I am truly grateful to have been awarded the Alain VanRyckeghem Scholarship from Pi Chi Omega in 2025. During this eventful year, I have made great strides in progress for my dissertation research and professional development, which I am happy to share in this article.
Currently, I am a fourth-year Ph.D. candidate in Dr. Chow-Yang Lee’s urban entomology lab at the University of California, Riverside (UCR). My dissertation research focuses on insecticide resistance in the German cockroach. The two main objectives of my research are: (1) investigate the current status of resistance in field populations and (2) compare the performance of insecticide rotations and mixtures as resistance management strategies. For my first objective, I have been conducting resistance profiling of 20 strains of German cockroaches that were recently collected from various locations throughout the continental US. Based on my current data, the patterns in resistance status of the field-collected strains align with my preliminary findings. Most strains exhibited high levels of deltamethrin resistance, but fipronil resistance was highly variable and indoxacarb resistance was relatively low among the strains. These findings reinforce the prevailing opinion that German cockroach management should shift away from pyrethroid sprays and that gel baits are likely a more effective option. Nonetheless, baits should still be incorporated as part of rotations or mixtures, as resistance is still present. Furthermore, higher frequencies of kdr and Rdl mutations were correlated with resistance towards deltamethrin and fipronil respectively, underscoring the role of these mutations in contributing to resistance. This was my first foray into investigating target-site mutations, and it was exciting to view the chromatograms generated from sequencing my PCR products. I am still wrapping up the final stages of this project, but I am definitely aiming to get this work published sometime this year!
The second portion of my research involves a direct comparison of insecticide rotations and mixtures by simulating these treatments on laboratory colonies of German cockroaches with differing levels of resistance. Rotation treatments consisted of the application of three gel bait formulations which were rotated quarterly, while mixture treatments utilized a mixture of two gel bait formulations applied together. Every 6 months, cockroaches were sampled to track changes in the level of resistance and involvement of resistance mechanisms. By now, this large-scale simulation experiment has been underway for almost 18 months since the initial gel bait treatment. While it is still too early to make any definitive conclusions, the results obtained from the first year of the experiment suggest that resistance evolution varies between rotations and mixtures, and that these resistance management strategies may still select for cytochrome P450-based metabolic detoxification.
In addition, I was able to publish the results on one of my side projects titled “Differential toxicological responses of brownbanded and German cockroaches (Blattodea: Ectobiidae) to commercial gel baits”. Despite the common assumption that gel baits would perform similarly against both of these indoor pest cockroaches, we found that baits may show reduced performance against the brownbanded cockroach. Gel baits which are predominantly designed with German cockroaches in mind may be less attractive or palatable to brownbanded cockroaches, as a result of differences in the biology of the two species. Brownbanded cockroaches are less common than German cockroaches in the US as they require higher temperatures, but the implications of these findings may be useful for managing sporadic infestations in animal rearing facilities and pet stores, or in tropical regions where the species is far more common.
Among my personal highlights of the last year would have to be the annual meeting of the Entomological Society of America (ESA) in Portland, OR, where I was able to present part of my research on resistance profiling of German cockroaches. To my great surprise, I was awarded 1st place in the oral presentation competition for my section! On top of that, I received the Medical, Urban, and Veterinary Entomology (MUVE) Student Recognition Award presented at the MUVE Business Meeting. Aside from ESA 2025, I presented my research earlier in the year at UCR’s very own 34th Urban Pest Management Conference.
I believe that the Pi Chi Omega Scholarship and other similar awards are vital sources of encouragement for young scientists such as myself. These scholarships instill in us a tremendous sense of pride as we can tangibly see that our work is recognized and acknowledged by the experts in the field. Throughout the countless struggles of graduate school, I am thankful for these awards for inspiring me to continue my journey in furthering our knowledge of urban pests and ways to manage them. Once again, I would like to reiterate my sincere gratitude to Pi Chi Omega for your invaluable support and recognition.