Project : USDA ARS

ARS Home » Plains Area » Brookings, South Dakota » Integrated Cropping Systems Research » Research » Research Project #443351

Research Project: Enhancing Insect Ecosystem Services that Benefit Modern Cropping Systems

Location: Integrated Cropping Systems Research

2024 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
Progress was made for all Objectives. In Sub-objective 1A, researchers have continued to confirm bee identifications, reaching a total 139 species thus far at a research farm near Brookings, South Dakota. Data entry has begun for analysis of bee species by habitat. The number of species is already higher than expected and demonstrates a relatively high bee diversity at the research farm. The high diversity and corresponding information about habitat use will be valuable in understanding how wild bees use habitats in and around crop fields and for developing recommendations on ways to conserve wild bees. And for Sub-objective 1B, the sampling, identification and tallying of lady beetles has been completed for the study. Data from both years of the study are being collated in preparation for statistical analysis and subsequent write-up. The results will identify lady beetles that use alternate habitats near crop fields and suggest which habitats may be the best targets for conserving these important predators of crop pests. In Sub-objective 2A, ant and carabid beetle samples have been collected, identified, and analyses have begun for the final study comparing tillage effects on beneficial insects and ecosystem service provision. In sub-objective 2B, data on bee activity, nectar, pollen, and yield have been collected for 3 years. All specimens have been identified and counted and yield data obtained for these first 3 years. Final samples are planned for August 2024. Pollen samples will be shipped after the final year of sampling (2024) to ARS researchers in Tucson, Arizona, for nutrient analysis. Preliminary analyses suggest that planting cover crops in sunflower plots is beneficial to both sunflowers and bees. In Sub-objective 3A, samples were collected using two approaches. In one approach, 10 colonies of Bombus impatiens were deployed along with passive samplers at a single site located amid cropped land. Worker bees were collected biweekly and passive samplers were collected monthly from May through September. At the end of each month, colony materials were frozen and new colonies were placed at the same location. Bee and passive sampler specimens collected at the end of each month were analyzed for pesticide concentration. In the second approach, blue vane traps were deployed for 24 hours at 2-week intervals at 3 sites from May through September; passive samplers were deployed at the same sites for 2-week intervals. Bumble bees and Melissodes longhorned bees were separated, and species of bumble bees were identified. Pesticides are currently being analyzed in insect tissue and passive samplers to understand which ones may pose the greatest risks to bumble bees. In Sub-Objective 4A, soil samples were collected from plots established in a corn-soybean rotation with and without tillage in the spring, summer, and fall of each year. Soil samples were homogenized in the lab, and waxworms were added to each as bait for extracting insect-killing nematodes. Two nematode species were extracted from the soil samples and identified using morphological characteristics and molecular techniques. A single soil sample contained the insect-killing nematode Steinernema carpocapsae, and all other positive samples contained a free-living nematode Pristionchus pseudaerivorus, which was its first record in South Dakota. These results demonstrate progress in developing insect-killing nematodes for protection against crop pests. In Sub-Objective 4B, temperature ranges were assessed for an insect-killing nematode, S. carpocapsae, and a free-living nematode, P. pseudaerivorus, to infect western corn rootworm larvae and northern corn rootworm larvae in growth-chamber bioassays. A separate bioassay compared a field-collected strain of S. carpocapsae to a commercially available strain with regard to their abilities to survive extreme temperatures and infect western corn rootworm larvae. In addition, an isolate of Steinernema feltiae obtained from agricultural soils of upstate New York was applied into long-term continuous corn plots to assess its persistence and its efficacy against western corn rootworm in eastern South Dakota. Similarly, two rates of a strain of S. carpocapsae isolated from plots near Brookings, South Dakota, were applied to crop fields in Minnehaha County, South Dakota, to assess persistence and efficacy against soybean gall midge, a new pest of soybeans in the U.S. Altogether, the results have demonstrated substantial progress in developing insect-killing nematodes that protect crops against pests such as corn rootworms and soybean gall midge.

Accomplishments
1. Color poster updates the inventory of Hawaii lady beetles. Up-to-date knowledge of beneficial insects such as lady beetles is important for informing stakeholders about biological resources available for pest management. ARS researchers at Brookings, South Dakota, and Fort Pierce, Florida, personnel with the Hawaii Department of Agriculture and the Dana Anne Yee Foundation, and an independent graphic artist developed a poster on the Lady Beetles of Hawaii, which displays the state’s 50 diverse lady beetle species. A few hundred posters have been distributed throughout Hawaii, including public schools, museums, libraries, urban garden centers, and botanical gardens. In addition, a pdf of the poster has been made available online at https://www.ars.usda.gov/plains-area/brookings-sd/ncarl/ncarl-links/research-on-the-coccinellidae-lady-beetles/lady-beetles-of-hawai-i/. The inventory provides a resource for pest management specialists, horticulturalists, master gardeners, landscape architects, and policy makers in Hawaii and also serves as an outreach tool to educate the citizens of Hawaii about the biodiversity of biological pest management resources available in the state.

2. A native lady beetle bucks the trend. Lady beetles are important predators of pests, and the conservation of native species of lady beetles reflects wise stewardship of a natural resource for biological pest management in crop fields. However, the geographic ranges of at least three native species of lady beetle have contracted across the U.S. over the last few decades. In contrast, ARS researchers at Brookings, South Dakota, and collaborators at Chadron (Nebraska) State College found that the black-spotted pink lady beetle, a common predator of crop pests such as aphids and stalk borers, has actually been undergoing a slow but steady geographic range expansion over the last several decades. Reasons for the range expansion were not evident from the study. Nonetheless, the case of the black-spotted pink lady beetle is an important counterexample for pest management specialists that are working to conserve native predators for biological control of pests in field crops and for ecologists seeking to understand reasons for large-scale changes in the abundance and distribution of biological control agents such as lady beetles. Understanding ways to promote natural biological control agents such as lady beetles may lead to improved pest management of field crops.

3. Rye cover crop termination at or before soybean planting has minimal effect on Midwestern soybean yield. Interest is growing among Midwestern farmers regarding the potential benefits of establishing cereal rye as a cover crop, but they are concerned about the implications and potential trade-offs of this practice. ARS researchers at Brookings, South Dakota, and collaborators from 10 land-grant universities in the U.S. Midwest evaluated the effects of cereal rye cover crop termination at or before soybean planting on soybean seed yield in field experiments from 2019 to 2021 across 28 location-years. Treatments consisted of no cereal rye, cereal rye termination before soybean planting, and termination at planting. Cereal rye was chemically terminated at each termination timing. Cereal rye biomass and soybean yield were assessed. Results showed that delaying rye termination increased rye biomass, but its impact on soybean yield was inconsistent. Delayed termination did not reduce soybean seed yield in 25 of 28 location-years compared to a no cover crop treatment. Altogether, the results suggest that Midwestern farmers who adopt cereal rye as a winter cover crop have a flexible management window for terminating cereal rye, as termination had minimal effect on soybean seed yield.

4. New distributional record and thermal tolerance determined for the non-native pavement ant. The pavement ant was discovered on the east coast of the U.S. over 100 years ago, but few records of it exist in the central Great Plains. Pavement ants dominate insect communities in agricultural landscapes consisting of corn and soybean throughout parts of the Midwest. ARS researchers at Brookings, South Dakota, and collaborators at Augustana University (South Dakota) recently discovered the species in South Dakota and created an updated range map of its distribution. In doing so, they documented its expansion over the past few decades, especially when community science platforms became available in the early 2000s. The collaborative team also determined traits such as cold and heat tolerance in the ants to help understand how their physiology may aid or hinder future expansion into other parts of the central Great Plains, and thus predict implications for their presence in Midwestern corn and soybean fields.

5. Will bees be able to handle droughts. Ongoing climate change has increased temperatures and drought frequency in many parts of the world, potentially intensifying the desiccation risk for insects. Because resisting desiccation becomes more difficult at higher temperatures and lower humidity, avoiding water loss is a key challenge. To address this, ARS researchers at Brookings, South Dakota, and collaborators at the Ruder Boškovic Institute in Croatia began examining the interaction of temperature and environmental humidity on desiccation resistance in bees. Results suggest (1) warmer or drier conditions accelerated bumble bee water loss and (2) warmer but not drier conditions hastened mortality. Combined, the results raise important questions about the mechanisms underpinning water loss in bees and suggest that frequent access to nectar may be especially important for bumble bees’ water balance and survival in a warmer and drier climate. The results of this research are important in understanding ways to protect bumble bees from drought and extreme temperatures.

6. First evaluations of insect-killing nematodes against soybean gall midge. The soybean gall midge was identified as a new pest of soybean in the Midwestern U.S. in 2018 and has since spread to seven states. Midge-infested soybean plants wilt, abort pod development, and may ultimately die. Insecticides seem ineffective against soybean gall midge, so farmers need other management tools. ARS researchers at Brookings, South Dakota, and Byron, Georgia, evaluated the susceptibility of soybean gall midge larvae to different rates of four insect-killing nematode species in the laboratory. All four nematode species infected and killed soybean gall midge larvae, and a high application rate of nematodes killed more larvae than a low rate. The results demonstrate strong potential of insect-killing nematodes to suppress soybean gall midge and their potential as a new pest management tool for Midwestern farmers.

7. Western corn rootworm populations vary in susceptibility to insect-killing nematodes. Insect-killing nematodes can infect and kill larvae of the western corn rootworm (WCR), a global corn pest that costs farmers over $2 billion annually in yield losses and management expenses. However, it is unknown whether geographically distant populations of WCR vary in susceptibility to insect-killing nematodes. ARS researchers at Brookings, South Dakota, and Byron, Georgia, evaluated the susceptibility of 18 geographic populations of WCR with various characteristics (degree of resistance to insecticides, Bt, or crop rotation) to six nematode species, including a native isolate from soils in Brookings, South Dakota. WCR populations were infected at different rates by the same nematode species, and the native isolate had roughly 50% higher infection levels than a commercial isolate. These findings indicate that nematode species and the geography and specific characteristics of WCR populations are all important considerations as practitioners formulate improved strategies for rootworm management.

U.S. DEPARTMENT OF AGRICULTURE

Integrated Cropping Systems Research: Brookings, SD