Under the direction of Allen Cohen.

94 Pages·2013·1.95 MB·English

ABSTRACT
ZHA, CHEN. Evaluating the Dynamics of Anti-Fungal Compounds in Lepidoptera Larvae.
(Under the direction of Allen Cohen.)
Mold control is one of the most vital issues in insect rearing systems. Mold outbreaks can
alter the nutritional value of the diet, do harm to the insects, and even threaten the health of
people who work in insectaries. Antifungal agents are widely used in insect diets to suppress
the growth of mold; however, the potential detrimental effects of antifungal agents on insects
are always a concern. When there is a high level of antifungal agents in artificial diets, the
growth, development, survivorship and fecundity of insects are often negatively affected. To
study the mechanisms underlying those deleterious effects, nutritional indices were
determined for two representative lepidopterans, a butterfly and a moth, Vanessa cardui and
Heliothis virescens larvae reared on different concentrations of three widely used antifungal
agents: methyl paraben, potassium sorbate and sodium propionate. These antifungal agents
were administered in concentrations of 1,000, 5,000, and 10,000 parts per million (ppm). The
results show that a high level of antifungal agents in the diets of these insects will suppress
nutrient absorption and increase metabolic costs. Relative consumption rates and digestibility
increased with increasing antifungal agent concentration, possibly to compensate for the
declines in absorption and metabolism. Silk production and frass management by Vanessa
cardui larvae were reduced in the presence of the highest level of antifungal agents.
Evaluating the Dynamics of Anti-Fungal Compounds in Lepidoptera Larvae

by
Chen Zha

A thesis submitted to the Graduate Faculty of
North Carolina State University
in partial fulfillment of the
requirement for the Degree of
Master of Science

Entomology

Raleigh, North Carolina

2013

APPROVED BY:

________________________ ________________________
Allen C. Cohen Yasmin J. Cardoza
Chair of Advisory Committee

________________________ ________________________
David Orr Clyde Sorenson
© Copyright 2013 by Chen Zha
All Rights Reserved
BIOGRAPHY
Chen Zha was born April 11th, 1989 in Anhui province, China. His love of insects revealed
itself during his childhood. He studied life sciences in University of Science and Technology
of China. After having received his BS degree, he shifted his major into entomology under
the direction of Dr. Allen C. Cohen at North Carolina State University. His first research
effort in entomology focused on the influences of antifungal agents on insect nutritional
ecology, and he plans on working with chemical ecology of bed bugs and getting a PhD in
entomology at Rutgers University.

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ACKNOWLEDGEMENTS
I would like to thank everyone who helped me along the way, my advisor Dr. Allen Cohen,
fellow graduate students, professors and staff, and my parents who provide me economical
support studying abroad. Special thanks go to Drs. Yasmin J. Cardoza, David Orr and Clyde
Sorenson for being members of my graduate committee and for providing much help and
advice to guide my work. I also thank Dr. Fred Gould for providing H. virescens eggs from
his lab colony, and Sandra Paa for egg collection and technical support in rearing H.
virescens. Finally, I thank Dr. Consuelo Arellano for helping with the statistical analysis of
my data.

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TABLE OF CONTENTS

LIST OF TABLES ............................................................................................................ v

LIST OF FIGURES.......................................................................................................... vi

Evaluating the Dynamics of Anti-Fungal Compounds in Lepidoptera Larvae .............. 1
INTRODUCTION ................................................................................................. 2
MATERIALS AND METHODS ......................................................................... 16
RESULTS ............................................................................................................. 27
DISCUSSION ....................................................................................................... 30
REFERENCES .................................................................................................... 46

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LIST OF TABLES
Table 1. The ingredients of YC diet ................................................................................... 63

Table 2. Effects of antifungal agents on V. cardui feeding and growth ............................... 64

Table 3. Effects of antifungal agents on H. virescens feeding and growth .......................... 65

Table 4. Percent V. cardui larvae fed on diet columns contain different concentrations of
antifungal agents ............................................................................................................... 66

Table 5. Percent H. virescens larvae fed on diet columns contain different concentrations of
antifungal agents ............................................................................................................... 67

Table 6. Percent larvae fed on different diet columns with different pH ............................. 68

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LIST OF FIGURES
Figure 1. The effects of different concentrations of 3 antifungal agents on frass production ...
.......................................................................................................................................... 69

Figure 2. The effects of different concentrations of 3 antifungal agents on insect weight gain
.......................................................................................................................................... 70

Figure 3. The effects of different concentrations of 3 antifungal agents on consumption rate
(CR) .................................................................................................................................. 71

Figure 4. The effects of different concentrations of 3 antifungal agents on relative
consumption rate (RCR) .................................................................................................... 72

Figure 5. The effects of different concentrations of 3 antifungal agents on approximate
digestibility (AD) .............................................................................................................. 73

Figure 6. The effects of different concentrations of 3 antifungal agents on the efficiency of
conversion of ingested food to biomass (ECI) .................................................................... 74

Figure 7. The effects of different concentrations of 3 antifungal agents on the efficiency of
conversion of digested food to biomass (ECD) .................................................................. 75

Figure 8. Comparison among the 3 antifungal agents on frass production .......................... 76

Figure 9. Comparison among the 3 antifungal agents on insect weight gain ....................... 77

Figure 10. Comparison among the 3 antifungal agents on consumption rate (CR) .............. 78

Figure 11. Comparison among the 3 antifungal agents on relative consumption rate (RCR) ...
.......................................................................................................................................... 79

Figure 12. Comparison among the 3 antifungal agents on approximate digestibility (AD) . 80

Figure 13. Comparison among the 3 antifungal agents on the efficiency of conversion of
ingested food to biomass (ECI) .......................................................................................... 81

Figure 14. Comparison among the 3 antifungal agents on the efficiency of conversion of
digested food to biomass (ECD) ........................................................................................ 82

Figure 15. Freeze dried diet sample of 10,000ppm methyl paraben treatment, showing the
presence of white methyl paraben crystals which insects avoided to ingest ........................ 83

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Figure 16. “Frass management” of a V. cardui larva, showing that the frass was attached with
silk and kept away from diet .............................................................................................. 84

Figure 17. A comparison of V. cardui frass management behavior between 1,000 and
10,000ppm potassium sorbate (KS1 & KS3) treatments ..................................................... 85
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Evaluating the Dynamics of Anti-Fungal Compounds in Lepidoptera Larvae

C. Zha

Department of Entomology, North Carolina State University
Campus Box 7613, Raleigh, NC 27695

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