Location: Pest Management Research
2024 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 1. We carried out the final year of insect sampling for a study investigating how multi-species grazing practices and fire affect dung beetles, that can speed up nutrient cycling and reduce cattle fly pest issues. Little is known about the role of dung beetles in rangeland ecosystem function and production in the northern Great Plains, with stakeholders identifying this as a priority research need. Multi-species grazing practices and mob-grazing (using a large number of cattle grazing on a pasture for a short period of time) are popular with producers but impacts of these management approaches on dung beetles and rangeland health have not been examined. This study relates to Objective 1 to determine the role of rangeland insects, particularly grasshoppers, on rangeland ecosystem function and production.
Objective 2. We completed experiments on effects of temperature and desiccation on Mormon cricket embryonic development in the lab. Metabolic rate and water loss were compared between embryos in prolonged diapause, and those in later stages of development. This study relates to the Sub-objective 2C to identify causes of Mormon cricket mortality in egg beds, including temperature and desiccation. Experiments on effects of parental nutrition on offspring development were also completed. Nymphal Mormon crickets were fed a diet high in protein, one equal in protein to carbohydrates, or a diet high in carbohydrates and the time for eggs to develop after they were laid was measured over a ten-year period. In addition, Mormon cricket nymphal densities and densities of protein-rich prey (grasshoppers) were manipulated in field cages, and eggs were collected from the adults. Egg development rate as a function of temperature was measured to determine if maternal diet affected offspring development in the short-term. This study relates to Sub-objective 2D to 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.
During a multi-year grasshopper outbreak causing significant economic damage in the northern Great Plains, researchers in Sidney, Montana, continued and expanded collaborations with federal agencies, land grant universities, and the Smithsonian Institution to better understand factors leading to grasshopper outbreaks and determine if control programs provide multi-year benefits for producers. Aerial spray programs can cover millions of acres during grasshopper outbreaks in the western U.S., but information is lacking on whether these spray programs reduce grasshopper populations for multiple years, if spraying enhances or reduces pollinator health, and if spraying leads to enhanced rangeland forage for livestock. Grasshopper abundance, rangeland plant production, pollinator abundance, and forage quality data were collected at sites in eastern Montana that were either sprayed or not sprayed in 2021 and 2024. The Animal and Plant Health Inspection Service conducted a 300,000-acre spray program on federal land in eastern Montana in 2024. The data will assist ranchers, federal agency partners, and land managers in making pest management decisions and determining when it is cost effective to control grasshoppers.
Objective 3. Data from Mormon cricket and grasshopper survey points in Wyoming and Nevada were compiled with environmental parameters describing local vegetation, temperature, precipitation, and topography. The data were analyzed with spatial statistics, including MaxEnt and Log-Gaussian Cox Point Process (LGCP) modeling. This progress relates to Sub-objective 3B to model centers of endemism in Mormon cricket populations based on multi-annual life cycles and topographic variation in the Western U.S., and Sub-objective 3C to investigate the effects of annual to decadal scale weather patterns and spectral vegetation indices on pest insect outbreaks.
Objective 4. We completed statistical analyses examining the potential influence of grassland habitats on infestation by wheat stem sawfly and its control by Bracon parasitoids in wheat. Multi-species grazing practices and mob-grazing which uses large numbers of cattle to intensively graze a pasture for a short period of time are popular approaches, but the usefulness of these management approaches to reduce grasshopper problems have not been examined in the northern Great Plains. Grasshopper samples have been collected in five different rangeland management treatments over a 6-year period focused on reducing the dominance of the exotic grass Kentucky bluegrass. Alternative grazing management approaches could provide a sustainable cost-effective approach to reduce grasshopper pest problems. This research relates to Sub-objective 4A to examine the impact of rangeland management practices on grasshopper populations.
The wheat stem sawfly continues to devastate wheat production across the central and northern plains and has been identified by stakeholders as a priority pest target. We completed research assessing the performance of the parasitoid wasp, Bracon cephi, the most important biological control agent against the wheat stem sawfly, on different wild grass species common in Conservation Reserve Program and rangeland habitats with the goal of determining the relative role of grassland habitats as pest reservoirs vs natural enemy conservation habitats. We completed analysis on a study to assess whether proximity of wheat fields to grassland habitats increased infestation by wheat stem sawfly or its control by Bracon parasitoids. This research relates to Sub-objective 4B. Researchers continued collaborations with university extension partners in Colorado and Nebraska leveraging extension surveys to investigate how crop rotation and crop diversity influence wheat stem sawfly infestation intensity and biological control. ARS scientists continued collaboration with researchers at USDA-ARS in Colorado (Akron, Fort Collins) on three wheat stem sawfly studies: evaluating interactions between agronomic practices and crop resistance as strategies for wheat stem sawfly management, examining wheat stem sawfly pressure and biological control in Kernza, a novel perennial grain crop, and developing a novel methodology for the mass redistribution of parasitoids in straw bales, which has the potential to greatly increase biocontrol efficacy in Colorado where parasitoids are currently absent. ARS scientists completed compilation and preliminary analysis of data from a multi-year landscape study examining the influence of field size and landscape structure on alfalfa weevil population dynamics and biological control. We provided expertise and mentoring to a National Institute of Food and Agriculture funded postdoctoral fellow, who is examining the importance of Conservation Reserve Program grassland habitat for conservation of key biocontrol agents of wheat and alfalfa pests. This research relates to Sub-objective 4C.
Accomplishments
1. Cues used by Mormon cricket eggs to end diapause over a ten-year period. Mormon crickets have a multi-annual life cycle and can diapause as eggs in the soil for many years. ARS researchers in Sidney, Montana, conducted a ten-year study of egg development and hatching to address the question: how do Mormon cricket eggs time their development. Three mutually exclusive hypotheses were tested: counting seasonal cycles (like cicadas), duration of winter (a.k.a. ‘chill time’), and duration of the growing season (a.k.a. ‘forcing’). This research showed that embryonic development of Mormon crickets is generally dependent on duration of the growing season, but one lineage from Arizona showed evidence for dependence on chill time. Counting of the number of annual cycles was not evident in any lineage. The duration of the growing season required for half of the eggs to develop ranged from 84 to 144 weeks. These results will be applied to spatial models in the Mormon cricket range to better estimate egg accumulation in egg banks and the potential for outbreaks to better manage the populations.
2. Mormon crickets get immunity burst from eating grasshoppers. In addition to feeding on plants, Mormon crickets predate on invertebrates, including one another. Because Mormon crickets commonly occur with grasshoppers, ARS scientists in Sidney, Montana, tested whether grasshoppers were a source of dietary protein and affected Mormon cricket immunity to disease. As expected, grasshoppers were shown to be an important source of dietary protein for Mormon crickets with prey availability affecting Mormon cricket immunity to disease. This study was the first to investigate the immune response of a predator with increasing prey densities in an outdoor field setting. It also suggests that by consuming pest insects, Mormon crickets provide some beneficial services that need to be weighed against the costs, including damage to crops and livestock forage.
3. Assessing the role of semi-natural grasslands as pest sources vs. conservation habitat for parasitoids of the wheat stem sawfly. The wheat stem sawfly is a devastating pest of wheat across the northern Great Plains. Increasing economic infestations across the Central Plains in recent decades has resulted in increased stakeholder demand for sustainable management solutions. Biological control is a key component of effective management, and increasing the efficacy of native Bracon sp. parasitoids, the most important biological control agents of the wheat stem sawfly, is critical to reducing its economic impacts. Wheat stem sawfly attacks both wild grasses and small grain crops, where it is in turn attacked by its parasitoids. However, whether grassland habitats, or specific constituent grass species serve as sources of pests or biocontrol parasitoids moving over into wheat was unknown. Using a multi-year survey spanning 35 grassland sites, ARS researchers in Sidney, Montana, demonstrated that sawfly infestation in native wheatgrasses is high (38%–65%) and similar to that in wheat (55%). However, infestation was low (less than 10%) in a majority of grass species (12 of 17), suggesting that most wild grasses are not sawfly sources. Parasitism levels in native wheatgrasses were 3 times higher than those in wheat, suggesting that they could be important parasitoid sources. However, infestation and parasitism levels in wheat fields bordering rangeland and Conservation Reserve Programs (CRP) were not different from those bordering fallow. The research indicates that the value of grassland habitats for parasitoid conservation will depend greatly on which grass species are present, with important implications for developing grass seed mixes for restoration of grassland in CRP and roadsides, and reclamations following energy development.
Review Publications
Srygley, R.B., Senior, L. 2024. Illustrated review of Mormon cricket (Anabrus simplex) embryonic development. Journal of Orthoptera Research. 33:87-93. https://doi.org/10.3897/jor.33.98763.
Rand, T.A., Kula, R.R., Gaskin, J.F. 2024. Evaluating the use of common grasses by the wheat stem sawfly and its native parasitoids in rangeland and Conservation Reserve Program grasslands. Journal of Economic Entomology. 117(3):858-864. https://doi.org/10.1093/jee/toae046.
Srygley, R.B., Branson, D.H. 2023. Power bars: Mormon crickets get immunity boost from eating grasshoppers. Insects. 14(11). Article 868. https://doi.org/10.3390/insects14110868.
Herreid, J., Rand, T.A., Cockrell, D., Peairs, F., Jabbour, R. 2024. On-farm harvest timing effects on alfalfa weevil across the Intermountain West region of the United States. Frontiers in Insect Science. 4. Article 1324044. https://doi.org/10.3389/finsc.2024.1324044.
Srygley, R.B. 2024. Prolonged diapause in Mormon crickets: Embryonic responses to three measures of time. Journal of Insect Physiology. 155. Article 104634. https://doi.org/10.1016/j.jinsphys.2024.104634.
Rana Dangi, S., Allen, B.L., Jabro, J.D., Rand, T.A., Campbell, J.W., Calderon, R.B. 2023. Effect of alternative dryland crops on soil microbial communities in no-till durum systems. Soil Systems. 8(1). https://doi.org/10.3390/soilsystems8010004.
Campbell, J.W., Rand, T.A., Allen, B.L., Jabro, J.D., Rana Dangi, S., West, N.M., Morphew, A.R. 2024. Pollinators and other beneficial insects within two brassicaceous oilseeds and a cover crop mix under evaluation as fallow surrogates for dryland production systems of the northern Great Plains. Journal of Kansas Entomological Society. 96(3):78-92. https://doi.org/10.2317/0022-8567-96.3.78.
Vencl, F.V., Srygley, R.B. 2023. El Niño oscillations impact anti-predator defenses to alter survival of an herbivorous beetle in a neotropical wet forest. Journal of Tropical Ecology. 39. Article e34. https://doi.org/10.1017/S0266467423000226.
Heimbuch, N.G., McGranahan, D.A., Wonkka, C.L., Vermeire, L.T., Branson, D.H. 2023. Grasshopper abundance and offtake increase after prescribed fire in semi-arid grassland. International Journal of Wildland Fire. 32(12):1828-1833. https://doi.org/10.1071/WF23031.
West, N.M., Branson, D.H., Muscha, J.M., Campbell, J.W. 2023. Early impacts of invasive shrub removal on riparian arthropod communities. Ecological Restoration. 41(4):189-198. https://doi.org/10.3368/er.41.4.189.
Queste, L.M., Page, E., Rosser, N., Mallet, J.K., Srygley, R.B., McMillan, W., Dasmahapatra, K.K. 2024. Pervasive convergence in flight patterns enhances mimicry in aposematic butterflies. Proceedings of the National Academy of Sciences (PNAS). 121(11). Article e230088612. https://doi.org/10.1073/pnas.2300886121.
Srygley, R.B. 2024. Effects of parental diet on Mormon cricket egg diapause and embryonic development rate. Journal of Insect Physiology. 157. Article 104681. https://doi.org/10.1016/j.jinsphys.2024.104681.