SB
818

C578

ENT

Issued October 3, 1907.
CIRCULAR No, 95. (REVISION OF CIRCULAR No. 56.)

United States Department of Agriculture,

BUREAU OF ENTOMOLOGY.

L. O. HOWARD, Entomologist and Chief of Bureau.

THE MOST IMPORTANT STEP IN THE CONTROL OF THE BOLL WEEVIL.

By W. D. HuNTER,

In Charge of Cotton Boil Weevil Investigations.

It has been repeatedly pointed out in publications of the Depart-
ment of Agriculture that the most important step in controlling the
boll weevil is the removal of the plants from the field as early as
practicable in the fall. This was one of the original suggestions made
by the Chief of this Bureau when the boll weevil was confined to a
comparatively small area in Texas.. Much subsequent work has
shown the value of the original recommendation. Unfortunately the
process of fall destruction of plants for controlling the boll weevil
has been taken up but slowly by the planters. This is largely on
account of the practical difficulties relating to the tenant system and
the scarcity of labor which has interfered with picking out the crop.

The agitation of the necessity for procuring an early crop in order
to avoid damage by the cotton boll weevil has been carried on to such
an extent by the Department of Agriculture that the details have
become common knowledge. There is, however, a tendency on the
part of many planters to lose sight of the fact that procuring an
early crop .is but one step and is strictly secondary to the great
essential step, namely, the destruction in the fall of the plants in
the field. As a matter of fact, early planting, the use of early
varieties, and the use of fertilizers are simply to further the advan-
tage gained by the process of fall destruction.

A PRACTICAL ILLUSTRATION.

In the fall of 1906 the Bureau of Entomology conducted a large
practical field test of the effectiveness of fall destruction of the plants
in the control of the weevil. An isolated locality was found where
over 400 acres of cotton was grown. There was no other cotton
grown in any direction nearer than 15 miles. Through an agent of
the Bureau, Mr. J. D. Mitchell, to whom great credit is due for the
direct management of the matter, arrangements were made by con-
tracts with the farmers concerned under which all the cotton plants
were uprooted and burned during the first ten days in October. Pro-

11577—No. 95—07

2

vision was also made to prevent the growing of volunteer or sprout
cotton. In this way an opportunity was obtained for an ideal experi-
ment to show what may be accomplished by the procedure that the
Department now recommends. About 30 miles away from the local-
ity where the experiment was performed a considerable quantity of
cotton is grown. In this region the stalks were not destroyed in the
fall, and observations made here have been used as a check upon the
experimental area. The experiment was performed at Olivia in Cal-
houn County, and the cotton utilized as a check was located at Six-
Mile settlement in Lavaca County.

Mr. Mitchell visited the Olivia and Six-Mile localities early in
May of the present year (1907). At that time in the former area
extensive search revealed but a single weevil. In the Six-Mile local-
ity, however, the weevils were so numerous that pr actically all the
squares had been destroyed. Other examinations were made, all of
which showed the same advantage, in regard to freedom from the
weevil, of the area where the stalks were “destroyed in October over
the area in which the stalks were not destroyed. The last examina-
tion made up to the writing of this circular was on August 20. At
this time Mr. Mitchell found an average of over ten bolls per plant at
Olivia and only three bolls per plant in the check area. The cotton
at Olivia gave practically absolute assurance of a yield of 1,000
pounds of seed cotton per acre, while the cotton at the Six-Mile local-
ity did not promise more than about 350 pounds of seed cotton per
acre. It happens that the soil on the check area is much richer than
that at Olivia. In spite of this difference, however, the destruction
of the plants in October has caused the poorer land to produce prac-
tically three times as much cotton. /¢ 7s evident that the proper
age of the fields at Olivia resulted in an advantage to the
farmers, according to current prices for cotton, of nearly, if not fully,
$20 per ‘acre.

REASONS FOR THE DESTRUCTION OF THE PLANTS IN THE FALL.

There are four principal reasons why the process of fall destruc-
tion recommended in this circular should be practiced universally by
planters in infested regions:

First.—Fall destruction prevents absolutely the development of :
multitude of weevils which would otherwise become adult within :
few weeks of the time of hibernation. The destruction of the imma-
ture stages of weevils in infested squares and bolls is accomplished,
while the further growth of squares which may become infested later
is also prevented. This stops materially the development of weevils
which would normally hibernate successfully, and by decreasing the
number of weevils which will emerge in the spring the chances for
successful crop the following season are very greatly increased.

Second.—A pre tey manipulation of the stalls will bring about the
destruction of a great majority of the weevils which are already
adult.

Third.—It has been shown conclusively that the bulk of the weevils
which survive the winter are those which reach maturity late in
the season. It is evident that the weevils that pass the winter and

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attack the crop of the following season are among those developed
latest in the fall and which, in consequence of that fact, have not
exhausted their vitality by depositing eges for any considerable
length of time. Fall destruction of the plants, increasing the length
of the hibernating period, reduces many fold the number of weevils
in the fields that would otherwise emerge in the spring to damage the
cotton.

Fourth.—Clearing of the field in the fall makes it possible to prac-
tice fall plowing, which is not only the proper procedure in any
system of cotton raising, but also ereatly facilitates the early plant-
ing of the crop the following spring. The ground becomes clean by
this practice, so that but few places for shelter are left for the
weevils, and various climatic conditions still further reduce the num-
ber of the survivors.

DATA UPON WHICH THE FOREGOING REASONS ARE BASED.

The reasons for fall destruction given above are based upon a very
large amount of data from actual experiments and the work of
various planters. The information at hand was greatly amplified in
a series of large-scale experiments carried on during the winter of
1906-7. Three large cages (50 by 20 feet) were built over growing
cotton at Dallas, Calvert, and Victoria, in Texas. In different com-
partments of these cages nearly 70,000 weevils were placed; several
thousand in each compartment. After the weevils were placed in-
side, the plants were removed from the first section about the middle
of October. At regular subsequent dates other sections were treated
in exactly the same manner. Consequently the results for each
locality show exactly what a farmer could have accomplished by the
destruction of the plants at different times. The full results will
be published in a bulletin by Dr. W. E. Hinds and Mr. W. W.
Yothers, who have had direct charge of the work. In this connec-
tion it is necessary to call attention ‘to only a few features.

In practically all cases the smallest survival of weevils was found
in the cages from which the plants were removed at the earliest dates,
and the number of survivors increased regularly as the dates of
destruction became later. For instance, at Dallas out of between
two and three thousand weevils in each cage, only 2.5 per cent sur-
vived when the plants were removed on October 13; 4 per cent
survived destruction of the food supply on October 16; 6.2 per cent
survived destruction on October 19; 12.2 per cent survived destruc-
tion on November 6, and 14.7 per Genk survived destruction on Novem-
ber 12. These figures indicate that practically seven times as many
weevils survived after destruction of plants on November 12 as sur-
vived after a similar destruction on October 13. This is a most
striking illustration of the effect of early destruction.

In the cages at Dallas, Calvert, and Victoria, from which the
plants were removed in November, 14.26 per cent survived, while 4.41
per cent survived removal of the plants in October—that is, the
cutting off of the food supply in November resulted in the survival
of three times as many weevils as survived when the work was done
in October. These figures are based upon averages of eight large

[Cir. 95]

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‘ages at the three localities in which October destruction took place,
compared with seven similar cages in which the plants were removed
in November.

TIME FOR DESTRUCTION OF THE PLANTS.

It is naturally impossible to fix any date for the destruction of
the stalks which would apply to all localities and under all condi-
tions. The condition of the soil must be considered as well as the
maturity of the ctop. While the condition of the soil can not be
controlled, the time of the maturity of the crop, except in extremely
unfavorable seasons, 1s largely within the power of the planter, since
by early planting of early 1 maturing varieties the entire crop may be
mature before the usual time of picking of the first cotton from native
seed. Nevertheless, whatever modifications are necessary in different
localities and during different seasons, they do not decrease the gen-
eral strength of the recommendations.

The proper time for the destruction of the plants in the fall is
whenever the weevils have become so numerous that there is no
prospect that any more cotton will be made. It will be an easy
matter for any planter to determine this point by an examination of
a few plants in his field. Whenever it is found that all, or nearly
all, of the squares and some of the bolls are being punctured, there is
no hope for producing any more cotton. The farmer should then
wait until the bolls already set on the plants have opened, and
destruction should then take place immediately.

The rule should consequently be that the plants should be destroyed
in the fall whenever all or practically all of the fruit is being dam-
aged, regardless of whether this is in September or November. In
the ereat majority of cases in Texas and in Louisiana the month of
October would be the proper time. In many eases earlier destruc-
tion could and should be practiced. Nevertheless, it should not be
thought that fall destruction will be useless after the time mentioned.
Even until much later many weevils in the remains of bolls hanging
to the plants may be destroyed, but the process loses in value the
longer it is deferred. By all means, if possible, destruction of plants
should take place before frost, but destruction after frost, though not
nearly as efficacious as earlier destruction, should always be practiced
when it has not been possible to remove the plants previously.

METHOD OF REMOVING THE PLANTS.

The common practice of removing the cotton stalks from the fields
by the use of the stalk cutter (a “wheeled cylinder provided with
knives) is not effective in the fall destruction that should be practiced
to avoid the damage by the boll weevil. The stalks remaining in that
case during mild weather give rise to sprouts which furnish an
abundance of food to weevils that would otherwise starve. More-
over, the fact that this machine cuts the stalks into short pieces makes
the necessary collection of them difficult.

There are two effective methods of removing the plants from the
ground. One of these, the method to be preferred, is to cut the roots

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2 or 3 inches beneath the surface by the use of an ordinary plow.
The other is to pull out the stalks by the use of a lever provided with
a toothed notch which grasps the base of the plant. The latter
process is better adapted for use when the plants have been killed by
frost. When they are still green, or the ground is dry, it is fre-
quently a difficult matter to remove them with these levers. The
Department’s general recommendation, therefore, is that the plants
should be plowed out. As soon as possible after this is done they
should be collected by hand or by means of rakes and brought
together in large heaps or windrows. It is very important that this
collection should take place before the leaves have become dry and
have dropped off. When the plants are carried to heaps immediately
after uprooting, all of the leafage, which will dry in a few days,
remains to facilitate the burning of the stalks.

After the stalks have become dry enough they should be burned.
Tf the weather be fair, this can be done in about two weeks. If
rains cause a lengthening of this period, it would undoubtedly be
worth the cost to the planter to purchase crude oil sufficient to bring
about the complete burning of all the stalks.

It is not considered necessary to leave any trap rows to attract such
weevils as may have escaped the burning. The weevil seems to have
but little tendency to be attracted to such plants. After the destruc-
tion of the main crop the spread would probably be in all directions
and the numbers collected on the trap rows would consequently be
inconsiderable. The time and expense of properly carrying on the
hand picking of the weevils and infested fruit on trap rows would be
a considerable handicap to the method on many plantations. Never-
theless, on small places where suitable labor is abundant, traps could
conveniently be left. In such cases they should be situated on those
sides of the fields which are generally leeward. They should be
examined daily for weevils and infested squares and bolls, which
should be immersed in crude oil. After such collection for ten days
the trap plants should be uprooted and burned immediately with the
aid of crude oil.

The suggestion has been made at various times that grazing the
cotton fields with cattle is in some cases equivalent to destruction in
the way that has been suggested. However, in many parts of the
infested area there are not sufficient cattle to accomplish the work,
and, moreover, in very many fields the cattle, by disseminating John-
son grass and other plant pests, would undoubtedly do more harm
than good. At the same time the most thorough grazing always
leaves a few green sprouts or leaves upon which weevils may feed,
and of course leaves the stalks standing, so that the process of leafing,
for the benefit of the weevils, may continue indefinitely. Where the
conditions of the fields allow it and the supply of cattle is sufficient,
grazing the fields should be practiced, but this can not generally be
the case in the infested area.

DIFFICULTIES.
The Department of Agriculture understands that there are some

difficulties in the way of a universal following of the recommenda-
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tions given in this circular. The principal ones are the almost uni-
versal hope for a top crop and in the labor conditions consequent
from the more or less universal tenant system of producing the staple.
These difficulties are increased by the general scarcity of labor in the
South, which is becoming more and more a serious problem in raising
cotton,

Planters in infested localities must understand that with the pres-
ence of the weevil there is no longer any hope of a top crop. It is
true that after considerable cotton has matured, and after the plants
have applied their energy to the formation of seeds and lint, fall
rains often stimulate the production of a great number of squares.
Many planters are misled by this into the hope of gathering a large
{op crop. The joints of the plant are short and the squares are
formed rapidly and close together. Though weevils may have been
exceedingly numerous in the fields, the presence of this abundance of
food causes them to scatter, and they are consequently temporarily
somewhat less:in evidence. In many cases blooms appear and the
hope for a top crop increases. Nevertheless, this production of
squares also contributes to the production of a large number of
weevils late in the season and just at the time for their successful
hibernation. Asa result of this fact great injury is done to the crop
of the following season, with no gain whatever, or a very small one,
in the yield of the euaieuh season. From these considerations 1
seems plain that within the weevil territory all hope of a top crop
inust be given up and the destruction of the plants be practiced as
early in the fall as possible.

Another important difficulty hes in the tenant system. It is
usually the practice to terminate the work of the tenant with the
picking of the cotton, leaving the clearing of the field for the next
cropper. At present, after the cotton is picked the tenants fre-
quently move to other plantations or to other parts of the same plan-
tation. It should not be a difficult matter for planters to induce
their tenants to practice the fall destruction of the plants as the last
step in the production of a crop. In any case the plants have to be
removed before the ground can be prepared for planting the follow-
ing season; and the’ present recommendation merely involves apply-
ing, at a time some months earlier, the same amount of labor as is
necessary in the spring. The best. solution of the difficulty arising
from the tenant system would be in the inclusion, in the agreement
between the landlord and the tenant, of a provision which would
bind the latter to clean the land thoroughly before leaving it.

In a comparatively small area in southwestern Texas it might be
considered that there would be a further objection in the practice
which some farmers have of encouraging the growth of volunteer or

seppa cotton in the hope of procuring an early, and inexpensive crop.
As has been repeatedly pointed out by the Department of Agriculture,
this is beyond question the worst possible practice In w eevil-infested
regions. The disastrous experience of several counties in the southern
portion of the State during several seasons has abundantly demon-
strated the force of the warnings that have been issued from time to
time. The staple produced by “volunteer plants is short, kinky, and
undesirable. Before the advent of the weevil the only reason for en-
couraging such growth was to procure the first bale. Now, on account
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of its very detrimental bearing on the weevil problem, any attempt to
raise cotton from volunteer cotton should by all means be discouraged.

The point may be raised that the burning of the plants in the fall
removes valuable fertilizing constituents and that the continuance of
the practice would seriously reduce the fertility of the soil. In refer-
ence to this matter, however, it must be stated that the present general
practice 1s to clear the fields by burning the plants in the spring.
Therefore, practically the only additional draft upon the soil by the
method recommended is in the burning of many of the leaves and a
portion of the roots. However, destruction of the plants can only take
place after many of the leaves have fallen, and, in other cases, when
the plants have become completely defoliated by the cotton caterpillar.
The fertilizing constituents in various parts of the cotton plant have
been carefully determined. An estimate of the value of all the con-
stituents which could possibly be removed by fall destruction, based
upon the schedule of trade values adopted by experiment stations for
1898, shows that the loss per acre would be very small. It is plain
that the planter could not only regain this small loss but actually
greatly increase the fertility of the land by the use of commercial fer-
tilizers, which would cost an inconsiderable amount in comparison
with the gain in the following crop, as a result of lessened damage by
the boll weevil.

As a matter of fact, the preceding objections are not necessarily
serious. They deal with general changes in cotton culture made neces-
sary by the ravages of the boll weevil. As is beginning to be well
known to planters, it will not be possible for tenants to work as much
land as formerly. More cotton will be produced by decreasing acre-
ages and increasing the attention given to what remains. If this is
done the objections mentioned will largely disappear.

CONCLUSION.

Having studied and tested the methods of weevil control which
have been hitherto recommended, the writer firmly believes that the
destruction of the stalks in the early fall is the most effective method
known of actually reducing the numbers of the pest. This destruc-
tion will cost but a small fraction of the expense necessary in the
frequent picking up in the spring of the squares infested by the
hibernated weevils, and is far more thorough as a means of reducing
the numbers of the weevils than is the practice of picking hibernated
weevils from the young plants. Early destruction of the stalks is
essential to the greatest success of any system of controlling the pest.
All other practices recommended, though very valuable in securing a
crop, are of the greatest value as they are followed in connection with
this one prime essential. Since the earliest investigations of the boll
weevil made by this Department it has been recognized and pointed
out by Dr. L. O. Howard that this practice is of the first importance,
and the experience of recent years has added but certainty to this
conviction. A number of planters have adopted it, and their work
and large scale work by the Bureau of Entomology have abundantly

a See Bulletin 33 of the Office of Experiment Stations of this Department, pp.
81 to 142.

[Cir. 95]

ITHSONIAN INSTITUTION LIBRARIES

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3 9088 01272 7632

demonstrated its effectiveness. /¢ must not be thought that the
procuring of the immediate crop is the only thing to be desired.
Early and complete destruction of the stalks is undoubtedly the most
important single element insuring success for the subsequent year.

Concerted action in fall destruction is, of course, desirable. The
ereatest benefit will only result when whole communities adopt the
method. But no planter should hesitate on account of the indiffer-
ence of his neighbors. The fact that weevils move about but little
until the time when the bulk of the crop is safe will assist materially
in saving one field though nearby ones have not been properly treated,
and even under such circumstances the success of the method in one
field will be a powerful stimulus toward its general adoption the
following season.

It is true that the recommendations contained in this circular
involve considerable change in the practice of producing cotton.
Nevertheless the important changes that have been brought about up
to this time in the use of improved seed and fertilizers have also
been revolutionary in their character. It is hoped by the Department
that the agencies that assist in that matter—namely, organizations of
business men—will everywhere devote the same energy toward en-
couraging the practice of what is after all the most important step
in maintaining the supremacy of the cotton crop in the weevil regions.

Approved :
JAMES WILSON,
Secretary of Agriculture.
Wasuineton, D. C., September 12, 1907.
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