• TABLE OF CONTENTS
HIDE
 Front Cover
 Front Matter
 Introduction
 Historical review of poisoning
 A study of boll weevil activit...
 Characteristics of boll weevil...
 Poison ingestion
 Diluted calcium arsenate
 Application of poison to dry and...
 Day and night poisoning
 Syrup mixtures for spraying
 Syrup mixtures for mopping
 Summary and conclusions






Group Title: Bulletin - University of Florida Agricultural Experiment Station ; 192
Title: How the boll weevil ingests poison
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00026682/00001
 Material Information
Title: How the boll weevil ingests poison
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: p. 145-172 : ill., charts ; 23 cm.
Language: English
Creator: Grossman, Edgar F
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1928
 Subjects
Subject: Boll weevil -- Control   ( lcsh )
Cotton -- Diseases and pests -- Control   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references.
Statement of Responsibility: by Edgar F. Grossman.
General Note: Cover title.
Funding: This collection includes items related to Florida’s environments, ecosystems, and species. It includes the subcollections of Florida Cooperative Fish and Wildlife Research Unit project documents, the Florida Sea Grant technical series, the Florida Geological Survey series, the Howard T. Odum Center for Wetland technical reports, and other entities devoted to the study and preservation of Florida's natural resources.
 Record Information
Bibliographic ID: UF00026682
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000923499
oclc - 18173060
notis - AEN4050

Table of Contents
    Front Cover
        Page 145
    Front Matter
        Page 146
    Introduction
        Page 147
    Historical review of poisoning
        Page 147
        Page 148
    A study of boll weevil activities
        Page 149
        Page 150
    Characteristics of boll weevil locomotion
        Page 151
    Poison ingestion
        Page 151
        Page 152
        Page 153
        Page 154
        Page 155
        Page 156
    Diluted calcium arsenate
        Page 157
        Page 158
        Page 159
    Application of poison to dry and wet cotton plants
        Page 160
        Page 161
        Page 162
        Page 163
        Page 164
        Page 165
    Day and night poisoning
        Page 166
    Syrup mixtures for spraying
        Page 166
        Page 167
        Page 168
    Syrup mixtures for mopping
        Page 169
        Page 170
        Page 171
    Summary and conclusions
        Page 172
Full Text



January, 1928


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION







HOW THE BOLL WEEVIL

INGESTS POISON


By EDGAR F. GROSSMAN









TECHNICAL BULLETIN












Bulletins will be sent free upon application to the
Agricultural Experiment Station
GAINESVILLE, FLORIDA


Bulletin 192







BOARD OF
P. K. YONGE, Chairman, Pensacola
E. W. LANE, Jacksonville
A. H. BLENDING, Leesburg
W. B. DAVIS, Perry


CONTROL
E. L. WARTMANN, Citra
J. T. DIAMOND, Secretary, Talla-
hassee.
J. G. KELLUM, Auditor, Tallahassee


STATION EXECUTIVE STAFF
WILMON NEWELL, D. Sc., Director ERNEST G. MOORE, M. S., Asst. Ed
JOHN M. SCOTT, B. S., Vice-Director IDA KEELING CRESAP, Librarian
S. T. FLEMING, A. B., Asst. to Di- RUBY NEWHALL, Secretary
rector K. H. GRAHAM, Business Manager
J. FRANCIS COOPER, B. S. A., Editor RACHEL MCQUARRIE, Accountant
MAIN STATION-DEPARTMENTS AND INVESTIGATORS


AGRONOMY
W. E. STOKES, M. S. Agronomist
W. A. LEUKEL, Ph. D., Asso.
C. R. ENLOW, M. S. A., Asst.*
FRED H. HULL, M. S. A., Asst.
A. S. LAIRD, M. S. A., Asst.
ANIMAL INDUSTRY
JOHN M. SCOTT, B. S., Animal
Industrialist
F. X. BRENNEIS, B. S. A., Dairy
Herdsman
CHEMISTRY
R. W. RUPRECHT, Ph.D., Chemist
R. M. BARNETTE, Ph. D., Asst.
C. E. BELL, M. S., Asst.
H. L. MARSHALL, M. S., Asst.
J. M. COLEMAN, B. S., Asst.
J. B. HESTER, B. S., Asst.
COTTON INVESTIGATIONS
W. A. CARVER, Ph. D., Asst.
M. N. WALKER, Ph. D., Asst.
E. F. GROSSMAN, M. A., Asst.
RAYMOND CROWN, B.S.A., Field Asst.
ECONOMICS, AGRICULTURAL
C. V. NOBLE, Ph. D., Ag. Economist


BRUCE MCKINLEY, B. S. A., Asst.
M. A. BROKER, M. S. A., Asst.
ECONOMICS, HOME
OUIDA DAVIS ABBOTT, Ph. D., Chief
L. W. GADDUM, Ph. D., Asst.
C. F. AHMANN, Ph. D., Asst.
ENTOMOLOGY
J. R. WATSON, A. M., Entomologist
A. N. TISSOT, M. S., Asst.
H. E. BRATLEY, M. S. A., Asst.
HORTICULTURE
A. F. CAMP, Ph. D., Asso. Hort.
M. R. ENSIGN, M. S., Asst.
HAROLD MOWRY, Asst.
G. H. BLACKMON, M. S. A., Pecan
Culturist
PLANT PATHOLOGY
O. F. BURGER, D.Sc., Plant Pathologist
G. F. WEBER, Ph. D., Asso.
K. W. LOUCKS, B. S., Asst.
ERDMAN WEST, B. S., Mycologist
VETERINARY MEDICINE
A. L. SHEALY, D.V.M., Veterinarian
D. A. SANDERS, D. V. M., Asst.
E. F. THOMAS, D. V. M., Lab. Asst.


BRANCH STATION AND FIELD WORKERS
W. B. TISDALE, Ph. D., Plant Pathologist, in charge, Tobacco Experiment
Station (Quincy)
Ross F. WADKINS, M. S., Lab. Asst. in Plant Pathology (Quincy)
JESSE REEVES, Foreman, Tobacco Experiment Station (Quincy)
J. H. JEFFERIES, Superintendent, Citrus Experiment Station (Lake Alfred)
W. A. KUNTZ, A. M., Assistant Plant Pathologist (Lake Alfred)
R. L. MILLER, Assistant Entomologist (Lake Alfred)
W. L. THOMPSON, Assistant Entomologist (Lake Alfred)
F. R. DARKIS, Ph. D., Assistant Chemist (Lake Alfred)
GEO. E. TEDDER, Foreman, Everglades Experiment Station (Belle Glade)
R. V. ALLISON, Ph. D., Soils Specialist (Belle Glade)
J. H. HUNTER, M. S., Assistant Agronomist (Belle Glade)
J. L. SEAL, M. S., Assistant Plant Pathologist (Belle Glade)
H. E. HAMMAR, M. S., Field Assistant (Belle Glade)
L. O. GRATZ, Ph. D., Associate Plant Pathologist (Hastings)
A. N. BROOKS, Ph. D., Associate Plant Pathologist (Plant City)
A. S. RHOADS, Ph. D., Associate Plant Pathologist (Cocoa)
STACY O. HAWKINS, Field Assistant in Plant Pathology (Homestead)
D. G. A. KELBERT, Field Assistant in Plant Pathology (Bradenton)
R. E. NOLEN, M. S. A., Field Assistant in Plant Pathology (Monticello)
FRED W. WALKER, Assistant Entomologist (Monticello)
E. D. BALL, Ph. D., Associate Entomologist (Sanford)

*In cooperation with U. S. Department of Agriculture.








HOW THE BOLL WEEVIL INGESTS POISON
By EDGAR F. GROSSMAN
INTRODUCTION

The successful poisoning of the cotton boll weevil, Anthono-
mus grandis Boh., has long been a question of economic im-
portance. Although great progress has been made, there is still
a deplorable usage of poor poisoning methods for controlling
the boll weevil.
An understanding of the manner in which the weevil takes
up poison should direct control measures, thereby eliminating
the haphazard methods of poisoning the cotton fields and insur-
ing an efficient distribution of poison.
The writer, in a preliminary report, presented data establish-
ing the supposition that a boll weevil, when crawling, accident-
ally accumulates poison on its snout tip and later, on feeding or
by mandibular activity, introduces the poison into its intestine.
Subsequent experimentation, including 4,660 individual weevil
tests, was conducted to present (a), how poison is ingested by
the boll weevil; (b), whether or not calcium arsenate analyzing
40 percent total arsenic pentoxide can be successfully diluted;
and (c), the advantages or disadvantages encountered by the
use of syrup mixtures as a mopping or spraying poison.

HISTORICAL REVIEW OF POISONING
Immediately upon the discovery of the seriousness of cot-
ton boll weevil damage, attempts were made to poison the weevil.
Paris green or London purple mixed at the rate of 1 pound to
150 gallons of water was recommended for spraying when the
cotton bolls began to form.' Turning from the unsuccessful use
of this poisoning method, attention was given entirely to cul-
tural methods of control until 1903-04, when Paris green, ap-
plied as a dust, was advocated by B. W. Marston.2 After drag-
ging along until 1905,' poisoning methods of controlling the
weevil were again dropped and no further work with poison was
reported until 1908,' when powdered lead arsenate was found to
be effective in killing the weevil. After additional experimenta-
'Howard, L. 0. Circ. 6, Div. Ent. U. S. Dept. Agr. April 1895.
'Report. Circ. 2, Louisiana Crop Pest Commission. November 1904.
'Report. Circ. 8, Louisiana Crop Pest Commission. 1906.
'Newell, Wilmon and T. C. Barber, Circ. 23, Louisiana Crop Pest Com-
mission. July 1908.








HOW THE BOLL WEEVIL INGESTS POISON
By EDGAR F. GROSSMAN
INTRODUCTION

The successful poisoning of the cotton boll weevil, Anthono-
mus grandis Boh., has long been a question of economic im-
portance. Although great progress has been made, there is still
a deplorable usage of poor poisoning methods for controlling
the boll weevil.
An understanding of the manner in which the weevil takes
up poison should direct control measures, thereby eliminating
the haphazard methods of poisoning the cotton fields and insur-
ing an efficient distribution of poison.
The writer, in a preliminary report, presented data establish-
ing the supposition that a boll weevil, when crawling, accident-
ally accumulates poison on its snout tip and later, on feeding or
by mandibular activity, introduces the poison into its intestine.
Subsequent experimentation, including 4,660 individual weevil
tests, was conducted to present (a), how poison is ingested by
the boll weevil; (b), whether or not calcium arsenate analyzing
40 percent total arsenic pentoxide can be successfully diluted;
and (c), the advantages or disadvantages encountered by the
use of syrup mixtures as a mopping or spraying poison.

HISTORICAL REVIEW OF POISONING
Immediately upon the discovery of the seriousness of cot-
ton boll weevil damage, attempts were made to poison the weevil.
Paris green or London purple mixed at the rate of 1 pound to
150 gallons of water was recommended for spraying when the
cotton bolls began to form.' Turning from the unsuccessful use
of this poisoning method, attention was given entirely to cul-
tural methods of control until 1903-04, when Paris green, ap-
plied as a dust, was advocated by B. W. Marston.2 After drag-
ging along until 1905,' poisoning methods of controlling the
weevil were again dropped and no further work with poison was
reported until 1908,' when powdered lead arsenate was found to
be effective in killing the weevil. After additional experimenta-
'Howard, L. 0. Circ. 6, Div. Ent. U. S. Dept. Agr. April 1895.
'Report. Circ. 2, Louisiana Crop Pest Commission. November 1904.
'Report. Circ. 8, Louisiana Crop Pest Commission. 1906.
'Newell, Wilmon and T. C. Barber, Circ. 23, Louisiana Crop Pest Com-
mission. July 1908.







Florida Agricultural Experiment Station


tion," powdered arsenate of lead was offered as a practical boll
weevil poison. The mortality of the weevil following application
of the lead arsenate was held to be due to ingestion of the poison
with food.
It was difficult, however, to alter the widespread belief that
the weevil could not get a lethal dose of poison by eating poi-
soned surfaces. Past experiences with London purple and Paris
green clearly showed the belief to be well founded, while early
experimentation with calcium arsenate, which itself was in an
experimental stage of development, probably augmented this
opinion.
After considerable delay a report of poison tests conducted
by the United States Department of Agriculture was finally pub-
lished in 1918.' Dissatisfied with the idea that the weevil in-
gested the poison with food while eating, a new idea was ad-
vanced in this report to the effect that the weevil drank the
poison with dew or other precipitation.
The importance of the water-drinking habit of the weevil in
connection with poisoning was examined by a number of work-
ers7 who found that the actual presence of dew had little to
do with the mortality of the weevil, after completing tests in
which powdered poisons were applied to plants protected from
dew and also to plants subjected to dew and other precipita-
tion.
With the dew theory still generally accepted by the cotton
growers and no definite information at hand regarding the
mariner in which the weevil actually obtained a toxic dose of
poison, the writer made a study of the boll weevil's activities
with the express purpose of ascertaining the manner of poison
ingestion. It was found that the poison particles were accident-
ally accumulated on the snout tip and later ingested by mandib-
ular activity alone or with the food material passing along the
snout to the intestine.1'" At about the same time Chemical

5Newell, Wilmon and G. D. Smith, Circ. 33, Louisiana Crop Pest Com-
mission. Dec. 1909.
6Coad, B. R. Bul. 731, Bureau of Entomology, U. S. Dept. Agr. July
1918.
7Newell, Wilmon and Eli K. Bynum, Jour. Econ. Ent., Vol. 13, No. 1,
pp. 123-135, Feb. 1920.
SHinds, W. E., Circ. 38, Alabama Polytechnic Institute, March 1920.
OWarren, D. C., Jour. Econ. Ent. No. 5, Vol. 15, pp. 345-349. October
1922.
"Grossman, E. F., Jour. Econ. Ent., No. 1, Vol. 18, p. 236. February
1925.







Bulletin 192, How the Boll Weevil Ingests Poison 149

Warfare Service investigators decided that "the weevil did not
obtain the bulk of the poison through feeding or drinking the
poisoned dew, but by more or less accidentally picking up the
particles of dust on its snout and subsequently ingesting the
same."" During the spring and summer of 1925, F. L.
Thomas" noted that the weevil in moving about the plants
frequently touches the surface with the tip of its beak and will,
on crawling over a poisoned surface, cover the snout tip with
the material.
Inasmuch as the manner in which the boll weevil ingests
poison bears directly on the manner in which the poison should
be dispersed, the subject was considered of sufficient importance
to handle in detail.

A STUDY OF BOLL WEEVIL ACTIVITIES
Assuming the possibility of trapping the weevil by taking ad-
vantage of some of its activities, the present writer conducted
a study of the weevil's habits both in the field and in the insec-
tary.
Experimental evidence was first sought to ascertain the cor-
rectness of the claims of certain manufacturers of boll weevil
poisons to the effect that their chemists had found an attract-
ant for the weevil. The poisons containing these "attractants"
were found to be decidedly negative with reference to having a
power to attract weevils, by failing to cause a single weevil to
deviate from its course of travel. If the mixture were in the
direct path of the weevil, the weevil would get to the mixture;
if not, the weevil would'not swerve a fraction of an inch towards
the mixture. The weevil also failed to respond to repellents.
Chemotropic experiments, however, are still being conducted
elsewhere and a number of workers still hope to trap the weevil
through its sense of smell.
Though the weevil, when in captivity, responds quickly to
light, field conditions are such that the use of light for trapping
"Thomas, F. L. 38th Annual Report, p. 20, Texas Agr. Exp. Sta. De-
cember 1925.
"Newell, Wilmon, E. F. Grossman and A. F. Camp. Bul. 180, Fla. Agr.
Exp. Sta. May 1926.
"Thomas, F. L. 39th Annual Report, pp. 28-29, Texas Agr. Exp. Sta.
December 1926.
"Walker, H. W. and J. E. Mills. Industrial and Engineering Chemis-
try No. 6, Vol. 19, pp. 703-722. June 1927.







Florida Agricultural Experiment Station


cannot be employed. The weevil is habitually inactive during
the night, as evidenced by the location of weevils in secluded
spots on the cotton plants after dark and finding them in the
same places at dawn. Furthermore, careful search during the
night has repeatedly failed to find weevils moving from plant to
plant in the field or even from place to place on the plant. It is
not impossible, however, that the discovery of an irritating
gas which would cause the weevils to leave their resting places
at night combined with the use of light traps would cause the
capture of weevils infesting a field.
The death-feigning habit of the weevil encouraged the manu-
facture of mechanical devices which dislodged weevils by tap-
ping the plants, catching them in a container as they "sulled"
and fell. It was found that these devices failed because a very
large percentage of the weevils remain in the cotton fruit and
buds, from which positions they cannot be dislodged.
Turning from the study, unprofitable from the viewpoint of
control measures, of the chemotropic, phototropic and death-
feigning activities of the weevil, observations were carried on
to determine the nature of the weevil's feeding habits.
It was found that the feeding habits of the hibernated weevil
differ from those of the field-hatched weevil. The former, after
its flight from hibernation quarters to the cotton fields, rarely
moves from plant to plant, feeding first in the buds and later on
the cotton squares as they appear. Even the movement of the
female from plant to plant in search of unpunctured squares for
egg laying is so limited that the first field infestations are
"spotted."
The field-hatched weevil, on the other hand, quickly spreads
over the cotton field, moving from plant to plant in search of
fresh squares for food and egg-laying. The greatest difference
between the hibernated and field-hatched weevils lies in the
stereotropic tendencies of the hibernated weevil which secretes
itself so thoroughly that a casual observer would think a field
weevil-free. This tendency to bring its body completely into
contact with solid bodies, strongest when the weevil enters hiber-
nation in the fall, appears to be retained to such an extent that
the hibernated weevil does not feed in the open bloom, which
is the favorite feeding place of the field-hatched weevil.
The economic importance of an understanding of these feed-
ing habits lies in the correct use of poisons for controlling the






Bulletin 192, How the Boll Weevil Ingests Poison 151

weevil, a discussion of which will be presented later when poison
applications are considered.

CHARACTERISTICS OF BOLL WEEVIL LOCOMOTION
The most significant observation made during the writer's
study of boll weevil activities was the determination of the man-
ner in which the boll weevil crawled from place to place. A char-
acteristic dipping or bobbing of the snout which brought the
mouth parts (Fig. 80A) of the weevils in contact with the surface
over which the weevil
crawled, was noted. This
dipping is more pronounced
when the weevil meets an
intersection of branches or
leaf stems or any sur-
face which presents a break
in an otherwise smooth A B
plane. Such a snout dip- Fig. 80.--Boll weevil snout, showing
mouthparts at tip of snout. A, looking
ping always takes place ex- into snout, mandibles opened; B, side
cept when the weevil be- view; both enlarged 15 times.
comes excited and crawls rapidly, in which case the snout is
held stretched out almost parallel to the surface.
Having noted the close contact between the mouth parts of
the weevil and the surface over which the weevil crawls, it
seemed probable that the weevil would pick up small particles
of powdered materials on its snout while crawling over a sur-
face dusted with such materials.

POISON INGESTION
Close observation showed that boll weevils crawling about on
cotton plants which had been dusted with calcium arsenate had
their snouts tipped with white. Such weevils were kept in cap-
tivity to determine the percent mortality that would result from
the snout dipping, but as the history of the individual weevils
was not known the data thus collected could not be interpreted.
Consequently it became necessary to devise series of experi-
ments to ascertain whether the poison particles, accidentally ac-
cumulated on the snout, would be ingested and subsequently
kill the weevil.






Bulletin 192, How the Boll Weevil Ingests Poison 151

weevil, a discussion of which will be presented later when poison
applications are considered.

CHARACTERISTICS OF BOLL WEEVIL LOCOMOTION
The most significant observation made during the writer's
study of boll weevil activities was the determination of the man-
ner in which the boll weevil crawled from place to place. A char-
acteristic dipping or bobbing of the snout which brought the
mouth parts (Fig. 80A) of the weevils in contact with the surface
over which the weevil
crawled, was noted. This
dipping is more pronounced
when the weevil meets an
intersection of branches or
leaf stems or any sur-
face which presents a break
in an otherwise smooth A B
plane. Such a snout dip- Fig. 80.--Boll weevil snout, showing
mouthparts at tip of snout. A, looking
ping always takes place ex- into snout, mandibles opened; B, side
cept when the weevil be- view; both enlarged 15 times.
comes excited and crawls rapidly, in which case the snout is
held stretched out almost parallel to the surface.
Having noted the close contact between the mouth parts of
the weevil and the surface over which the weevil crawls, it
seemed probable that the weevil would pick up small particles
of powdered materials on its snout while crawling over a sur-
face dusted with such materials.

POISON INGESTION
Close observation showed that boll weevils crawling about on
cotton plants which had been dusted with calcium arsenate had
their snouts tipped with white. Such weevils were kept in cap-
tivity to determine the percent mortality that would result from
the snout dipping, but as the history of the individual weevils
was not known the data thus collected could not be interpreted.
Consequently it became necessary to devise series of experi-
ments to ascertain whether the poison particles, accidentally ac-
cumulated on the snout, would be ingested and subsequently
kill the weevil.







Florida Agricultural Experiment Station


Individual weevils were placed on a surface which had been
lightly covered with powdered calcium arsenate, and, after al-
lowing them to crawl a short distance, the snout tip of each
weevil was examined. The tips were white, being covered with
calcium arsenate dust which stuck to the mouth parts. The wee-
vils were then placed singly on cotton squares. Some of the
weevils succeeded in knocking the dust off of their snouts while .
working their way through the closely fitting square bracts
while others proceeded to feed with the dust still sticking to
the snout tip. Those weevils which fed without knocking the
dust off either died or were rendered inactive.
At this stage of the experimental work a heavy frost killed all
the cotton and it became necessary to substitute banana as a
sustaining food for the weevils collected for continuing the tests.
(That banana, changed often enough to prevent molding, was a
suitable food for the weevils became evident when weevils
caught November 20 were kept active in an incubator at 220 C.
throughout the winter until March 19 when they were fed cot-
ton leaves.) Proceeding with banana as food material, records
were taken of some 400 individual weevils to show the effect of
the following treatments:
a. Individual weevils were held securely with a pair of for-
ceps, in such a manner that the snouts only were tipped with
dry calcium arsenate. The weevils were then placed singly in
vials containing food and set aside for a maximum period of five
days during which time a number of the weevils given this
treatment died.
a.2 A test similar to "(a)" but with an additional dipping of
the snout after a period of 12 hours.
a.3 "(a)" repeated with three dippings at 12-hour periods.
Data secured from these tests showed, at the end of a five-day
period, an average of about 50 percent mortality for one dipping
of the snout, about 60 percent for two dippings and about 70
percent for three dippings. These data indicate that the weevil
gets the calcium arsenate dust on its snout tip accidentally and
later, when chewing or boring, introduces the poison into the
intestine, provided, of course, that the dust has not been knocked
off.
b. Single weevils were so placed that on crawling towards the
light they would pass over a fine line of calcium arsenate, there-







Bulletin 192, How the Boll Weevil Ingests Poison 153

by accomplishing the snout dipping themselves. Removed to a
vial containing food the weevils were then set aside for mortal-
ity rate determination.
These tests bore additional evidence towards establishing the
idea of an accidental accumulation of poison on the snout tip
while crawling over thoroughly dusted cotton plants.
c. In order to determine whether or not calcium arsenate
was an irritant, various parts of the weevil's body were covered
with the dust in such a manner that it could not be subsequently
carried to the snout.
There was no suggestion of irritation or poisoning noted,
which indicates that the poison must be ingested before affect-
ing the weevil.
d. Weevils were placed in vials containing poisoned food.
The low percent (about 20 percent) weevil mortality obtained
from these tests was surprising, pointing out the possibility of
the weevil getting too little calcium arsenate on eating through
the poisoned surface to the interior of the food. These tests tend
to discourage the idea, long held, that the calcium arsenate
should be blown into the cotton squares where the weevil does
its feeding and egg laying.
e. Weevils were placed in petri dishes containing 1/2 cc. dry
calcium arsenate.
All these weevils died within 24 hours. This was undoubtedly
due to the fact that the weevils thus confined were constantly
opening and closing their mandibles in an effort to escape from
the dish. The continual efforts to bore a passage out forced a
large quantity of calcium arsenate into the snout and intestine.
f. Untreated weevils were placed individually in vials con-
taining food in order to test the general condition ("natural
mortality") of the weevils used for the experiments.
The mortality rate of these weevils varied from 0 to 15 per-
cent, averaging about 10 percent for a 5-day period.
SNOUT DIPPING EXPERIMENTS
Though the above experiments well illustrate the snout dip-
ping accumulation of calcium arsenate, over 4,000 additional
weevils were later tested in order to validate the foregoing con-
clusions.
Assuming that the more often a weevil dips its snout into cal-
cium arsenate, the greater is the chance for obtaining a lethal
dose of poison, 770 weevils were dipped at three-hour intervals







Florida Agricultural 'Experiment Station


into calcium arsenate one, two, three, and four times, respec-
tively. They were then placed individually in vials containing
cotton squares which were renewed from time to time to provide
a constant supply of fresh food. The mortality rate of the
weevils was recorded for a period of five days only, as the suc-
ceeding days gave very little actual difference between the
"natural mortality" rate and the rates obtained from the vari-
ously treated weevils.
An analysis of Table I, which gives a summary of the 770
weevil tests, shows that the percent mortality increased with
the number of dippings. This indicates that the weevil may have
successfully knocked one dipping of calcium arsenate off of the
snout. However, when two, three, or more dippings occur, they
would eventually retain a poisonous dose on the snout, to be
carried later to the intestine, on feeding. This condition in it-
self points out the necessity of distributing the poison over the
largest possible plant area in the field for boll weevil control,
since the weevil, on crawling from place to place on "dusted"
surfaces, repeatedly dips its snout into the poison.
TABLE I.-MORTALITY OF WEEVILS WITH SNOUT DIPPED AT 3 HOUR INTER-
VALS IN POWDERED CALCIUM ARSENATE 1, 2, 3, AND 4 TIMES, RESPECTIVELY.

Number Weevils Dead Each Day
0 -'0 0.^ *-OL 0





1 13 11 22 17 1
2 21 44 38 37 4
3 27 31 32 41 6
4 23 19 25 28 3
5 16 12 9 7 7
Total dead .... 100 117 126 130 21
Percent dead 62 73 84 87 14
Weevils alive
at end of exp. 60 43 24 20 129
-Percent alive 38 27 16 13 86







Bulletin 192, How the Boll Weevil Ingests Poison 155

Comparison of the data in the above table is easily made by
means of figure 81, in which the daily percentage of mortality
is aggregated to show the total mortality rate of the individual
groups at the end of each day.

PERCENT [ i "


.. i _ i



7- : --









Fig. 81.-Graph showing percent weevils killed by dipping the snout at
3-hour intervals into powdered calcium arsenate, one, two, three, and
four times respectively.

Experiments were conducted in which the weevil was so placed
that it would crawl towards the light, passing over a single fine
line of powdered calcium arsenate, thereby automatically pick-
ing up some of the poison on the snout tip. Although the mor-
tality rates in these experiments do not show so clear a grada-
tion as in the previous set of experiments, probably due to the
small number of weevils tested (300), there is, nevertheless, a
decided mortality present. These results again substantiate the
idea that the poison need not be blown into the squares but
should be well distributed over the entire plant. This becomes
evident in view of the fact that the weevil obtained its dosage

vial into which each weevil was placed immediately after crawl-
ing over the calcium arsenate contained an unpoisoned square
upon which the weevil fed.
upon which the weevil fed.








156 Florida Agricultural Experiment Station

TABLE II.-MORTALITY OF WEEVILS DIPPING THEIR SNOUTS IN POISON BY
CRAWLING THROUGH A FINE LINE OF POWDERED CALCIUM ARSENATE AT
3 HOUR INTERVALS 1, 2, 3, AND 4 TIMES RESPECTIVELY.
Number Weevils Dead Each Day








1 5 11 2 4 1
2 15 15 14 7 3
3 16 17 17 7 4
4 16 8 8 4 2
5 11 3 3 3 4

Total dead .... 63 54 44 25 14
Percent dead 79 90 88 83 18
Weevils alive








at end of exp. 17 6 6 5 66
Percent alive 21 11 2 14 1
2 15 15 14 7 3
3 16 17 17 7 4
4 16 8 8 4 2
5 11 3 3 3 4
Total dead -..- 63 54 44 25 14
Percent dead 79 90 88 83 18
Weevils alive
at end of exp. 17 6 6 5 66
Percent alive 21 10 12 17 82


...... a--i-- \ I i I I t I I I:
Fig. 82.-Diagram showing the mortality rate of weevils crawling over a
fine line of powdered calcium arsenate at 3-hour intervals, 1, 2, 3, and
4 times respectively.







Bulletin 192, How the Boll Weevil Ingests Poison 157

Figure 82 presents a summation of the above data in graph
form.
DILUTED CALCIUM ARSENATE
Due to the difficulties encountered in the early stages of the
manufacture of a satisfactory brand of calcium arsenate, rigid
specifications for this material were made and all calcium arsen-
ate to be used for boll weevil control was required to meet these
specifications: "Not less than 40 percent arsenic pentoxide. Not
more than 0.75 percent water-soluble arsenic pentoxide. Density
not less than 80 or more than 100 cubic inches per pound.""
At this time also recommendations, based upon experimental
work, were made to use the pure calcium arsenate without the
addition of any diluent whatsoever; mention was made, however,
of the possibility of diluted mixtures being used in the future.
Inasmuch as no later recommendations for the use of diluted
calcium arsenate were offered, the writer undertook to compare
the efficiency of a 50-50 mixture of calcium arsenate and hy-
drated lime with that of a standard brand of undiluted calcium
arsenate.
Since the weevil, when crawling over a poisoned surface, con-
tinually dips its snout into the poison, the supposition that less
of the poison equally well distributed would be effective, ap-
peared sound. Consequently, a number of weevil tests (1,110)
were carried out after choosing hydrated lime as both a cheap
carrier and diluent for making the diluted mixture to be com-
pared with the undiluted calcium arsenate.
Of the two groups of weevils used for these tests, one was
snout dipped into each of the two materials while the other
group was allowed to crawl through a line of the poisons. The
relative toxicity of the two poisons, (a) the 50-50 mixture of
calcium arsenate and hydrated lime and (b) pure calcium arsen-
ate, are compared in Tables III and IV. Though the pure cal-
cium arsenate in the snout dipping tests shows a consistently
higher rate of mortality than the mixture does, the tests in
which weevils crawled over a line of the two materials show
a remarkable similarity in their effect.

"Coad, B. R. and T. P. Cassidy, Bul. No. 875, Bureau of Entomology,
U. S. Dept. Agr., July, 1920.









TABLE III.--A COMPARISON OF TIE MORTALITY OF WEEVILS WITH SNOUT DIPPED AT 3 HOUR INTERVALS 1, 2, 3, AND 4
TIMES RESPECTIVELY IN (a) POWDERED CALCIUM ARSENATE AND (b) A 50-50 MIXTURE OF POWDERED CALCIUM ARSENATE O0
AND HYDRATED LIME.
Number of Weevils Dead Each Day
d Wh P Calcium Arsenate Treated With a 50-50 Mixture of Powdered
Treated With Powdered Calcium Arsenate Calcium Arsenate and Hydrated Lime
-u Check 3"
Days Q) ("Natural
.4 ~ > mortality")
1 H 9ZP (70Z
4-1 U 4. 4 C1 s Weevils)



1 8 9 17 13 2 5 8 2 1
2 11 18 12 21 13 14 12 20 2
3 10 11 8 9 4 7 8 10 4
4 6 7 8 8 6 7 7 5 1
5 6 5 6 1 5 7 5 5 2
Total dead .... 41 50 51 52 30 40 40 42 10
Percent dead 52 63 73 74 43 56 56 60 14
Weevils alive
at end of exp. 39 30 19 18 40 30 30 28 60
Percent alive 48 37 27 26 57 44 44 40 86









TABLE IV.-A COMPARISON OF THE MORTALITY OF WEEVILS CRAWLING AT THREE HOUR INTERVALS 1, 2, 3, AND 4 TIMES RE-
SPECTIVELY THROUGH A FINE LINE OF (a) POWDERED CALCIUM ARSENATE AND (b) A 50-50 MIXTURE OF POWDERED CAL-


CIUM ARSENATE AND HYDRATED LIME.
Number of Weevils Dead Each Day


Treated with Powdered Calcium Arsenate


Treated with a 50-50 Mixture of Powdered
Calcium Arsenate and Hydrated Lime


h
01
'5
8
B

ka~
UOY


Bca)


rgo
5fi


Q m


*S|
QE~-4'-
-)
-5 c ?
U o


>
A CC
0 CO
Ur),3
UFsl|


Vlh
%~
c~E~~

b~,
Ut~IV


Ch
("N
mor

we


CF 0
UpQ1
a Pg
_.K a)
SH g


1 3 11 2 4 2 2 1 2

2 13 15 14 7 13 23 16 6

3 12 17 17 7 12 18 14 7

4 12 8 8 4 9 6 13 6

5. 6 3 3 3 9 4 2 5

Total dead 46 54 44 25 45 53 46 26

Percent dead 77 90 88 83 75 88 92 87

Weevils alive
at end of exp. 14 6 6 5 15 7 4 4

Percent alive 23 10 12 17 25 12 8 13


Days


ieck
natural
tality")
(60
evils)






3



2

3

13
22 0


47

78


I -








Florida Agricultural Experiment Station


The information given in tables III and IV is presented in
graph form in figures 83 and 84 in such a manner that direct
comparison of the two poisons can be more easily made.

Dipped
PERCENT Once Dipped Twice Dipped 3 Times Dippcd 4 Times



40 -
DAYS W11
r t t f I I t i
Fig. 83.-Chart showing a comparison of the total percentage of mortality
among weevils with snouts dipped 1, 2, 3, and 4 times; heavy line (A)
powdered calcium arsenate; broken line (B) a 50-50 mixture of pow-
dered calcium arsenate and hydrated lime.
Crawled
PERCENT Once w Crawled Twice Crawled 3 Times j Crawled 4 Times

60-- ---- ----
o ,i___I __zzz -. !
20 Io ,- ...- N-o.


Fig. 84.-Chart showing a comparison of the total percentage of mortality
among weevils which crawled 1, 2, 3, and 4 times through a fine line
of "A" (heavy line) powdered calcium arsenate and "B" (broken line) a
50-50 mixture of powdered calcium arsenate and hydrated lime.

APPLICATION OF POISON TO DRY AND WET
COTTON PLANTS
Even though a number of experiments have been conducted by
various workers who agreed that the presence of dew was not
necessary when distributing calcium arsenate dust, there is still
a tendency to consider the water-drinking habit of the weevil
an important factor in successful poisoning, necessitating a dis-
tribution of the poison while the cotton plants are wet with dew.
In order to present a direct comparison between dry and wet
conditions, poison was applied to dry cotton leaves over which
weevils were caused to crawl. Likewise weevils were placed on
leaves which had been poisoned while wet and which were still
wet when used for the tests, thereby offering the weevil poisoned
water for drinking. The mortality rate of the two groups of
weevils was secured from a total of 1,060 individual tests, and








TABLE V.-A COMPARISON OF THE MORTALITY OF WEEVILS CRAWLING AT 3 HOUR INTERVALS, 1, 2, AND 3 TIMES RESPECTIVE-
LY OVER COTTON LEAVES TREATED WITH POWDERED CALCIUM ARSENATE (A) WITH THE LEAVES DRY AND (B) WITH THE
LEAVES WET.

Number Weevils Dead Each Day


(A) Leaves Dry.


o4


U 04
S^
Ca fi
CSCS
C^sOC
c'S c0 0
C"S
Ci]^


'.4
C02
o
U 4 g
CSC
2cS l


C

Swa
F4 c

h Qoo
>iiS


(B) Leaves Wet.


> ra
o ~p
C3 CIO

WS
U' C3 0
Cw
-^"W
Ui-l'-


I ..i_


1

2

3

4

5

Total dead ....

Percent dead

Weevils alive
at end of exp.

Percent alive


$4
Q

> U n)

CSg


a)co
ZO
qr'
nt?rdoa


Check
("Natural
"Mortality")
(100 weevils)


11 8 12 2 3 6 4

14 10 10 5 8 18 3

7 10 23 10 14 14 4

5 4 8 5 12 11 5

6 10 5 9 10 4 6

43 42 58 31 47 53 22

54 53 73 40 60 66 22


37 38 22 49 33 27 78

46 47 27 60 40 34 78


Days


I








TABLE VI.-A COMPARISON OF THE MORTALITY OF WEEVILS CRAWLING AT 3 HOUR INTERVALS, 1. 2, AND 3 TIMES RESPEC-
TIVELY OVER COTTON LEAVES TREATED WITH A 50-50 MIXTURE OF POWDERED CALCIUM ARSENATE AND HYDRATED LIME
(A) WITH THE LEAVES DRY AND (B) WITH THE LEAVES WET.

Number Weevils Dead Each Day

(A) Leaves Dry. (B) Leaves Wet.


Days






1

2

3

4

5

Total dead

Percent dead

Weevils alive
at end of exp.

Percent alive


I) -
0 0)=

00




7

3

7

3

9

29

36


S 51

1 64


SE-

c3 c


2

2

10

10

5

29

36


51

64


oa

CD



3

5

8

13

7

36

45


44

55


C _
o0 C





2

6

2

11

3

24

30


56

70


s -*






10

4

6

5

9

34

43


46

57


" IJ^


C C

O cc

3

5

10

16

11

45

56


35

44


Check
("Natural
"Mortality")
(100 weevils)




4

3

4

5

6

22

22


78

78







Bulletin 192, How the Boll Weevil Ingests Poison 163


IDRS t f t I 4 I \ I i f 4
Fig. 85.-Graphs from data presented in Tables V and VI. I. The relative
mortality percentages of weevils crawling at 3-hour intervals over dry
and wet leaves poisoned with pure calcium arsenate 1, 2, and 3 times
respectively. II. The same with a 50-50 mixture of calcium arsenate and
hydrated lime substituted for undiluted calcium arsenate. III. A com-
parison of undiluted and diluted (the 50-50 mixture) calcium arsenate
showing the mortality percentage among weevils crawling once, twice,
and three times over dry poisoned leaves. IV. The same over wet poi-
soned leaves.







Florida Agricultural Experiment Station


indicates that there is but a slight difference between the weevils
which crawled over dry poisoned leaves and those which crawled
over wet ones. The presence of dew, therefore, is not a factor
which should determine the time of day for the most effective
distribution of powdered poison.
Table V presents the data obtained by using pure calcium ar-
senate for the poisoning. Table VI represents similar tests with
a 50-50 mixture of calcium arsenate and hydrated lime substi-
tuted for the undiluted poison. A comparison of the two tables
reveals a consistent lower rate of mortality for the diluted cal-
cium arsenate used under both dry and wet conditions.
Figure 85 shows the same information in graphic form.
In the foregoing tests diluted calcium arsenate appeared to
be less toxic than the pure material. Nevertheless, field tests
show an equal toxicity.
In 1924, seven single acre-plots were so arranged that a corn
barrier separated each plot from the others. Four of these plots
were treated with a 50-50 mixture of calcium arsenate and hy-
drated lime and the remaining three were treated with an un-
diluted standard make of calcium arsenate. The plots, one type
soil, all planted with the same seed, fertilized and cultivated
alike, and poisoned at the same time, were well adapted to show
any significant differences between the two materials used for
boll weevil control. The average yields of both were very close,
with the diluted calcium arsenate plots slightly in the lead.
The tests conducted in 1925, embodying eight calcium arsen-
ate, and five diluted calcium arsenate acre-plots, gave practically
the same results.
Severe wind storms in the spring of 1926 materially reduced
the cotton stand and consequently a very small yield of seed
cotton per acre resulted. The 12 plots, 1/8 acre each, separated
from each other by corn barriers, were so arranged that pure
calcium arsenate and diluted calcium arsenate plots were adja-
cent to each other. The yield of each plot was multiplied by 8
to obtain the yield of seed cotton on an acre basis. A comparison
of the yield averages agrees with those obtained in 1924 and
1925, as can be seen in Table VII.
The general similarity of the toxicity of the two materials
in the field and the differences obtained in the laboratory prob-
ably can be accounted for by the constant activity of the weevil







Bulletin 192, How the Boll Weevil Ingests Poison 165

in the field by obtaining the poisons on the snout tip repeatedly,
whereas the activity of the weevil in the laboratory was limited
to a certain number of dippings.
While tests of mixtures containing calcium arsenate as the
only poison have been reported in this paper, it is, nevertheless,
pertinent to call attention to the fact that the Chemical Warfare
Service" "" has presented, along with other valuable boll wee-
vil information, several new -poisons for boll weevil control,
chiefly fluosilicates and calcium arsenate containing less than
40 percent arsenic pentoxide. These poisons applied to the cot-
ton plants in powdered form or in molasses mixtures are ingested
by the weevil in the same manner that pure and diluted calcium
arsenate are.

TABLE VII.-COMPARISON, IN POUNDS SEED COTTON PER ACRE, OF THE
EFFICIENCY OF PURE POWDERED CALCIUM ARSENATE AND A 50-50 MIx-
TURE OF CALCIUM ARSENATE AND HYDRATED LIME.
POUNDS SEED COTTON PER ACRE
1924 1925 1926
Calcium I Calcium Calcium
Arsenate "Mixture" Arsenate "Mixture" Arsenate "Mixture"

803 879 1004 1095 228 260
806 898 1175 1101 136 156
942 790 976 908 224 292
919 1348 1113 234 184
1020 1084 280 254
814 232 220
1048
1070
*2551 3486 8455 5301 1334 1366

t850 871 1057 1060 222 228


*Sum of yields.
tAverage yield per acre.
yields from 1% acre plots.


1924 and 1925 full acre plots. 1926 computed


"Walker, H. W. and J. E. Mills, Jour. Econ. Ent. No. 4, Vol. 19, p. 600.
August 1926.
"Mills, J. E., Jour. Econ. Ent. No. 4, Vol. 19, pp. 601-2. August 1926.
"Walker, H. W. and J. E. Mills, Industrial and Engineering Chemistry
No. 6, Vol. 19, pp. 703-722. June 1927.







Florida Agricultural Experiment Station


DAY AND NIGHT POISONING
Throughout the cotton belt, field experiments have been con-
ducted to determine the relative value of day and night dusting.
With practically all experimental work showing a greater yield
of cotton when the poison was applied at night, the consensus
of opinion is that night dusting is preferable to day dusting. The
better weevil control obtained by night dusting was first be-
lieved to be due directly to the water-drinking habit of the wee-
vil, the dew at night supplying the necessary water. As a matter
of fact, night dusting is more satisfactory because at that time
the atmosphere is usually quiet. Under these conditions the dust
clouds can settle over the entire field, whereas brisk or even
light breezes, which usually occur during the day, blow a large
percentage of the poison away.
The greater portion of the cotton growing area is subject to
heavy dews during quiet nights, resulting, in many cases, in the
opinion that dew not only is an aid to an effective distribution
of poison but is a necessity. Successful dusting, however, in
large areas where dew is rare and laboratory tests in which the
weevil shows as great a mortality percentage when poisoned on
dry materials as when poisoned on wet materials, waive the as-
sumed importance of dew or other precipitation as an aid in con-
nection with boll weevil control.

SYRUP MIXTURES FOR SPRAYING
There are still a few cotton growers who consider as profitable
the practice of spraying a calcium arsenate-water-syrup mixture
onto the cotton plants. Wherever comparative tests have been
conducted, however, the sprayed plots yielded considerably less
seed cotton per acre than the dusted plots. The probable explana-
tion for the failure of the spray to secure good control lies in
the fact that the spray solution forms a varnish-like film of poi-
son which does not readily stick to the snout of the boll weevil
as it crawls over the poisoned surface.
In order to substantiate this explanation weevils were caused
to crawl over cotton leaves sprayed with a mixture of 1 pound
of calcium arsenate, 1 gallon of syrup and 4 gallons of water.
In one group, weevils crawled over leaves still wet with the mix-
ture and in another group the mixture was allowed to dry on the
leaves before the weevils crawled on them.







Florida Agricultural Experiment Station


DAY AND NIGHT POISONING
Throughout the cotton belt, field experiments have been con-
ducted to determine the relative value of day and night dusting.
With practically all experimental work showing a greater yield
of cotton when the poison was applied at night, the consensus
of opinion is that night dusting is preferable to day dusting. The
better weevil control obtained by night dusting was first be-
lieved to be due directly to the water-drinking habit of the wee-
vil, the dew at night supplying the necessary water. As a matter
of fact, night dusting is more satisfactory because at that time
the atmosphere is usually quiet. Under these conditions the dust
clouds can settle over the entire field, whereas brisk or even
light breezes, which usually occur during the day, blow a large
percentage of the poison away.
The greater portion of the cotton growing area is subject to
heavy dews during quiet nights, resulting, in many cases, in the
opinion that dew not only is an aid to an effective distribution
of poison but is a necessity. Successful dusting, however, in
large areas where dew is rare and laboratory tests in which the
weevil shows as great a mortality percentage when poisoned on
dry materials as when poisoned on wet materials, waive the as-
sumed importance of dew or other precipitation as an aid in con-
nection with boll weevil control.

SYRUP MIXTURES FOR SPRAYING
There are still a few cotton growers who consider as profitable
the practice of spraying a calcium arsenate-water-syrup mixture
onto the cotton plants. Wherever comparative tests have been
conducted, however, the sprayed plots yielded considerably less
seed cotton per acre than the dusted plots. The probable explana-
tion for the failure of the spray to secure good control lies in
the fact that the spray solution forms a varnish-like film of poi-
son which does not readily stick to the snout of the boll weevil
as it crawls over the poisoned surface.
In order to substantiate this explanation weevils were caused
to crawl over cotton leaves sprayed with a mixture of 1 pound
of calcium arsenate, 1 gallon of syrup and 4 gallons of water.
In one group, weevils crawled over leaves still wet with the mix-
ture and in another group the mixture was allowed to dry on the
leaves before the weevils crawled on them.







TABLE VIII.-WEEVILS CRAWLING AT 3 HOUR INTERVALS, 1, 2, 3, AND 4 TIMES RESPECTIVELY OVER
SPRAYED WITH A MIXTURE OF CALCIUM ARSENATE, WATER, AND SYRUP.


DRY AND WET LEAVES


Number Weevils Dead Each Day

Crawled Over Dry Leaf Crawled Over Wet Leaf
Check
Days ("Natural
Sr mortality")
*rn a) a m (30
S| ,. weevils)
oEEo EE-o oEio










Total dead 6 7 11 6 1 1 3 4 3
Percent dead 20 23 37 20 3 3 10 13 10


Weevils alive
at end of exp. 24 23 19 24 29 29 27 26 27
Percent alive 80 77 63 80 97 97 90 87 90
I __ I_ I_ -L_







168 Florida Agricultural Experiment Station

TABLE IX.-A COMPARISON OF WEEVILS CRAWLING OVER DUSTED AND
SPRAYED LEAVES
Number Weevils Dead Each Day
Crawled Over Crawled Over
Dusted Leaf Sprayed Leaf

Days I
0 C> Cd CC) C




1 8 8 0 2 0
2 16 36 2 2 2
3 12 20 3 2 2
4 18 16 4 10 2
5 7 .... 3 7 5
Total dead 61 80 12 23 11
Percent dead 76 100 15 29 14
Weevils alive
at end of exp. 19 0 68 57 69
Percent alive 24 0 85 71 86

Data obtained from these tests are presented in Table VIII. It
is a significant fact that the percent mortality among the wee-
vils crawling over the wet sprayed leaf was practically identical
with the "natural mortality" percent. Those weevils which
crawled over the dried sprayed surface showed but a small in-
crease in the mortality rate. On the other hand, weevils crawl-
ing over wet and dry leaves dusted with both pure and diluted
powdered calcium arsenate (see tables V and VI), showed a pro-
nounced mortality rate.
Additional data, in which a direct comparison of weevils
crawling over dusted and sprayed leaves is made, is given in
Table IX. Again there is no increase of the mortality rate over
the "natural mortality" among weevils crawling over the wet
sprayed leaves, and the increase among those weevils crawling
dver the dried sprayed. leaves shows but a slight increase. The
reevils crawling over leaves dusted with powdered calcium
senate, however, show a high mortality rate.







Bulletin 192, How the Boll Weevil Ingests Poison 169

These tests, supported by the poor boll weevil control obtained
in the field by using liquid poisons for spraying, point out the
superiority of dusting with powdered calcium arsenate. The use
of syrup mixtures for spraying, therefore, is not recommended
for boll weevil control.

SYRUP MIXTURES FOR MOPPING
In the past the use of mixtures of calcium arsenate, water,
and syrup for mopping purposes has been unduly criticised, but
a better understanding of the manner in which syrup mixtures
are ingested by the weevil, augmented by carefully planned
field tests, has brought about a more favorable consideration of
this poisoning method.
The efficiency of the syrup mixture depends upon the man-
ner in which it is applied to the cotton plants. Failure to provide
accurate laboratory conditions, whereby other influencing fac-
tors are eliminated, led to the erroneous belief that the boll wee-
vil responded chemotropically to the sweetened poison to eventu-
ally congregate at the plant bud where the mixture was applied.
As a matter of fact weevils do go to the plant bud, but this activ-
ity is due solely to their geotropic movements. The weevil when
placed on an inclined surface, other factors such as light, air
currents, etc., eliminated, will crawl upwards. On the plants in
the field the weevil takes an upward path while crawling. Con-
senquently when the cotton plant is small and there is but one
avenue of upward march, the main stem, the weevil will reach
the bud and if sweetened poison is applied at that point, will get
into it.
When the cotton plants are larger and have a number of
branches, the weevil in its upward journey will crawl along any
one of the branches. In order to poison the terminal ends of
each branch not only would too much poison be required but also
the labor would be too costly. The use df syrup mixtures, conse-
quently, for controlling the boll weevil on large cotton plants is
not profitable, whereas the use of calcium arsenate dust at that
time is economical.
Under many localized conditions, particularly where there is
no dense timber, the boll weevil emerges comparatively early
from hibernation, having completed the emergence by the end
of June. Since the cotton plants are small during this period,
such conditions can be handled easily with syrup mixtures







Florida Agricultural Experiment Station


throughout the month of June. After the hibernated weevils
have been killed, further control measures usually are not nec-
essary.
In view of the fact that field tests indicate that syrup mix-
tures have a quicker toxic effect on the boll weevil than has pow-
dered calcium arsenate, laboratory tests were conducted to de-
termine the mortality rate of weevils with their snouts dipped
into a number of different mixtures of calcium arsenate, water,
and syrup. (Table X.)
It is a significant fact that a single dipping of the snout into
a syrup mixture results in a much quicker and greater mortality
rate than snout dipping into calcium arsenate. After the syrup
mixture has once become mechanically attached to the snout tip,
a weevil rarely succeeds in avoiding ingestion of the sweetened
poison.
Though syrup mixtures do not attract boll weevils, the mix-
tures, by being mopped into the bud of small cotton plants, are
placed in such a manner that the weevils cannot avoid getting
a lethal dose of poison. Not only do the weevils accidentally get
their snouts into the syrup mixture but also they often feed
greedily on the mixture after they have once obtained some on
their snouts. While weevils feed on good grade syrups they do
not feed on blackstrap molasses unless they have been deprived
of food for several days. Since weevils have a constant food sup-
ply in the field they do not become starved to such an extent
that they feed on the blackstrap molasses. Consequently, it be-
comes necessary to use a good brand of syrup to insure the
greatest possible kill. The failure of commercially-made mop-
ping mixtures to give as good weevil control as the home-made
mixtures used by experimental workers probably can be ascribed
to the use of blackstrap molasses in the commercial mixtures
instead of the table syrup which is generally used in the home-
made mixtures. Furthermore, syrup must be considered as a
carrier for the calcium arsenate and as such must be well mixed
with the poison. Since calcium arsenate has a tendency to settle
to the bottom of the mixture, the mixture must be constantly
stirred while being applied to the cotton plants. The importance
of stirring becomes evident in view of the fact that the mortal-
ity rate among weevils fed on the supernatant fluid is far below
that among weevils fed on well stirred syrup mixtures.
Since syrup mixtures show a high mortality rate among wee-
vils which obtain some of the mixture and since the mixture







TABLE X.-THE MORTALITY OF BOLL WEEVILS WITH THEIR SNOUTS DIPPED ONCE INTO A MIXTURE
WATER AND SYRUP.


OF CALCIUM ARSENATE;


Number of Weevils Dead Each Day Alive at
Mixture Weevils Total End of
Used Day 2 Days 3 Days 4 Days 5 Days Experiment

*Check 40 1 0 3 4 3 11 29
tl:1:1 45 41 0 1 3 .. 45 0
1:1:2 30 28 1 1 30 0
1:1:3 25 24 0 0 0 0 24 1
1:2:1 20 15 0 2 0 2 19 1
1:2:2 20 19 0 1 .. 20 0
1:2:3 10 10 .. .. 10 0
1:3:1 20 20 .. 20 0
1:3:3 35 31 0 2 1 0 34 1
2:1:1 30 26 2 1 0 1 30 0
2:1:2 10 10 .. 10 0
2:1:3 25 24 1 ... 25 0
2:2:1 30 22 2 0 3 1 28 2
2:2:3 10 10 .. 10 0
2:3:1 20 20 -- .... 20 0
2:3:2 15 15 .. .. 15 0
2:3:3 20 20 -. -. 20 0
3:1:1 30 24 3 1 0 0 28 2
3:1:2 10 10 .. .. 10 0
3:1:3 25 25 .. .. 25 0
3:2:1 10 7 3 .. .. 10 0
3:2:3 10 9 0 0 1 10 0
3:3:1 35 29 4 0 2 .. 35 0
3:3:2 10 9 0 0 1 10 0
*Weevil snouts dipped into unpoisonedsyrup to obtain "natural mortality" rate.
fMixtures of pounds calcium arsenate, gallons water, and gallons syrup respectively.







Florida Agricultural Experiment Station


can be applied so that weevils obtain the poison, they are recom-
mended for mopping onto small cotton plants at the rate of
about a gallon of the mixture per acre.

SUMMARY
1. The boll weevil has not been controlled by taking advan-
tage of its chemotropic, phototropic, or death-feigning activities.
2. A characteristic dipping of the snout brings the mouth
parts of the weevil in contact with the surface over which the
weevil crawls. Consequently, when a weevil crawls over a poi-
soned surface it accidentally and unavoidably accumulates the
poison particles on the snout tip and later, on feeding or by
mandibular activity alone, ingests the particles into the stomach.
3. There is no indication that the water-drinking habit of
the weevil is an important factor for successful distribution of
calcium arsenate, since there is no appreciable difference in the
mortality among boll weevils exposed to either dry or wet poi-
soned plants. Distribution of poison at night, however, is prefer-
able to day poisoning, not on account of the presence of dew but
because at that time the atmosphere is usually quiet.
4. Test plots treated with a 50-50 mixture of calcium arsen-
ate and hydrated lime yielded as much seed cotton per acre for
three consecutive years as did plots treated with undiluted cal-
cium arsenate.
5. In view of the low rate of mortality obtained among wee-
vils crawling over cotton plants sprayed with a mixture of cal-
cium arsenate, water, and syrup, the use of syrup mixtures for
spraying is not recommended for boll weevil control.
6. On the other hand, when more concentrated mixtures are
mopped onto the bud of small cotton plants, a high rate of mor-
tality is obtained.
CONCLUSIONS
1. As the boll weevil accumulates poison particles on the snout
tip while crawling from place to place and later ingests the poi-
son, the poison should be applied over the greatest possible
plant surface.
2. Calcium arsenate diluted with hydrated lime when well
mixed and distributed will control the weevil as well as the un-
diluted material.
3. Syrup mixtures, though not suitable for spraying, can be
used for mopping on small cotton plants for boll weevil control.




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