Table Of ContentEVALUATION OF THE ENTOMOPATHOGENIC FUNGUS
BEAUVERIA BASSIANA ON THE
RED IMPORTED FIRE ANT, SOLENOPSIS INVICTA
By
ROBERTO MANOEL PEREIRA
DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OFTHE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF
THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1991
A Eduardo, Ricardo, Angela, Alberto, e Rodrigo,
que construiram a base de tudo.
AJulia, Carolina, Marcel, Denise, e outros por vir,
uma nova geragao de esperanqas.
ACKNOWLEDGMENTS
I thank Dr. Jerry L. Stimac for his guidance and friendship during
the course of my studies at the University of Florida, and Dr. Sergio B.
Alves for the support and teachings in the last 10 years. I am also very
grateful for the help offered by Drs. Drion G. Boucias, Clayton W. McCoy,
and James W. Kimbrough, and for the support from the faculty and staff of
the Department of Entomology and Nematology of the University of
Florida
My gratitude is extended to Lois Wood for her ever-present helping
hand, and for entertaining stories. I would also like to acknowledge the
help of people who in many ways contributed to the completion of this
work, namely: Lisa Huey, Robin Register, Reginald Coler, Hugh Smith, Dr.
Tomas Zoebisch, and Dr. David Oi.
I am grateful for the patience and understanding of my wife Bete,
and for the loving and nurturing home she creates for our daughters and
me.
in
TABLE OF CONTENTS
page
ACKNOWLEDGEMENTS
iii
LIST OF TABLES
vii
LIST OF FIGURES
ix
KEY TO ABBREVIATIONS
xi
ABSTRACT
xii
CHAPTERS
INTRODUCTION
1 1
Geographic Distribution and Introduction of Fire Ants
into the United States 1
Importance 2
Present Control Methods 4
Natural Enemies 5
Microbial Agents 7
Use of Beauveria bassiana in Insect Control 10
Beauveria bassiana as a Microbial Control for Fire
Ants 11
Objectives 14
2 DOSE-RESPONSE OF THE RED IMPORTED FIRE
ANTS, SOLENOPSIS INVICTA, WORKERS TO
BEAUVERIA BASSIANA CONIDIA
17
Introduction 17
Materials and Methods 19
Fungus 19
Ants and Soil 20
IV
Spray Tower and Spraying Procedure 21
Dose-Response Experiments 22
Mortality Assessment and Analysis of Results .... 24
Results 25
Direct Spray Experiments 25
Soil Incorporation Experiments 30
Surface Exposure Experiments 38
Discussion 42
Effect of Fungus in Direct Spray Experiments 42
Effect of Conidia Mixed into Soil 44
Infection of Ants by Conidia in Soil and on Plate
Surface 46
TRANSMISSION OF BEAUVERIA BASSIANA
3
WITHIN ARTIFICIAL FIRE ANT NESTS IN THE
LABORATORY
48
Introduction 48
Materials and Methods 51
Fungus and Inoculation of Ants 51
Preparation of Artificial Colonies 52
Experimental Procedures 52
Estimation of Number of Conidia in Cadaver Pile 54
. .
Experiments with Conidia Formed on Ants 54
Assessment of Survival and Analysis of Results ... 55
Results 57
Experiments with Live Infected Ants in
Plaster-Bottom Cups 57
Experiments with Live Infected Ants in Soil 61
Experiments with Dead Infected Ants 64
Conidia per Ant 70
Experiments with Conidia Formed on Ants 70
Discussion 74
4 GROWTH OF BEAUVERIA BASSIANA IN FIRE
ANT NEST SOIL WITH AMENDMENTS 79
Introduction 79
Materials and Methods 81
Fungus 81
Amendments 82
Preparation of Soil Plates and Inoculation 83
Observations, Measurements and Analysis of
Results 85
Results 86
Mycelial Inoculum 86
Conidial Inoculum 88
Ant Inoculum 93
Discussion 94
Effects of Inoculum Types 94
Effects of Amendments 99
5 CONCLUSIONS AND IMPLICATIONS OF
RESULTS ON THE MICROBIAL CONTROL OF
SOLENOPSIS INVICTA WITH THE
ENTOMOPATHOGENIC FUNGUS BEAUVERIA
BASSIANA 102
APPENDICES
A EFFICIENCY OF WASHING PROCEDURE IN
ESTIMATION OF NUMBER OF CONIDIA PER
ANT AFTER APPLICATION OF CONIDIAL
SUSPENSIONS 112
B EVALUATION OF EFFECT OF SOIL ANTAGONISM
ON BEAUVERIA BASSIANA INFECTION OF FIRE
ANT WORKERS
114
LITERATURE CITED 117
BIOGRAPHICAL SKETCH 135
VI
LIST OF TABLES
table page
1-1 Effective dose of B. bassiana against insect pests under
several experimental conditions as reported by different
authors 12
2-1 Lethal concentrations (conidia / ml of suspension) of B.
bassiana against S. invicta, when suspensions are
directly sprayed on the ants which are maintained in
clean plastic cups for 15 days 28
2-2 Lethal times (days) for B. bassiana against S. invicta,
when suspensions are directly sprayed on the ants,
which are maintained in clean plastic cups for 15 days 29
. . . ,
2-3 Lethal concentrations (conidia / ml of suspension) of B.
bassiana against S. invicta, when suspensions are
directly sprayed on the ants which are maintained in
plastic cups containing either sterile or nonsterile fire
ant nest soil for 15 days 33
2-4 Lethal concentrations (conidia / g of soil) of B. bassiana
against S. invicta, when suspensions are applied to
either sterile or nonsterile fire ant nest soil, and ants are
maintained in soil for 15 days 37
2-5 Lethal concentrations (conidia / mn\2 of plastic Petri
dish) of B. bassiana against S. invicta, when suspensions
are directly sprayed on Petri dishes and ants are allowed
to walk in the dishes for 24 hours before being
transferred to clean plastic cups for 15 days 40
VII
2-6 Lethal times (days) for B. bassiana against S. invicta,
when suspensions are sprayed on Petri dishes and ants
are allowed to walk in the dishes for 24 hours before
being transferred to clean plastic cups for 15 days 41
3-1 Mean survivals of ants and mean weights of surviving
ants in colonies receiving different percentages of B.
bassiana-iniected individuals and maintained in
containers with no soil (Experiment 1) 59
3-2 Mean survivals of ants and mean weights of surviving
ants in colonies receiving different percentages of B.
bassiana-iniected individuals and maintained in
containers with no soil (Experiment 2) 60
3-3 Mean survivals of ants and mean weights of surviving
ants in colonies receiving different percentages of B.
bassiana-iniected individuals and maintained in soil
(Experiment 1) 63
3-4 Mean survivals of ants and mean weights of surviving
ants in colonies receiving different percentages of B.
bassiana-iniected individuals and maintained in soil
(Experiment 2) 65
3-5 Mean survivals of ants and mean weights of surviving
ants in colonies receiving different percentages of B.
bassiana-iniected cadavers and maintained in containers
with no soil 66
3-6 Mean survivals of ants and mean weights of surviving
ants in colonies receiving different percentages of B.
bassiana-iniected cadavers and maintained in containers
with soil 67
A-l Results of the estimation of washing efficiency of
procedure used in the estimation of dose of conidia per
ant after spraying of conidial suspension 113
B-l Percent mortality and infection of fire ant workers (S.
invicta) exposed to nest soil containing conidia of the
fungus B. bassiana 116
VIII
LIST OF FIGURES
E^
figure
2-1 Mortality and infection of S. invicta treated with direct
spray of B. bassiana conidial suspensions and
maintained in clean plastic cups for 15 days 27
2-2 Mortality and infection of S. invicta treated with direct
spray of B. bassiana conidial suspensions and
maintained in plastic cups containing sterile fire ant
nest soil for 15 days 31
2-3 Mortality and infection of S. invicta treated with direct
spray of B. bassiana conidial suspensions and
maintained in plastic cups containing nonsterile fire ant
nest soil for 15 days 32
2-4 Mortality and infection of S. invicta maintained for 15
days in sterile fire ant nest soil treated with B. bassiana
34
conidia
2-5 Mortality and infection of S. invicta maintained for 15
days in nonsterile fire ant nest soil treated with B.
36
bassiana conidia
2-6 Mortality and infection of S. invicta exposed to Petri
dish surface treated with direct spray of B. bassiana
conidial suspensions, and maintained in in clean plastic
cups for 15 days 39
IX
3-1 Number of conidia per cup and per gram of ants
produced on S. invicta cadavers, in population either
with 100% of B. bassiana-infected insects or with
mixture of 50-50% of healthy and infected ants 71
3-2 Mortality of S. invicta treated with direct spray of B.
bassiana conidial suspensions prepared from conidia
produced either on SDAY plates or on ant cadavers from
experiments with or without soil 72
4-1 Diameter of 15-day old B. bassiana colonies on sterile
and nonsterile fire ant nest soil amended with different
materials and inoculated with dry mycelium particle 87
4-2 Number of B. bassiana colony forming units (CFU's)
produced after 15 days of incubation on either sterile or
nonsterile fire ant nest soil amended with different
materials and inoculated with dry mycelium particle 89
4-3 Number of B. bassiana colony forming units (CFU's)
produced after 15 days of incubation on either sterile or
nonsterile fire ant nest soil amended with different
materials and inoculated with conidial suspension 91
4-4 Diameter of 10-day old B. bassiana colonies on sterile fire
ant nest soil amended with different materials and
inoculated with conidial suspension 92
4-5 Diameter of 15-day old B. bassiana colonies on sterile
and nonsterile fire ant nest soil amended with different
materials and inoculated with with fire ant (S. invicta)
abdomens
95
4-6 Number of B. bassiana colony forming units (CFU's)
produced after 15 days of incubation on either sterile or
nonsterile fire ant nest soil amended with different
materials and inoculated with fire ant (S. invicta)
abdomens 96
