Location: Integrated Cropping Systems Research
2023 Annual Report
Objectives
Objective 1: Conduct research to develop fundamental and applied knowledge of predacious lady beetles, ants, and bees within cropping systems.
Subobjective 1.A: Establish a baseline inventory of bee species and determine patterns in their distribution among crops at the ESDSWRF.
Subobjective 1.B: Determine favorable alternative habitats for native species of agrobiont lady beetles.
Objective 2: Conduct research to determine the impact of cover crops, crop rotations, and tillage on ground-dwelling predators and bees and their ecosystem services, such as predation and pollination.
Subobjective 2.A: Evaluate how spring tillage compared to no-tillage production practices in corn and soybean affect beneficial ant and ground beetle activity, diversity, and predation of sentinel pest insects.
Subobjective 2.B: Evaluate how cover crops interact with pollinators to improve yield of sunflowers in crop rotations.
Objective 3: Conduct research to quantify exposures and responses of non-target arthropods, such as bumble bees, to environmental conditions and pesticides in agricultural systems.
Subobjective 3.A: Determine concentrations of agricultural pesticides in a single species of native pollinator over the course of a growing season.
Objective 4: Conduct research to improve understanding of the direct and indirect interactions among plants and soil invertebrates, such as entomopathogenic nematodes and ground beetles, in relation to soil health and pest management.
Subobjective 4.A: Identify endemic EPN from corn-soybean rotated fields with and without tillage and assess their efficacy against WCR larvae.
Sub-objective 4.B: Evaluate EPN efficacy against soil-dwelling arthropod species in greenhouse and laboratory trials.
Approach
Agriculture faces a challenge to intensify production in ways that are both agronomically and environmentally sustainable. As such, it will need to rely increasingly on a variety of invertebrate-mediated ecosystem services (IMES) such as biological pest control and pollination. However, knowledge gaps persist about the composition of beneficial invertebrate guilds in agroecosystems, what limits their value, and how various cropping practices impact their functionality. In response, this project will address these knowledge gaps with research to generate fundamental and applied knowledge about bees, lady beetles, ground beetles, ants, and entomopathogenic nematodes (EPN). Specifically, we will inventory bees, determine their distribution patterns among crops, and quantify their exposures to agricultural pesticides. We will determine alternative habitats to corn and soybean that support native species of agrobiont lady beetles. Studies will also inventory ground beetles in corn and soybean and evaluate how tillage practices impact ground beetles and beneficial ants. Additional studies will identify EPN endemic to crop fields and evaluate their infectivity against soil-dwelling pests.
The research will have an array of positive impacts. For instance, it will facilitate the generation of hypotheses about factors driving bee diversity and will, along with improved pesticide exposure assessments for native bees, aid in developing conservation strategies. Determining what alternative habitats favor lady beetles will help to ensure these predators of crop pests are conserved in agricultural landscapes. An improved understanding of how ants and ground beetles respond to cropping practices will lead to recommendations that more effectively support their suppression of agricultural pests. Identification and characterization of locally adapted, efficacious EPN will provide producers with a long-term, non-chemical management strategy to suppress subterranean pest populations. Ultimately, the research will enhance the potential of ecosystem services from bees, lady beetles, ants, ground beetles, and EPN to increase agricultural sustainability.
Progress Report
Substantial progress was made on this research project in its first year. This included progress on Objective 1 to develop fundamental and applied knowledge of predacious lady beetles, ants, and bees within cropping systems. For Subobjective 1A, researchers processed over 27,000 bee specimens, identified a majority of them, measured the distance between the wings of all bees as a proxy for their body size, and made significant progress in compiling the data. A majority of bee species was identified and confirmed by experts. Additional challenging morphospecies are in the process of being identified. A checklist of South Dakota bumble bees was published, along with a new state record for a species of pumpkin bee from eastern South Dakota. In addition, one year of trapping was completed among a variety of habitats near Brookings, South Dakota, to determine their favorability for lady beetles, in support of Subobjective 1B. Researchers tallied and identified lady beetles from the first year of sampling various habitats.
For Subobjective 2A, long-term research plots were utilized to evaluate how spring tillage versus no-tillage in corn and soybean affected beneficial ant and ground beetle activity and diversity and the predation of sentinel pest insects. Ants and ground beetles were collected in June, July, and August using pitfall traps across 64 plots. Specimens have been sorted, and species-level identifications have begun for both ants and ground beetles. Preliminary results suggest more predation of sentinel prey in no-till plots.
Progress toward meeting Objective 2B included sampling by 288 transect walks during peak bloom of sunflowers in plots with or without cover crops. Bee specimens have been pinned, sorted, and identified to species. Nectar quantity and quality was quantified for 40 flowers, pollen was collected from 80 flowers for plant essential nutrient analysis, and 480 flowers were bagged at various stages to determine yield with and without pollinators in cover crop and non-cover crop plots. Additional measures of sunflower plant biomass, yield, and root samples were collected and processed.
With regard to Objective 3, researchers found that native bees collected in eastern South Dakota contained detectable levels of insecticides, fungicides, and herbicides. Results of preliminary tests were used to refine sampling methods to increase capture rate of bees. Other preliminary tests validated the potential of using managed colonies of the common eastern bumble bee as surrogates for wild bees. Research is proceeding with both blue vane traps and managed colonies to accomplish this Objective.
For Subobjective 4A, long-term research plots evaluating the impact of tillage versus no tillage in a corn/soybean rotation were continued and used to sample endemic entomopathogenic nematodes and test their efficacy against rootworms. Nematodes were isolated from 16 of 320 soil samples in Fall 2022 and 278 of 640 samples collected in Spring 2023 from the plots. Species were identified and then confirmed with DNA sequencing.
With regard to Subobjective 4B, methods were developed to evaluate (1) nematode efficacy against various soil-dwelling arthropods and (2) their tolerance to environmental extremes. Researchers also conducted laboratory tests to evaluate nematodes’ ability to infect and kill rootworms and to tolerate extreme heat and cold. Nematode mortality increased with temperature and all nematodes died at 43.0°C. Nematodes did not survive temperatures below freezing in the lab, and researchers are investigating different methods to evaluate cold tolerance. One nematode species collected in 2022 proved efficacious, as it infected and killed rootworms in a laboratory test.
Accomplishments
1. Thermal tolerance of a billion-dollar pest. Western corn rootworm (WCR) is an economically important pest, with estimates of its damage and control in corn exceeding $1 billion annually. Despite extensive research on WCR, an understanding of its tolerance for hot and cold temperatures is still lacking. ARS researchers in Brookings, South Dakota, addressed this knowledge gap by subjecting two WCR strains to temperatures ranging from 2.5°C to 43.0°C and measuring their survival. One strain suspends development during winter, whereas the other does not. However, the two strains showed little difference, with their survival steadily decreasing as temperatures approached lower and upper limits. The findings will be vital for predicting WCR survival and its potential spread under future climate-change scenarios.
2. Researchers update nearly 100-year-old checklist of South Dakota bumble bees. Bumble bees are economically important pollinators that have been understudied across much of the Upper Midwestern United States, including the state of South Dakota. ARS researchers at Brookings, South Dakota, and their collaborators at South Dakota State University updated the checklist of South Dakota bumble bees, which was last published in 1925. The checklist is important to conservationists because it documents that the majority of the state’s 29 bumble bee species, including six of conservation concern, had been recorded within the past two years. However, the critically endangered rusty-patch bumble bee, variable cuckoo bumble bee, and Suckley’s cuckoo bumble bee have not been recorded in the state for more than 50 years. These latter findings suggest that additional efforts may be needed to locate these three species or facilitate their re-establishment within the state.
3. Rootworm colonies support global research across a diverse range of scientific fields. Unique colonies of western and northern corn rootworms have been maintained for decades by ARS researchers at Brookings, South Dakota. Over the years, the colonies have been used by research teams around the world to study rootworm biology, resistance to control tactics, insect genomics, food science, and aspects of plant biology. Nine studies that used the Brookings colonies were published as scientific articles in the last year alone. This particularly high rate of scientific publications demonstrates the value of the Brookings rootworm colonies globally across a wide range of scientific fields.
4. Clay caterpillars as stand-ins for estimating real-world predation by insects. Sentinel prey—whether dead or alive, adults or immature stages—have been useful for estimating predation by beneficial insects in the field. However, sentinel prey studies vary in their methods, making comparisons of predation across studies challenging. Artificial clay caterpillars are a promising approach to overcome the challenge to standardize estimates of predation on sentinel prey. The clay caterpillars mimic naturally occurring pests, but the aspect of clay caterpillar color remains relatively unexplored. ARS researchers at Brookings, South Dakota, tested if color was important by deploying brown, cream, green, gray, terracotta, or white clay caterpillars onto corn, soybean, and prairie plants. Green and terracotta-colored caterpillars were attacked the most, and the rate at which they were attacked was related to the overall abundance of insects in the field. Thus, clay caterpillars could be useful surrogates to standardize estimates of insect predation if their color is adequately considered.
5. Giant pumpkin bee newly recorded from South Dakota. A giant pumpkin bee, known by its scientific name Eucera (Xenoglossa) kansensis, was newly recorded for the state of South Dakota in 2013 and in subsequent years by ARS researchers at Brookings, South Dakota, and collaborators at South Dakota State University. The pumpkin bees were found in two counties on the eastern edge of the state and associated with a wide range of habitats that did not necessarily include their known floral host plants of pumpkins and wild cucurbits. The records represent a northern extension of the giant pumpkin bee’s geographic range. The finding is important to conservationists in understanding the diversity of wild bees in the region. It is also important to the state’s producers of pumpkins, squash, and cucumbers because it identifies an additional specialist pollinator for their crops.
Review Publications
Hesler, L.S., Beckendorf, E.A., Martens, A.P., Johnson, P.J. 2023. A new state record of Eucera (Xenoglossa) kansensis (Hymenoptera: Apidae) in South Dakota, USA. Insecta Mundi. 0985:1-6. https://centerforsystematicentomology.org/insectamundi/0985_Hesler_etal_2023.pdf.
Roeder, K.A., Dorland, M.S., Daniels, J.D. 2022. Importance of color for artificial clay caterpillars as sentinel prey. Entomologia Experimentalis et Applicata. 171(1):68-72. https://doi.org/10.1111/eea.13251.
Coates, B.S., Walden, K.O., Lata, D., Vellichirammal, N.N., Mitchell, R.F., Andersson, M.N., Mckay, R., Lorenzen, M.D., Grubbs, N., Wang, Y., Han, J., Xuan, J., Willadsen, P., Wang, H., French, B.W., Bansal, R., Sedky, S.F., Souza, D., Bunn, D., Meinke, L.J., Miller, N.J., Siegfried, B.D., Sappington, T.W., Robertson, H.M. 2023. A draft Diabrotica virgifera virgifera genome: insights into control and host plant adaption by a major maize pest insect. BMC Genomics. 24. Article 19. https://doi.org/10.1186/s12864-022-08990-y.
Roeder, K.A., Daniels, J.D. 2022. Thermal tolerance of western corn rootworm: critical thermal limits, knock-down resistance, and chill coma recovery. Journal of Thermal Biology. 109. Article 103338. https://doi.org/10.1016/j.jtherbio.2022.103338.
Pereira, A.E., Huynh, M.P., Paddock, K.J., Ramirez, J.L., Caragata, E.P., Dimopoulos, G., Krishnan, H.B., Schneider, S.K., Shelby, K., Hibbard, B.E. 2022. Chromobacterium Csp_P biopesticide is toxic to larvae of three Diabrotica species including strains resistant to Bacillus thuringiensis. Scientific Reports. 12. Article 17858. https://doi.org/10.1038/s41598-022-22229-6.
Runyon, J.B., Beckendorf, E.A., Hesler, L.S. 2022. A new species of Chrysotus Meigen (Diptera: Dolichopodidae) from soybean fields in South Dakota, USA. ZooKeys. 1135:171–180. https://doi.org/10.3897/zookeys.1135.95026.
Martens, A.P., Johnson, P.J., Roeder, K.A., Beckendorf, E.A., Daniels, J.D., Hesler, L.S. 2022. A revised checklist of South Dakota bumble bees (Hymenoptera, Apidae). Journal of Hymenoptera Research. 94:271–286. https://doi.org/10.3897/jhr.94.94584.
Roeder, D.V., Remy, S., Roeder, K.A. 2023. Temperature dependent lipid content in the red harvester ant, Pogonomyrmex barbatus. Journal of Insect Science. 23(3). Article 14. https://doi.org/10.1093/jisesa/iead040.
