• TABLE OF CONTENTS
HIDE
 Copyright
 Title Page
 Introduction
 Acknowledgement
 The point method of making infestation...
 The survey method of making infestation...
 Counts of boll weevils in...
 A new method of making infestation...
 Analysis of counts made in light...
 Conclusions






Group Title: Bulletin - University of Florida. Agricultural Experiment Station - no. 241
Title: Methods for making counts of boll weevil infestation
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027744/00001
 Material Information
Title: Methods for making counts of boll weevil infestation
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 22 p. : ; 23 cm.
Language: English
Creator: Grossman, Edgar F
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1931
 Subjects
Subject: Boll weevil -- Counting   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Edgar F. Grossman.
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station) ;
 Record Information
Bibliographic ID: UF00027744
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: aleph - 000924094
oclc - 18204485
notis - AEN4698

Table of Contents
    Copyright
        Copyright
    Title Page
        Page 1
        Page 2
    Introduction
        Page 3
    Acknowledgement
        Page 3
    The point method of making infestation counts
        Page 4
    The survey method of making infestation counts
        Page 5
    Counts of boll weevils in the field
        Page 6
    A new method of making infestation counts
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
    Analysis of counts made in light and heavily infested fields
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
    Conclusions
        Page 22
Full Text





HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida






Bulletin 241


November, 1931


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
Wilmon Newell, Director





METHODS FOR MAKING COUNTS OF


BOLL WEEVIL INFESTATION


By EDGAR F. GROSSMAN






CONTENTS
PAGE
INTRODUCTION ........................................................... 3
THE POINT METHOD OF MAKING INFESTATION COUNTS-----------................................ 4
THE SURVEY METHOD OF MAKING INFESTATION COUNTS.............................. 5
COUNTS OF BOLL WEEVILS IN THE FIELD.......................... .....-.......... 6
A NEW METHOD OF MAKING INFESTATION COUNTS---...............-----...................------ 7
ANALYSIS OF COUNTS MADE IN LIGHT AND HEAVILY INFESTED FIELDS.... 12
CONCLUSIONS .......----..-.....-------.....--------------------- 22






TECHNICAL BULLETIN





Bulletins will be sent free upon application to
the Agricultural Experiment Station,
GAINESVILLE, FLORIDA
LIBRARY
FLORIDA EXPERIMFENT STATION
QAINESV'L.t.1L, 0f,119










BOARD OF CONTROL

P. K. Yonge, Chairman, Pensacola
A. H. Blanding, Bartow
W. B. Davis, Perry
Raymer F. Maguire, Orlando
Frank J. Wideman, West Palm Beach
J. T. Diamond, Secretary, Tallahassee


EXECUTIVE STAFF

John J. Tigert, M.A., LL.D., President of the
University
Wilmon Newell, D.Sc., Director
H. Harold Hume, M.S., Asst. Dir., Research
Sam T. Fleming, A.B., Asst.Dir., Administration
J. Francis Cooper, M.S.A., Editor
R. M. Fulghum, B.S.A., Assistant Editor
Ida Keeling Cresap, Librarian
Ruby Newhall, Secretary
K. H. Graham, Business Manager
Rachel McQuarrie, Accountant


MAIN STATION, GAINESVILLE
AGRONOMY
W. E. Stokes, M.S., Agronomist
W. A. Leukel, Ph.D., Associate
G. E. Ritchey, M.S.A., Assistant*
Fred H. Hull. M.S., Assistant
J. D. Warner, M.S., Assistant
John P. Camp, M.S., Assistant
ANIMAL HUSBANDRY
A. L. Shealy, D.V.M., Veterinarian in Charge
E. F. Thomas, D.V.M., Assistant Veterinarian
R. B. Becker, Ph.D., Associate in Dairy In-
vestigations
W. M. Neal, Ph.D., Asst. in Animal Nutrition
P. T. Dix Arnold, B.S., Assistant in Dairy In-
vestigations
CHEMISTRY
R. W. Ruprecht, Ph.D., Chemist
R. M. Barnette, Ph.D., Associate
C. E. Bell, M.S.. Assistant
J. M. Coleman, B.S., Assistant
H. W. Winsor, B.S.A., Assistant
H. W. Jones. M.S., Assistant
ECONOMICS, AGRICULTURAL
C. V. Noble, Ph.D., Agricultural Economist
Bruce McKinley, A.B., B.S.A., Associate
M. A. Brooker, Ph.D., Associate
Zach Savage, M.S.A., Assistant
ECONOMICS, HOME
Ouida Davis Abbott, Ph.D., Head
L. W. Gaddum, Ph.D., Biochemist
C. F. Ahmann, Ph.D., Physiologist
ENTOMOLOGY
J. R. Watson, A.M., Entomologist
A. N. Tissot, Ph.D., Assistant
H. E. Bratley, M.S.A.,.Assistant
E. F. Grossman, M.A., Asso., Cotton Insects
P. W. Calhoun, Assistant
HORTICULTURE
A. F. Camp, Ph.D., Horticulturist
Harold Mowry, B.S.A., Associate
M. R. Ensign, M.S., Associate
A. L. Stahl, Ph.D., Assistant
G. H. Blackmon, M.S.A., Pecan Culturist
C. B. Van Cleef, M.S.A., Greenhouse Foreman

*In cooperation with U.S.D.A.


PLANT PATHOLOGY
W. B. Tisdale, Ph.D., Plant Pathologist
George F. Weber, Ph.D., Associate
R. K. Voorhees, M.S., Assistant
Erdman West, M.S., Mycologist


BRANCH STATIONS

NORTH FLORIDA STATION, QUINCY
L. O. Gratz, Ph.D., Associate Plant Pathologist
in Charge
R. R. Kincaid, M.S., Asst. Plant Pathologist
W. A. Carver, Ph.D., Asso. Cotton Specialist
R. M. Crown, B.S.A., Asst. Agronomist, Cotton
Jesse Reeves, Farm Superintendent

CITRUS STATION. LAKE ALFRED
John H. Jefferies, Superintendent
Geo. D. Ruehle, Ph.D., Asst. Plant Pathologist
W. A. Kuntz, A.M., Asst. Plant Pathologist
.B. R. Fudge, Ph.D., Assistant Chemist
W. L. Thompson, B.S., Assistant Entomologist

EVERGLADES STATION, BELLE GLADE
R. V. Allison, Ph.D., Soils Specialist in Charge
R. W. Kidder, B.S., Farm Foreman
R. N. Lobdell, M.S., Associate Entomologist
F. D. Stevens, B.S., Sugarcane Agronomist
H. H. Wedgeworth, M.S., Asso. Plant Path.
B. A. Bourne, B.S., Asso. Plant Physiologist
J. R. Neller, Ph.D., Associate Biochemist
A. Daane, Ph.D., Associate Agronomist
M. R. Bedsole, M.S.A., Assistant Chemist
Fred Yount, Office Assistant

SUB-TROPICAL STATION, HOMESTEAD
H. S. Wolfe,Ph.D.,Asso. Horticulturist in Chg.
L. R. Toy, B.S.A., Asst. Horticulturist
Stacy O. Hawkins, M. A., Assistant Plant
Pathologist


FIELD STATIONS

Leesburg
M. N. Walker, Ph.D., Asso. Plant Pathologist
W. B. Shippy, Ph.D., Asst. Plant Pathologist
K. W. Loucks, M.S.. Asst. Plant Pathologist
C. C. Goff, M.S., Assistant Entomologist
J. W. Wilson, Ph.D., Assistant Entomologist
Plant City
A. N. Brooks, Ph.D., Asso. Plant Pathologist
R. E. Nolen, M.S.A., Field Asst. in Plant Path.
Cocoa
A. S. Rhoads, Ph.D., Asso. Plant Pathologist
Hastings
A. H. Eddins, Ph.D., Asso. Plant Pathologist
West Palm Beach
D. A. Sanders, D.V.M., Associate Veterinarian
Monticello
Fred W. Walker, Assistant Entomologist
Bradenton
David G. Kelbert, Asst. Plant Pathologist









METHODS FOR MAKING COUNTS OF

BOLL WEEVIL INFESTATION

By EDGAR F. GROSSMAN

INTRODUCTION

The necessity of knowing the approximate severity of insect
damage in the field led to the development of various methods
of infestation counts, whereby either the relative abundance, or
the activity, of insect pests could be determined. Several meth-
ods have been devised especially for making infestation counts
to measure the activity of the cotton boll weevil (Anthonomus
grandis Boh.). Since the intelligent use of control methods de-
pends to a large extent on the accuracy of the initial infestation
counts, rather detailed accounts of a number of the methods
which are in present use are herewith presented.
Except when the eradication of some insect pest is planned, a
thorough examination of all plants in an infested area is seldom
made. Where the insect pest is to be controlled, however, an
examination of various numbers of plants, usually a very small
percentage of the plants in the infested area, is made. Such
examinations of restricted numbers of plants are very difficult
to handle, since estimates of infestations derived from field
counts usually vary considerably when repeated in the same
field in immediate sequence of each other. As a consequence,
numerous methods for gaining information relative to field in-
festations have been devised.
The necessity of obtaining accurate counts of boll weevil in-
festation throughout the infested areas in the cotton belt became
evident with the advent of means of poisoning the weevil with
calcium arsenate. About three months after the cotton seed has
ACKNOWLEDGMENTS
In answer to a letter of inquiry sent to those interested in making in-
festation counts, the following workers responded by outlining in detail
their respective methods of obtaining cotton boll weevil infestation counts:
Dwight Isley, Arkansas; O. M. Chance, Chesley Hines, Clay Lyle, Missis-
sippi; W. E. Hinds, Louisiana; R. W. Leiby, North Carolina; C. O. Eddy, M.
H. Brunson, South Carolina; F. L. Thomas, Texas; G. A. Maloney, United
States Department of Agriculture; and H. W. Walker, Chemical Warfare
Service.









METHODS FOR MAKING COUNTS OF

BOLL WEEVIL INFESTATION

By EDGAR F. GROSSMAN

INTRODUCTION

The necessity of knowing the approximate severity of insect
damage in the field led to the development of various methods
of infestation counts, whereby either the relative abundance, or
the activity, of insect pests could be determined. Several meth-
ods have been devised especially for making infestation counts
to measure the activity of the cotton boll weevil (Anthonomus
grandis Boh.). Since the intelligent use of control methods de-
pends to a large extent on the accuracy of the initial infestation
counts, rather detailed accounts of a number of the methods
which are in present use are herewith presented.
Except when the eradication of some insect pest is planned, a
thorough examination of all plants in an infested area is seldom
made. Where the insect pest is to be controlled, however, an
examination of various numbers of plants, usually a very small
percentage of the plants in the infested area, is made. Such
examinations of restricted numbers of plants are very difficult
to handle, since estimates of infestations derived from field
counts usually vary considerably when repeated in the same
field in immediate sequence of each other. As a consequence,
numerous methods for gaining information relative to field in-
festations have been devised.
The necessity of obtaining accurate counts of boll weevil in-
festation throughout the infested areas in the cotton belt became
evident with the advent of means of poisoning the weevil with
calcium arsenate. About three months after the cotton seed has
ACKNOWLEDGMENTS
In answer to a letter of inquiry sent to those interested in making in-
festation counts, the following workers responded by outlining in detail
their respective methods of obtaining cotton boll weevil infestation counts:
Dwight Isley, Arkansas; O. M. Chance, Chesley Hines, Clay Lyle, Missis-
sippi; W. E. Hinds, Louisiana; R. W. Leiby, North Carolina; C. O. Eddy, M.
H. Brunson, South Carolina; F. L. Thomas, Texas; G. A. Maloney, United
States Department of Agriculture; and H. W. Walker, Chemical Warfare
Service.






Florida Agricultural Experiment Station


been planted the first cotton squares appear on the plant. At
about the same time the characteristic feeding and egg-laying
punctures made by the boll weevil appear in the small squares,
and the boll weevil damage commences. The necessity of apply-
ing poison economically to control the boll weevil renders in-
festation counts important since the damage caused by the
weevils must first be of sufficient intensity to warrant the
poisoning.
As outlined by F. L. Thomas there are two distinct types of
infestation counts used in determining boll weevil population
and injury; the point method and the survey method. The
point method consists chiefly of the examination of cotton plants
at certain points established in the field which are revisited
each time infestation counts are made. The survey method, on
the other hand, consists of infestation counts made at random
while walking diagonally or circling through the field.

THE POINT METHOD OF MAKING INFESTATION COUNTS

There are several variations of the point method in use. Some
workers suggest the examination of 100 squares taken from
adjacent plants in from four to eight centrally located points in
the field, the number of groups to be examined depending on the
size of the field. Other workers suggest that the points be es-
tablished in those parts of the field where the greatest infesta-
tion may be expected. Another variation of the point method
embodies the selection of but three points in the field, one at
either end and one in the central part of the field. Still another
variation calls for five points, one near each corner and one in
the center of the field.
In addition to the variations which concern the location of
the points, there are also several differences of opinion relative to
the manner in which the plants are recorded and the number of
squares to be included in the counts. The squares are generally
selected from adjacent-plants and in some cases the number of
plants necessary to yield 100 squares is recorded, and in other
cases no record is kept. Again, some workers consider 100
squares sufficient while others hold that 500 squares are neces-
sary for accurate estimations of the percent infestation. One
group of workers measures the length of the row on which the
counts are made.






Bull. 241, Making Counts Boll Weevil Infestation


Still further grounds for differences of opinion rest in the
nature of the squares themselves which are to be included in the
counts. Some entomologists suggest that all of the squares
large enough to be attacked by the boll weevil should be included
in the count. Others maintain that only those which are large
enough to have the bracts opened for the examination of the
bud itself should be examined, and still others prefer counting
only those squares which are at least one-third grown.
Some entomologists remove the punctured squares from the
plants, while others leave them on the plants. A few workers
include the fallen squares in their counts.

THE SURVEY METHOD OF MAKING
INFESTATION COUNTS

In contrast with the adherents of the point method wherein
the same parts of the field are revisited for subsequent infesta-
tion counts, those who advocate the survey method suggest that
counts be made at random, either while walking diagonally
through or circling the field. The survey method is likewise at-
tended with numerous variations, greatest among which is the
determination of the total number of squares which should be
examined. One worker suggests that from 25 to 50 squares
be counted at various unmarked points while walking through
the field in a circular path. Others suggest the same number of
squares be selected from points located in a diagonal line through
the field. Still others recommend a count of 100 squares at each
place of examination. Totals of from 100 to 500 squares have
been advocated for infestation counts in small fields, while as
large a number as 5,000 have been suggested for larger fields.
Again the question relative to the size of the squares examined
presents itself. As in the point method, recommendations are
made for examining all of the squares just large enough to be
attacked by the boll weevil; squares large enough to exhibit a
well formed bud; or squares which are one-third grown. All
of the squares which are examined, both the infested and the
uninfested ones, are usually picked off the plant, though some
entomologists do not remove any of the squares from the plant.
Several workers recommend a combination of the survey and
point methods. Five points are selected, one in each corner
and one in the center of the field, and in addition to the counts






Florida Agricultural Experiment Station


in these places, random counts are taken near trees, buildings,
ditch banks, fence rows, and other places which offer the boll
weevil suitable hibernation quarters.
It is indeed difficult to select any particular method and dis-
card the other methods which have been adapted to securing
infestation counts, since in each of the many methods there are
some valuable suggestions.

COUNTS OF BOLL WEEVILS IN THE FIELD

In several of the cotton states no attempt is made to determine
the number of boll weevils infesting the field. Where, however,
boll weevil counts are recommended, several slight variations in
making the counts are found. Generally the terminal buds of
200 to 400 consecutive plants are examined for boll weevils in
three or four localities of the field. A more elaborate method
requires a thorough examination of not only the terminal buds
but also the under sides of the leaves of 500 plants if the cotton
has not been chopped, and 200 plants if the cotton has been
chopped to a stand.
Other recommendations include the careful examination of
10 yards of row in 10 different localities well distributed over the
field. Still others require the examination of 100 yard rows
in several parts of the field. In small cotton fields five widely
separated sections of 20 yards of row each are designated for
examination. Assuming 5,000 yards of plant row per acre, the
counts can be interpreted on a weevil-per-acre basis.
Where a definite length of row is not examined, the stand (the
number of plants per acre) is estimated and then the ratio of
the number of weevils per plant can be translated into the num-
ber of weevils per acre.
As a whole, the differences encountered among the reported
methods for obtaining a count of the boll weevil population in
the field are not striking.
In Florida there is no great need for determining the number
of boll weevils infesting the fields. Early in the season before
the cotton plants begin to grow squares, the boll weevils do very
little damage. By the time the squares appear the percent in-
festation can be used for deciding whether or not the infesta-
tion warrants the inauguration of control methods in any par-
ticular field.






Bull. 241, Making Counts Boll Weevil Infestation 7

A NEW METHOD OF MAKING INFESTATION COUNTS
In 1925, Camp and Calhoun' devised a new method for mak-
ing infestation counts, and this method has met with success
in Florida, especially in small test-plot fields. The evident re-
duction of labor connected with obtaining reliable infestation
counts, together with the marked success of the method, led the
author to make a thorough examination of the merits of the
method.
As in the survey method, a diagonal path through the field
is followed while taking random infestation counts. Instead
of stripping a specified number of squares off the plants, how-
ever, a specified number of plants was designated for the counts
and all squares large enough to be attacked by the boll weevil,
either for feeding or egg-laying purposes, were counted on each
plant. Only one plant in any one locality was examined and
only 20 plants were examined in small cotton fields. Where the
fields were large two or more series of 20 plants each were in-
cluded in the infestation count. The number of infested squares
divided by the total number of squares counted on the 20 plants
yielded the infestation percent for the field.
TABLE I.-PERCENT OF BOLL WEEVIL INFESTATION ON DATES INDICATED IN
16 HALF-ACRE COTTON PLOTS IN 1926, AS DETERMINED BY THE 20-PLANT
METHOD.

Plot Date of infestation counts and the percent of infestation
number July 1 July 8 July 15 | July 23 I July 30

1 0.5 8.1 8.3 13.2 5.2
2 0.0 0.0 5.4 0.0 11.7
3 0.0 0.0 6.3 0.7 4.0
4 0.5 0.0 1.0 0.7 13.1
5 7.5 2.1 3.1 4.1 8.0
6 7.3 3.1 7.4 1.2 3.6
7 7.9 9.7 17.4 22.3 12.0
8 0.0 0.0 1.0 11.0 22.3
9 0.4 0.4 0.6 1.4 12.3
10 3.3 8.7 13.3 15.2 52.4
11 0.8 0.0 0.0 3.2 14.3
12 0.6 2.3 1.8 6.8 43.3
13 3.3 5.9 11.7 17.3 46.6
14 1.6 1.2 12.0 11.9 56.0
15 1.4 1.8 4.3 23.8 42.0
16 16.5 34.0 53.4 71.2 72.9
Tables I and II show the infestation count data collected from

'Head and Assistant, respectively, of the Department of Cotton Investi-
gations, Florida Agricultural Experiment Station. Original data unpub-
lished.







Florida Agricultural Experiment Station


TABLE II.-PERCENT OF BOLL WEEVIL INFESTATION ON DATES INDICATED
IN 52 QUARTER-ACRE PLOTS IN 1928, AS DETERMINED BY 20-PLANT
METHOD.

Plot Date of infestation counts and the percent of infestation
numhbr June 6 JIune 13Vune 20June 271 July 4 July 11July 18!July25 Aug. 1


......... r


0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 11.1
0.0 0.0
0.0 26.0
0.0 0.0
0.0 30.4
0.0 0.0
0.0 0.0
0.0 4.2
10.0 25.4
0.0 0.0
0.0 0.0
0.0 10.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 1.2
0.0 0.0
0.0 0.0
12.5 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
7.1 0.0
0.0 0.0
0.0 0.0


0.0 0.0 0.6
0.0 0.9 0.3
0.9 0.4 0.0
7.7 12.9 0.5
0.0 0.8 0.0
10.8 16.5 6.9
3.0 3.7 0.0
9.8 15.5 8.2
0.0 8.2 0.0
7.8 1.3 0.4
7.8 4.1 0.9
14.3 13.6 7.9
15.7 10.5 4.3
9.8 13.3 23.0
9.5 18.6 18.1
27.3 39.4 17.1
18.9 5.5 0.4
0.0 1.6 0.6
0.0 0.6 0.2
27.3 23.4 10.8
0.0 0.0 3.3
0.0 0.0 1.1
3.6 3.1 6.3
5.8 10.7 3.2
0.0 0.0 1.0
0.0 0.0 0.0
0.0 0.0 0.0
0.0 1.8 0.0
0.0 0.0 0.0
0.0 5.3 0.0
0.0 1.0 0.5
0.0 3.1 0.0
0.0 0.0 0.0
0.0 0.0 0.0
0.0 0.0 0.0
0.0 0.0 0.4
0.0 0.0 0.0
0.0 1.3 0.0
4.1 2.1 0.0
0.9 0.0 0.0
0.0 0.0 0.4
1.0 0.0 0.6
0.0 0.0 0.0
3.1 4.4 2.0
4.2 1.0 2.6
0.0 1.1 0.5
0.0 0.0 0.0
0.0 0.0 0.0
0.0 0.0 0.0
0.6 0.0 0.4
0.0 0.0 0.4
0.0 0.0 0.0


0.8
0.0
0.0
11.3
0.5
5.0
13.4
24.2
5.2
1.7
8.0
9.9
18.6
18.7
30.0
20.9
2.7
1.2
2.3
33.0
4.0
4.8
3.0
3.3
0.0
0.0
0.0
0.0
1.3
0.0
0.4
0.8
0.0
0.0
0.0
0.0
4.5
0.0
0.3
0.0
6.9
1.1
0.0
5.2
7.3
2.6
0.8
0.0
0.6
0.9
0.2
0.0


40
41
42
43
44
45
46
47
48
49
50
51
52


2.4 12.4
3.8 20.3
12.1 46.1
51.7 62.8
5.2 18.9
33.3 45.3
46.2 61.3
60.1 40.2
19.6 53.6
13.8 52.3
52.2 53.1
54.6 57.5
49.9 50.2
51.5 46.7
43.0 62.0
58.4 60.1
18.8 37.5
27.0 44.9
25.4 57.3
45.3 71.7
3.2 34.0
0.0 47.4
9.0 40.7
14.7 34.3
0.0 -12.6
0.3 14.2
0.0 14.2
1.5 7.1
7.3 29.0
0.8 9.8
2.3 13.5
1.2 5.1
3.7 15.9
0.4 7.1
1.0 4.6
1.4 3.3
1.8 13.2
1.6 19.3
4.7 18.2
3.3 10.3
27.5 43.9
6.5 30.3
0.8 8.3
41.2 34.1
38.7 63.7
21.3 38.8
8.2 26.1
7.3 33.5
22.1 28.2
3.2 18.0
0.3 8.7
7.2 6.8


8.7
33.3
50.0
48.7
29.0
53.6
59.3
55.6
56.5
58.0
47.7
60.7
58.2
50.2
42.3
50.5
46.4
50.7
60.9
63.3
58.2
62.8
48.8
60.8
30.9
33.0
38.7
27.8
14.0
28.3
33.3
17.4
28.6
15.2
7.1
31.9
38.5
55.1
27.8
27.4
50.0
25.7
20.2
59.6
68.3
53.4
26.9
43.8
38.1
63.4
38.2
28.7






Bull. 241, Making Counts Boll Weevil Infestation


16 half-acre plots in 1926, and 52 quarter-acre plots in 1928,
respectively, the 20-plant method having been used throughout
these counts. The dates on which the infestation counts were
taken and the percent infestation for each plot on the specified
date are also presented. The tables indicate that the counts ap-
proached an accurate estimation of the percent infestation of
each plot at each count since, from week to week, very few ir-
regularities appeared. All of these plots were vigorously poison-
ed by various methods of weevil control and the records of the
percent infestation along with the yield of seed cotton were
largely used in interpreting the relative value of the control
methods in use.
TABLE III.-DATA SECURED FROM 20 TRIAL TESTS OF THE 20-PLANT
METHOD OF MAKING INFESTATION COUNTS.


Number Number
of of
trial squares
in count


Totals


Number
of
infested
squares


Percent
infesta-
I tion


29.41
14.71
27.78
34.48
30.23
25.53
11.11
8.57
20.93
23.33
28.57
17.92
27.03
16.67
19.51
15.38
17.65
30.44
26.00
26.67

23.40


Actual IPercent
percent I Deviation deviation
infesta- from actual from ac-
tion of I infestation tual in-
field I festation

21.68 + 7.73 35.65
21.68 7.17 33.07
21.68 + 6.10 28.14
21.68 + 12.80 59.04
21.68 + 8.55 39.44
21.68 + 3.85 17.76
21.68 10.57 48.75
21.68 13.11 60.47
21.68 0.75 3.46
21.68 + 1.65 7.61
21.68 + 6.89 31.78
21.68 3.76 17.34
21.68 + 5.35 24.68
21.68 5.01 23.11
21.68 2.17 10.01
21.68 6.30 29.06
21.68 4.03 18.59
21.68 + 8.76 40.41
21.68 + 4.32 19.93
21.68 + 4.99 23.02

21.68 + 1.72 7.93


Though the validity of the infestation counts obtained from
the 20-plant method has not been seriously questioned, an ad-
ditional test to determine the effectiveness of the method was
conducted. This test included 20 separate 20-plant counts made
on the same day (June 15, 1928) the actual infestation percent
of the half-acre cotton field was determined by examining all the
plants in the field. (This complete infestation count is later dis-
cussed at length.) As a consequence the percent deviation from






Florida Agricultural Experiment Station


the known infestation of the field could be easily determined.
The complete data of each trial are presented in Table III.
Eighteen of the 20 trials showed a relatively large percent devia-
tion from the actual percent infestation, but two of the trials
registered under 10 percent deviation. A comparison of these
infestation counts with those recorded in Table VIII indicate
that the 20-plant method gave results very similar to those ob-
tained by examining every 25th plant in the field. The percent
deviation from the actual field infestation varied considerably
less than did the percent deviation obtained from an infestation
count in which every 50th plant in the field was examined.
A comparison of the 20-plant method with the data in Table V
indicates that, while the percent infestation secured by the 20-
plant method varied between 8.57 percent and 34.48 percent, the
variation of the percent infestation for whole rows of plants
varied between 11.38 percent and 48.35 percent. The 20 trials
of the 20-plant method included an actual examination of only
842 squares, while the 12 whole-row counts included the exam-
ination of 1,651 squares. It is a significant fact that had the
variations in the deviations from the actual infestation percent
been equally great in both the 20-plant method and complete row
counts, there still remains a marked saving of labor in applying
the 20-plant method.
Furthermore, a comparison of the 20-plant method with the
data in Table VI indicates that the percent infestations secured
for the 20 trials of the 20-plant method varied considerably less
than did the complete counts conducted in the 50-plant units,
which varied from 1.96 percent to 56.25 percent.
The supposition that a path followed diagonally through the
field yields more accurate infestation counts than random counts
taken in any section of the field is supported by a series of ex-
periments in which counts of the squares on plants selected
solely by chance were recorded. Based on the knowledge that
the half-acre cotton field yielded an infestation of 21.68 percent,
random counts of 20 plants each were taken by numbering each
square-bearing plant in the field and subsequently drawing 20
numbers from a box in which slips of paper bearing the num-
bers of all the plants were placed. The data secured from 20
such trials are presented in Table IV. Variation which extended
from 3.57 percent to 42.62 percent infestation were recorded.
These variations were greater than the ones resulting from the
random counts made in a diagonal line through the field. The





Bull. 241, Making Counts Boll Weevil Infestation


average of the 20 trials, however, showed a deviation of but 4.06
percent from the actual field infestation. A total of 904 cotton
squares were included in these trials.
TABLE IV. COTTON BOLL WEEVIL INFESTATION DATA SECURED FROM
RANDOM 20-PLANT COUNTS IN WHICH THE PLANT NUMBERS WERE
DRAWN BY LOT.
Actual Deviation Percent
Number Number Number Percent percent from deviation
of cf of infesta- infesta- actual from
trial squares infested tion tion infesta- actual
in count squares of field tion infestation

1 39 6 15.39 21.68 6.29 29.01
2 36 6 16.67 21.68 5.01 23.11
3 54 10 18.52 21.68 3.16 14.58
4 42 9 21.43 21.68 0.25 1.15
5 36 4 11.11 21.68 -10.57 48.75
6 42 11 26.19 21.68 + 4.51 20.80
7 37 10 27.02 21.68 + 5.34 24.63
8 39 8 20.51 21.68 1.17 5.40
9 61 26 42.62 21.68 + 20.94 96.73
10 56 3 5.36 21.68 16.32 75.28
11 60 11 18.33 21.68 3.35 15.45
12 62 19 30.65 21.68 + 8.97 41.37
13 42 8 19.05 21.68 2.63 12.13
14 40 9 22.50 21.68 + 0.82 3.78
15 45 7 15.55 21.68 6.13 28.27
16 39 8 20.51 21.68 1.17 5.40
17 44 7 15.91 21.68 5.77 26.61
18 39 13 33.33 21.68 + 11.65 53.74
19 63 12 19.05 21.68 2.63 12.13
20 28 1 3.57 21.68 18.11 83.53

Totals 904 188 20.80 21.68 0.88 4.06

Regardless of the method which one might select for deter-
mining the percent of infestation in any field, the fact remains
that the larger the number of squares examined, the more accu-
rate the approximation of the percent infestation will be.
The most accurate method which reduces the number of
squares to be examined is, then, the most suitable method for
current use. That the 20-plant method is more accurate than.any
other method need not be claimed in order to advocate its general
use, because it most assuredly reduces the amount of labor al-
ways attendant with infestation counts.
It has been the author's observation that all cotton workers
who have had considerable experience in making careful sur-
veys of cotton fields, can determine, without actually making
infestation counts, the condition of the field infestation with an
astounding degree of accuracy. For carefully conducted ex-





Florida Agricultural Experiment Station


perimental plots in which the relative value of various boll
weevil control methods are determined, however, infestation
counts have an intrinsic value.

ANALYSIS OF COUNTS MADE IN LIGHT AND HEAVILY
INFESTED FIELDS
To enable the reader to compare the effectiveness of the vari-
ous methods of making infestation counts when applied to a
particular field of known infestation, a half-acre field of cotton
was selected for two complete infestation counts, one before a
heavy infestation made its appearance, and the other after a
relatively heavy infestation had occurred. The first count was
made on June 15, 1928 when each plant in a half-acre field of
unpoisoned cotton was carefully examined in order to record
accurately three classes of data; first, the number of squares
on each plant which were large enough for the boll weevil to
attack; second, the number of squares which had been punctured
by the boll weevil, for either feeding or egg-laying purposes;
and third, the number of weevils populating the field. The field
examination was completed in about five hours and consequently
the constantly increasing number of growing and punctured
squares was sufficiently limited in order to regard the informa-
tion obtained as applicable for consideration as a whole.
The data secured from the survey showed that there were
2,107 plants in the field; that 756 of these plants had one or more
squares large enough to show boll weevil damage; that a total
of 1,651 squares were counted, of which number 358, or 21.68
percent, were damaged by weevils; and that a total of 66 weevils
were found in the field.
It is interesting to note that the lowest percent infestation,
11.38 percent, occurred in Row 9 (Table V), and the highest in-
festation, 48.35 percent, occurred in Row 6. These were 10.30
points (47.51 percent deviation) below and 26.67 points (123.02
percent deviation) above, respectively, the actual percent in-
festation of the whole field, which had an infestation of 21.68
percent. Two rows, 1 and 8, were within two points of the actual
infestation percent, while the others varied between the high
and low percent found in Rows 6 and 9.
When the rows are separated into groups of 50 plants each
(Table VI) a still greater range of differences in group infesta-
tion percentages is noticeable. The second group of Row 7 re-





Bull. 241, Making Counts Boll Weevil Infestation


corded but 1.96 percent, which is 19.72 points (90.96 percent
deviation) below the actual field infestation, and the second
group of Row 10 recorded 56.25 percent, which is 34.75 points
(160.29 percent deviation) higher than the actual infestation.
Three of the sections came within two points (less than 10 per-
cent deviation) of the actual infestation.
TABLE V.-THE NUMBER OF PLANTS, THE TOTAL NUMBER OF SQUARES AND
INFESTED SQUARES, THE PERCENT INFESTATION AND THE NUMBER OF
WEEVILS FOUND IN EACH ROW IN THE HALF-ACRE FIELD EXAMINED ON
JUNE 15, 1928.
I Total
Total Total number Percent Total
Row number number of infested infestation number
number of plants of squares squares in row weevils
in row in row in row in row

1 150 107 21 19.63 4
2 162 82 33 40.24 7
3 162 136 19 13.97 4
4 192 97 28 28.87 5
5 181 115' 15 13.04 2
6 141 91 44 48.35 8
7 152 204 25 12.25 1
8 201 77 18 23.38 5
9 172 167 25 11.38 5
10 236 139 56 41.48 13
11 158 214 40 18.69 3
12 196 222 34 15.32 9

Totals 2,107 1,651 358 21.68 66


Boll weevils, likewise, showed a great diversity in abundance
in various parts of the field (Table VII). Over a third of the
50 plant groups yielded no boll weevils at all, and over a quarter
of the total number of groups yielded but one weevil each, while
three groups yielded 5, 6, and 9 weevils, respectively. The esti-
mation of the weevil population per acre from any counts made
in this field would vary considerably. Estimates based on counts
made on whole rows (420 linear feet) would range from 24 to
512 weevils per acre, whereas 132 weevils per acre (66 weevils
actually having been found in the half-acre) would be the cor-
rect indication of the weevil population.
Further detailed analysis of the field was deemed advisable
to determine the deviations that partial counts would show when
compared with the total infestation counts. As has already been
indicated, the actual infestation of the field was determined by
counting all the squares on all plants in the field. The next step








TABLE VI.-THE PERCENT INFESTATION OF COTTON SQUARES IN GROUPS OF 50 PLANTS IN EACH OF 12 Rows.


First group of fifty
plants in row

Total Number Percent
number squares infesta.
squares infested tion


59

36

63

42

47

39

120

35

73

53

99

101


18.64

36.11

9.52

30.95

19.15

48.72

15.83

14.29

20.55

30.19

15.15

11.88


Total
number
of
plants
in row


150

162

162

192

181

141

152

201

172

236

158

196.


17.24

20.00

12.50

15.00

7.14

23.91'


4"

14

25'

10

2'

25'


o0

5

66

4

0'

4'


0.00"

35.71

24.00'

40.00

0.00'

16.00'


Fifth group of fifty
plants in row

Total Number Percent
number squares infes-
squares infested station
I


0"


24'M


15" 62.50"o


'Two plants only;
"Thirty-six plants only.


Row
number


Second group of Third group of fifty Fourth group of fifty
fifty plants in row plants in row plants in row

Total NumberPercent Total Number Percent Total Numbe Percent
number squares infesta- number squares infesta- number squares infesta-
squares infested tion squares infested tion squares infested, tion

34 8 23.53 14 2 14.29 ............ ..... ............

30 13 43.33 8 2 25.00 8' 52 62.502

39 4 10.26 18 1 5.56 16' 82 50.002

29 9 31.03 19 3 15.79 78 3' 42.86'

30 3 10.00 18 2 11.11 20' 1' 5.00'

19 5 26.32 33' 20' 60.611 ..... .............


1.96

33.33

3.77

56.25

30.99

14.00


'Forty-one plants only; 'Twelve plants only; 'Forty-two plants only; 'Thirty-one plants only;
'Twenty-two plants only; 'Eight plants only; 'Forty-six plants only; 'One plant only;






Bull. 241, Making Counts Boll Weevil Infestation 15

to be taken was the determination of the infestation if only the
squares on every alternate plant were included in the count.
This was followed by counts including every 5th plant, every
10th plant, every 25th plant, and finally, every 50th plant, re-
spectively.
TABLE VII.- THE NUMBER OF BOLL WEEVILS FOUND IN GROUPS OF 50
COTTON PLANTS IN EACH OF TWELVE ROWS, THE GROUPS IN SUCCESSION
IN THE ROWS.
oI Number boll weevils found in each row
Row Number I
number of plants First Second I Third I Fourth I Fifth
in row group group group group group

1 150 0 2 2 -
2 162 0 0 4 *3 -
3 162 0 0 1 *3 -
4 196 2 1 1 *1 -
5 181 1 0 1 *0 -
6 141 1 1 *6 -
7 152 0 0 1 *0 -
8 201 0 3 1 1 -
9 172 1 0 1 *3 -
10 236 2 0 1 1 *9
11 158 0 1 2 *0 -
12 196 2 0 2 *5

*Not a complete section of 50 plants.

The resulting records obtained from these counts are pre-
sented in Table VIII. In the first series, where the squares on
every alternate plant were included in the count the deviation fell
below 10 percent in the counts of both the even and the odd num-
bered plants. Where every 5th plant was included in the counts
only one group fell below a 10 percent deviation, the other groups
ranging from 12.41 percent to 35.10 percent. The infestation
records secured from four out of the five groups, however, could
be used for estimating the percent infestation of the field, since
the approximation was fairly close.
The 10 groups in which all squares on every 10th plant were
included in the count showed considerable variation: The devi-
ation of only four of the 10 groups fell below 10 percent, while
that of the remaining six groups varied from 21.77 percent to
58.58 percent. With the exception of two, possibly three, groups
the infestation count secured from any one of the 10 groups,
however, could be considered valid in field work.






Florida Agricultural Experiment Station


TABLE VIII.-COUNTS OF INFESTED COTTON SQUARES WITH THE DEVIATION
AND PERCENT DEVIATION FROM THE ACTUAL FIELD INFESTATION IN VARI-
OUS PLANT GROUPS.


Numb
Number plants square
included in count count


All plants:
1, 2, 3, etc. 1,


Every other plant:
1, 3, 5, etc. 836
2, 4, 6, etc. 815

1,

Every fifth plant:
1, 6, 11, etc. 327
2, 7, 12, etc. 337
3, 8, 13, etc. 312
4, 9, 14, etc. 320
5, 10, 15, etc. 355


Every tenth plant:
1, 11, 21, etc.
2, 12, 22, etc.
3, 13, 23, etc.
4, 14, 24, etc.
5, 15, 25, etc.
6, 16, 26, etc.
7, 17, 27, etc.
8, 18, 28, etc.
9, 19, 29, etc.
10, 20, 30, etc.


ler
es
ed



651


651


1,651


Number Percent
squares infesta-
infested tion



358 21.68


195
16S




76
64
58
56
104




47
36
24
23
66
29
28
34
33
38


1,651


358








358













358


23.33
20.00




23.24
18.99
18.59
17.50
29.29


29.75
21.05
15.69
15.23
34.38
16.96
16.87
21.39
19.53
23.31


[ Percent
Deviation deviation
from from
actual actual
infestation infestation


+ 1.65
- 1.68


+ 7.61




+ 8.07
- 0.63
- 5.99
- 6.45
+ 12.70
- 4.72
- 4.81
- 0.29
- 2.15
+ 1.63


7.20
12.41
14.25
19.28
35.10


37.22
2.90
27.63
29.75
58.58
21.77
22.19
1.34
9.92
7.52







Bull. 241, Making Counts Boll Weevil Infestation


TABLE VIII.-COUNTS OF INFESTED COTTON SQUARES WITH THE DEVIATION
AND PERCENT DEVIATION FROM THE ACTUAL FIELD INFESTATION IN VARI-
OUS PLANT GROUPS-Continued.


Number plants
included in count


Every 25th plant:

1, 26, 51, etc.
2, 27, 52, etc.
3, 28, 53, etc.
4, 29, 54, etc.
5, 30, 55, etc.
6, 31, 56, etc.
7, 32, 57, etc.
8, 33, 58, etc.
9, 34, 59, etc.
10, 35, 60, etc.
11, 36, 61, etc.
12, 37, 62, etc.
13, 38, 63, etc.
14, 39, 64, etc.
15, 40, 65, etc.
16, 41, 66, etc.
17, 42, 67, etc.
18, 43, 68, etc.
19, 44, 69, etc.
20, 45, 70, etc.
21, 46, 71, etc.
22, 47, 72, etc.
23, 48, 73, etc.
24, 49, 74, etc.
25, 50, 75, etc.


Number
squares
counted


Number
squares
infested


Percent
infesta-
tion




20.83
14.81
20.69
17.65
30.77
21.88
25.30
20.00
26.15
32.53
30.77
18.75
11.76
16.95
28.38
15.52
18.52
25.40
14.67
17.86
26.47
14.55
14.58
12.86
33.77


I Percent
Deviation deviation
from from
actual actual
infestation infestation


- 0.85
- 6.87
- 0.99
- 4.03
+ 9.09
+ 0.20
+ 3.62
- 1.68
+ 4.47
+ 10.87
+ 9.09
- 2.93
- 9.92
- 4.73
+ 6.70
- 6.15
- 3.16
+ 3.72
- 7.01
- 3.82
+ 4.79
- 7.13
- 7.10
- 8.82
+ 12.09


3.92
31.69
4.57
18.59
41.93
0.92
16.70
7.75
20.62
50.14
41.93
13.51
45.76
21.82
30.90
28.41
14.58
17.16
32.83
17.62
22.09
32.89
32.75
40.68
55.77









18 Florida Agricultural Experiment Station

TABLE VIII.-COUNTS OF INFESTED COTTON SQUARES WITH THE DEVIATION
AND PERCENT DEVIATION FROM THE ACTUAL FIELD INFESTATION IN VARI-
OUS PLANT GROUPS-Continued.
SPercent
Number Number Percent Deviation deviation
Number plants squares squares infesta- from from
included in count counted infested tion actual actual
infestation infestation

Every 50th plant:
1, 51, 101, etc. 38 10 26.32 + 4.64 21.40
2, 52, 102, etc. 25 3 12.00 9.68 44.65
3, 53, 103, etc. 29 5 17.24 4.44 20.48
4, 54, 104, etc. 26 7 26.92 + 5.24 24.17
5, 55, 105, etc. 28 12 42.86 + 21.18 97.69
6, 56, 106, etc. 33 2 6.06 15.62 72.05
7, 57, 107, etc. 36 6 16.67 5.01 23.11
8, 58, 108, etc. 39 7 17.95 3.73 17.20
9, 59, 109, etc. 38 9 23.68 + 2.00 9.23
10, 60, 110, etc. 38 13 34.21 + 12.53 57.75
11, 61, 111, etc. 35 10 28.57 + 6.89 31.78
12, 62, 112, etc. 33 6 18.18 3.50 16.14
13, 63, 113, etc. 32 3 9.38 -12.30 56.73
14, 64, 114, etc. 30 4 13.33 8.35 38.51
15, 65, 115, etc. 44 16 36.36 + 14.68 67.71
16, 66, 116, etc. 35 3 8.57 13.11 60.47
17, 67, 117, etc. 41 8 19.51 2.17 10.01
18, 68, 118, etc. 31 10 32.26 + 10.58 48.80
19, 69, 119, etc. 42 7 16.67 5.01 23.11
20, 70, 120, etc. 23 3 13.04 8.64 39.85
21, 71, 121, etc. 29 9 31.03 + 9.35 43.13
22, 72, 122, etc. 26 5 19.23 2.45 11.30
23, 73, 123, etc. 24 2 8.33 13.35 61.58
24, 74, 124, etc. 35 0 0.- 21.68 -
25, 75, 125, etc. 42 17 40.48 + 18.80 86.71
26, 76, 126, etc. 34 5 14.71 6.97 32.15
27, 77, 127, etc. 29 5 17.24 4.44 20.48
28, 78, 128, etc. 29 7 24.14 + 2.46 11.35
29, 79, 129, etc. 25 2 8.00 13.68 63.10
30, 80, 130, etc. 37 8 21.62 0.06 0.28
31, 81, 131, etc. 31 12 38.71 + 17.03 78.55
32, 82, 132, etc. 47 15 31.91 + 10.23 47.19
33, 83, 133, etc. 36 8 22.22 + 0.54 2.49
34, 84, 134, etc. 27 8 29.63 + 7.95 36.67
35, 85, 135, etc. 45 14 31.11 + 9.43 43.50
36, 86, 136, etc. 30 10 33.33 + 11.65 53.74
37, 87, 137, etc. 31 6 19.35 2.33 10.75
38, 88, 138, etc. 36 5 13.89 7.79 35.93
39, 89, 139, etc. 29 6 20.69 0.99 4.57
40, 90, 140, etc. 30 5 16.67 5.01 23.11
41, 91, 141, etc. 23 6 26.09 + 4.41 20.34
42, 92, 142, etc. 40 7 17.51 4.17 19.23
43, 93, 143, etc. 32 6 18.75 2.93 13.51
44, 94, 144, etc. 33 4 12.12 9.56 44.10
45, 95, 145, etc. 33 7 21.21 0.47 2.17
46, 96, 146, etc. 39 9 23.08 + 1.40 6.46
47, 97, 147, etc. 29 3 10.34 11.34 52.31
48, 98, 148, etc. 24 5 20.83 0.85 3.92
49, 99, 149, etc. 35 9 25.71 + 4.03 18.59
50, 100, 150, etc. 35 9 25.71 + 4.03 18.59
1651 358






Bull. 241, Making Counts Boll Weevil Infestation


The percent deviation from the actual infestation varied still
more in the groups when each 25th plant was counted. But four
of the 25 groups showed less than 10 percent deviation and only
10 of the groups approximated the actual infestation sufficiently
to be of practical value.
Where every 50th plant was counted, the accuracy of the in-
festation counts in the field was greatly reduced. Only seven of
the 50 groups fell below a deviation of 10 percent. The infesta-
tion counts ranged from no infestation at all to a percentage
which was 97.69 percent in excess of the actual field infestation.
The foregoing analysis by groups clearly indicates that, in
order to obtain reasonably accurate counts of early season boll
weevil infestation, large numbers of cotton squares and plants
must be carefully examined. The most desirable method of
determining the infestation of the field, however, is one in which
the smallest possible number of squares need be examined.
Late season infestations, on the other hand, are usually rather
severe and consequently more uniformly spread over the entire
cotton field. Consequently, the counting of relatively few squares
will usually indicate the percent infestation whereupon any
suitable control method for combating the boll weevil can be ap-
plied to the field. This assumption was substantiated by another
complete infestation count made on July 16, 1928.
This second examination of the field required 12 hours for
completion and as a consequence the part of the field which was
examined at the end of the count had increased somewhat in
infestation percentage. The increase, however, in the face of
the heavy infestation recorded, was negligible. The data secured
from this second count showed that there were 1,997 plants in
the field, a loss of 110 plants since June 15; that 1,914 of these
plants had one or more squares which were large enough to show
boll weevil damage; that a total of 26,303 squares were counted,
of which number 11,772, or 44.76 percent, were damaged by
weevils; and that a total of 395 weevils were found in the field.
It is a significant fact that the variations between the high-
est percent infestation counted, 56.04 percent for Row 11 (Table
IX) and the lowest count, 30.43 percent for Row 3, showed rel-
atively small deviations from the actual infestation of the field,
which was found to be 44.76 percent. Infestation counts of nine
of the 12 rows approximate the infestation of the field as a
whole so closely that they could ordinarily be used, since they






Florida Agricultural Experiment Station


showed a deviation of but from 5.23 percent to 15.91 percent
from the actual infestation percent.
TABLE IX. THE NUMBER OF PLANTS, THE TOTAL NUMBER OF SQUARES
AND INFESTED SQUARES, THE PERCENT INFESTATION, AND THE NUMBER
OF WEEVILS FOUND IN EACH ROW IN THE HALF-ACRE FIELD EXAMINED
JULY 16, 1928.
STotal I Total
Total Total number of Percent number
Row number number infested infesta- of
number of plants of squares squares tion in weevils
in row in row in row row in row

1 113 762 248 32.55 2
2 144 1,866 745 39.82 20
3 153 1,995 607 30.43 17
4 193 2,811 1,058 37.64 27
5 172 1,760 829 47.10 29
6 133 2,476 1,003 40.51 41
7 149 2,037 1,035 49.93 40
8 199 2,211 1,123 50.79 43
9 168 2,441 1,189 48.71 57
10 230 3,978 1,878 47.21 54
11 155 2,111 .1,183 56.04 32
12 188 1,819 873 47.99 33

Totals 1,997 26,303 11,772 44.76 395


As was the case with the infestation counts of June 15, the
division of each row into 50 plant groups (Table X) increased the
deviation of the percent infestation among the groups. The
third group in Row 1 recorded but 23.64 percent infestation
while the second group in Row 11 showed an infestation of 64.91
percent. These counts, however, as well as all intermediate
counts, are well above the danger point of insect infestation and
would call for the immediate application of some method of
control.
Whereas over a third of the 50-plant groups yielded no weevils
on June 15, all of the groups which were examined on July 16
(Table XI) with the exception of one, yielded from one to 25
weevils per group. The 395 weevils captured were well distrib-
uted over the field and almost any method which might be ap-
plied toward ascertaining the weevil population of the field could
be used successfully.
The infestation count made in June, at which time relatively
few cotton squares had formed and comparatively few weevils
had appeared, indicated strongly that a large number of squares
must be examined in order to determine the actual percent of






TABLE X.--THE PERCENT INFESTATION OF COTTON SQUARES IN GROUPS OF 50 PLANTS IN EACH OF 12 Rows.
First Group of 50 I Second group of 50 Third group of 50 plants Fourth group of 50 plants
Total plants in row plants in row in row in row
Row number Total Number Percent Total Number Percent Total Number Percent Total Number Percent
number ofplants number squares infesta- number squares infesta- number squares infesta- number squares infesta-
_m rw squares infested tion squares infested tion squares infested tion squares infested tion

1 113 294 102 34.69 303 107 35.31 165' 39' 23.64' ................ ....... .................

2 144 795 356 44.78 650 243 37.38 421' 146' 34.68 ................ ........ ...............
3 153 931 284 30.50 574 205 35.71 490 118 24.08 ..................................
4 193 1,076 408 37.92 769 261 33.94 613 245 39.97 353' 144' 40.79'
5 172 805 367 45.59 451 227 50.33 328 135 41.16 176' 100" 56.822
6 133 1,313 570 43.41 719 271 37.69 4443 162' 36.49' .............. ............. ..................
7 149 962 535 55.61 627 322 51.36 484 178 36.78 .............. ..................................
8 199 791 330 41.72 549 313 57.01 489 274 56.03 363 206 56.75
9 168 981 462 47.09 774 354 45.74 514 264 51.36 172' 109" 63.37'
10 230 1,011 448 44.31 1,220 588 48.20 793 357 45.02 954' 485' 50.84'
11 155 786 410 52.16 758 492 64.91 576 281 48.78 ............................... .................

12 188 647 291 44.98 405 215 53.09 500 234 46.80 267' 133' 49.81'

'Thirteen plants only; 'Forty-four plants only; 'Thirty-three plants only; 'Forty-three plants only;
"Twenty-two plants only; 'Eighteen plants only; 'Eighty plants; 'Thirty-eight plants only.






22 Florida Agricultural Experiment Station

TABLE XI. THE NUMBER OF WEEVILS FOUND IN GROUPS OF 50 PLANTS
IN EACH OF 12 Rows.
Number boll weevils found in each row
Number
Row of ns First Second Third Fourth Fifth
number in row group group group group group
I n ro of 50 of 50 of 50 of 50 of 50
plants plants plants plants plants

1 113 1 1 *0 -
2 144 15 3 *2 -
3 153 7 8 2 -
4 193 8 9 8 *2 -
5 172 10 9 7 *3 -
6 133 17 15 *9 -
7 149 22 11 7 -
8 199 13 12 9 9 -
9 168 25 14 16 *2 -
10 230 13 9 9 14 *9
11 155 13 9 10 -
12 188 9 4 16 *4

*Not a complete section of 50 plants.

light infestations with any degree of accuracy. The count made
in July, when there were many squares and weevils in the fi2ld,
however, indicated that the examination of relatively few
squares would suffice for making a fairly accurate determination
of the percent infestation of a field which was heavily infested.

CONCLUSIONS

Analysis of a half-acre cotton field in which all squares on all
plants were examined, indicated that the greater the number of
squares examined the closer the estimated percent infestation
approaches the actual percent infestation of a lightly infested
field. Heavily infested fields, however, require the examination
of relatively few squares.
Consideration of an outline of the various methods of obtain-
ing infestation counts indicated that one method was as satis-
factory as any other and consequently that the method involv-
ing the least labor is most suitable for general use. The 20-
plant method which involves comparatively little labor has been
found to be satisfactory.
The determination of the number of boll weevils in a sparsely
populated field is attendant with great errors, regardless of the
method employed.




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