Location: Pest Management Research
2025 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: ARS researchers at Sidney, Montana analyzed samples from the final year of sampling in a study investigating how multi-species grazing practices and fire affect dung beetles that can enhance nutrient cycling and reduce cattle fly pests. Little is known about their role in cattle production systems and stakeholders have identified this as a priority research need. Multi-species grazing practices and using many cattle to graze for a short period of time are popular with producers but impacts on dung beetles have not been fully examined. Objective 2: Mormon cricket eggs are unusual in that they can arrest development (diapause) and remain in the soil for multiple years. ARS research has shown that embryonic development of Mormon crickets is generally dependent on duration of the growing season rather than chill time or number of annual cycles. The duration of the growing season required for 50% of the embryos to develop was well over one year. This research informs farmers and pest managers that Mormon crickets may remain in the soil in a location and life stage for which current insecticidal practices may not be effective. Laboratory demonstration of a multiannual lifecycle in Mormon crickets motivated the evaluation of long-term survivorship and hatching of eggs in the field. Eggs at high elevations in the Bighorn Mountains developed more slowly than the same genetic stock at low elevation sites, requiring 6-8 years vs. 2-3 years for one-half of the eggs to hatch. Mortality was greatest at high elevations where the eggs were in the ground the longest. A previously unknown fungus that infects the eggs was only observed at high elevation sites. State entomologists report that knowledge of egg bed longevity improves forecasting and reduces the cost and impact of management of this pest. Information on insect development timing is beneficial to land managers and surveyors by indicating when insects should be surveyed. To fill a gap in our knowledge of maternal effects on offspring development, the roles of Mormon cricket nutrition in determining the length of egg diapause and egg development rates were examined. Although parental nutrition played a significant role in the duration of egg diapause and development rate, parents with high protein diets laid eggs that diapaused for less time and developed faster. Egg development rate was particularly sensitive to the density of Mormon crickets in which the mother was caged, suggesting that females lay eggs that develop faster when they are in migratory swarms.
Mormon crickets are a major pest, and yet little is known about the effect of temperature on development of Mormon cricket life stages. To fill this gap, the effects of temperature on development of Mormon cricket embryos and hatching and development of nymphs were measured on a Wyoming high elevation population, an Idaho mid- elevation population, and an Oregon low elevation population. Within each egg stage, the peak temperature for development was found to change. This study provides a complete set of curves relating development through the life stages of this important economic pest across elevations at which it occurs. The curves are a more precise measure than degree-days to predict egg development and hatching and improve models of population growth. In addition, pest managers can more accurately predict hatch and nymphal growth to better time management operations. During an economically devastating grasshopper outbreak, researchers in Sidney, Montana, expanded collaborations with federal agencies, land grant universities, and the Smithsonian to examine the efficacy of large- scale grasshopper control programs. Aerial control programs can cover millions of acres during grasshopper outbreaks, but information is lacking on whether this reduces grasshopper populations long term, benefits pollinator health, and enhances forage for livestock over multiple years. Grasshopper abundance, plant production, pollinator abundance, and forage quality data were collected in association with a USDA Animal and Plant Health Inspection Service, Plant Protection and Quarantine control program. This data assists ranchers, federal agency partners, and land managers in making cost-effective pest management decisions.
Objective 3: ARS scientists in Sidney, Montana, developed new statistical methods that enabled location specific estimation of how population density, weather, and vegetation characteristics shape grasshopper and Mormon cricket abundances. Grasshoppers and Mormon crickets are the major rangeland pests and cause significant economic harm to grazing operations and agricultural production. Results indicate that grasshopper and Mormon cricket numbers during prior years can be used in conjunction with local weather and long-term weather to predict future grasshopper and Mormon cricket outbreaks. These findings will be used to prioritize grasshopper and Mormon cricket monitoring and treatments in advance of future outbreaks to improve management effectiveness. A population model for the migratory grasshopper (Melanoplus sanguinipes) in Wyoming has been adapted to aid in vegetative biomass estimation by the USDA Forest Service, Rangeland Production Monitoring Service. ARS has Cooperative Research Agreements (CA #59-3032-4-001 and #58-3032-2-005) with the University of Colorado in Boulder to apply machine learning to further this approach and develop software tools to forecast grasshopper and Mormon cricket densities.
Objective 4: ARS researchers initiated grasshopper sampling in a collaborative study investigating how livestock grazing, fire and rangeland seeding can reduce grasshopper populations. The usefulness of popular alternative livestock grazing practices to reduce grasshopper problems have not been fully examined.
Grasshopper samples have been collected in treatments focused on reducing the exotic grass Kentucky bluegrass and enhancing rangeland health. Alternative grazing management approaches could provide a cost- effective approach to reduce grasshopper problems. 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. ARS researchers in Sidney, Montana, completed and published projects demonstrating that sugar resources (e.g., floral nectar in cover crops and honeydew associated with aphids) enhance longevity of Bracon cephi, the most important biological control agent against the wheat stem sawfly. The results suggest that cover crops and cropping system diversification are key to increasing efficacy of the beneficial parasitoids. ARS researchers published a multi-year survey spanning 35 sites demonstrating that parasitism levels in wheatgrasses are 3x higher than those in wheat, suggesting these grasses are important parasitoid sources. We completed a study to assess whether proximity of wheat fields to grassland habitats, or the composition of landscapes, increased infestation by wheat stem sawfly or its control by parasitoids. The research suggests that surrounding wheat fields are the primary source of wheat stem sawfly, while incorporating wild grasses into Conservation Reserve Program grasslands, roadside plantings or reclamations could significantly benefit parasitoid conservation. The results also suggest that Kernza (an intermediate wheat grass variety gaining traction as a potential perennial grain crop) could provide key conservation habitat for parasitoids. We are currently conducting collaborative research with ARS in Colorado to test this hypothesis. ARS scientists in Sidney, Montana, are co-leading ongoing research collaborations with ARS scientists in Colorado involving: 1) evaluating agronomic practices and crop resistance as strategies for wheat stem sawfly control 2) development of an innovative beneficial bug baler project for mass redistribution of Bracon parasitoid in support of wheat stem sawfly biological control. We demonstrated that Bracon can be effectively transported and established in wheat using this technique, with current research focused on refinement and on-farm implementation of the technique. ARS researchers in Sidney, Montana, continued collaborations with university extension partners in Colorado and Nebraska leveraging pest survey data to investigate how crop rotation and crop varieties influence wheat stem sawfly infestation intensity and biological control. Alfalfa weevil continues to be a major pest in the northern Great Plains. Insecticides are the most used control strategy, but insecticide resistance is reducing control efficacy. ARS scientists in Sidney, Montana, are identifying field and landscape drivers of alfalfa weevil population dynamics and biological control with the goal of developing effective sustainable management approaches and reducing chemical inputs.
ARS scientists completed field work and co-authored a publication on a cross regional collaborative study (University of Wyoming, Colorado State University) examining effects of harvest timing on alfalfa weevil population dynamics and biological control. The results suggest that early harvest is a viable alternative to insecticides for weevil control. ARS scientists completed field work and sample processing on a multi-year landscape study examining the influence of field size and landscape structure on alfalfa weevil population dynamics and biological control. ARS scientists continue to provide mentoring and field support to a National Institute of Food and Agriculture funded postdoctoral fellow on a project examining the importance of Conservation Reserve Program grassland habitat for conservation of key biocontrol agents of alfalfa and wheat pests. ARS in Sidney, Montana, is collaborating with researchers in Chile and Canada to develop habitat management approaches for the management of alfalfa insect pests.
Accomplishments
1. Parental diet affects Mormon cricket egg development. Mormon crickets have been evaluated as a high protein additive to poultry feed, but prolonged diapause of Mormon cricket eggs currently hampers rearing for both laboratory experiments and feed stock. To address this problem, ARS scientists in Sidney, Montana, manipulated parental nutrition and measured the duration of egg diapause and the rate of egg development as a function of temperature. Parents with high protein diets laid eggs that diapaused for less time and developed faster. In addition, egg development rate was particularly sensitive to the density of Mormon crickets in which the mother was caged, with a doubling of density increasing the rate of development by nearly 50%. Increasing dietary protein and rearing densities of Mormon crickets are viable means to shorten diapause in both laboratory and commercial rearing of the insects.
2. Synthesizing pest monitoring data to identify drivers of sawfly infestation across regions.. Wheat stem sawfly is a $350 million/yr pest in the Great Plains of North America with limited management options. Researchers at USDA-ARS Sidney, Montana, and Fort Collins, Colorado, University of Nebraska, and Colorado State University used a multi-model inference approach to identify field and landscape drivers of sawfly infestation by synthesizing pest monitoring data from over 418 sites spanning four years and three states. The team found that predictors of sawfly infestation varied across states with winter wheat crop cover dominating in Montana, Conservation Reserve Program cover dominating in Colorado, while field-scale wheat rotation frequency dominated in North Dakota. The research identifies diversification with non-host crops as a key strategy to combat wheat stem sawfly, while underscoring the need to develop regionally tailored management recommendations since responses to specific host crops, and the scale of response, varied across regions. This work has fostered key cross- entity, cross regional collaborations between ARS and University researchers facilitating and accelerating the development of regionally tailored recommendations for sawfly management.
3. Determining the effectiveness of grasshopper outbreak control programs. Grasshoppers cause $1.7 billion dollars in forage damage annual on rangeland in the central and western U.S., leading to competition with livestock and potentially resulting in the overuse of plant resources. Aerial applications of insecticides occurred over 300,000 acres in eastern Montana in 2024 to control grasshopper outbreaks. Researchers at USDA-ARS Sidney, Montana, USDA Animal and Plant Health Inspection Service, Plant Protection and Quarantine (APHIS PPQ) and Montana State University collaborated to assess multi- year responses of target and non-target insects and rangeland forage production to large-scale aerial pesticide spraying for grasshopper outbreaks. This project addresses a major stakeholder gap requested by USDA Animal and Plant Health Inspection Service, Plant Protection and Quarantine and the National Grasshopper Management Board and is informing pest management of grasshoppers across hundreds of millions of acres of rangeland. The results of the project indicate that the historic assumption of a multi-year economic return and forage enhancement from controlling grasshoppers does not always occur and that more accurate outbreak prediction tools are needed to assist ranchers and land managers.
Review Publications
Vencl, F.V., Bartram, S., Winter, K., Boland, W., Srygley, R.B. 2024. Effects of elevated CO2 and temperature on the performance of a diet specialized Neotropical herbivore and its host plant. Biotropica. Article e13371. https://doi.org/10.1111/btp.13371.
Rana Dangi, S., Allen, B.L., Jabro, J.D., Rand, T.A., Campbell, J.W., Calderon, R.B. 2024. Soil microbial properties of durum growth after camelina, carinata, CC mix and fallow. Agronomy Journal. 14(9). https://doi.org/10.3390/agronomy14092050.
Toledo, D.N., Hendrickson, J.R., Kobilansky, C.L., Liebig, M.A., Kronberg, S.L., Christensen, R., Archer, D.W., Branson, D.H., Rand, T.A., Campbell, J.W., Igathinathane, C. 2024. The LTAR Grazing Land Common Experiment at Northern Plains. Journal of Environmental Quality. 53:921-929. https://doi.org/10.1002/jeq2.20604.
Bradshaw, J.D., Rand, T.A., Peirce, E.S., Nachappa, P., Osterholzer, A., Easterly, A.C., Creech, C.F., Struckmeyer, B., Poss, D.J., Schmale, D., Linnebur, A., Mankin, K.R., Miner, G.S., Hardy, C.D., Floyd, B.A., Kleinman, P.J. 2025. ‘Beneficial Bug Baler’: A novel technique for mass relocation of Bracon in support of Cephus cinctus biocontrol in wheat, Triticum aestivum, 2024. Arthropod Management Tests. 50(1). Article tsaf072. https://doi.org/10.1093/amt/tsaf072.
West, N.M., Campbell, J.W., Rand, T.A., Waite, E.S., Palmrose-Kreiger, C., Sylvain, Z.A., Branson, D.H. 2025. Reclaimed oil pads harbor higher Carabidae (Coleoptera) abundances and species richness - but fall short of reestablishing the native prairie community. Environmental Entomology. 54(3). Article nvaf037. https://doi.org/10.1093/ee/nvaf037.
Srygley, R.B. 2025. Effects of parental photoperiod and elevation on egg diapause, mortality, and synchronous hatching of Mormon crickets Anabrus simplex. Journal of Insect Physiology. 165.104866. https://doi.org/10.1016/j.jinsphys.2025.104866.
Wonkka, C.L., McGranahan, D.A., Muscha, J.M., Branson, D.H., Campbell, J.W., West, N.M. 2025. Long-term plant community dynamics following Russian olive removal and vegetation restoration. Restoration Ecology. Article e70148. https://doi.org/10.1111/rec.70148.