Location: Pest Management Research
2021 Annual Report
Objectives
OBJECTIVE 1: Determine the role of rangeland insects, particularly grasshoppers, on rangeland ecosystem function and production.
OBJECTIVE 2: Identify climatic and biotic ecological drivers of pest population dynamics of wheat stem sawflies, grasshoppers and Mormon crickets.
Subobjective 2A: Develop and verify growing degree day models of Mormon cricket embryonic development and hatch.
Subobjective 2B: Investigate the duration that Mormon cricket eggs remain in egg beds.
Subobjective 2C: Identify causes of Mormon cricket mortality in egg beds, including temperature and desiccation.
Subobjective 2D: Identify cues that cause Mormon cricket females to lay eggs that break diapause and hatch after one, two, or several winters to improve applicability of Mormon crickets as high protein component of feed and food.
Subobjective 2E: Identify vegetation variables (e.g. increase in invasive grasses) associated with shifts in grasshopper abundance and community structure.
Subobjective 2F: Identify forage quality effects on grasshopper performance and spectral bandwidth differences in vegetation.
OBJECTIVE 3: Develop predictive models of rangeland and crop insect pest distribution, population growth and impact to allow land managers to address outbreaks at earlier stages and optimize control efforts.
Subobjective 3A: Model embryonic development and hatch of Mormon crickets across elevations in the Western U.S.
Subobjective 3B: Model centers of endemism in Mormon cricket populations based on multi-annual life cycles and topographic variation in the Western U.S.
Subobjective 3C: Investigate the effects of annual to decadal scale weather patterns and spectral vegetation indices on pest insect outbreaks.
Subobjective 3D: Model the effect of El Niño Southern Oscillation on plant primary productivity and grasshopper outbreaks in the Western U.S.
OBJECTIVE 4: Design sustainable approaches (e.g. roadside and conservation plantings, landscape diversification, rangeland fire and grazing management) to manage key crop and rangeland insects, such as wheat stem sawfly, alfalfa weevil, pea aphids, grasshoppers, and their natural enemies.
Subobjective 4A: Examine the impact of rangeland management practices on grasshopper populations.
Subobjective 4B: Identify factors enhancing Bracon cephi abundance and efficacy in controlling wheat stem sawfly populations.
Subobjective 4C: Identify field and landscape drivers of alfalfa weevil population dynamics and biological control.
Approach
Grasshoppers, Mormon crickets, wheat stem sawfly, and alfalfa weevil significantly damage rangeland and crop productivity in the Central and Western United States. Grasshoppers and Mormon crickets consume ~$1.7 billion of forage annually in the U.S. and wheat stem sawfly causes ~$250-350 million in crop damage annually. These pests are high priority targets for ranchers, farmers and federal and state land managers, since current control strategies are inadequate, costly and/or result in unacceptable environmental impacts due to the historical reliance on broad spectrum insecticides. The long-term goal of this proposed research is to develop innovative, environmentally sound and sustainable management alternatives for control of these pests which currently lack sustainable control measures. To achieve this end, we will pursue research to broaden the ecological knowledge of these pests, improve pest risk assessments, and enhance prevention of pest outbreaks. We will develop a sound understanding of pest impacts on rangeland production and determine climatic and biotic drivers that cause crop and rangeland pests to exceed economic thresholds in the Great Plains. We will design sustainable habitat and landscape approaches to manage these pests and their natural enemies. Pursuing research in ecology, forecasting and prevention will provide the foundational knowledge necessary to achieve the ultimate goal of developing ecologically-based and economically practical management strategies that reduce economic impacts and promote food security, while decreasing environmental impacts of control measures. We will communicate our results through meetings, publications and presentations targeting land management agencies, farmers and ranchers, academic societies, industry and state extension services.
Progress Report
Objective 3. Researchers at Sidney, Montana investigated the effects of annual to decadal scale weather patterns and spectral vegetation indices on pest insect outbreaks. In early 2021, ARS scientists conducted several meetings with Animal and Plant Health Inspection Service (APHIS) Plant Protection and Quarantine (PPQ) field staff and database managers to coordinate transfer of common data sites (CDS) information to the ARS Sidney, Montana. The CDS data documents grasshopper and Mormon cricket occurrences throughout the Western U.S. since the late 1940’s and provides species-level identification of grasshoppers. We began statistical analysis of the CDS data to compare changes in grasshopper density and species composition to monthly, yearly, and multi-decadal changes in temperature and precipitation. The goal of this research is to determine what climatic variables are associated with enhanced grasshopper population growth rates in Montana and Wyoming.
We constructed statistical models that quantified the effect of the El Niño Southern Oscillation on grasshopper outbreaks in the Western U.S. Scientists compared shifts in grasshopper abundance documented since the late 1940’s to measures of El Niño Southern Oscillation variability recorded by the National Oceanic and Atmospheric Administration. The ultimate goal of the analysis is to better predict when and where grasshopper outbreaks are most likely to occur Due to the novelty of their approach, ARS scientists were invited to discuss their analysis with the ARS SCINet (Scientific Computing Initiative and Network) Executive Committee and with ARS Grand Challenge-Synergies leadership in hopes of developing technical procedures and workflows that may be adapted for use by other ARS scientists.
Researchers modeled subsurface and above ground temperatures for 10 sites where Mormon cricket bands were observed in Utah and compared them to empirical data collected between 2012 and 2020. This relates to the Sub-objective to model centers of endemism in Mormon cricket populations based on topographic variation in the western U.S. ARS scientists have found that a hybrid model combining surface temperature when snow levels are above 3 cm with above ground temperature has improved the above ground model agreement with our empirical data. Researchers also measured the development rate of Mormon cricket embryos from a mid-elevation site in Idaho to compare with data from a high-elevation site in Wyoming and a low-elevation site in Oregon. This relates directly to the sub-objective to model embryonic development and hatch across elevations.
Objective 4: Researchers completed data analysis on a project identifying the major pest insects associated with alternative oilseed and cover crops being trialed as fallow replacement crops in the northern Great Plains. We completed preliminary lab and greenhouse studies examining the influence of sugar resources (e.g., nectar and honeydew associated with different aphid/plant combinations) on the performance (longevity and fecundity) of Bracon cephi, the most important biological control agent against the wheat stem sawfly. ARS scientists completed the second year of a collaborative study examining effects of harvest timing on alfalfa weevil population dynamics and biological control, and completed the first year of field work on a study examining the influence of field size and landscape structure on alfalfa weevil population dynamics and biological control.
Also related to Objective 4: We investigated whether multi-species grazing practices and fire can reduce rangeland grasshopper populations and simultaneously increase the abundance of dung beetles that reduce livestock fly problems. Grasshoppers respond to rangeland conditions, providing opportunities for reducing pest grasshoppers with livestock grazing and fire. Multi-species grazing practices and mob-grazing are popular with producers and can improve carrying capacity, however impacts of these management approaches on grasshoppers and dung beetles have not been examined. Plots were established and grasshopper and dung beetle samples were collected in five different rangeland management treatments focused on reducing the dominance of the exotic grass Kentucky bluegrass. Grasshopper sampling was also conducted in the first year of an additional patch burn grazing experiment with sheep and cattle.
Accomplishments
1. Modeling grasshopper outbreaks in response to El Niño. Grasshopper outbreaks in the United States destroy approximately 20% of rangeland forage annually valued at ~$1.67 billion (2019 dollars) and are major threats to crops throughout the West. The intensity of grasshopper outbreaks varies by year and some locations are often impacted much more severely than others. Periodic drought associated with long-term climate cycles, like El Niño, may be one factor causing grasshopper outbreaks. Researchers in Sidney, Montana, compared grasshopper outbreaks reported over the last 70 years to long-term climate records. Grasshopper modeling revealed that grasshopper densities in the Northern Great Plains decreased during peak El Niño years, but grasshoppers in the Southern Great Plains increased to outbreak levels during these time periods. Grasshopper modeling results will be used to help prioritize grasshopper monitoring and treatments in advance of outbreaks to maximize management effectiveness.
2. Modeling potential U.S. invasion by the Central American locust. The Central American locust is a large, swarming locust that is endemic to Central America. When in a swarming phase, the locust can devour crops like rice, wheat, citrus, and lentil over very large geographic areas inflicting millions of dollars in economic harm. Although no Central American locust occurrences have yet been documented in the U.S., the insect has been found within less than 300 miles of the U.S.-Mexico border. There is concern that changing climate conditions may enable the Central American locust to invade the U.S. in the future. Researchers in Sidney, Montana, have developed statistical models to assess the chance of invasion by Central American locusts. Modeling results suggest that locations in Central Texas and Southern Arizona may be vulnerable to locust invasion beginning around the year 2040, however, environmental conditions may not contribute to outbreaks until the year 2060.
3. Pest complexes associated with novel bioenergy and cover crops in the Northern Plains. Identifying the dominant pests associated with novel crops being considered in diversification efforts is important information to forecast impacts on their production, and determine whether these novel crops are likely reservoirs of pests moving over into cash crops in a region. Researchers in Sidney, Montana, surveyed insect pest communities in two bioenergy crops (carinata or camelina) and a 10-species forage/cover crop being trialed as fallow replacement crops for dryland productions systems of the Northern Plains. Crucifer flea beetles, the most important pests of canola in the region, were the dominant pests associated with carinata and the cover crop mix while the pest complex associated with camelina was dominated by generalist lygus bugs. Crucifer flea beetle densities were 200-1000 times greater in carinata relative to camelina. The results suggest that crucifer flea beetles have the potential to become serious pests of carinata, while camelina is both less likely to be attacked by, or serve as a reservoir of, these important pests of canola. Thus, camelina could be a good fit to replace fallow and increase crop diversity in regions with high canola acreage and a history of flea beetle problems.
4. Mormon cricket growth rate increases with elevation. Some chemical control agents must be applied to nymphs, and the efficacy of microbial control is also stage-sensitive. Many managers use degree day estimates of pest occurrence after spring thawing to plan surveying and control efforts. Because average temperature and the duration of the growing season decline with increasing elevation, researchers in Sidney, Montana, investigated the growth rate of Mormon crickets across elevation from 300-9000 feet. The minimum temperature for growth declined from 61°F to 58°F with increasing elevation, and the growing degree days required to reach adult remained the same among populations. As a result, for any given temperature, growth rate increased with elevation. For pest management, a base temperature from mid-elevation of 60°F and 916 degree days accumulated from egg hatching to adult are reasonable estimates for applications from sea level to 9000 feet.
Review Publications
Lucas, J.M., Jonas, J., Laws, A., Branson, D.H., Pennings, S.C., Prather, C.M., Strickland, M.S. 2021. Functional and taxonomic diversity of grasshoppers differentially shape above- and below-ground communities and their function. Functional Ecology. 35(1):167-180. https://doi.org/10.1111/1365-2435.13682.
Srygley, R.B. 2020. Elevational changes in Mormon cricket life histories: Minimum temperature for nymphal growth declines with elevation. Environmental Entomology. 50(1):167-172. https://doi.org/10.1093/ee/nvaa151.
Srygley, R.B. 2021. Elevational and latitudinal changes in cold tolerance of nymph and adult Mormon crickets Anabrus simplex (Orthoptera: Tettigoniidae). Environmental Entomology. 50(3):699-705. https://doi.org/10.1093/ee/nvab009.
Sabal, M.C., Boyce, M.S., Charpentier, C.L., Furey, N.B., Luhring, T.M., Martin, H.W., Melnychuk, M.C., Srygley, R.B., Wagner, C., Wirsing, A.J., Ydenberg, R.C., Palkovacs, E.P. 2021. Predation landscapes influence migratory prey ecology and evolution. Trends in Ecology and Evolution. 36(8):737-749. https://doi.org/10.1016/j.tree.2021.04.010.
Jabro, J.D., Allen, B.L., Rand, T.A., Rana Dangi, S., Campbell, J.W. 2021. Effect of previous crop roots on soil compaction in 2 yr rotations under a no-tillage system. Land. 10(2):202. https://doi.org/10.3390/land10020202.
Humphreys Jr, J.M., Young, K.M., Cohnstaedt, L.W., Haney, K., Peters, D.C. 2021. Vector surveillance, host species richness, and demographic factors as neuroinvasive West Nile Disease risk factors. Viruses and Bacteriophages. 13:5. https://doi.org/10.3390/v13050934.
Peirce, E.S., Rand, T.A., Cockrell, D.M., Ode, P.J., Peairs, F.B. 2021. Effects of landscape composition on wheat stem sawfly (Hymenoptera: Cephidae) and its associated Braconid parasitoids. Journal of Economic Entomology. 114(1):72-81. https://doi.org/10.1093/jee/toaa287.
