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| CIRCULAR NO. 107. . Issued January 12, 1909,

United States Department of Agriculture,
BUREAU OF ENTOMOLOGY,

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

WHAT CAN BE DONE IN DESTROYING THE COTTON BOLL
WEEVIL DURING THE WINTER.

By W. D. ELUNTER,
In Charge of Southern Field Crop Insect and Tick Investigations.

IMPORTANCE OF WINTER WORK.

The boll weevil attracts greatest attention during the growing season
of cotton, for the simple reason that its damage is then most evident.
When the infested squares are falling by millions every day the planter
is driven to most strenuous efforts to check the loss. The summer
season, however, is the one in which it is most difficult to combat the
weevil. The pest can be attacked in various ways at different seasons
of the year. This circular attempts to point out what can be done in
the winter when the weevils are in hibernating quarters and when nat-
ural conditions are assisting the farmer greatly by reducing the number
that will be able to survive until spring. At this time the farmer can
undoubtedly accomplish more than by hand-picking weevils and squares
or any other direct method of control that can be put into operation in
the summer season. A great advantage that winter work has in many
cases is that it involves no special outlay and consequently adds nothing
to the cost of producing cotton.. The work can be done during the
quiet period of the winter and at such times as will not interfere with
the general work of the plantation. Even on plantations run largely or
entirely by “wages hands’’ this work would undoubtedly warrant an
outlay on the part of the planter. As a matter of fact the winter season
could well be made the most active of the year as far as the destruction
of the weevil is concerned.

It is true that the Texas farmers have not paid much attention to
work against the weevil in the winter, but this does not by any means
indicate that such work will not be of prime importance to the planters
in Louisiana and Mississippi. Nature has afforded the Texas farmer
many advantages over the planter in the eastern part of the cotton belt.
As'has been pointed out in other publications of the Bureau of Ento-
mology, the Mississippi Valley planter will be compelled to contend
against many more weevils each spring than the climatic conditions in -
Texas have ever permitted to survive. For instance, in the spring of
1908 it was determined by Mr. Wilmon Newell, secretary of the State
crop pest commission of Louisiana, that as many as 6,000 hibernated
weevils per acre made their appearance in certain cotton fields in Avoy-
elles Parish, Louisiana. This shows a survival of weevils far beyond
what has ever been found in Texas. There are many other indications

of the special seriousness of the weevil problem in the Mississippi Val-
. AG——31

2

ley. All this demonstrates that the planters in regions recently invaded
by the weevil must resort to every means of control that is known and
must utilize to the fullest extent such methods as the Texas farmers
may not have been compelled to practice.

The all-important step in the control of the weevil is the destruction
of millions of individuals and the prevention of the development of
many more by uprooting and burning the cotton plants in the fall.
This is a step that indications show clearly is going to be indispensable
in the Mississippi Valley. In the light of what is now known it would
be folly for planters to attempt to produce cotton unless they follow
this practice religiously. If, for any reason, the cotton plants have not
been removed in the fall, some good can be accomplished by’ their
removal later in the season. The proper thing to be done by the
planter who desires to reduce weevil damage to the minimum is to
combine the fall destruction of the plants with such measures, to be
taken later in the season, as are outlined in this circular. The advice
now given is not to depend upon winter work altogether for the control
of the weevil. The winter work is merely a second step, to be taken in
connection with the destruction of the weevils and the prevention of the
maturity of the fall broods by uprooting and burning the plants. Where
that step has not been taken, the work outlined in this circular is the
main dependence of the planters at this time.

WHERE WEEVILS ARE TO BE FOUND DURING THE WINTER.

The whole question of what can be done to destroy the weevils in
the winter depends upon where they are to be found. The Bureau of
Entomology has taken pains to determine the localities in which the
weevils secrete themselves during the winter months. Some weevils
fly outside of the cotton fields into the timber before frost has killed the
cotton. Of course, such individuals as fly great distances from the
cotton fields, or into heavy timber, are entirely beyond the reach of the
planter. The remainder of the weevils, however—those remaining in
and about the cotton fields—are more or less at the mercy of the
planter for several months during the winter.

In cotton fields and in their immediate vicinity weevils have been
found hibernating in four principal situations: First, in burrs and un-
opened bolls on the plants; second, in bolls or portions of bolls that
have been knocked to the ground; third, under such trash as leaves
and grass abounding in most cotton fields; fourth, in the cracks in the
ground caused by drying.

The numbers of weevils found in the situations just mentioned show
clearly what opportunities the farmer has for their destruction. On
January 16, 1907, a field near Wolfe City, Tex., showed from 363 to
1,500 live weevils per acre in the burrs still hanging to the plants.
These were generally in the partly opened locks where weevils had
matured in the fall, but some were in locks from which all of the cotton
had been removed. On January 27, 1907, as many as 2,250 weevils
per acre were found on the ground in a cotton field near Dallas, Tex.
The number was determined by raking all of the trash carefully from a
square rod of ground and examining it in the laboratory. On Decem-
ber 18 living weevils at the rate of 1,056 per acre were found at Dallas.
On January 16 820 living weevils per acre were found in burrs and
under leaves and grass in a cotton field at Victoria, Tex. On Novem-

A6é-—31

2°
3)

ber 15 4 weevils were found in the cracks around the bases of 22
cotton plants growing near Dallas. This indicates a total number of
weevils per acre in such situations in this field of 1,090.

Practically all of the weevils to be found in the situations described
ean be killed by raking and burning the trash, except those in cracks
in the ground, and these, in the majority of cases, would probably be
Erushed by winter plowing of the fields.

PLOWING NOT EFFECTIVE.

The point may be raised that winter plowing, by burying the weevils
found in trash on the surface, might have the same effect as burning.
On the contrary, experiments have shown that weevils can easily make
their way through several inches of soil. Consequently such work in
general is as likely to protect as to destroy the weevils. Of course, if
heavy rains should follow immediately after plowing, it is possible that
some soils would be so compacted as to prevent the emergence of
weevils. Nevertheless, this could not happen under usual conditions.
In the case of weevils in cracks, destruction would not result from
burial but from crushing.

What has just been stated should not be taken to mean that winter
plowing should not be followed. As a matter of fact, the winter work-
ing of the fields should be practiced, not only on general principles, but
to assist in procuring an early crop. The present purpose is merely to
point out how to destroy the boll weevil in the winter. Regardless of
its other benefits, winter plowing can not be depended upon to actually
kill many weevils.

WEEVILS THAT CAN BE REACHED OUTSIDE OF COTTON FIELDS.

In addition to those in the cotton fields themselves, many weevils
can be reached that have found winter quarters along turn-rows, in
ditches, along fences, and in the trash that is frequently allowed to
accumulate around seed houses. Fire is again the agent of destruction
at the command of thefarmer. Careful burning of turn-rows and ditches
and cleaning of fence corners and similar situations will result in the
death of many weevils that might survive to damage the crop of the
following season.

The work of burning and cleaning the plantation should not stop
with the immediate vicinity of cotton fields. Many weevils fly into
corn fields, where they find suitable quarters for passing the winter.
These fields, on a cotton plantation, should be cleaned during the win-
ter as thoroughly as the fields where cotton has been growing or is to be
grown during the next season. It has been found that sorghum fields
furnish exceptionally favorable opportunities for hibernating weevils.
The heavy stubble left by this crop catches grass and general débris
blown about by the wind, which then becomes heavily matted. Here
many weevils are to be found during the winter. In many cases in
Texas the earliest appearing weevils and the greatest damage to the
crop have been shown to be chargeable to neighboring sorghum fields
which have served as winter quarters for the pest.

Many weevils undoubtedly find hibernating quarters in trash along
railroad rights of way as well as along wagon roads. The importance
of such means furnished the weevil for passing the winter becomes great
where, as in many cases, the roads or railroads pass through localities

AG —31

A

where cotton fields adjoin the public property. It should be the duty
of railroad and county authorities in such cases to assist the farmers as
far as practicable by removing the shelter for the weevil.

WEEVILS IN COTTON SEED.

Cotton seed has frequently been supposed to furnish exceptionally
favorable winter quarters for the weevil. It has been shown that many
weevils pass through the gins and are later to be found in the bulk cot-
ton seed in storage. Up to a certain time in the winter cotton seed is
very likely to contain live weevils. Many experiments, however, have
shown that very few are able to survive in this medium until spring.
This seems to be due principally to the absence of moisture. Repeat-
edly numbers of weevils have been placed in cotton seed in the fall.
Altogether 6,600 weevils have been used in these experiments. They
were plaved under a variety of conditions. Although many have sur-
vived until the middle of winter, only two lived until the first of April.
It is therefore clear that cotton seed itself is not an especially dangerous
commodity. Although it is true that the earliest weevils frequently
make their appearance in the vicinity of seed houses, this is to be
accounted for by the fact that the insects find quarters under the build-
ing and under the trash that is allowed to accumulate in such situations
rather than in the cotton seed itself.

CONCLUSION.

The climatic and labor conditions surrounding cotton production in
Louisiana and Mississippi leave no doubt that the planters in those
States must not overlook any important means of controlling the boll
weevil. This circular points out one important and inexpensive means
that can be practiced by every planter. It is of special importance in
the humid regions recently invaded where fears of disaster are now
commonly entertained. The Department of Agriculture urges that
cotton raisers take advantage of the enemy while they have the oppor-
tunity and by the means herein described greatly increase the chances
for producing a crop the coming season. -

Approved:
JAMES WILSON,
Secretary of Agriculture.

WASHINGTON, D. C., December 19, 1908.
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