Weevils are destructive pests that feed on plant roots, stems, and stored produce. Their larvae damage crops from within, while adults chew holes in leaves and seeds. This makes them tough to control with simple contact sprays. Using the right insecticide — preferably one that penetrates deeply or acts systemically — can make all the difference.

Effective weevil control often requires a two‑pronged approach: targeting both larvae in the soil and adults on foliage. Systemic insecticides, soil drenches, and residual sprays are commonly used in combination with good sanitation practices. By choosing the right product and application method, you can break the weevil lifecycle and protect your plants long-term.

Below are 10 of the top insecticides for managing weevils, along with application strategies, buyer guidance, and frequently asked questions.

10 Best Insecticides For Weevil Control

1. Imidacloprid Granules — Superior for Soil Application

Imidacloprid is a systemic neonicotinoid that is easily taken up through plant roots and provides sustained protection. When applied as granules around the base of plants, it targets root-feeding weevil larvae effectively.

Because of its long residual action, it is well suited for perennials, shrubs, and fruit trees, reducing the need for frequent reapplication. The systemic nature ensures that pests feeding anywhere on the plant will ingest the active ingredient.

Be careful with application rates — overuse can harm non-target insects such as pollinators. Rotate with other modes of action to reduce resistance risk and integrate with cultural controls like mulching and soil disturbance.

2. Thiamethoxam — Excellent for Soil and Foliar Use

Thiamethoxam moves through the plant’s vascular system, making it effective for both soil-drenched seedlings and foliar applications on mature plants. It targets weevil larvae in the soil and adults feeding on leaves.

Its mobility within the plant ensures that even hidden stages ingest the insecticide. In many commercial and garden settings, thiamethoxam reliably reduces weevil populations.

Always follow label instructions and observe rotation schedules to minimize resistance. As with other systemic insecticides, integrating with other practices (e.g., hand-picking, barriers) increases control efficacy.

3. Dinotefuran — Fast-Acting for Quick Adult Knockdown

Dinotefuran is a potent neonicotinoid that provides rapid knockdown when adults ingest treated tissue. Its systemic action ensures hidden weevils are also affected.

Use as a soil drench or foliar spray to deliver the insecticide into the plant’s vascular system. This helps reach early instar larvae and adult weevils on foliage.

Because of its effectiveness, use dinotefuran responsibly. Rotate with other active ingredients to prevent resistance development, and always wear protective gear during application.

4. Spinosad — Best for Organic or Reduced‑Risk Programs

Spinosad, derived from naturally occurring bacteria, is effective against many weevil species. It works both on contact and when ingested, making it a versatile choice.

You can apply spinosad as a foliar spray or soil drench. While it doesn’t translocate as strongly as systemic options, it still provides reliable control, especially for smaller infestations.

Because it’s reduced-risk, spinosad is more compatible with beneficial insects when used properly. Follow label directions, and consider combining it with mechanical methods such as hand removal or trap cropping.

5. Bifenthrin — Best for Long-Lasting Residual Control

Bifenthrin is a pyrethroid insecticide with strong residual activity on soil and foliage. It’s particularly effective for weevil larvae that live in the soil surface and adults that feed on leaves.

Apply as a soil treatment or foliar spray, ensuring thorough coverage of leaf undersides and the soil surface. The residual effect can last several weeks, helping prevent re-infestation.

Because it is broad-spectrum, bifenthrin can impact non-target species, including beneficial insects. Use it judiciously and as part of a rotation program rather than relying on it exclusively.

6. Chlorantraniliprole — Ideal for Targeted Action

Chlorantraniliprole is an anthranilic diamide insecticide that is effective against many larval weevil species. It targets insect muscles, causing feeding cessation and mortality.

It can be used as a soil drench or a foliar spray, depending on the product formulation. Its systemic-like movement makes it useful for suppressing larvae and adults.

Because of its selective mode of action, it has lower toxicity to many beneficial insects. Use as part of an IPM plan, and rotate with other classes to maintain effectiveness.

7. Metarhizium anisopliae — Natural Biological Control

Metarhizium anisopliae is a fungal biocontrol agent that infects weevils on contact and gradually kills them from within. It works well in soil applications targeting larvae.

Apply as a soil drench or incorporate into compost or potting mix. Once in the environment, the fungus can persist under favorable conditions, helping maintain long-term suppression.

Because it’s a biological control, it’s safer for beneficial insects and the environment. However, it may act more slowly than chemical insecticides and works best when combined with other control tactics.

8. Neem Oil (Azadirachtin) — Broad-Spectrum Reduced-Risk Option

Neem oil, containing azadirachtin, interferes with insect development and feeding. While not strongly systemic, it offers a reduced-risk option for both larvae and adult weevils.

Spray neem oil on leaves and soil, targeting weevil adults and larvae near the surface. Multiple applications may be needed as neem oil degrades relatively quickly.

Neem is more compatible with beneficial insects than many synthetic insecticides. Use it in rotation and integrate with non-chemical controls for optimal results.

9. Carbaryl — Classic Choice for Serious Infestations

Carbaryl (Sevin) is a broad-spectrum carbamate insecticide that affects many weevil species. It is effective on contact and ingestion, though it has limited systemic action.

Use as a foliar spray where contact with adults is likely, or on soil where larvae are present. Ensure thorough coverage for maximum effect.

Because of its broad-spectrum action, carbaryl can harm beneficial organisms. Use it judiciously, and follow all safety instructions. Rotate with other insecticide classes when possible.

10. Soil-Applied Systemic Granules (Mixed Active) — Best for Long-Term Landscape Protection

Some granular products combine systemic insecticides with other actives to deliver long-lasting control — especially useful for perennial plants, shrubs, and trees.

Apply granules around the root zone, water them into the soil, and let the plant absorb the active ingredient over time. This method protects against both root-dwelling larvae and above-ground adults.

Use as part of a comprehensive IPM plan. Monitor application rates, and avoid overuse to preserve efficacy and minimize environmental risks.

6 Buyer’s Tips for Choosing Weevil Insecticides

• Identify the weevil species (adult vs. larval stage) — this influences which product works best.
• Select an active ingredient labeled specifically for weevils and for your plant type.
• Use a combination of treatments: soil drenches for larvae, foliar sprays for adults.
• Rotate between modes of action to prevent resistance build-up.
• Always follow label instructions for safe and proper application.
• Incorporate cultural controls — sanitation, removing infested material, and monitoring — for long-term suppression.

6 Frequently Asked Questions

1. Can I use systemic insecticides for both adult and larval weevils?

Yes — systemics applied via soil drench can reach root-dwelling larvae, while foliar systemic or residual sprays affect adults.

2. Are biological controls effective against weevils?

They can be, especially fungal agents like Metarhizium anisopliae, but results may be slower than chemical treatments.

3. Will insecticides harm beneficial insects?

Potentially, yes — use selective or reduced-risk options and apply when pollinators are less active.

4. How often should I reapply insecticides?

Follow label guidelines — some soil systemics last for weeks, while contact sprays may need reapplication every 7–14 days.

5. Can I use insecticides on food crops with weevil problems?

Some products are labeled for edible plants — check pre-harvest intervals and usage restrictions.

6. Is resistance a concern with weevil insecticides?

Yes, rotating between different modes of action is critical to managing resistance risk.

Conclusion

Weevil control is most effective when you target both larvae in the soil and adults feeding on foliage. Products like imidacloprid, thiamethoxam, dinotefuran, and biocontrol agents like Metarhizium offer powerful tools for suppression.

Use soil drenches, foliar sprays, and reduced-risk options as part of an integrated pest management (IPM) strategy. Monitoring, sanitation, and resistance management are key for long-term success.

By choosing the right insecticide and applying it smartly — and rotating your modes of action — you can significantly reduce weevil damage and protect your plants for seasons to come.