How to Use Crop Covers Against Rootworm

Rootworms are among the most destructive pests in agriculture, particularly affecting corn crops and causing significant yield losses. Managing these pests effectively requires an integrated approach, and one of the promising methods is the use of crop covers. Crop covers, also known as row covers or floating covers, serve as physical barriers that protect plants from insect pests, including rootworms. This article explores how to use crop covers against rootworm, offering practical guidance on material selection, application techniques, and integration with other pest management strategies.

Understanding Rootworm and Its Impact

Before diving into crop covers, it is essential to understand the pest you are combating. Rootworms belong to the genus Diabrotica, with the Western Corn Rootworm (Diabrotica virgifera virgifera) being the most notorious species in North America. These beetles lay eggs in the soil near corn roots, and when larvae hatch, they feed aggressively on the roots. Root feeding damages the plant’s ability to absorb water and nutrients, leading to lodging (plants falling over), reduced nutrient uptake, and diminished yields.

Traditional control methods include crop rotation, chemical insecticides, and genetically modified (GM) rootworm-resistant corn varieties. However, increasing pesticide resistance and environmental concerns necessitate alternative or complementary approaches like crop covers.

What Are Crop Covers?

Crop covers are sheets or nets made from materials such as polyester, polyethylene, or polypropylene designed to protect plants from insects while allowing light, air, and moisture penetration. They can be either:

Floating row covers: Lightweight fabrics laid directly over crops without support.
Supported row covers: Fabric held above crops by hoops or frames.

These covers create a physical barrier preventing insects from reaching the plants for feeding or egg-laying.

Benefits of Using Crop Covers Against Rootworm

Physical exclusion: Crop covers prevent adult rootworms from reaching plants to lay eggs.
Reduced pesticide use: By controlling pests physically, farmers can minimize insecticide applications.
Environmental safety: Covers reduce chemical runoff and protect beneficial insects.
Improved microclimate: Covers can moderate temperature fluctuations and moisture levels.
Versatility: Covers can protect young seedlings during vulnerable growth stages.

Selecting the Right Crop Cover Material

Choosing the appropriate crop cover material is crucial for effective rootworm control:

1. Mesh Size

Rootworm adults are relatively large insects (about 6-8 mm long), so the mesh size of the cover must be fine enough to prevent their passage but still allow airflow and light penetration.

Recommended mesh size: 0.6 mm or smaller typically blocks rootworm adults.

2. Fabric Weight

Lightweight fabrics (0.5-1 oz per square yard): Allow better light transmission and airflow but may tear easily.
Heavier fabrics (>1 oz per square yard): More durable but could reduce sunlight exposure.

3. UV Resistance

UV-stabilized fabrics last longer under sun exposure without degrading.

4. Breathability

Materials that allow air and moisture exchange help prevent heat buildup and fungal diseases underneath.

When to Apply Crop Covers

Timing is critical since crop covers are most effective when applied before rootworm adults become active:

In most regions, rootworm beetles emerge in late spring to early summer, generally after corn has germinated.
Apply covers immediately after planting or as soon as seedlings emerge.
Covers should remain in place throughout the adult beetle flight period (several weeks).

How to Install Crop Covers Against Rootworm

Step 1: Prepare Your Field

Ensure soil preparation and planting are complete.
Make sure seedlings have emerged uniformly enough to be covered efficiently.

Step 2: Lay Out the Cover Material

Depending on your choice between floating or supported covers:

Floating covers: Gently lay fabric directly over seedlings without damaging them.
Supported covers: Install hoops or frames over rows before placing fabric on top.

Step 3: Secure Edges Firmly

Rootworm adults can enter through openings at edges:

Bury edges of fabric into the soil (4-6 inches deep).
Use soil mounds, staples, pins, or weights along edges.

Step 4: Monitor Regularly

Check for tears or gaps weekly; repair immediately if found.

Step 5: Remove at Proper Time

Remove covers once the adult beetle flight period ends, usually after six weeks, to allow normal pollination and growth processes.

Integrating Crop Covers with Other Control Methods

Crop covers work best as part of an integrated pest management (IPM) system rather than a standalone strategy.

Crop Rotation

Rotating corn with non-host crops such as soybeans breaks rootworm life cycles by depriving larvae of food sources. Use crop covers alongside rotation for enhanced protection during vulnerable stages.

Resistant Corn Varieties

Planting genetically modified corn expressing Bt toxins targeting rootworms adds a biological barrier complementing physical exclusion by crop covers.

Biological Control Agents

Beneficial nematodes and entomopathogenic fungi target rootworm larvae in soil. Using crop covers can reduce adult populations while encouraging natural enemies to flourish beneath the protected canopy.

Targeted Insecticide Use

When necessary, apply insecticides judiciously based on scouting data rather than prophylactically. Crop covers reduce overall pest pressure, potentially lowering chemical input needs.

Challenges and Considerations When Using Crop Covers for Rootworm Control

While promising, using crop covers has limitations:

Labor Intensity

Installing and removing row covers over large acreages requires significant labor investment.

Cost of Materials

High-quality fabrics may be expensive upfront but can pay off through yield preservation and reduced pesticide costs.

Potential Impact on Pollination

Corn is wind-pollinated; if row covers are left too long or tightly sealed after tasseling begins, pollination may be impaired resulting in poor kernel development.

Heat Stress Risks

In hot climates or seasons, covers might increase temperature under fabric leading to plant stress unless breathable materials are used.

Limited Larval Control

Crop covers primarily prevent adult egg-laying but do not affect larvae already present in soil; thus timing is critical for success.

Case Studies: Success Stories Using Crop Covers Against Rootworm

Several growers have reported success using crop covers:

A Midwestern US farm implemented floating row covers immediately post-emergence resulting in a 70% reduction in root damage compared to uncovered controls.
An organic farmer combined cover cropping with row covers achieving effective control without pesticides while maintaining yields comparable to conventional fields.

These real-world examples highlight how crop covers can be an effective tool when properly managed.

Best Practices Summary for Using Crop Covers Against Rootworm

Choose a UV-stabilized fabric with <0.6 mm mesh size.
Apply immediately after seedling emergence.
Secure edges tightly by burying or weighing down.
Monitor regularly for damage or gaps.
Remove before tasseling to ensure pollination.
Combine with other IPM practices like crop rotation and resistant varieties.
Avoid excessive heat buildup by selecting breathable materials.
Be prepared for initial labor investment but consider long-term benefits.

Conclusion

Rootworm continues to challenge corn producers worldwide by causing severe economic losses if left unmanaged. Employing crop covers presents an environmentally friendly physical barrier that prevents adult beetles from laying eggs on roots, thereby disrupting their lifecycle early on. While not a silver bullet solution alone, integrating crop covers with other sustainable practices like crop rotation and biological controls forms a holistic approach that enhances overall pest management success.

By carefully selecting materials, timing application correctly, monitoring conditions beneath covers, and combining strategies within an IPM framework, farmers can effectively use crop covers against rootworm while promoting healthier crops and reducing reliance on chemical pesticides. As agricultural technology advances and sustainability becomes paramount, innovative pest control methods like crop covering will play an increasingly vital role in protecting global food security.