Wyoming

Wyoming
Wyoming is within:
Country:	United States

Rangeland portal / Wyoming

Wyoming is a large, sparsely populated western U.S. state defined by its open plains, rugged mountains, and diverse ecosystems ranging from alpine forests to sagebrush steppe. The dry climate and extensive rangelands create ideal conditions for grasshopper populations, which are part of the natural ecology but can periodically surge and cause significant damage. State and federal agencies regularly monitor and manage grasshopper outbreaks to protect rangeland health and agricultural productivity.

State ecology

Wyoming's landscape is a mix of high plains, sagebrush steppe, rolling grasslands, and rugged mountain ranges, including parts of the Rocky Mountains and the Greater Yellowstone Ecosystem. Much of the state consists of semi-arid rangeland, supporting a wide array of native grasses, forbs, and shrubs adapted to dry conditions. These ecosystems provide prime breeding grounds for grasshoppers. Outbreaks have historically caused significant damage to Wyoming's grazing lands and agricultural crops, threatening both native ecosystems and ranching economies.

As of 1998, southeastern Wyoming had experienced high grasshopper densities in 27 of the previous 31 years, making it the most persistently infested region in the United States at that time. Historically, grasshopper problems in Wyoming have been most common in Big Horn, Washakie, Hot Springs, Sheridan, Johnson, Campbell, Crook, Weston, Converse, southern Natrona, Niobrara, Goshen, and Platte counties. Other counties have experienced fewer outbreaks due to factors like elevation, vegetation (pine forests or deserts), and other yet-to-be-understood variables.

Chronic grasshopper outbreaks in Wyoming are closely associated with the Ponderosa pine forest vegetation class. Despite its name, the "forest" resembles a savannah, with open or scattered trees and a grass understory. The unique and complex environmental conditions that create these pine savannahs may contribute to the persistence of grasshopper outbreaks.

Species gallery

• Highlighted species for Wyoming
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  Flabellate grasshopper (Melanoplus occidentalis)
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  Pronotal range grasshopper (Cratypedes neglectus)
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  Turnbull’s grasshopper (Aeoloplides turnbulli)
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  Crackling forest grasshopper (Trimerotropis verruculata)
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  Sprinkled broad-winged grasshopper (Chloealtis conspersa)
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  Dusky grasshopper (Encoptolophus costalis)
• 
  Dawson's spur-throat grasshopper (Melanoplus dawsoni)
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  Clear-winged grasshopper (Camnula pellucida)
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  Platte range grasshopper (Mestobregma plattei)
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  Sagebrush grasshopper (Melanoplus bowditchi)
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  Mottled sand grasshopper (Spharagemon collare)
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  Pallid-winged grasshopper (Trimerotropis pallidipennis)
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  Wyoming toothpick grasshopper (Paropomala wyomingensis)
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  Great basin grasshopper (Trimerotropis sparsa)
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  Migratory grasshopper (Melanoplus sanguinipes)
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  Cudweed grasshopper (Hypochlora alba)

Species of management concern

Wyoming is home to around 100 grasshopper species, with 15 of them identified as major pests of rangeland or cropland. The six major grasshopper pest species found in southeastern Wyoming are White-whiskered grasshopper (Ageneotettix deorum), Striped grasshopper (Amphitornus coloradus), Big-headed grasshopper (Aulocara elliotti), Western spotted-winged grasshopper (Cordillacris occipitalis), Migratory grasshopper (Melanoplus sanguinipes), and Two-striped grasshopper (Melanoplus bivittatus). The first four primarily damage rangeland, M. bivittatus targets croplands, and M. sanguinipes affects both. Although outbreaks can involve more than 16 species, typically one or a few of these dominate. The Mormon cricket (Anabrus simplex) is also noteworthy for its destructive impact when large swarms migrate from rangelands to croplands.

Some grasshopper species overwinter as nymphs, emerging earlier in the spring than those that overwinter as eggs. In southeastern Wyoming, brown-spotted range grasshopper (Psoloessa delicatula), velvet-striped grasshopper (Eritettix simplex), and pasture grasshopper (Melanoplus confusus) are among the first to appear. While these species can occasionally damage rangeland when abundant, such occurrences are rare. They should not be mistaken for early hatches of egg-overwintering species.

View U.S. Grasshopper Forecast Hazard Maps

Grasshopper management

Wyoming manages grasshoppers through a decentralized system built around 23 county Weed & Pest Control Districts, one for each county. These districts are the practical frontline: they work with ranchers, farmers, state and federal land managers, and other partners to monitor outbreaks, provide technical guidance, organize coordinated responses, and sometimes offer pesticide access or cost-share assistance. Statewide coordination comes from the Wyoming Department of Agriculture and the Wyoming Weed & Pest Council.

The system is designed for local flexibility. Grasshopper pressure, funding, staffing, landownership, and agricultural priorities differ greatly across Wyoming, so each county district can tailor its activities to local conditions rather than follow a uniform state treatment program. This is especially important in rangeland landscapes, where infestations often span multiple private and public properties and effective action depends on neighboring land managers participating together.

Wyoming’s approach emphasizes integrated pest management: early monitoring, identification of economically important pest species, treatment only when justified by density and likely damage, and coordination at the relevant landscape scale. When treatment is needed, local and state partners may use methods intended to reduce pesticide use and conserve beneficial organisms, including reduced-rate or alternating-swath approaches associated with the Reduced Area and Agent Treatment strategy (RAATs). Larger or multi-county outbreaks can also trigger support through the state’s Emergency Insect Management Program and collaboration with federal agencies such as USDA APHIS (above paragraphs pers. comm. Scott Schell U. Wyo. Extension Entomology Specialist to Mira Ries GLI project coordinator Sept 24, 2026).

​The University of Wyoming has been instrumental in advancing grasshopper research and management, particularly concerning rangeland ecosystems. Through its Department of Ecosystem Science and Management, the university has collaborated with agencies like USDA-APHIS and the Cooperative Agricultural Pest Survey Program to develop comprehensive, species-based surveys and management strategies.​

Additionally, the university has established many valuable resources on their platform "Grasshoppers of Wyoming and the West", including field guides, distribution maps, and management strategies.

Featured resource

• 
  Field Guide to Common Western Grasshoppers

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Outbreaks

Outbreak problem areas in Wyoming

Grasshopper outbreaks are a recurring issue in Wyoming, particularly in the state’s rangelands, where favorable environmental conditions and abundant forage can lead to rapid population growth. These outbreaks, which vary in intensity and location from year to year, can cause significant damage to both native vegetation and agricultural lands, prompting ongoing monitoring and management efforts.

For maps of Wyoming grasshopper population dynamics over the years click here

Organizations

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Resources

Name	Year published	Resource link	Descriptive keyword	Language	Author
APHIS regulatory documents	2018		Early warning, Ecology, Public health, Social science, Culture, insecticide, Infestations, Environmental assessment, Rangeland management, Pesticides, Bundle, Environmental impact	English	Animal and Plant Health Inspection Service
ARS grasshopper species fact sheets	1994		Management, Species identification, Series	English	Agricultural Research Services, United States Department of Agriculture
CARMA		View	Prototype cropland, Advice, Rangeland management, Crop health, Grasshoppers, Infestations, Outbreaks	English	Scott Shell Extension Entomology, University of Wyoming
Common Wyoming pest grasshoppers		View	Life cycle, Species identification, Biodiversity, Grasshoppers	English	University of Wyoming, Scott Schell, Alexandre Latchininsky, B.A. Shambaugh
Court rejects federal pesticide-spraying program on millions of acres of western rangelands	2025		Ecology, Spraying, Chemical control, Infestations, Management, Governance, Conservation, Land use management, Habitat	English
Distribution Atlas for Grasshoppers and the Mormon Cricket in Wyoming			Map, Survey, Archive, Population dynamics	English	University of Wyoming
Field Guide to Common Western Grasshoppers	2002		Species identification, Field guide	English	United States Department of Agriculture, Robert E. Pfadt
Grasshopper biology and monitoring		View	Monitoring, Biology, Grasshoppers, General locust education	English	University of Wyoming, Judee Wargo
Grasshopper infestation continues after pesticide spray canceled	2023		Spraying, Ecology, Environmental science, Infestations, Emergency response, Chemical control, Grazing	English	Alaina Mencinger
Grasshopper Integrated Pest Management User Handbook	2000		Biological control, Chemical control, Monitoring, Modeling, Population dynamics, Rangeland management, Decision making, Bundle, Ecology, Pesticides, Biopesticide, Integrated pest management	English	Agricultural Research Services, United States Department of Agriculture
Grasshopper watch	2022		Grasshoppers	English
Grasshoppers (Acrididae) of Colorado	1982		Biology, Species identification, Ecology, Behavior, Physiology, Management	English	Colorado State University, John Capinera, TS Sechrist
Grasshoppers Are Descending on the West in Swarms	2021		Grasshoppers	English
Grasshoppers of the Western United States		View	Management, Species identification, Key	English	United States Department of Agriculture
Grasshoppers their habits and damage	1964	View	Grasshoppers, Outbreaks, Natural enemies, Ecology, Habitat, Quality illustrations, Species identification	English	United States Department of Agriculture
Hopper helper		View	Survey, Life cycle, Species identification, Integrated pest management	English	Wendal Cushing
Key to Wyoming grasshoppers			Species identification, Information hub, Glossary	English	University of Wyoming, Timothy J. McNary
Las Vegas resident shares experience as swarms of grasshoppers return to valley	2024		Outbreaks	English
Mega Disasters: Super Swarms of Locusts	2021		General locust education, Video	English
Montana.gov Orthoptera Field Guides		View	Species identification, Management, Biology, Distribution, Map, Rangeland management, Information hub, Website	English
Mormon cricket 'sludge' blankets northern Nevada roads causing crashes	2024		Media article, Outbreaks	English
Mormon cricket biology and management poster		View	Life cycle, Economics, History, Spraying, Habitat, Migration, Grasshopper development, Distribution, Species identification, Map, Photos	English	University of Wyoming, APHIS Plant Protection and Quarantine
Overview of the APHIS Rangeland Grasshopper and Mormon Cricket Suppression Program	2022		Management, Chemical control, Grasshoppers, Governance, Video	English	APHIS PPQ Science & Technology Insect Management and Molecular Diagnostics Laboratory (Phoenix Station), United States Department of Agriculture
Overview of the APHIS Rangeland Grasshopper and Moron Cricket Suppression Program	2022		Video, Grasshoppers, Management, Educational video	English	United States Department of Agriculture, APHIS Plant Protection and Quarantine
Pest Grasshoppers of the West	2005	View	Management, Species identification	English	University of Wyoming
Protecting U.S. rangeland from grasshoppers and Mormon crickets	2021	View	Outbreaks, Infestations, Mormon crickets, Rangeland management, insecticide	English	United States Department of Agriculture
Rangeland Grasshopper and Mormon Cricket suppression program	2019	View	Public health, Governance, Culture, Grasshoppers, Economics, Environmental assessment, Life cycle, Biology	English	United States Department of Agriculture
Rangeland Grasshopper Management	1993		Management, Species identification, Control	English	University of Wyoming, Jeffrey Lockwood, Scott Schell
The Grasshoppers of the Western U.S. Lucid mobile app	2016		Management, Species identification	English	APHIS PPQ Science & Technology Insect Management and Molecular Diagnostics Laboratory (Phoenix Station), United States Department of Agriculture, Center for Plant Health Science and Technology of the USDA
UC Integrated Pest Management for Home Gardeners and Landscape Professionals	2013	View	Life cycle, Pesticide management, Management	English	University of California Statewide Integrated Pest Management Program
USDA APHIS historical meeting report collection			APHIS archive 2024, Historical document, Annual report, Uncurated archive, Collection	English	United States Department of Agriculture, Animal and Plant Health Inspection Service
USDA APHIS-PPQ-Science & Technology Phoenix Lab Rangeland Unit project summary	2021		Summary, Set, Project, Project report	English, Spanish, French	APHIS PPQ Science & Technology Insect Management and Molecular Diagnostics Laboratory (Phoenix Station), Animal and Plant Health Inspection Service, United States Department of Agriculture
Wyoming Grasshopper Maps			Map, Survey, Archive, Population dynamics	English	University of Wyoming

Rangeland portal / Wyoming