Do Spur-Throated Grasshoppers Cause Damage to Crops?

Spur-throated grasshoppers are a common group of insects found in many parts of the world. Known for their distinctive spur or projection between their front legs, these grasshoppers belong to the subfamily Melanoplinae within the family Acrididae. While they are an integral part of many ecosystems, one question that concerns farmers, gardeners, and agricultural professionals is whether spur-throated grasshoppers cause damage to crops. This article explores the biology, behavior, and impact of spur-throated grasshoppers on agriculture, with a focus on their potential to harm crop yields.

Understanding Spur-Throated Grasshoppers

Spur-throated grasshoppers are characterized by a small spine or “spur” located on the throat area between their front legs. This feature helps distinguish them from other grasshopper types. There are numerous species within this group, with some of the most common ones in North America including Melanoplus differentialis (differential grasshopper), Melanoplus sanguinipes (migratory grasshopper), and Melanoplus femurrubrum (red-legged grasshopper).

These insects undergo incomplete metamorphosis, progressing through egg, nymph, and adult stages. Nymphs resemble smaller versions of adults but lack fully developed wings. They typically hatch in spring or early summer and mature through several molts over weeks.

Feeding Behavior and Diet

Spur-throated grasshoppers are primarily herbivores. Their diet consists mainly of grasses, forbs (broadleaf plants), and crops such as wheat, corn, alfalfa, and soybean. They use strong mandibles to chew plant material, often consuming leaves, stems, flowers, and seed heads.

While feeding preferences vary among species and life stages, many spur-throated grasshoppers display generalist tendencies—they will eat a wide range of plants available in their habitat. This flexibility allows them to exploit various food sources but also increases the likelihood that they will feed on cultivated crops.

Potential Crop Damage Caused by Spur-Throated Grasshoppers

The key concern for farmers is the extent to which spur-throated grasshoppers damage crops. The answer is nuanced: these insects can cause significant damage under certain conditions but are usually manageable.

Types of Damage

Defoliation: Grasshoppers feed on leaves by chewing holes or stripping entire sections. Leaf loss reduces photosynthesis capacity, which can stunt plant growth.
Stem and Head Feeding: Some species consume tender stems or reproductive parts like flowers and seed heads. This can directly reduce yield or quality.
Seedling Destruction: Young plants are more vulnerable. Grasshopper feeding can kill seedlings outright, reducing crop stand density.

Multiple Crop Impact: Because spur-throated grasshoppers consume various plants, they may damage several crop types simultaneously during outbreaks.

Severity of Damage

Damage severity depends on multiple factors:

Population Density: Small numbers often cause negligible harm; however, during population outbreaks—sometimes termed “grasshopper plagues”—damage can be extensive.
Crop Type: Some crops are more susceptible due to palatability or growth stage timing.

Environmental Conditions: Dry years favor grasshopper population growth since fewer fungal diseases and predators control them.
Cropping Practices: Monocultures or areas with abundant weedy hosts can support larger populations.

Economic Impact

In outbreak years, spur-throated grasshoppers have caused millions of dollars worth of losses worldwide. They can defoliate fields rapidly when present in high densities. For example:

In the U.S. Great Plains region, outbreaks periodically destroy hay meadows and cereal grains.
In Canada’s prairie provinces, migratory spur-throated species have inflicted severe damage to wheat and barley crops.
In some cases, farmers may need to replant fields or use costly insecticides to protect yields.

Life Cycle Influence on Crop Damage Timing

Understanding the life cycle phases helps predict when damage is most likely:

Egg Stage: Eggs overwinter in soil pods. Soil disturbance during planting can affect hatching success.
Nymph Stage: Nymphs emerge in spring when young seedlings appear—this stage is critical since vulnerability is high.

Adult Stage: Adults usually peak mid to late summer; they tend to feed more heavily and disperse widely.

Early detection of nymphs can allow timely intervention before widespread crop damage occurs.

Natural Controls and Management Strategies

While spur-throated grasshoppers can be problematic pests during outbreaks, natural controls often keep populations in check:

Natural Predators and Parasites

Birds such as meadowlarks and sparrows actively feed on grasshoppers.
Predatory insects including spiders, beetles, wasps, and ants consume nymphs and adults.
Pathogenic fungi like Entomophaga grylli infect large numbers during wet conditions.

Cultural Practices

Farmers use several strategies to manage grasshopper populations proactively:

Crop Rotation: Changing crops disrupts habitat continuity for egg laying.
Tillage: Soil tillage in fall or spring can destroy egg pods.
Weed Control: Reducing non-crop host plants decreases food sources.
Resistant Crops: Selecting less palatable varieties reduces feeding damage.

Chemical Control

When populations exceed economic thresholds, insecticides may be applied:

Selective insecticides target grasshoppers while minimizing harm to beneficial insects.

Timing applications at early nymph stages maximizes effectiveness.
Integrated pest management (IPM) approaches combine monitoring with targeted treatments.

Monitoring and Thresholds for Control

Regular field scouting is essential to identify population levels before damage occurs. Thresholds vary by crop but generally include:

8–10 nymphs per square meter at seedling stage
20–30 adults per square meter later in season

If counts exceed these levels over multiple areas within a field, management actions may be warranted.

Conclusion: Do Spur-Throated Grasshoppers Cause Damage to Crops?

Yes—spur-throated grasshoppers can cause significant damage to agricultural crops under favorable conditions that lead to high population densities. Their feeding habits result in leaf loss, stem injury, flower destruction, and seedling mortality that reduce both yield and quality of important food crops such as wheat, corn, soybeans, alfalfa, and more.

However, not all spur-throated grasshopper presence equates with crop loss. Many populations remain at low levels controlled by natural predators and environmental factors without causing economic harm. The key lies in monitoring populations carefully throughout the growing season to detect rising numbers early.

By combining cultural practices like crop rotation and weed management with timely chemical control when needed—and leveraging knowledge about their biology—farmers can mitigate the risk posed by spur-throated grasshoppers effectively. Thus, while they are capable pests in certain circumstances, good integrated pest management practices ensure that spur-throated grasshoppers do not always become devastating crop destroyers.

References

Capinera, J.L., Scott R.D., & Walker T.J., Field Guide to Grasshoppers, Katydids & Crickets of the United States — Cornell University Press
USDA Agricultural Research Service — Grasshopper Pest Management Resources
Integrated Pest Management Guidelines for Field Crops — University Extension Services