Toxicity and Laboratory Performance of Insecticides to Field-Collected German Cockroaches (Dictyoptera: Blattellidae) by Xiaoyan Wu A thesis submitted to the Graduate Faculty of Auburn University in partial fulfillment of the requirements for the Degree of Master of Science Auburn, Alabama December 10, 2016 Keywords: Blattella germanica, insecticides, toxicity, repellency, laboratory performance Approved by Arthur G. Appel, Chair, Professor of Entomology Xing Ping Hu, Professor of Entomology Nannan Liu, Professor of Entomology Beatrice N. Dingha, Research Scientist, North Carolina A&T State University Abstract The toxicity and resistance levels of five technical grade insecticides (permethrin, chlorpyrifos, propoxur, imidacloprid, and fipronil) were determined for adult males of seven strains of the German cockroach, Blattella germanica (L.). One laboratory reared susceptible strain combined with six field-collected strains. Using topical application methods, fipronil was the most toxic insecticide to all seven strains. The LD50 values of fipronil to the susceptible strain and the field-collected strains B, D, E, G, H, and I were 1.33, 2.62, 11.53, 5.07, 7.66, 5.15, and 10.15 ng/insect, respectively. The field-collected strains were most resistant to permethrin among the five insecticides, except for strain H. The resistance ratios of strains B, D, E, G, and I to permethrin were 31.8, 37.3, 51.9, 34.9, and 37.5, respectively. With a resistance ratio of 6.4, the field-collected strain H was most resistant to chlorpyrifos. The field-collected strains had nearly no resistance to propoxur. Strains B, H, and I were not significantly resistant to imidacloprid when compared to the susceptible strain. Based on the different resistance ratios for each insecticide, we conclude that the field-collected strains had different treatment histories. The repellency and performance of five selected insecticide formulations (each of which included one of the above insecticides) were determined using Ebeling choice boxes against male adult German cockroaches. Permethrin was the most repellent insecticide to the susceptible strain and field-collected strains B, E, G, and I with mean repellency of 55.97%, 66.89%, 85.92%, 27.16%, and 53.66%, respectively. Fipronil was the most repellent to strain D with repellency of 41.72%, and the five insecticides were similar in their repellency against strain H. ii Fipronil reached PI values of 100 during the 14 d experiment and tPImax/2 < 2 d. Chlorpyrifos reached PImax 100 for the susceptible strain and field-collected strains D and H during the 14 d experiment as well. Permethrin, propoxur, and imidacloprid did not reach PI values of 100 during the 14 d experiment. According to the repellency and performance index, fipronil may provide effective control in field, while other insecticides may be incapable of providing good field performance. iii Acknowledgements I would like to thank everyone who encouraged and helped me during my master’s study. I would like to thank Dr. Arthur G. Appel for accepting me as his graduate student. His support, patience, and guidance in my project, and his passion for cockroaches encouraged me during the two years. I would like to thank my committee members, Dr. Nannan Liu, Dr. Xing Ping Hu, and Dr. Beatrice N. Dingha, for reviewing the manuscript and their suggestions for my project. I would like to thank Dr. Ting Li for her help with the topical application and Ms. Marla Eva for her assistance in the laboratory. I would like to thank my teachers at China Agricultural University for encouraging me to apply for the 3+2 program so that I could start my master’s study here at Auburn. I would like to thank Caixing Xiong, Xiaodi Wang, Jing Li, Cheng Qian, and my roommate Pan Wang, for their encouragement and support. Also, I would like to thank my friends in China for being supportive during my master’s study, which helped me when I was overwhelmed with the stresses of graduate school. My deepest gratitude goes to my family for their continuous encouragement, support, and their confidence in me throughout graduate school. I would like to thank my father, Yong Wu, and my mother, Weihong Chen, for their patience and support when I encountered difficulties and was stressed. Although they are thousands miles away, their support for me always make me feel that I am surrounded by love. I would like to thank my parents for encouraging me to apply for this program and their financial support during the first year as well. iv Table of Contents Abstract ........................................................................................................................................... ii Acknowledgements ........................................................................................................................ iv List of Tables ................................................................................................................................. vi List of Figures .............................................................................................................................. viii Introduction ..................................................................................................................................... 1 Resistance to insecticides by field-collected German cockroach strains (Dictyoptera: Blattellidae) ....................................................................................................................................................... 23 Repellency and performance of selected insecticides to field-collected German cockroaches (Dictyoptera: Blattellidae) ............................................................................................................ 46 References ..................................................................................................................................... 87 v List of Tables Table 1. List of participants. ················································································ 37 Table 2. Mean masses of German cockroach strains measured in grams ···························· 38 Table 3. Toxicity of permethrin topically applied to the German cockroaches ····················· 39 Table 4. Toxicity of chlorpyrifos topically applied to the German cockroaches ···················· 40 Table 5. Toxicity of propoxur topically applied to the German cockroaches ······················· 41 Table 6. Toxicity of imidacloprid topically applied to the German cockroaches ··················· 42 Table 7. Toxicity of fipronil topically applied to the German cockroaches ························· 43 Table 8. Relationship between resistance ratios of selected insecticides ····························· 44 Table 9. Correlation between body mass and resistance················································ 45 Table 10. Toxicity of insecticides against the susceptible strain of the German cockroach. ······ 60 Table 11. Toxicity of insecticides against the German cockroach strain B. ························· 61 Table 12. Toxicity of insecticides against the German cockroach strain D. ························· 62 Table 13. Toxicity of insecticides against the German cockroach strain E. ························· 63 Table 14. Toxicity of insecticides against the German cockroach strain G. ························· 64 Table 15. Toxicity of insecticides against the German cockroach strain H. ························· 65 Table 16. Toxicity of insecticides against the German cockroach strain I. ·························· 66 Table 17. Repellency of insecticides against the susceptible German cockroach strain determined in Ebeling choice boxes. ········································································ 67 Table 18. Repellency of insecticides against the German cockroach strain B determined in Ebeling choice boxes. ············································································ 68 vi Table 19. Repellency of insecticides against the German cockroach strain D determined in Ebeling choice boxes. ············································································ 69 Table 20. Repellency of insecticides against the German cockroach strain E determined in Ebeling choice boxes. ············································································ 70 Table 21. Repellency of insecticides against the German cockroach strain G determined in Ebeling choice boxes. ············································································ 71 Table 22. Repellency of insecticides against the German cockroach strain H determined in Ebeling choice boxes. ············································································ 72 Table 23. Repellency of insecticides against the German cockroach strain I determined in Ebeling choice boxes. ············································································ 73 Table 24. Relationship between day and performance index of control against German cockroaches repelled in Ebeling choice boxes. ·············································· 74 Table 25. Relationship between day and performance index of permethrin against German cockroaches repelled in Ebeling choice boxes. ·············································· 75 Table 26. Relationship between day and performance index of chlorpyrifos against German cockroaches repelled in Ebeling choice. ······················································ 76 Table 27. Relationship between day and performance index of propoxur against German cockroaches repelled