Scale Insects on Plants – Removing Scale Bugs On Plants Indoors and Out

Scale insects have piercing/sucking mouthparts and are found all over the world. There are about 8000 distinct forms of plant scale, and they, like aphids and spider mites, prey on a wide variety of plants, shrubs, and trees. They are visible as slightly elevated bumps in the stems, twigs, branches, and foliage of all plant life. They can be difficult to see since, as adults, they do not move.

Instead, they carefully conceal themselves under camouflaged waxy structures that fit in with the host plant. These insects get their name from their scale cover, which is a waxy shell. Adult bugs produce a waxy substance and build a shell or shelter to protect themselves from predators, the environment, and most insect control methods. In this post, we’ll look at the many varieties of scale insects and give information to assist you identify and deal with them.

Here are some short methods for treating plant scale.

What Does Scale Look Like On Plants?

There are various varieties of scale insects, including armoured scale and soft scale. For the most part, the scale coverings protect both species. The scale is a protective layer with a texture that ranges from firm and smooth to moderately flexible to soft and cottony. Plant scales are commonly brown in colour, although they can also be black, dark red, white, yellow, pink, grey, green, or glassy and translucent.

Black scale insects on dracaena
Black scale insects on dracaena Credit: Secretlondon, via Wikimedia Commons

Fluffy or woolly scale insects are native to Australia. They are somewhat bigger than the other varieties and stand out due to their fluffy, white scale structures.

Scale Insect Size, Appearance, and Behaviour

Soft Scale Insects

Soft scale insects range in length from 1/8 to 1/4 inch. They feed on the phloem tissue of plants. A plant’s vascular tissue is crucial for transporting metabolic products such as glucose from the leaves throughout the plant. Soft scale insects drain surplus sap from the phloem to form honeydew, a delicious, sticky liquid. This fluid and the insects it attracts can be seen on the leaves and stems of a pest-infested shrub, plant, or tree. Take a deeper look if you discover your plant’s leaves are glued together and it is crawling with flies, wasps, and/or ants.

The soft scale not only provides a hiding area for adult insects, but it also serves as a safe place for female insects to deposit eggs. During the initial development stage, the crawlers normally migrate out onto the host plant and feed on the leaf. During the second stage, the nymphs return to the plant’s branches and twigs to complete developing and construct their protective scales. Soft scale insects have legs and can move around, but only very slowly. Female scale insects of both types mate with males with wings when completely developed. Males are extremely elusive, and you are unlikely to ever see one. Female insects deposit eggs behind their protective scales after mating and then die. Soft scale insects can survive the winter as adults or as nymphs.

Armoured Scale Insects

While soft scale insects produce honeydew, armoured scale insects do not. Armoured scale insects are somewhat smaller than their soft scale insect cousins. These bugs are generally long and spherical in shape. They do not feed on the plant’s phloem. Instead, they consume individual plant cells. Armoured scale insects are difficult to identify due to their small size and excellent camouflage abilities. Their stiff shells typically mimic the host plant’s surface. They can go unnoticed until they get completely entrenched and the plant suffers.

Armoured scales go to new plant tissues as crawlers and settle down to consume and grow their scale covers. They seldom wander far, and their shelters are usually located fairly close to the parent scale. When scale crawlers arrive at a suitable location, they settle in and construct a waxy shell to protect themselves. After this, the armoured scale variant loses its legs and becomes immobile. They spend the remainder of their brief lives in the same location. Adults and armoured scale crawlers do not do this. Instead, the eggs overwinter beneath the mother insect’s protective shell. It is critical to understand the differences in these organisms’ overwintering behaviour, as well as the timing of the nymph stages of both species. This knowledge is useful in determining how to effectively control and remove pests.

Stop The Crawlers Before They Spread!

To maximize the effectiveness of your eradication efforts, determine the type of scale bug you have and trap it during the crawler stage. You’ll want to catch them as soon as they emerge from the parent scale. Be aware that in addition to moving around on their own, the wind can carry them onto nearby plants. They may also hitchhike on the feet of birds or other sorts of animals travelling from tree to tree.

What Does Damage From Plant Scale Look Like?

If allowed to stay in place for more than one season, a scale infestation can spread very quickly. It is possible for these pests to cover a plant before you notice their presence entirely. You may not see the damage done to the plant until the population level is nearly out of control. When this happens, you will notice some signs of plant illness, along with the physical presence of the pests.

Dead Branches:

Armoured scale insects typically cause more damage than soft scaled insects. The hard-scaled type feeds on plant tissues, destroying individual cells. The loss of the cells affects the plant’s capacity to transfer materials throughout its limbs, resulting in the death of entire branches. If you find plant branches decaying, an armoured scale insect infestation is likely. A heavy infestation might kill the plant.

Leaf Discoloration and Loss:

Armored scales not only feed on individual cells in plant and tree stems and limbs, they may also consume the leaves. When this occurs, the leaves may become yellow or purple. It can be difficult to discern if this damage is caused by hard scale insects because many other species of insects create similar damage.

Clusters of Scales:

When clusters of hard scales of armoured scale insects are observed, they are likely to be both old, abandoned scales and fresh scales from active insects. Both may be removed with a dull blade or your fingernail. The old scales will simply scrape off, but the newer ones may be more difficult to remove. Both varieties leave a white, waxy residue.

Honeydew and Sooty Mold:

Honeydew on a plant infested with soft scale insects should alert you to their existence. Soft scale insects can also produce sooty mould. Plants are not harmed by the mould, but they are unattractive.

Large Dead Zones:

A severe soft scale infestation will result in individual limb damage before reaching a plant’s or tree’s leaves. Soft scale insects induce branch tip dieback and leaf distortion in addition to limb loss. In a bad infestation, large sections of a tree canopy can be affected.

How Can You Control Scale Insects?

Organic scale insect treatment is the most effective and simple way to manage these pests. Ladybugs and parasitic wasps are beneficial insects that prey on scale insects. If you establish a favourable garden environment, you may never need to manage scale insects. When biological control against some scale pests is no longer effective, population reduction strategies must be applied.

Identification Your First Step

The first step is to identify the insect. Scale insect crawlers should be removed as soon as they appear. It is best to deal with them as soon as they hatch, while they are actively looking for feeding spots. You want to capture them before they migrate and construct their own shelters.

Monitor: Watch For Activity

Once you’ve determined the sort of scale bug, begin hunting for emerging crawlers. They may be difficult to see with the naked eye, especially against the plant’s backdrop. Consider using a magnifying glass.

Verify The Crawlers Movement

Here are a few other tricks you can use to verify the presence of crawlers:

  • Place pieces of double-sided tape on the branches of your plant, shrub or tree to trap a few crawlers when they emerge. Once you trap them, you’ll know it’s time to deal with them.
  • Hold a white paper plate or sheet of white paper under a branch and shake it. If yellow or red specks the size of a pinhead or smaller appear on the white background, it is time to treat for crawlers.
  • Check every few days during the active season of the crawler type on your plant to catch them and treat them as soon as they begin crawling. [source]

How to Get Rid of Scale Insects

With proper timing, scale insects are not difficult to eradicate. Indoors or outdoors, keep these scale insect control tips in mind:

  • Always begin with non-toxic or mildly toxic options – Neem oil or Insecticidal soap.
  • Give your plants a thorough watering before treating for scale insects or releasing predatory insects.
  • Release predatory insects at dusk after giving your plants a “foliar watering.” This will encourage the insects to stay in place, quench their thirst after traveling and provide them with a place to sleep at sundown.
  • If you release predatory insects during the day, they are likely to fly away.
  • When using chemical solutions, remember to wear protective chemical clothing and gear. This includes long sleeves and pant legs, rubber gloves, a respirator or spray mask and eye protection.
  • Avoid using chemical pesticides indoors. Doing so could have a negative impact on your pets, family members and you.

Neem Oil
Neem oil, is a pesticide extracted from the Indian neem tree. It works as an antifeedant on scale, mealybug, aphids and others. The is considered safe to plants, humans and wildlife.
Spray neem oil weekly at a rate of 2 tablespoons per gallon of water to control scale and loosen sooty mold. Apply when temperature will not exceed 80 degrees Fahrenheit.
Insecticidal Soap
Insecticidal soap has long been a pest control tool in the gardeners tool box.
A insecticidal soap solution only kills pests on contact; it has no residual action. Soap spray may damage plants, especially at higher concentrations or at temperatures above 32 °C (90 °F). [source]
For a 1 Quart Solution mix in 1 quart of water 1 tablespoon of soap. Shake well!

How To Treat Scale Insects On Houseplants

Scale insects, aphids, wooly aphids and spider mites may also invade your indoor plants. Just as with outdoor plants, vigilance and quick action help you keep them under control.
Here’s how:

  • Examine your houseplants for signs of scale insect infestation.
  • Move infested plants away from other houseplants. Plants scale travels well and can infect other plants.
  • Gently wipe and scrape scale off by hand using a soft cloth.
  • Bath the affected plant with lukewarm water and a couple of drops of dish soap or insecticidal soap or Neem oil (our recommended choice).
  • Spray the affected plant (in a shaded,well-ventilated area) using insecticidal soap or Neem oil (our recommended choice). Be sure to spray leaves and the undersides thoroughly.
  • Introduce predator insects (IPM or integrated pest management) if your indoor plants are in a sunroom or other area separate from your living area.
  • Ladybugs make a charming addition to your plant area. Ladybugs love eating scale and can help keep aphids, and spider mites under control.
  • If your ladybug population becomes too great, open the window and let some of them fly away.
  • Examine your plants regularly and keep the leaves clean to prevent re-infestation.

How To Get Rid Of Scale Insect Pest On Outdoor Plants?

The waxy coverings of the adults protect them from almost any sort of pesticide or treatment. The nymphs are a different matter.
They are vulnerable to a wide variety of pesticides, and it is easy to eradicate them with low impact pest control methods.

Sprays: Insecticidal Soap, Horticultural Oil, Neem Oil

In the springtime spray plants with insecticidal soap or a thorough spray application of horticultural oil.
Because the crawlers are so vulnerable, with the right timing, you can have significant effects with fairly benign substances such as horticultural oil (Neem oil) and insecticidal soap.
These are excellent choices because they do not leave a lingering residue.
For this reason, you can use them to do away with the immature scale insects with little impact on natural enemies of these pests.

Manually Remove Old and New Plant Scales

When you time it correctly, you can use horticultural oils and/or insecticidal soaps to do away with the crawlers and eliminate most of the scales.
Well established scale and those hatching eggs for an extended period of time may require multiple applications along with some scrubbing and scraping to remove them.

Apply A Dormant Treatment Of Horticultural Oil Spray

You can also apply a horticultural oil spray treatment during the winter to address adults and nymphs overwintering under scales.
This dormant application of oil suffocates the plant scale bugs. Dormant oil treatment will not have any effect on eggs overwinter under scales.

Treat For Every Type Of Plant Scale Bug Present

Be aware that several different types of plant scale may co-exist on your plants. This means you must be aware of the life cycle of each type of scale.
Some produce several generations annually, so you’ll need to spray more than once to succeed in controlling all of them.
For heavy infestations, spray thoroughly with horticultural oil or insecticidal soap once every couple of weeks throughout the spring and summer of a given year.
When spraying make sure to thoroughly spray and cover the leaves, stems, trunks, and undersides of leaves with the spray solution.
This should get the scale infestation under control without doing too much damage to your existing natural predators.

Increase The Population Of Natural Predators

Be sure to get a good population of natural predators in place for the next growing season. Once you eradicate a scale insect infestation, cultivate a healthy natural predator population of:
… and other predatory insects keep all sorts of juice-sucking insects under control with no interference or effort from you.
Letting nature manage your scale insects is a smart, healthy, effective way to deal with them.

Outdoor plants often “attacked” by plant scale bugs:

What About Plant Scale Insecticide Sprays?

Sometimes horticultural oils and insecticidal soaps do not give the needed control.
When horticultural oils and insecticidal soaps do not work, or you are dealing with a very severe infestation, you may wish to look into low impact insecticides available to licensed technicians. Among them are:

  • Pyriproxyfen is an insect growth regular which mimics a natural hormone in insects disrupting their growth. It affects mostly young insects and eggs.
  • Buprofezin is a growth regulator, banned in some countries, especially toxic to aquatic organisms, low toxicity to humans and other mammals.

These substances work by interfering with insect growth and are classified as IGRs (insect growth regulators). They do not affect adult scale insects, and they are relatively easy on the natural predator population.
In addition to these reasonably mild pesticides, other choices do have a residual effect. Even so, these should be applied when crawlers are most active for the greatest impact. These types of pesticides contain pyrethroids, such as:

  • Lambda-cyhalothrin an organic man-made compound used as a pesticide, a pyrethroid that mimics the naturally occurring insecticide pyrethrum which come from the flowers of chrysanthemums.
  • Permethrin a broad-spectrum chemical, it kills indiscriminately, can harm beneficial insects, including bees, and aquatic life, used in mosquito control programs.
  • Bifenthrin an insecticide used to control of red imported fire ants, highly toxic restricted use pesticide,

They also contain carbaryl and acephate. These chemicals have a residual effect that lasts up to two weeks during dry weather. Any nymphs emerging from beneath their scales during that time will be killed. Keep in mind you must reapply the product if it rains.

Malathion has long been recommended for scale pest control. However, residues of foliar broad-spectrum insecticides sprays like Malathion can last for weeks in the landscape and garden. Malathion can be highly toxic to pollinators and natural predators.

Use Of Systemic Scale Bug Insecticide

Systemic insecticides work by moving through a plant via its conductive tissues. One such product is imidacloprid, which is most useful for management of soft scale insects.
Imidacloprid is sold under trade names Kohinor, Admire, Advantage, Gaucho, Merit, Confidor, Hachikusan, Premise, Prothor, and Winner. [source]
Imidacloprid also is used to control aphids, cane beetles, thrips, stink bugs, locusts, and a variety of other insects that damage crops.
The application is to the soil surrounding the affected plant. Professionals may apply imidacloprid by injecting it into the soil or directly into the trunk of an affected tree.
Another systemic insecticide is dinotefuran, which is applied in granule form to the soil surrounding the affected plant.
Dinotefuran is sold under trade names Safari, Zylam, Alpine.
Professionals sometimes mix a solution that can be:

  • Sprayed on tree bark
  • Used as a soil drench
  • Injected into the soil

This chemical moves through the plant very quickly and thoroughly and is effective against both armored and soft scale insects.

Note: Dinotefuran is also used to control fleas, bed bugs, along with insect pests such as aphids, whiteflies, thrips, leafhopper, leafminer, sawfly, mole cricket, white grubs, lace bugs, billbugs, beetles, mealybugs, sawfly larvae, and cockroaches in leafy vegetables, in residential and commercial buildings, outdoor uses for professional turf management, turf farms, professional ornamental. [source]

Protect Your Pollinators And Natural Predator Insects!

The downside of systemic pesticides – they also kill beneficial insects.
Do not use systemic pesticides on plants attractive to bees, butterflies, ladybugs, parasitic wasps and other desirable garden dwellers.
Just as with other products, this type of pesticide must be applied when the crawlers are active.
However, apply after flowers finish blooming as this will reduce the likelihood of the pesticide negatively impacting pollinators and other positive garden fauna.
Furthermore, do not use systemic pesticides on shrubs or trees planted near flowering plants that attract bees, butterflies, and other pollinators as the substance may spread to these plants.
Always follow pesticide labels precisely. Be aware that these labels are legal documents.
Instructions on the label may change from time-to-time, and instructions found online may not match the directions on your pesticide container. Always read the pesticide label on the container in your possession and follow the instructions exactly.

When Should You Call A Professional?

When dealing with a major infestation on a tree, your best bet is to call on a professional to help you deal with scale infestation.
They have the experience needed to monitor scale insect activity and apply the right choice in product safely and effectively. Pest control professionals can save you a lot of time and the life of your tree.
A professional tree care company has access to chemicals and methods for scale insect management not available to the general public.
Quick, efficient treatment will prevent the spread of the insects.
Keep in mind, if your tree dies, you will have to remove it or have it removed, and this is not a cheap process. [source]

Smart Gardening And Plant Care Practices Discourage Scale Insects!

There are more than 3000 species of scale insects in North America.
No matter where you live or what type of plant you care for and grow, it may be attacked by scale insects at one time or another.
Following the above-recommended ways to get rid of scale insects you’ll be able to control the most common plant scales on your plants such as:

  • Cottony cushion scale
  • Amoured scale
  • Common Brown scale
  • Soft scale
  • Euonymus scale
  • Oystershell scale
  • Many or types of cochineal scale

Remember, the key to preventing any pest infestation is to keep your plants, shrubs, and trees healthy.
Understand and meet the needs of your plants. Examine and groom them regularly. Water and feed correctly. When you do this, you can prevent scale insect infestation and, indeed, an outbreak of most types of plant pests.

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