Grasshoppers are a persistent pest in dryland farming, particularly during warm, dry conditions that favour their population growth. Effective control strategies must combine proactive monitoring, cultural practices, biological controls, and selective chemical use.
Monitoring and Early Detection
Field Scouting:
Regularly check field edges, pastures, and grassy areas where grasshoppers tend to lay eggs.
Use sweep nets and visual counts to estimate population density. Record observations to identify hotspots and prioritize control efforts.
Weather-Based Predictions:
Monitor weather patterns, as dry and warm spring conditions can lead to high grasshopper populations.
Use regional pest forecasting systems to anticipate outbreaks.
Cultural Control Practices
Crop Residue Management:
Remove or incorporate crop residues that provide food and shelter for grasshoppers.
Field and Pasture Rotation:
Rotate crops to disrupt the food sources and breeding cycles of grasshoppers.
Trap Crops:
Plant sacrificial crops (e.g., oats or millet) at field edges to lure grasshoppers away from primary crops.
Destroy trap crops once they attract significant grasshopper populations.
Habitat Management:
Mow or manage vegetation in non-cropped areas to reduce grasshopper breeding grounds.
Biological Control Options
Natural Predators:
Encourage populations of natural predators such as birds (e.g., crows and starlings), ground beetles, and parasitic wasps.
Pathogenic Control:
Use products containing fungal pathogens like Metarhizium anisopliae, which specifically target grasshoppers.
Beneficial Insects:
Maintain diverse insect populations, including predatory insects that can naturally suppress grasshopper numbers.
Chemical Control Methods
Insecticide Application:
Use insecticides like carbaryl, diflubenzuron, or malathion when grasshopper densities exceed economic thresholds.
Apply early in the nymph stage (before they develop wings), as they are more vulnerable and localized.
Bait Formulations:
Apply insecticidal baits mixed with bran or other attractants along field edges or hotspots.
Effective in minimizing widespread chemical application while targeting grasshoppers.
Integrated Timing:
Coordinate insecticide application with regional pest management programs to maximize effectiveness and reduce grasshopper migration.
Preventive Measures
Egg Bed Management:
Disturb soil in known grasshopper breeding areas during fall or early spring to expose and kill eggs.
Avoid overgrazing pastures, as bare soil can encourage grasshopper egg laying.
Crop Selection:
Plant early-maturing or fast-growing crops to escape peak grasshopper feeding periods.
Barriers:
Install physical barriers, such as dense hedgerows or fine mesh fences, to protect vulnerable crops from grasshopper migration.
Case Studies
Regional Collaboration:
A group of farmers worked with local pest management authorities to coordinate bait application, successfully reducing grasshopper infestations over a large area.
Biological Success:
A dryland operation introduced Metarhizium anisopliae fungal sprays, reducing grasshopper numbers without harming beneficial insects.
Proactive Habitat Management:
A rancher managed field edges and pasture rotation to minimize grasshopper breeding grounds, reducing reliance on insecticides.
Economic Thresholds for Intervention
Economic thresholds help determine when grasshopper populations pose a significant risk to crops, warranting intervention. Thresholds vary by crop type, growth stage, and local conditions.
General Guidelines:
Cereal Crops: 8–12 grasshoppers per square meter (approx. 80–120 per square yard).
Forage Crops: 15–20 grasshoppers per square meter (approx. 150–200 per square yard).
Pastures: 20–30 grasshoppers per square meter (approx. 200–300 per square yard).
Scouting Tips for Thresholds:
Conduct counts at several locations in the field.
Use a one-square-meter frame or a similar-sized visual reference for consistent counts.
Average the counts across multiple areas to determine overall population density.
Specific Insecticide Recommendations
Proper selection and application of insecticides can effectively reduce grasshopper populations while minimizing environmental impact.
Carbaryl:
Commonly used for grasshopper control in both agricultural and non-crop areas.
Available as sprays and baits; apply during early nymph stages for best results.
Diflubenzuron:
A growth regulator that targets young grasshoppers by preventing molting.
Works best when applied early in the season, before grasshoppers reach adulthood.
Malathion:
A broad-spectrum insecticide effective against adult grasshoppers.
Use with care to avoid harming beneficial insects like pollinators.
Spinosad:
natural insecticide derived from soil bacteria, effective against grasshoppers while being less harmful to non-target species.
Commonly used in organic farming.
Application Best Practices
Timing:
Apply insecticides in the early morning or late afternoon when grasshoppers are most active.
Target nymphs before they mature and develop wings, as they are less mobile and more concentrated.
Spot Treatment:
Focus on field edges, ditches, and other high-density areas to conserve resources and reduce environmental exposure.
Equipment:
Use ground sprayers or aerial applications depending on field size and severity of infestation.
Ensure even coverage and avoid overlapping applications.
Diagrams for Scouting Methods
Field Sampling Grid:
Divide the field into quadrants or grids.
Randomly select sampling points within each grid for population counts.
Sweep Netting:
Use a durable sweep net with a diameter of 38–46 cm (15–18 inches).
Take 20–30 sweeps in a zigzag pattern across the field.
Count grasshoppers collected and estimate density based on sample area.
Square Frame Sampling:
Place a one-square-meter frame (or equivalent) on the ground in multiple locations.
Count the number of grasshoppers within the frame.
Repeat across various parts of the field for an accurate average.
Additional Preventive Measures
Sources of Preventative Materials and information:
Farmers and ranchers in Alberta's Special Areas have access to several resources for forecasting and managing grasshopper outbreaks:
Alberta Agriculture and Irrigation's Grasshopper Forecast Maps:
This resource provides annual grasshopper survey maps based on adult grasshopper counts conducted in late July and August. These maps help predict potential grasshopper risks for the upcoming season.
Prairie Pest Monitoring Network (PPMN):
The PPMN offers monitoring protocols and coordinates insect pest surveillance across the Canadian prairies. They provide weekly updates, insect prediction models, and real-time maps to assist in forecasting pest populations, including grasshoppers.
Alberta Insect Pest Monitoring Network:
This network provides real-time maps and monitoring tools for various insect pests, including grasshoppers. It offers valuable data to support timely decision-making in pest management.
Grasshopper Identification and Control Methods Booklet:
Developed by the University of Lethbridge, this booklet aids in identifying major pest species and outlines control methods, assisting in early detection and management of grasshopper populations.
Alberta Climate Information Service (ACIS):
ACIS provides weather-based insect pest prediction models, including those for grasshoppers. These models help predict pest development stages and potential outbreak periods based on current and forecasted weather conditions.
Utilizing these resources can enhance preparedness and response to grasshopper outbreaks in Alberta's Special Areas.
Community-Wide Management:
Collaborate with neighboring farmers and local agricultural organizations for coordinated control efforts, reducing the likelihood of reinfestation.
Case Study with Economic Impact
Integrated Grasshopper Management in Alberta’s Drylands:
A farmer faced a severe grasshopper infestation threatening wheat crops. Using early scouting, they identified population densities of 10–15 grasshoppers per square meter, exceeding the economic threshold.
Actions Taken:
Applied diflubenzuron early in the season to control nymphs.
Introduced trap crops on field edges to lure and target grasshoppers.
Implemented habitat management by mowing non-crop areas post-harvest.
Results: Saved an estimated 20% of yield potential compared to untreated fields.
Reduced pesticide costs by 15% through targeted application