How to Get Rid of Scale on Plants

Scale insects are small sap-sucking bugs that can infest indoor and outdoor plants. They attach themselves to stems, leaves, and trunks to feed, covering themselves with a protective waxy shell that resembles fish scales. An infestation can stunt plant growth, cause leaf yellowing and drop, and even kill plants if left untreated. Getting rid of scale requires persistence and patience to break their life cycle. But with the right approach, you can eliminate scale bugs and restore plant health.

Identifying Scale Insects

The first step is learning to recognize scale insects on your plants. There are over 8000 species of scale bugs, but some of the most common on household plants include:

Soft scales – These scale insects have soft, oval bodies under their protective covers. Common soft scales are brown soft scale, cottony cushion scale, and European fruit lecanium scale. They produce large amounts of honeydew that encourages sooty mold growth.

Armored scales – Armored scales have hard, shield-like covers that don’t secrete honeydew. Look for round, flat, or elongated armored scales like oystershell, pine needle, greedy, and calico scales.

Mealybugs – Though not technically a scale, mealybugs look like fluffy white cotton and also suck plant sap.

Check the stems, undersides of leaves, branches, and trunks for bump-like scale colonies. Gently scrape scales with your fingernail – living scales will be firmly attached while dead ones come off easily. Honeydew, sooty mold, yellowing leaves, and stunted growth are also signs of an infestation.

Removing Scale by Hand

For light infestations of soft scale, you may be able to remove them manually. This works best for houseplants or small garden plants.

Tools needed:

Cotton swabs or old toothbrush
Isopropyl alcohol
Tweezers
Gardening gloves

Steps:

Dip the cotton swab in alcohol to moisten it.
Gently rub individual scales with the swab to loosen and scrape them off the plant.
Use tweezers to remove any remaining scale body parts.
Repeat daily to catch any surviving juvenile scales during their crawler stage before they can form new protective covers.

While labor intensive, this mechanical control can eliminate light scale infestations and is safe for most plants. Make sure to check all leaf undersides, branches, and stems.

Using Horticultural Oils on Plants

Horticultural oils and insecticidal oils like neem oil can smother and kill scale insects without harming most plants. The oils suffocate scales and disrupt their waxy covering.

How to apply oils:

Use pure horticultural oil and follow label diluting instructions.
Spray plants thoroughly including leaf undersides until dripping.
Apply every 1-2 weeks for 2-3 applications.
Adding a small amount of insecticidal soap helps the oil adhere and penetrate scales better.
Oils are safe for most plants except some delicate ferns and flowers. Test spray a leaf first.
Do not apply oils in direct sun or temperatures over 90°F as it may burn foliage.
Horticultural oils kill only juvenile crawler stages so repeat applications are needed to disrupt the scale lifecycle. But they offer organic control without harsh pesticides.

For severe infestations, oils may not be potent enough for complete control. But they are an eco-friendly option to try first before moving onto insecticide sprays.

Scale Insect Sprays and Systemics

While oils smother scale insects externally, systemic insecticides are absorbed by plants and kill scales from the inside out. The insecticide travels through the plant’s vascular system, poisoning scale bugs as they feed.

Some common chemical options include:

Insecticidal soaps – Potassium salts of fatty acids disrupt soft scale insect membranes. Spray plants thoroughly every 5-7 days.
Pyrethroids – Bifenthrin, cyfluthrin, lambda cyhalothrin and other pyrethroids kill on contact. But scale likely requires multiple applications a week apart.
Neonicotinoids – Systemic insecticides like imidacloprid are taken up by plants’ vascular systems and kill sucking pests for weeks or months with one application.
Horticultural oils – As mentioned above, these smother soft scales through suffocation.

Always follow label instructions carefully for dilution rates and frequency to avoid plant damage. Monitor for scale survivors and repeat treatment if needed. Rotate between insecticide classes to prevent resistance.

Ant Control for Scale Problems

Ants and scale insects have a symbiotic relationship. Not only do ants feed on the sugary honeydew secreted by soft scales, but they protect and spread scales to new growth. Controlling ants around infested plants is key for scale management.

Ant control tips:

Remove any food sources attracting ants like ripe or rotting fruit.
Apply diatomaceous earth around pot rims or garden beds to deter foraging worker ants.
Use Tanglefoot or another sticky barrier on plant stems to stop ants from climbing up.
Bait ant traps and granular baits with boric acid or hydramethylnon can also reduce ant populations over time.

Preventing ants from tending and transporting scale bugs will increase the effectiveness of your other control methods. Focus on ant elimination in combination with horticultural oils or insecticidal soaps for best results.

Natural Predators to Battle Scale

In addition to chemical sprays, biological control uses natural predators to kill scales. Lady beetles, green lacewings, and parasitic wasps all feed on scale colonies:

Ladybeetles – Both adult ladybugs and larvae devour scales greedily. Buy live ladybugs to release or attract them with companion plants.
Lacewings – Lacewing larvae are sometimes called “aphid lions” for their voracious appetites. They will also eat scale insects.
Parasitoid wasps – Tiny parasitic wasps lay eggs inside scales. When wasp larvae hatch, they consume and kill scales from inside their protective covers.

You can purchase live lady beetles, lacewing eggs, or parasitic wasps to release. Or plant pollen and nectar-rich flowers to draw these beneficial insects to your garden. Combining predators with some sprays like oils or soaps can eliminate scale without harsh pesticides. Monitor carefully and release more beneficials if needed.

Severe Infestations May Require Dormant Sprays

For severe, widespread scale infestations on trees or woody shrubs, spraying a horticultural oil or lime sulfur fungicide during dormancy may be required:

Dormant season – Late fall to early spring when plants are not actively growing is the safest time for dormant sprays.
Horticultural oils – Pure oils smother overwintering juvenile scale stages on bark and branches.
Lime sulfur – Dilute lime sulfur fungicide/insecticide also controls overwintering scale. It leaves a lingering residue to kill crawlers in spring.
Cover thoroughly – Spray all bark surfaces, branches, stems, and any remaining foliage to penetrate scales’ protective covers.
Wear protective gear – Lime sulfur can cause skin and eye damage. Wear goggles, gloves, long sleeves, pants, and boots when spraying.

While dormant sprays can seem extreme, they may offer the only chance at knocking back extensive, established scale populations to save trees and shrubs. Always follow label safety precautions.

Preventing Future Scale Infestations

Once you eliminate current scale pests, take preventive steps to avoid repeated attacks:

Inspect new plants closely – Quarantine and inspect new plants. Treat with insecticidal soap before bringing indoors.
Remove heavily infested plants – Prune off severely infested branches or remove badly infested plants to eliminate pest reservoirs.
Promote plant health – A healthy, vigorous plant can better withstand pests. Ensure optimal growing conditions.
Monitor routinely – Periodically check plants closely for signs of scale return like honeydew or sooty mold. Catch infestations early.
Encourage natural predators – Use companion plants and avoid broad-spectrum pesticides that kill beneficial insects like ladybugs that eat scale pests.

With diligent monitoring and a combination approach of mechanical removal, horticultural oils, targeted insecticides, and biological control, you can eliminate destructive scale insects and keep them from coming back.

Frequently Asked Questions About Controlling Scale Bugs

How do you get rid of scale insects organically?

Some organic options to kill scale insects include horticultural oils, neem oil, and insecticidal soap sprays. Hand removal and releasing ladybugs or parasitic wasps for biological control are also organic approaches.

What is the fastest way to get rid of scale bugs?

Systemic insecticides are absorbed by plants and can kill scale insects faster than topical sprays. Imidacloprid and other neonicotinoids provide 1-2 months of scale control with just one soil application in some cases.

How do you kill scale with alcohol?

Rubbing individual soft scales with a cotton swab dipped in 70% isopropyl alcohol can manually remove and kill them. It dissolves the waxy protective coating. Repeat daily to control light infestations.

Why do I still have scale after spraying?

It often takes multiple, thorough spray applications to penetrate the protective covers of scale insects. Their immobile life stages are resistant. Rotate between insecticidal soap, horticultural oils, and other insecticides. Target the crawler stages.

What home remedy kills scale insects?

A simple homemade 1:1 mix of isopropyl alcohol and water sprayed liberally on plants can help control soft scales. Horticultural oils made from oils like neem, cottonseed, or soybean also smother scales effectively. Insecticidal soap sprayed repeatedly can eliminate scales.

When should I spray for scale bugs?

The best time to spray is early spring just as scale crawler eggs hatch. Targeting this juvenile mobile stage before more protective covers form allows sprays to penetrate easier. Spray every 5-7 days for 2-3 weeks to kill crawlers as they emerge.

Key Takeaways on Scale Removal

Identify scale insects – Look for bump-like colonies on stems and undersides of leaves. Honeydew and sooty mold are signs of soft scales.
Remove soft scales manually – Rub with alcohol-soaked cotton swabs to dissolve protective coating on individuals.
Apply horticultural oils – These organic oils smother scales and disrupt crawlers’ waxy coverings.
Use systemic insecticides – Neonicotinoids like imidacloprid kill scale bugs for weeks or months after one plant application.
Control ants – Prevent ants from tending scales. Apply sticky barriers and use baits.
Release natural predators – Ladybugs, green lacewings, and parasitic wasps all prey on scales.
Combine treatments – Alternate oils, soaps, insecticides, and predators for most effective control.

Conclusion

Scale insects can infest indoor and outdoor plants when their populations go unchecked. Their sap-sucking damages plants while promoting sooty mold growth. But with persistence using mechanical removal, horticultural oils, targeted insecticides, biological control, and ant elimination, you can break scale’s life cycle and restore plant health. Combining multiple treatment methods often provides the best control over these challenging pests. With vigilance and prompt action at the first signs of scale bugs, you can keep them from spreading and protect your plants.