.

The use of poisons, either London purple or Paris green, as described
in the paragraph quoted, is thoroughly practicable and undoubtedly
will be of value. The careful study, however, of the weevil dam-
age in Texas conducted by the Division during the last three or
four years has demonstrated that the prevention of weevil damage is
more a question of the adoption of a proper system of cultivation
than of remedial or preventive schemes, such as the use of poisons.
In other words, it is admitted by intelligent planters everywhere that
the presence of the weevil is made possible by a system of culture
which admits of the existence of volunteer cotton, and if the methods
followed are such as to prevent such volunteer growth the weevil
will rarely if ever be troublesome.

In our publications on this insect, therefore, great stress has been
given to the cultural method of control, which is undoubtedly the one
thoroughly effective means of avoiding loss from the boll weevil.
The details of this method are repeated at the close of this circular.

Unfortunately a great deal of the cotton culture in Texas is of the
rather careless sort, and there probably always will be more or less
volunteer cotton in fields unless very stringent regulations are passed
and great care is taken to see that these are strictly enforced. The
poisoning of volunteer cotton in early spring remains, therefore, a
procedure of importance and of considerable practical utility.

The present season attention has again been directed to this or a
very similar method of control, in the course of the investigation of
the weevil conditions in Texas by Professor Townsend, a field agent
of the Division. In the course of this work it was discovered that

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the weevils seemed to have a marked fondness for sweets, such as
molasses, and would eat the latter when smeared on cotton stalks or
young shoots either with or without an admixture of arsenic. After
eating the poisoned sweets the beetles died within 8 to 24 hours.
After some weeks of experimentation in the field, chiefly at Cuero,
Tex., Professor Townsend recommends and indorses very heartily two
formulas, one for the treatment of young planted cotton and the
other for the destruction of the overwintered beetles on the volunteer.

FORMULA FOR VOLUNTEER COTTON.

The undiluted molasses is mixed with one-fourth its volume of
arsenic and applied to the volunteer stalks in spring when the leaves
are beginning to appear. The molasses must be kept well stirred to
prevent the arsenic from settling, and may be smeared on the stalks
of the volunteer cotton with a stick or brush. All untreated plants
must be killed and only a few poisoned plants should be left to the
acre. This applies to districts where the folhage of the cotton is
killed in winter. In warmer districts, where the foliage is not always
killed in winter, all but a few of the plants should be killed and up-
rooted, and the remainder smeared with the poisoned molasses, all
squares and bolls having been removed to insure the quickest effect.
Itis believed that the weevils will be attracted to these poisoned plants
by the molasses and will be killed, and this will obviate the necessity
of treating the young planted cotton.

FORMULA FOR PLANTED COTTON.

White arsenic (arsenious acid) 1? to 2 ounces boiled in a gallon of
water until thoroughly dissolved; two or three gallons of the cheapest
erade of molasses, and one barrel (40 gallons) of water. Stir the
molasses into the water, then add the dissolved arsenic and mix the
whole thoroughly. Apply to the plant with a force pump and spray
nozzle as in spraying for the cotton-leaf worm.

This mixture is designed for use particularly on young cotton
plants, and may also be used for the poisoning of volunteer cotton
with a knapsack sprayer or larger apparatus, as described in the
quotation from Circular 18. The only advantage of the sweetened
or sirupy wash over Paris green, London purple, or arsenite of cop-
per, as ordinarily used, is in its being supposed to attract the weevil;
so that, even although the entire plant might not be wetted with the
mixture, the weevil would be attracted by the sweetened bait to the
parts struck by the liquid.

+

It should be remembered that the white arsenic recommended is
very caustic and is very much more apt to burn or scald plants than
are the other arsenicals just mentioned, and it is quite probable that
either London purple or arsenite of copper, which are of about the
same cost as white arsenic, will be preferable to the latter.

The cheap grade of molasses referred to can be laid down in Texas
at a rate of 10 cents per gallon. White arsenic costs about 10 cents
a pound retail, but wholesale can be obtained for much less. London
purple and Paris green also cost about 10 cents a pound retail. A
barrel of the mixture at the prices quoted will cost about 25 cents,
and should spray an acre or more of young planted cotton. The
much heavier mixture for volunteer cotton is used in very limited
quantities and a small amount will cover a large area. The direc-
tions and cautions given at the outset for spraying for the boll weevil
are equally applicable to the molasses and arsenic wash described.
For field work, however, a large machine is necessary, such as the
mounted horse spray machines commonly used for treatment of
potato farms.

It should be remembered that this treatment rests merely on some
preliminary experiments made with confined weevils on poisoned
plants, and its success on a large scale remains to be demonstrated.
Its greatest value will come, undoubtedly, in the treatment of vol-
unteer plants and young planted cotton, and its success with the lat-
ter will, undoubtedly, diminish as soon as the plants have formed a
head or become at all bushy. It is given publicity by means of this
circular, to get planters to test it fully in field trials, which alone will
demonstrate its value or worthlessness.

THE CULTURAL METHOD OF CONTROLLING THE BOLL WEEVIL.

It should be remembered that the poisoning of the volunteer and
also of the young planted cotton is suggested merely as a means of
correcting a condition which has resulted from imperfect cultivation,
and that the great value of the cultural method of control should
not be lost sight of.

The description of this method given in our last circular on the
boll weevil is as follows:

The careful investigation of this weevil during the past two or three years by
the Division of Entomology has fully demonstrated the supreme importance of
the cultural method of control, to which fact we gave special prominence in our
first circular on this insect. There can be no question now that in the proper
system of growing cotton a practically complete remedy for the weevil exists.

In the first place, it has been established beyond question that the conditions of
cultivation which make volunteer growth possible also make the continuance

5

of the weevil inevitable. Of first importance is the early removal of the old
cotton in the fall, preferably in November or earlier. This can be done by throw-
ing out the old plants with a plow, root and all, and afterwards raking them
together and burning them. This treatment should be followed, as promptly as
may be, by deep plowing, say to a depth of 6 or 8inches. This leaves the field
comparatively clean of old cotton stalks, facilitates thorough cultivation the
following year, and, at the same time, collects and destroys all the weevil larvee
and pupe in the cotton at the time, and also most of the adults. The escaping
beetles will be buried by deep plowing, and will not again reach the surface.
Few, if any, of them will succeed in hibernating in the absence of the ordinary
rubbish in the fields in which they winter. Fields treated in this way have given
a practical demonstration of the usefulness of the method.

The greatest danger from the weevil is due to the presence of volunteer cotton,
which means early food for the weevils in the spring and abundant means for
their overwintering, and the effort made to retain volunteer and get early cot-
ton, or the ‘‘first bale,” is a very serious menace to cotton culture within the
weevil district.

This cultural method, if generally practiced, will undoubtedly prove a perfect
remedy for upland cotton, and will vastly reduce weevil damage in the lowlands,
where the weevil is more apt to winter, perhaps in adjoining woods or roadside
vegetation. The early removal of cotton by the means suggested is especially
advised whenever the presence of the weevil shows that the picking of a top
crop is problematical. In such instances it would be well to uproot and destroy
cotton stalks in September or October, as would have been thoroughly feasible
for much of the upland cotton in 1896. If this cultural method can be enforced,
either by State legislation or by the cooperation and insistence on the part of
landowners that their renters shall carry out the system outlined, the weevil
difficulty can undoubtedly in very large measure be overcome.

In connection with the system of fall treatment of the cotton, constant and
thorough cultivation of the growing crop as late as possible is of considerable
value, and is also what should be done to insure a good yield. With a crossbar
to brush the plants many of the blossoms and squares containing weevils will be
jarred to the ground and buried, together with those already on the ground, in
moist soil, and a large percentage of the material will rot before the contained
insects have developed.

Somewhat in line with the last paragraph is the collection and de-
struction of the infested bolls and weevils from the plants themselves.
A complex machine has been devised for this purpose by Mr. Stron-
hall, of Beeville, Tex. In operation this apparatus passes over one
row at a time and brushes the plants from both directions vigorously
by means of revolving brushes working in opposite directions, and
the stung bolls and squares which fall readily are caught on receiving
trays and carried to bags and may be ultimately burned or otherwise
destroyed. The machine may be adjusted to plants of different ages
within certain limits, but becomes less effective as the plants get
larger. As witnessed in operation the present season by Mr. Town-
send, it proved, on young plants, to be very effective and satisfactory,
collecting a large percentage of the weevils and the stung bolls and

6

squares. The temporary advantage of the use of this machine no
doubt will be considerable and may materially protect the early cot-
ton; it probably will not be of much service as a protection for late
cotton or the second crop.
L. O. Howarp,
Entomologist.
Approved :
JAMES WILSON,
Secretary.

WASHINGTON, D. C., July 1, 1898.

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