Location: Integrated Cropping Systems Research
2022 Annual Report
Objectives
Objective 1. Develop strategies to manage insects in cropping systems, focusing on biology with regards to resistance evolution, insect health and diversity, and the value of these strategies to sustainable crop production. [NP304, Component 3, Problem Statement 3A2].
Subobjective 1a. Assess the risk to susceptible western corn rootworm, and hence insect resistance management, from adult feeding on corn tissue expressing toxic Bacillus thuringiensis (Bt)-proteins.
Subobjective 1b. Evaluate neonicotinoid seed treatments for usefulness to U.S. crop production.
Subobjective 1c. Compare pest and beneficial insect levels between a soybean pest management system that uses an aphid-resistant cultivar versus one that relies on conventional insecticides.
Subobjective 1d. Compare pest and beneficial insect levels, soil properties, plant growth, yield, and seed composition of soybean when grown alone and with an oilseed relay crop.
Subobjective 1e. Evaluate cover-cropping scenarios within crop rotations that encourage ecosystem services from beneficial insects.
Subobjective 1f. Develop procedures for hazard assessments of pesticides to nontarget organisms.
Subobjective 1g. Establish exposure pathways for pesticides and non-target organisms and determine how plant diversity within the farmscape affects these exposure pathways.
Objective 2. Develop innovative strategies for managing weeds in dynamic cropping systems, and assess the benefits of these strategies that rely on bottom-up approaches to weed management (such as the use of cover crops) within diverse crop rotations. [NP304, Component 2, Problem Statement 2A2].
Subobjective 2a. Develop a methodology to convert red clover to cropland without tillage.
Subobjective 2b. Determine the best annual clovers to use as cover crops to control post-harvest weeds without tillage.
Approach
Pest management is crucial in cropping systems, and strategies to control weeds and insect pests need to be integrated with agronomic and other management goals to achieve sustainable cropping systems. In the northern Great Plains, corn rootworms, soybean aphids, and weeds greatly reduce agricultural productivity and profitability through yield loss and costly control measures. Widely adopted management tactics have initially reduced economic loss from these pests, but their utility needs reassessment in light of herbicide-tolerant weeds, insect adaptation to resistance transgenes, secondary pest outbreaks, and unwitting impacts on pollinators, natural enemies, and soil health. This project plan proposes research to address strategies used against major pests such as corn rootworms and soybean aphid, refine tactics for weed management in organic production systems, and determine the value and drawbacks to pest management and ecosystem services from diversifying crop rotations, incorporating cover crops, and using various plant-incorporated protectants. The research will be instrumental in developing management practices that increase farming efficiency and improve environmental and economic sustainability.
Progress Report
The previous 5-year research project and 2-year bridging project reflected emphases to generate knowledge about insect pest and weed management tactics for sustainable cropping systems in the Northern Great Plains (NGP). The bridging project was necessary during a period of critical vacancies in three scientist positions. Nevertheless, significant progress was made during the course of the bridging project in evaluating the impact of management practices on the structure and activity of beneficial insect communities. These studies included (1) evaluations of insect activity and predation in till and no-till systems, (2) evaluation of real and artificial sentinel prey to quantify the potential for biological control of pests via predation, and (3) surveys of insects in various cropping systems and non-cropped areas to inform future research objectives. Studies conducted during the bridging phase laid a foundation for research proposed in a new project plan to generate fundamental knowledge about beneficial invertebrates and determine how particular practices promote ecosystem services valuable for sustainable crop production in the NGP. Research generated >$600K of extramural funding to the location to support synergistic research. This funding supported two master’s students, whose research led to 3 publications. Multiple research updates were presented to stakeholders in meetings with commodity and producer groups, conservationists, and other scientists.
Accomplishments
1. Research potential for northern corn rootworm greatly enhanced by development of a non-diapausing laboratory colony. The northern corn rootworm (NCR) and western corn rootworm are important pests of corn that together cost U.S. growers about $2B in yield losses and control costs annually over the last several years. The NCR typically produces only one generation per year and has an obligatory overwintering stage as eggs in the soil. Studies with wild populations are, therefore, difficult and lengthy. To combat this, ARS scientists in Brookings, South Dakota, and Columbia, Missouri, and scientists at the University of Missouri, developed a non-diapausing NCR laboratory colony and established robust protocols for rearing it. The non-diapausing strain, along with improvements to the rearing system, will be important to researchers, as it will allow them to produce up to six generations of NCR per year, greatly accelerating research to manage this important pest.
2. Scientists document the first cases of field-evolved resistance in western corn rootworm to Bt corn hybrids with both Cry3Bb1 and Cry34/35Ab1 proteins. Western corn rootworm (WCR) has field-evolved resistance to transgenic (Bt) corn expressing the Cry3Bb1 protein across the U.S. Corn Belt. Hybrids known as pyramids, which contain Cry3Bb1 plus the Cry34/35Ab1 protein, have been increasingly used to counter WCR resistance to Cry3Bb1 alone. However, susceptibility of WCR populations to that pyramid has not been assessed. ARS scientists in Brookings, South Dakota, along with scientists at the University of Nebraska, determined the susceptibility of corn hybrids with Cry3Bb1 alone or Cry3Bb1 + Cry34/35Ab1 to WCR populations collected from areas of northeastern Nebraska with a history of planting Bt corn that expressed Cry3Bb1 and Cry34/35Ab1. All field populations showed some level of resistance to one or both Bt hybrids when compared to susceptible control populations in laboratory tests. Most WCR populations exhibited incomplete resistance to Cry3Bb1 + Cry34/35Ab1 corn (92%) and complete resistance to Cry3Bb1 maize (79%). The results demonstrated a landscape-wide WCR Cry3Bb1-resistance pattern in areas characterized by long-term continuous corn production and associated planting of Cry3Bb1 hybrids. The resistance may be important to corn farmers and pest management practitioners because it suggests that the use of a multi-tactic integrated pest management approach is needed in areas of continuous corn production to slow or mitigate resistance evolution to Bt corn hybrids.
3. Fourteen-year survey documents significant lady beetle declines in field-crops. Lady beetles are major predators of aphids and other pests of field crops. At least three kinds of native lady beetles largely disappeared from cropland in North America following the establishment of invasive lady beetle species in the 1980s. Additional invasive lady beetle species have established since then. To assess the status of lady beetles, ARS scientists in Brookings, South Dakota, surveyed five types of field crops and restored prairie in eastern South Dakota from 2007 to 2020 using sweepnets and timed searches. Overall, 17,338 predatory lady beetles comprising 10 species were sampled. Two invasive species (sevenspotted lady beetle and harlequin lady beetle) ranked third and fourth in abundance. For native and non-native species combined, significant declining trends were evident among adult and immature lady beetles in corn and for adults in soybean. Declines of lady beetles in these crops in late summer could substantially reduce overwintering populations that emerge to colonize early-season crops the following spring, thus potentially disrupting biocontrol services in cropland both early and late in the season. These findings may concern both farmers and conservationists because the potential for decreased biocontrol of pests from lady beetles may lead to more use of insecticides in agricultural fields, thereby increasing crop production costs and environmental impacts.
4. Higher attack rates and consumption of pests are related to higher diversity of perennial polyculture cropping systems compared to conventional corn-soybean systems. The agricultural landscape of the Midwestern U.S. has been simplified over the past 100 years with large portions of land converted primarily to monocultures of corn and soybean. ARS scientists in Brookings, South Dakota, and scientists at the University of Illinois, tested how increasing plant diversity (i.e., moving from monoculture to polyculture) impacts one beneficial arthropod group, the ants, over an annual cycle. The scientists found that polycultures of clovers, grasses, and woody perennials harbored more ant species (17 species) compared to conventional monocultures (7 species) and that increased diversity was correlated with significantly higher attack rates and consumption of pests. The findings are important to Midwestern farmers because they provide strong evidence that Midwestern landscapes may be modified to support beneficial insects like ants while still producing economically viable alternative commodities.
Review Publications
Reinders, J.E., Reinders, E.E., French, B.W., Meinke, L.J. 2021. Evidence of western corn rootworm (Diabrotica virgifera virgifera LeConte) field-evolved resistance to Cry3Bb1 + Cry34/35Ab1 maize in Nebraska. Pest Management Science. https://doi.org/10.1002/ps.6752.
Roeder, K.A., Benson, B.F., Weiser, M.D., Kaspari, M. 2021. Testing the role of body size and litter depth on invertebrate diversity across six forests in North America. Ecology. 103(2). Article e03601. https://doi.org/10.1002/ecy.3601.
Huynh, M.P., Nielson, C.N., French, B.W., Ludwick, D.C., Geisert, R.W., Pereira, A.E., Barry, J.M., Meihls, L.N., Schneider, S.K., Hibbard, B.E. 2021. Development of a non-diapausing strain of northern corn rootworm with rearing techniques for both diapausing and non-diapausing strains. Scientific Reports. 11. Article 17944. https://doi.org/10.1038/s41598-021-97452-8.
Hesler, L.S., Beckendorf, E.A. 2021. Declining abundance of Coccinellidae (Coleoptera) among crop and prairie habitats of eastern South Dakota, USA. Frontiers in Conservation Science. 2. Article 742036. https://doi.org/10.3389/fcosc.2021.742036.
Roeder, D.V., Paraskevopoulos, A.W., Roeder, K.A. 2022. Thermal tolerance regulates foraging behavior of ants. Ecological Entomology. 47(3):331-338. https://doi.org/10.1111/een.13118.
Roeder, K.A., Harmon-Threatt, A.N. 2022. Woody perennial polycultures increase ant diversity and ant-mediated ecosystem services compared to conventional corn-soybean rotations. Agriculture, Ecosystems and Environment. https://doi.org/10.1016/j.agee.2022.108025.
