How One Entomologist is Exploring Insect Pests in Midwestern Agroecosystems

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Adrian Pekarcik, Ph.D. (left), shows undergraduate researchers Matt Lorentz (center) and Kim Gault (right) how to sample for Asiatic garden beetle grubs using a golf hole cup cutter.

By Karl Roeder, Ph.D.

Editor’s Note: This is the next post in the “Standout ECPs” series contributed by the Entomological Society of America’s Early Career Professionals (ECP) Committee, highlighting outstanding ECPs that are doing great work in the profession. (An ECP is defined as anyone within the first five years of obtaining their terminal degree in their field.) Read past posts in the Standout ECPs series.

Adrian Pekarcik, Ph.D.

Adrian Pekarcik, Ph.D., is an incoming research entomologist with U.S. Department of Agriculture’s Agricultural Research Service (USDA-ARS). His research focuses on identifying effective and sustainable management practices for pests in field crops. Previously, Adrian worked with Alana Jacobson, Ph.D., on sugarcane aphids in Alabama sorghum and with Kelley Tilmon, Ph.D., on Asiatic garden beetles in Ohio corn and soybean. Adrian has received numerous awards and fellowships for his work, including a predoctoral fellowship from the USDA National Institute of Food and Agriculture (NIFA) and a USDA North Central Sustainable Agriculture Research and Education (SARE) grant. Below, we ask Adrian a few questions about his research.

Roeder: During your graduate studies, you worked in a number of different cropping systems with a variety of pests. Were you always interested in agroecosystems and insects?

Pekarcik: I actually never intended to study insects while in undergrad. I started out as a pre-med student until taking organic chemistry. I then started taking more ecology and plant biology courses and really found my niche. I thought I was going to study plant ecology, until I participated in the University of Virginia’s Blandy Experimental Farm REU [Research Experiences for Undergraduates] program at the State Arboretum of Virginia.

At Blandy, many evenings were spent roaming around the arboretum grounds with the other students in search of the insects that inhabited them. I was fascinated by the diversity and abundance of species in the arboretum and was excited for the next insect to fly to any given outdoor light. I finally took an entomology course my senior year and knew it was something I’d want a career in. During my senior year at Ohio Wesleyan University, I completed an honor’s thesis with Dr. Laurie Anderson looking at the influence of land use type (e.g., mowed grass, restored riparian habitat, and forest) on ant communities. This experience motivated me to pursue graduate school in entomology.

During my master’s at Auburn University, I joined the lab of Dr. Alana Jacobson and switched gears. I studied the sugarcane aphid, Melanaphis sorghi, a new pest of sorghum in Alabama at the time (2014). Its biology was fascinating! Populations consisted of parthenogenic females that needed to survive on live plants throughout the winter since there was no egg stage. Interestingly, only five males were reported around the world. The females have a telescoping of generations, which means that progeny developing inside a female already are developing their own offspring. They reproduce via live birth and they can have as many as eight offspring in a 24-hour period, allowing for exponential growth. Populations would quickly reach hundreds of thousands of aphids per leaf in a few weeks.

I conducted insecticide trials, evaluated commercially available sorghum varieties for host-plant resistance, and assessed combinations of tactics to develop an integrated pest management plan. This was my first experience in agriculture, let alone pest management. The severity of sugarcane aphid in sorghum was an eye-opening experience, and identifying and evaluating management tools that both minimized pest pressure and increased yield gave me a sense of purpose; I was working toward something much larger than myself.

This motivated me to pursue a Ph.D. in entomology with Dr. Kelley Tilmon, field crops entomologist at Ohio State. I have spent the past 5-plus years studying the Asiatic garden beetle, Maladera formosae (syn. M. castanea), which emerged as a significant pest of field corn in northern Ohio, southern Michigan, and northern Indiana as early as 2007.

What is the most interesting research challenge that you have encountered, and what was your approach to solving it?

Studying the Asiatic garden beetle (AGB) while at Ohio State has been the biggest challenge I have encountered to date. When I started my research, I quickly realized that most of the primary literature originated from the 1930s in horticultural and turfgrass systems of Long Island, New York, and New Jersey. Yet, nearly 100 years later AGB emerged as a significant early-season pest of field corn in the Great Lakes region, for unknown reasons.

Overwintered grubs resume feeding in springtime at the same time farmers in the region plant corn. Grub root feeding causes corn seedlings to stunt, wilt, discolor and die, leading to extensive plant stand losses under high pressure. Infestations were being reported in fields treated with seed- or in-furrow applied insecticides. Products commonly used for AGB in turf systems were seemingly ineffective in field crops. Farmers had little success in managing this pest, and there was little to no information about this species for the region or system, aside from anecdotal observations.

I needed to reassess the timing and spatial distribution of AGB in field-cropping systems of the Great Lakes region to better aid in management. This was also my first time conducting on-farm research as opposed to small plot studies. I worked closely with OSU extension educators in the affected region to learn more from their experiences in the county and to meet and learn from affected farmers who had dealt firsthand with AGB. These conversations ultimately guided my research goals.

In particular, it was apparent that grub feeding was concentrated in the sandiest soils of each field. This region has abundant sandy soils left behind from glaciation events. As a result, I focused my efforts to sandy soils and covered a manageable 5-acre area that included some heavier soils. I first evaluated sampling methods for AGB grubs and adults (a Scarab beetle) that were economical and feasible for field-cropping systems. After identifying the best sampling methods, I met with researchers at Michigan State University, where we established an extensive AGB sampling network across Ohio and Michigan in coordination with extension staff to continue assessing the timing and spatial distribution of AGB in field crops.

This field research provided many observations that led to additional projects investigating entomopathogenic nematodes as a biological control, spatial distribution via GIS, and population genetics work to try and understand why populations began infesting corn.

As you continue to work in agroecosystems, what question/hypothesis/topic interests you the most? And why?

I ultimately want to identify sustainable, long-term natural pest management strategies that promote beneficial insects and reduce pesticide use. Pesticides are an incredible resource when used properly with economic threshold levels. However, they can be overused, which leads to other issues like insecticide resistance and the failure of products, in addition to runoff and sublethal effects on beneficial organisms like pollinators and predators. Otherwise, some insect pests are poorly understood and difficult to scout, monitor, and kill with insecticides. It is important that we have these effective tools for as long as possible for food security.

To ensure this, I am most interested in identifying sustainable and resilient solutions to insect pest management problems in field crops (e.g., corn and soybean). In particular, I want to learn more about beneficial organisms in field-cropping systems and determine which agricultural practices have the least impact on their populations. By taking steps to promote beneficial populations, rates of predation, parasitism, or infection should increase and ultimately suppress insect pest populations below economically damaging levels.

I am also interested in conducting long-term studies to assess the resiliency of beneficial organisms with respect to various management practices to determine when they become profitable for the farmer’s time, efforts, and costs. I ultimately want to produce management tools that are meaningful for the stakeholders and will actually be implemented.

As an incoming USDA research entomologist, are you shifting gears to a new topic? Could you tell us more about the main goals of your upcoming research?

Instead of focusing on individual insect pests, I will begin researching soil-dwelling beneficial organisms like entomopathogenic nematodes (EPNs) and ground beetles present in field crops of the north central region and understand how agricultural practices like tillage or cover crops influence their distribution and ability to infect/predate pest populations.

EPNs are naturally occurring obligate parasites of insects that occur in all soils (except for Antarctica) and can survive environmental extremes, even in the absence of insect hosts. I first learned about EPNs through a North Central Region SARE grant, where I isolated species from corn fields infested with AGB and evaluated their ability to infect and kill grubs in the greenhouse and field. This summer, I will conduct similar research and first identify the naturally occurring EPNs present in a corn-soybean rotation with and without tillage in eastern South Dakota. This will let us know whether crop rotation or tillage influences the presence and persistence of EPN species. I will then assess isolated EPNs’ abilities to tolerate extreme cold and heat and desiccation and to infect hosts like corn rootworm larvae and waxworms, which are highly susceptible to EPN infection.

The ultimate goal of this work is to establish local populations of the most resilient EPNs across entire fields that will persist for years after the initial application. This will increase the chances that insect larvae in the soil encounter and become infected by EPNs.

Otherwise, I am also interested in how agricultural practices like tillage and crop rotation affect the activity, diversity, and predation rates of predators like ground beetles. I was able to participate in a collaborative project assessing the influence of rye cover crop in soybean on slug (pest) and ground beetle (predator) populations over time. This summer, I will similarly be identifying the ground beetle species present throughout the growing season in the same corn-soybean rotated plots with and without tillage that will be used to sample for EPNs.

Identifying agricultural management practices that do not impact beneficial communities could help increase EPN infection rates and ground beetle predation rates in corn and soybean and reduce or eliminate the need for insecticides.

Having recently defended your dissertation, do you have any advice for undergraduate students interested in graduate school or even new graduate students just starting on their journey?

My first piece of advice for all undergraduate students considering graduate school in the sciences is to get a master’s degree first, even if you are sure you want a Ph.D. I learned the fundamentals of experimental design, data analysis, and how to present my findings during my master’s, all while making every mistake along the way. I learned many invaluable lessons during my master’s, which gave me a much different mindset going into my Ph.D. (which was on a different insect pest and cropping system) that got me off to a productive start. Additionally, I had to take fewer courses during my Ph.D. because I already completed them. This allowed me to take electives in GIS and have more time for research.

Next, all students should utilize their university resources (e.g., expertise of faculty members, training on specialized equipment, electives, mental health resources, library services, extension networks, discounts, etc.), which you are ultimately paying for with tuition and student fees. For example, Auburn University’s library would deliver books directly to graduate students on campus!  During my Ph.D., I also made it a goal to publish a paper with each of my committee members to make sure I learned something from each of them while in graduate school.

Lastly, always ask questions whenever you have them. It can be difficult navigating the graduate school curriculum, knowing which forms to fill out and when to submit, or whether a research technique is worthwhile. Whether you ask your advisor or a faculty member, fellow graduate students, or staff member, someone will point you in the right direction. By asking others for clarification or assistance, you will save yourself precious time.

Finally, what is your favorite insect and why?

This is a question I get all the time, and it is the most difficult one to answer. Insects are overwhelmingly diverse with several million species estimated. They also perform a wide variety of ecosystem services that we depend on. I had the privilege of volunteering at Ohio State’s Bug Zoo, where Jeni Filbrun creates and maintains displays showcasing live arthropods from around the world. I was particularly fond of the blue feigning death beetles, which did exactly as their name suggested. Elementary students were astounded to watch the beetles play dead, and they were more than willing to handle the specimens.

I also enjoyed the Australian walking sticks, which would sway side to side to mimic a branch moving anytime someone would pass. Coincidentally, we would hold meetings in the Bug Zoo in our previous entomology building, and the arthropods would find ways to interrupt. One time the rose-haired tarantula fell from the ceiling of its enclosure and made a loud thud during a student’s defense. The feeder crickets have chirped at just the right moment on a few too many occasions, and once in a while something would get loose.

Thanks Adrian! You can learn more about Adrian’s work via the Agronomic Insect Pest Lab at Ohio State University or his Google Scholar profile.

Karl Roeder, Ph.D., is a research entomologist with the USDA-Agricultural Research Service in Brookings, South Dakota and the North Central Branch representative to the ESA Early Career Professionals Committee. Email: karl.roeder@usda.gov.

  

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