The ABC’s – Agriculture, Beneficial Beetles and Conservation: Reflections from an LTER Fellow

Cynthia Fiser is a graduate student in Doug Landis’s lab in the Michigan State University Department of Entomology. Her research looks at the impact of perennial prairie strips on the dispersal of ground beetles in row crop agriculture.

Flower selfie of Cindy in the field!

Rolling hills of wheat, corn and soybean are a beautiful and nostalgic feature of the summer landscape in the Midwest. Here, agriculture is as much a part of the culture as the economy – anyone who attends a county fair would agree! However, the pressure placed on our agricultural landscapes to meet global demands for food, fuel and fiber takes a toll on the natural landscape. Land used to grow crops was once forest, grassland or prairie rich with biodiversity; as these natural habitats decline and fragment, so too does the health and diversity of the wildlife that call them home. So, the question remains: how do we support the local farming community and culture, while also increasing available land to support natural biodiversity? 

Conservation managers, policymakers and scientists are currently working to answer this question. One potential solution is the establishment of perennial prairie strips directly into row crop agriculture, compared to the more common method of adjacent grasslands and fallow fields. The idea originated at Iowa State University under the S.T.R.I.P.S program (Science-based Trials of Rowcrops Integrated with Prairie Strips), with the intention of reducing the flow of water and nutrients from croplands to local water sources. The strips were also comprised of native prairie grasses and flowers, which enhanced ecosystem services and local biodiversity. Ecosystem services are benefits from the natural environment that enhance human health and well-being; these include pollination, pest suppression and soil carbon sequestration – among many others. The Long-Term Ecological Research (LTER) main site at Kellogg Biological Station (KBS) in southwest Michigan adopted experimental prairie strips in 2019 to further test how ecosystem services, biodiversity and other metrics are impacted by cropping practices. Of the many services, I chose to study pest predation by natural predators as it is particularly important to farmers, and prairie strips may provide beneficial habitat to support a community of natural predators within croplands. 

Floral diversity of mature prairie strip in wheat field. Photo by Cindy Fiser.

Often found scurrying along the arid earth of wheat, corn and soybean stalks, ground beetles scavenge for the larvae and eggs of invertebrate pests. These charismatic Coleoptera are known for their iridescent armor and consistent presence around the home and field; however, their appetites have made them popular among ecologists for decades. Carl Lindroth famously detailed the diversity of ground beetles (Coleoptera: Carabidae) of North America in the mid 20th century, but studies aimed at understanding their behavior and use in human-dominated landscapes continues to this day. Over 400 species of ground beetles are found throughout agricultural landscapes in North America, with many native to the Midwest. Although known as “opportunistic feeders” for their tendency to eat whatever prey they find, ground beetles can be specialized into predators of common insect pests and herbivores that consume weed seeds. Few ground beetles are themselves pests! These attributes make ground beetles useful for research in the practical application of conservation within agriculture. 

KBS-LTER is a unique place to conduct an experiment, and my research benefited from the availability of decades of diverse data collection in agricultural systems. My experiment focused on two of the treatments currently in place at the LTER main cropping site: reduced input (less agrochemicals applied than traditional intensive practices) and biologically-based (no application of agrochemicals, but rotary hoed to suppress weed growth), both of which were established in 1989. In 2019, the LTER adopted prairie strips into both the reduced input and biologically-based treatments. As the prairie strips take several years to reach maturity, I was able to study the historical community of ground beetles (from samples collected in 2019) and compare that to the shifted community at strip maturity (2021). I identified 44 species and 25 genera of ground beetles, including predators and herbivores alike. To study the possibility of spillover ecosystem services, my data included surveys both in the strip and at multiple distances into the row crop. 

With an understanding of who is there, I then wanted to ask what are they doing? As a 2022 KBS-LTER Graduate Fellow, I had the opportunity to answer this question and conduct a predation experiment with the LTER prairie strips and surrounding row crops. I wanted to know, 1) are ground beetles providing predation services within row crops with prairie strips, and 2) does the management of the row crops impact predation services provided by ground beetles? 

Insect prey card within invertebrate exclosure (May 2022). Photo by Cindy Fiser.

In order to study the predation services of ground beetles, I used both weed seeds and insect pests as prey items. The experiment started in early May and continued through September to account for emergence and peak activity times of the many species. It is important to understand not only what the beetles are consuming, but also when, as the timing of pest suppression could be important for effective early management of pest species. Preliminary results show high levels of invertebrate predation for insect pests in both the prairie strip and row crop, averaging 60% of prey items removed or attacked. When the experiment included predation by vertebrate (rodents, birds, etc.) I often found 100% removal of prey in both cropping treatments. Further, ground beetles are not the only invertebrate predators capable of supplying pest predation services to farmers, especially with the addition of suitable habitat in the prairie strips. I observed high rates of predation from other beneficial invertebrates such as harvestmen, spiders and ants. 

Agricultural comprises much of the landscape of the Midwest, including land shared by communities both human and natural alike. Preserving the health and well-being of both is critical for the sustainability of our food systems and culture. In a world already plagued by the climate crisis and biodiversity loss, it is time to adopt conservation practices into management decisions. Prairie strips are an adaptable, low-maintenance solution to conserving biodiversity in agricultural landscapes while also providing ecosystem services. Although ground beetles are voracious predators, they are most efficient at pest suppression when part of a larger community of invertebrate predators. The inclusion of prairie strips into row crops offers both increased abundance of beetles and an overall increase in the predation of pests within row crops. Like ground beetles, our communities are also most efficient when part of a larger and more diverse team; with the assistance of farming communities, academic researchers, policymakers and advisors, we too can support and enrich the land. I thank KBS-LTER, Michigan State University, and the Landis Lab for the opportunity and support to conduct this research as well as the many LTER scientists who came before me. I am not done yet! With this research, I look forward to collaborating with the greater LTER and agricultural community to study the impacts of prairie strips on invertebrate biodiversity, dispersal, and predation within the croplands of Michigan.