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Slugs

Overview

Slugs are a significant pest that can cause extensive damage to various crops across the United States and Canada. These soft-bodied, shell-less mollusks thrive in moist environments and are particularly problematic in regions with high humidity and frequent rainfall. Slugs feed on a wide range of crops, including vegetables, cereals, and legumes, by rasping plant tissues with their radula (a tongue-like organ with tiny teeth).

In vegetable crops such as lettuce, cabbage, and tomatoes, slugs can cause severe defoliation and damage to fruits, leading to reduced marketability and yield losses. In cereals like wheat and barley, slugs can damage seedlings and young plants, impacting crop establishment and growth. Legumes such as soybeans and peas are also at risk, as slugs can feed on leaves and pods, reducing both yield and quality.

Effective management of slugs involves cultural practices, such as reducing field moisture and removing debris, as well as chemical control using molluscicides. Integrated pest management strategies are essential for minimizing slug damage and protecting crop yields.

Photo Credit: Gary Bernon, USDA APHIS, Bugwood.org

slugs

How to Identify Slugs

Identifying slugs is crucial for effective management. Here are specific and detailed characteristics to help farmers recognize these pests:

General Appearance:

  • Body Shape: Slugs have elongated, soft, and flexible bodies that are typically cylindrical and taper towards the tail.

  • Size: They can range in size from a few millimeters to several inches long, depending on the species.

  • Color: Slugs can vary in color, including shades of gray, brown, black, yellow, and even green. Some species may have mottled or striped patterns.

  • Texture: Their bodies are covered in a slimy mucus that helps them move and prevents desiccation. The mucus can leave a shiny, silvery trail on surfaces they traverse.

Anatomical Features:

  • Tentacles: Slugs have two pairs of retractable tentacles on their head. The upper pair, which is longer, contains the eyes, while the lower pair is used for sensing the environment.

  • Mantle: The mantle is a saddle-shaped structure located behind the head. It covers the slug's internal organs and may have a small, vestigial shell or a respiratory opening (pneumostome) on the right side.

  • Foot: The foot is the muscular underside of the slug that it uses for locomotion. It produces mucus to facilitate movement.

Behavior and Habitat:

  • Moisture Preference: Slugs thrive in moist environments and are often found in areas with high humidity, such as under mulch, leaf litter, rocks, and debris.

  • Nocturnal Activity: Slugs are primarily nocturnal and are most active during the night or on overcast, rainy days. They avoid direct sunlight to prevent desiccation.

  • Feeding Damage: Slugs feed by rasping plant tissues with their radula, creating irregular holes and ragged edges on leaves, stems, and fruits. They can also leave behind slime trails on plants and soil.

Monitoring:

  • Visual Inspection: Regularly inspect fields, especially in moist and shaded areas, for the presence of slugs and their feeding damage.

  • Traps: Use slug traps, such as boards or tiles placed on the soil surface, to monitor slug populations. Check traps in the morning when slugs are likely to be hiding underneath.

Key Identifying Features:

  • Elongated, Soft Body: Lacking a shell, with a slimy texture.

  • Two Pairs of Tentacles: Upper pair with eyes, lower pair for sensing.

  • Mantle: Saddle-shaped structure behind the head, sometimes with a respiratory opening.

  • Mucus Trails: Shiny, silvery trails left on surfaces.

By closely examining these characteristics, farmers can accurately identify slugs and implement appropriate control measures.

Geographic Impact of Slugs

Slugs have a significant geographic impact across various regions in the United States and Canada, particularly in areas with high humidity and frequent rainfall. Their presence and impact can vary depending on the local climate, soil conditions, and crop types. Here’s a detailed overview of their geographic impact:

United States:

  • Pacific Northwest: Slugs are particularly problematic in the Pacific Northwest, including states like Washington, Oregon, and Northern California. The region's cool, wet climate provides ideal conditions for slug populations to thrive, impacting a wide range of crops, including vegetables, berries, and ornamental plants.

  • Midwest: In the Midwest, states such as Ohio, Indiana, and Illinois experience significant slug infestations, especially in fields with heavy, clay soils and high organic matter. Crops like soybeans, corn, and various vegetables are commonly affected.

  • Northeast: The humid and temperate climate of the Northeast, including states like Pennsylvania, New York, and New Jersey, supports slug populations that can damage vegetable crops, ornamental plants, and small grains.

  • Southeast: In the Southeast, states like Georgia, North Carolina, and Florida also face slug issues, particularly in no-till fields and areas with high moisture levels. Crops such as peanuts, soybeans, and vegetables are at risk.

Canada:

  • British Columbia: The coastal regions of British Columbia, with their mild and wet climate, are highly conducive to slug infestations. Slugs can cause significant damage to vegetable crops, berries, and ornamental plants.

  • Ontario and Quebec: In the central provinces of Ontario and Quebec, slugs are a common pest in agricultural fields, particularly in areas with heavy soils and high organic matter. Crops like soybeans, corn, and various vegetables are affected.

  • Maritime Provinces: The Maritime Provinces, including Nova Scotia, New Brunswick, and Prince Edward Island, also experience slug problems due to their humid and temperate climate. Slugs can impact a variety of crops, including potatoes, vegetables, and small grains.

Timing of Slug Impact

Slugs typically emerge and begin to impact fields across the United States during the cooler, wetter periods of the year. Their activity is closely tied to moisture levels and temperature, making them most problematic in the spring and fall. Here’s a detailed timeline of their emergence and impact:

Emergence:

  • Spring: Slugs become active in early spring as temperatures rise above 40°F (4°C) and soil moisture increases due to melting snow and spring rains. This period usually spans from March to May, depending on the region.

  • Fall: Slugs also become active in the fall when temperatures cool down and moisture levels rise again, typically from September to November.

Key Impact Periods:

  • Spring: During the spring, slugs feed on newly emerging seedlings and young plants, causing significant damage to crops such as vegetables, cereals, and legumes. This is a critical period for crop establishment, and slug damage can lead to poor stand development and reduced yields.

  • Summer: In regions with high humidity or irrigated fields, slugs can remain active throughout the summer, especially during periods of overcast weather or after rainfall. However, their activity generally decreases in hot, dry conditions.

  • Fall: In the fall, slugs can cause damage to late-season crops and newly planted winter crops. They feed on leaves, stems, and fruits, leading to reduced marketability and yield losses.

How to Manage Slugs

Managing slugs in corn and soybeans requires an integrated approach that combines cultural practices, monitoring, and chemical control. Here are detailed strategies for managing slugs in these crops:

Cultural Practices:

  1. Field Sanitation: Remove plant debris, weeds, and other organic matter that can provide shelter and breeding grounds for slugs.

  2. Tillage: Implementing tillage can disrupt slug habitats and expose them to predators and environmental conditions that reduce their populations.

  3. Crop Rotation: Rotate crops to break the life cycle of slugs and reduce their population buildup.

  4. Drainage: Improve field drainage to reduce moisture levels, making the environment less favorable for slugs.

  5. Row Spacing and Plant Density: Adjust row spacing and plant density to improve air circulation and reduce humidity around the plants.

Monitoring:

  1. Traps: Use slug traps, such as boards or tiles placed on the soil surface, to monitor slug populations. Check traps in the morning when slugs are likely to be hiding underneath.

  2. Field Scouting: Regularly inspect fields, especially in moist and shaded areas, for the presence of slugs and their feeding damage.

Chemical Control:

  1. Molluscicides: Apply molluscicides to control slug populations. Some effective products include:

    • Iron Phosphate: Safe for use around crops and non-toxic to pets and wildlife. It disrupts the feeding of slugs, causing them to stop eating and die.

    • Metaldehyde: Effective but should be used with caution as it can be toxic to pets and wildlife. Apply in bait form to target slugs directly.

    • Ferric Sodium EDTA: Another effective molluscicide that is less toxic to non-target organisms.

Specific Recommendations for Corn and Soybeans:

  1. Timing: Apply molluscicides early in the season when slugs are most active and before they cause significant damage to seedlings.

  2. Application Method: Use bait formulations to target slugs directly. Scatter the bait evenly around the base of the plants and in areas where slugs are likely to hide.

  3. Reapplication: Reapply molluscicides as needed, especially after heavy rains, which can wash away the bait.

Integrated Pest Management (IPM):

  1. Combine Methods: Use a combination of cultural practices, monitoring, and chemical control to manage slug populations effectively.

  2. Threshold Levels: Establish threshold levels for slug damage and apply control measures when populations exceed these levels.

  3. Record Keeping: Keep detailed records of slug activity, control measures applied, and their effectiveness to inform future management decisions.

By implementing these strategies, farmers can effectively manage slugs in corn and soybeans, minimizing crop damage and protecting yields.

Every product that labels SLUGS as a weed, pest, or disease the product can be applied against is shown below. Click any product for label and more information.
BIO-SUL Slug & Snail BaitBioLink® Insect & Bird RepellantBrandt® Antixx® PlusBug-N-Sluggo®Celite® 610Deadline® Bullets™Deadline® GT™Deadline® M-Ps™ Mini Pellets (5481-507)Deadline® Ornamental™Deadzone™Dominus®Durham® Metaldehyde 3.5Durham® Metaldehyde 7.5Envirepel 50™Ferroxx® Slug and Snail BaitImidan® 70-W (Water Soluble Bags)IronFist™ Slug And Snail BaitLeaf Life® Sluggo® Snail and Slug BaitLock Out®Mesurol® 75-WMetarex® 4% Snail And Slug BaitSlug-Fest All Weather FormulaSlugger 4.0 Slug & Snail BaitSluggo® Slug and Snail BaitValley Ag Slug Hammer Slug Bait