Scale Insects: All About Them And How To Get Rid Of Them

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Ew, scale insects! Whether flat against leaves or fruit, or lumpy bumps on branches or stems, this widespread superfamily of insects is well over 8000 species strong. Many of them are agricultural pests, while others prey on trees or other plant life.

But they’re all sap-sucking invaders who can spread a wide variety of plant diseases, and nobody wants to discover them on their plants! Today, we’ll go over a variety of these insects, and I’ll tell you how to get them out and keep them out of your green spaces.

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Organic Products To Kill Scale Insects:

Environmental Products to Kill Scale Insects:

Prevention Options For Scale Insects:

Scale Insect Overview

Common Name(s) Scale insects, scale pests, scales, mealybugs, soft scales, armored scales, cottony cushioned scales, coffee scales, tea scales, tortoise scales, euonymus scales, wax scales, ground pearls, felt scales, cochineal, kermes, and thousands of other names
Scientific Name(s) Over 8000 species with unique names
Family Coccoidea superfamily, multiple families of insects beneath that
Origin Worldwide
Plants Affected Most food crops, ornamental plants, trees, and grasses
Common Remedies Horticultural oils, neem oil, AzaMax and other azdirachtin products, Safer Soap and other insecticidal soaps, beneficial predatory insects like lacewings and ladybugs, diatomaceous earth and Tanglefoot Tangle-Trap to keep ants away from the scale insects

Types Of Scale Insects

There are about 8,000 types of scale insects. All of these fall into the superfamily Coccoidea, but are subdivided from there into smaller family groups. Let’s go over some of the most prominent types of scale bugs and talk a bit about their similarities and differences.

Coccidae, ‘Soft Scales’, ‘Tortoise Scales’, ‘Wax Scales’

Coccidae 'Pink Wax Scale'
Coccidae, ‘Pink Wax Scale’. Source: treegrow

The coccidae are a family of scale insects that often produce a waxy coating. This coating can protect them against many forms of insecticide, although any oily insecticide will likely stay on long enough to have effect.

One of the best-known in this family is Coccus viridis, also known as coffee scale or green scale. Coffee scale is a major agricultural pest in coffee crops.

Other species of wax scales include tree dwellers like the cottony maple scale (Pulvinaria innumerabilis) or the calico scale (Eulecanium cerasorum). These scales flatten themselves against tree branches to feed.

Psuedococcidae, ‘Mealybugs’

Psuedococcidae 'Mealybug'
Psuedococcidae or ‘Mealybug’. Source: davidshort

While most people don’t realize that mealybugs are a form of scale, they are. Unlike most scale, they have legs, but they seldom if ever move once they’ve located a good feeding spot. Mealybugs are common greenhouse scale pests.

Widespread throughout agricultural areas, they also attack many commercial crops.

Diaspididae, ‘Armored Scales’

Diaspididae 'Armored Scale'
Diaspididae or ‘Armored Scale’. Source: Mollivan Jon

Over 2650 species of armored scale pests exist. Needless to say, these scales have an armor-like coating which they use to protect themselves from predators or insecticidal sprays.

One of the most stubborn examples of an armored scale is the San Jose scale, Quadraspidiotus perniciosus. This agricultural pest is widespread throughout the United States. While it was documented in the late 1800’s in San Jose, it originates from China.

In 1914, the San Jose scale was the first documented scale pest to develop resistance to insecticides.

Another major agricultural pest is the California Red Scale, Aonidiella aurantii. While its primary target is citrus trees, it also feeds on olives and other fruit, and can be found on some vegetables such as pumpkin.

Margarodidae, ‘Ground Pearls’, ‘Cottony Cushioned Scales’

Margarodidae 'Icerya purchasi' or 'cottony cushioned scale'
Margarodidae ‘Icerya purchasi’ or ‘cottony cushioned scale’. Source: gailhampshire

Ground pearls are strange-looking large scale insects. Many of them appear to be cottony or soft. Others look almost berry-like in their shape and coloration, such as the Armenian cochineal. They are larger than most other forms of scale, mostly because of their cottony exterior.

The photo above shows a variety of this scale with some ants on it, harvesting the honeydew which the scales provide.

Eriococcidae, ‘Felt Scales’

Eriococcidae sapsuckers farmed by ants
Eriococcidae ‘sapsuckers’ being farmed by ants. Source: John Tann

One excellent example of the Eriococcidae is the wooly beech scale, Cryptococcus fagisuga. These scales look more like lumps or bumps on a plant’s stem or branches, and can be mistaken for buds on the branch. Sapsuckers and other related scales are at risk from birds and beneficial predators like ladybugs.

Cochineal and Kermes (Dactylopiidae and Kermes)

Cochineal Scale Insect
Cochineal, a scale insect which is used to create a red dye. Source: Sandra-Photographie

These two types of scale insects need to be mentioned simply because they’re considered to be valuable!

Both cochineal bugs and kermes bugs are used to create natural red dyes.

Cochineal is the better known of the two. Native to South America and desert southwest regions of the United States, American cochineal lives on cacti. The dye produced from these scale insects is widely in use today as carmine.

It’s a primary colorant in lipstick, food products, and for some clothing items. Because of this, cochineal bugs are actually farmed as a viable dye source, especially in Peru.

Kermes is a lesser-known scale insect used to produce dye. Living on the sap of evergreen oak trees, this scale insect does not grow as large as cochineal insect colonies do. It is less commercially viable as a dye source, but creates a vibrant scarlet color when used.

There are a couple species of the Margarodidae scale family that also are used as red dye insects, although they are less plentiful and are seldom used now.

All About Scale Insects

Now that you have an inkling of the diversity of this persnickety pest, let’s go over their life cycles. We’ll also cover where they’re most likely to be found, and some information about their preferred plants.

Life Cycle of Scale Insects

Scale on oleander
Scale insects on oleander. Source: Scot Nelson

Most scales do not move once they’re adults, so the female will lay her eggs beneath her protective external coating. Over the space of 1-3 weeks, these scale eggs will hatch into a form that’s called a crawler.

These tiny larval crawlers will move away from their parent. Sometimes they will be caught and blown to other plants by the wind, and at other times they will simply move to a different portion of the same plant.

Once they’ve found a suitable place, the remainder of the scale’s life will be lived attached in that spot. Most species of scale lose their larval legs as they mature, and they feed on the plant’s sap.

Some forms produce honeydew, a sticky secretion that draws ants or fungal diseases to the plant.

Some varieties of male scale insects have wings, but they aren’t strong fliers. Instead, the wings are used to help guide the male if it’s caught and pulled from its plant in the wind.

However, the specifics of gender greatly vary amongst scale insects. Many are hermaphroditic, and those which do have gender may reproduce asexually as well as with fertilization.

Common Habitats for Scale Insects

Cochineal Scale
Cochineal scale on cactus pad. Source: The Marmot

The majority of adult scales are immobile and permanently attached to their desired host plant. However, the variety of plants is extremely wide.

There are scales like euonymus scales which prefer a specific type of evergreen tree but will as easily attack holly, ivy, and other evergreen plants, and those will be found around those plants. 

Other scales, like the cochineal shown above, will form colonies on large cactus plants. Widespread on prickly pear plants in the southwestern United States, these scales look like whitish deposits across the surface of the cactus pad.

Some forms of scale are extremely flat and hard to identify. If you see what appears to be a whitish coating on the underside of a plant leaf, you may have discovered a form of scale.

There is some correlation between the type of scale and its favored plant, but it’s not universal.

Still, armored scales tend to be more prevalent on harder plants such as trees or thick-branched foliage. Soft scales are usually on stems or leaves of ferns or other softer plant material.

What Do Scale Insects Eat?

Scale on persimmon tree
Heavy scale infestation on persimmon tree. Source: coniferconifer

All scale insects feed on the sap or plant juices of their host plant.

However, the range of plants affected is extremely wide. Some species prefer fruiting trees like orange, olive, or lemon. But there are species which attack a wide variety of bromeliads, flowering plants like roses, or even fruit and vegetable plants such as brassicas or beans.

Scale bugs can be found indoors or outdoors. Finding scale inside generally means that you brought an infested plant indoors. Spread of scale insects to other houseplants is a common risk, so you should be attentive to your indoor plants.

A plant which is suffering from scale infestation may show signs of drooping or yellowing. Whitish or yellowish patches on leaves, stems, or branches is a common sign. If not treated, your plants are at risk of numerous plant diseases or death.

How To Get Rid Of Scale Insects

Scale colony on leaf
Scale colony on leaf. Source: Scot Nelson

Now that you know what the scale pest is capable of, let’s go over some ways of getting rid of them. They can be tricky to combat, because it depends on which type of scales you have.

Soft scales secrete large amounts of honeydew, which can cause the growth of sooty mold. These scales tend to be harder to spot on plants, and can be hard to treat.

Armored scales do not secrete honeydew, so mold growth is far less likely around them. They are a bit more noticeable, but their exterior tends to protect them from some insecticidal measures.

Mealybugs tend to be the easiest to control, as they have no waxy coating nor hard exterior to protect them. However, they do reproduce quickly and can quickly become a problem.

Let’s go over some options for each type of scale now!

Organic Scale Insect Control

Scale insect on leaf
Scale insect on leaf. Source: Mick E. Talbot

Smother the scales. Scale insects may be resistant to some pesticides, but they can’t live if they can’t breathe. Regular applications of a horticultural oil such as Bonide All-Seasons Horticultural and Dormant Oil will help.

Cover all plant surfaces with the oil in an even layer, and all life phases of scales will suffocate.

Neem oil is a godsend. Not only does the oil coat like a horticultural oil, but it naturally contains azdirachtin, which will slowly poison most soft scales and mealybugs. You can use it on armored scales as well, but it will work like a horticultural oil in that usage.

As a last resort, a much stronger azdirachtin product may help tip the scales in your favor (so to speak). Try using a product like AzaMax, which is derived from neem oil naturally, inside greenhouses or indoor growing areas. Even better, it works against spider mites, aphids, leafhoppers, and other pests too!

Environmental Scale Insect Control

Wash your plants. This sounds a bit strange, but sometimes you can rub scales off of the leaves or stems/branches with no more than water and your hands.

If they’re particularly stubborn, use an insecticidal soap such as Safer Soap to try to loosen the scale the day before, and then try again. This is particularly useful in smaller infestations.

Invite in beneficial insects that eat the crawler stage. Both ladybugs and lacewings find the scale larvae quite tasty. Some species of birds will peck off adult armored scales, but they’re less likely to stick around than beneficial insects are.

Preventing Scale Insects

Ants tending scale insects
Ants tending scale insects. Source: S. Rae

If you see a few scale pests, dab them with alcohol. Use a cotton swab and coat them thoroughly. Alcohol will dehydrate the pests and cause them to come off the plant.

If you do this whenever you first notice them, and follow up with horticultural oil, you likely will not have major outbreaks.

Catch the problem early. Be attentive to your plants and you won’t have to go to war with scale pests.

Prune any infested branches and destroy them. If you find a single branch of a tree or bush that is infested with scale, carefully prune it away and get rid of it before they can spread. Spray down the plant thoroughly with a horticultural oil or neem oil to finish the job.

Finally, ants farm soft scale insects. Honeydew, the sticky, sweet secretion that soft scales exude, is a favorite food of some species of ants. Those ants will protect the source of their honeydew.

You can find a fascinating description of the process through the Ask A Biologist page of Arizona State University at this website.

To reduce the farming of scales, aphids, or other honeydew-producing pests by ants, you can use Tanglefoot Tangle-Trap around the trunks of trees or the base of rigid plants. The sticky surface will catch ants and prevent them from getting into the tree to protect other pests.

You can also place diatomaceous earth around the base of softer-stemmed plants and dust it on all the plant surfaces. A little ring of diatomaceous earth will deter ants from coming near. The dusting over the tops and bottoms of leaves and along the stems will deter scales from taking up residence.

Scale on plant stem
Scale insect on plant stem. Source: Mick E. Talbot

Frequently Asked Questions

Q: Can scale insects fly?

A: … sort of. While some male scale pests do have wings, they are vestigial at best. They’re not very strong fliers. In calm conditions (such as inside a greenhouse), you might see a few wobbly flying pests around your plants, but they’re just as likely to be whiteflies.

The females and hermaphroditic scales don’t fly, and spreading of the pest is generally done when they’re in their larval crawler stage.

Q: If I scrape off scale, will it get back on my plant?

A: What you scrape off will not climb back up, because once it’s attached to a leaf, the scale pest is fixed in place for the rest of its lifespan. However, tiny little crawlers may still be on the plant.

If you opt to scrape scale from your leaves, stems, branches or trunks, be sure to follow up with a thorough spraying of horticultural oil.


Are you ready to take on the scale infestation in your yard? What plants have you had to defend from the scale bugs, and what’s your favorite method to combat them? Tell me in the comments!


The Green Thumbs Behind This Article:


Lorin Nielsen
Lifetime Gardener

Kevin Espiritu
Founder

Are your plants yellowing or losing leaves? Do you have sooty mold growing on them? You may have scale insects. Learn how to wipe them out with our pest guide!
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28 thoughts on “Scale Insects: All About Them And How To Get Rid Of Them”

  1. I received a beautiful big cactus as a gift and I noticed it has a scale infestation. I believe it’s the hard shell scales. I’m scraping them off since I can’t remove a part of this cactus.. if I spray my cactus off with water and there’s some remaining scales that fall in the soil, will they survive in the soil or should I just keep wiping them off before spraying it?

    • They won’t survive in the soil as scale adheres to a specific location and sucks on the sap. They wouldn’t be able to climb back up and would likely die due to lack of food/water before they could recover.

  2. You mention pruning back and removing as much plant material covered by the scale as possible and destroying the affected plant matter. Would you put that in the compost? Or how would you destroying it? Thanks for the great advice. My bay and fig trees have been badly impacted.

    • Scale insects are easy to spot. You’ll know when they’re gone because you won’t see them on your plants anymore. For some types like mealybugs, you’ll also notice that the fluffy or web-like white material that they expel is also missing!

    • If you’re growing your bay laurel as a shrub or a tree, you may want to consider spraying it with horticultural oil. I recommend Bonide All-Seasons Horticultural and Dormant Oil for that purpose. Neem oil may also work well for you.

      As for whether freezing weather will kill it, the bay laurel is typically found in Mediterranean environments. Your plant may need some protection from cold weather if it’s small. Tree-sized older plants should have developed some natural protection from the cold, but young plants are at risk.

  3. You can add hydrangeas to the list of plants that can be victimized by scale insects.

    I planted a Limelight hydrangea in 2010. I have always pruned it back a third in October, when the huge blooms are perfect for bouquets lasting through our long and bleak Minnesota winters. The shrub has done beautifully, growing to eight feet in height, until this year.

    It’s in a location where it gets quite a bit of runoff from the neighboring yard when it rains heavily. This has been good for both the shrub and my water bill for eight years, but this year spring was unusually rainy, doubtless making the soil sodden and the Limelight susceptible to scale. In June, I discovered three stems with withered leaves. These were stems I had pruned last fall

    The poor shrub struggled mightily over the summer, sending up brand-new stems from under the main stems. (There are three main stems, but only two were affected.) Surprisingly, the shrub didn’t look half bad by the time I got a diagnosis of scale from the University of Minnesota Extension Division. With this excellent article, I was able to identify the insect as armored scale and learn how to get rid of it. Thanks, Kevin!

    This week I removed every single leaf in sight, cut the shrub back severely (halfway) and sprayed it top to bottom with enough All-Seasons Bonide horticultural oil to float a brick.

    Here’s how the scale progressed over the course of several weeks: It started with the leaf edges of the leaves crinkling, then proceeding to deteriorate until the entire leaf was distorted. On the stems, the armored scale first showed as slightly raised beige bumps that almost matched the stem in color; over time these got larger and turned white. In the final stage, the bumps became bigger and an appropriate deathly black.

    I have a second hydrangea, a tree-form Vanilla Strawberry only 25 feet away from the Limelight. I planted it this year, in early June. I had planned to wait until spring to prune it so as to enjoy seeing the snow-capped blooms from my living room window over the winter months. Now I’m wondering if it might have “caught” scale from tiny larval crawlers swept off the Limelight by the wind. I’ve examined it, but it’s hard to tell. Guess I’ll just have to keep a close eye on it.

    • There’s a whole host of plants that can be victimized by various scale insects, and unfortunately hydrangeas are one of many. They’re insidious little things! The only thing you can really do is to be watchful and treat when necessary.

  4. Thank you for all the information! Currently I am dealing with a soft scales infestation on my bonsai mistletoe fig. It’s a favorite plant of mine and I believe the scales came from an orchid I put next to it a few months ago. I don’t notice any scales on the orchid but I only recall noticing sticky honeydew on my fig after the introduction of the orchid unless scales are dormant on the fig and suddenly have another cycle of growth? In any case the fig was starting to drop a few leaves and I decided to treat with neem oil. In a matter of days most of the leaves and figs dropped. I now have basically a branch. Was this due to the use of the neem oil? Do you think my fig will have new growth? I need to treat with neem oil again but I’m afraid it may kill the little green new growth that is left. Any advice would be greatly appreciated!

  5. Will a product like Azamax work as a systemic solution to scale? I’m wondering if I can use it on my plants which have no, low, and medium levels of scale—topically every 5 days and systemically, via soil, every 10 days. Would this be a good way to guarantee killing the scale, even the adult ones?

    • It really depends on the plant in question as to how well it would work as a systemic option. However, it wouldn’t hurt to try it!

      Using it topically every 5 days should be more effective as a general rule, as the plant’s less likely to develop further scale issues if there’s regular treatment of the leaf and stem surfaces.

  6. We recently removed a shrub from our flower bed that was heavily infested with scale that I had tried, unsuccessfully, to treat for a few years. My question is, should we remove all of the mulch that was underneath or wait a while to plant something in its place or is it safe to plant something now? My fear is that the ground and area around it will be infested with scale.

    • Scale insects often do not move much when adults, but their larvae can. Still, if the scale is on the ground, it’s very unlikely that it will be able to make its way back up into new plants. It’s likely going to be safe to replant.

      Having said that, if you’re ever in doubt, clear it out. Removing and replacing the old mulch isn’t a bad idea if you ever have any concerns about whether it’s harboring pests. It should be able to be composted down over time, or you can simply dispose of it in your yard waste bin or trashcan.

  7. We have scale insect in Ethiopia which is much sever on the cactus
    I can send you the pictures and videos if you want.
    What is the solution for big scale infestation according to you?

  8. I have a majesty palm infected with about 100 scale insects. If I scratch them off but do not spray the plant with a horticultural oil, will the plant be hurt?

    In other words, does the horticultural oil heal the plant from the little holes the scale insects created?

    Thank you for the nice article! I have it saved to my bookmarks.

  9. Dear Kevin

    Your article has brought very useful information to me to combat this pest. I started hydroponics cultivation on a small scale 2 years ago. Each time my tomatoes and pepper plants got infected by scales and other insects and i had to destroy all the plants. Last week i applied alcohol on the scales and it seems to be working. Now i have more information on this insects and thanks a lot.

    From Mauritius

  10. Thanks for a very comprehensive article with good solutions. I’ve been dealing with scale on houseplants in my apartment, so spraying is somewhat difficult. I’ve tried Safer Soap, but the scale eventually comes back. It’s on oxalis and some succulents. Do you have a picture of the crawlers? I’m wondering what they look like.

    • I don’t have any of the crawlers available, but search around Google and you should be able to find some. Sorry to hear you have them – when I dealt with them they made my life hell!

  11. Thanks for the great in-depth article! Scale insects are subtle pests that can sneak up on you. I had a window garden with Phaelanopsis orchids and some of them seemed to be losing leaves. On closer inspection, there were thousands of scale insects under the leaves! I took the time to wash them off that time (using a Q-tip to dislodge them), but it was only a temporary fix since I’m sure larvae were in the orchid bark and around the roots, too. I washed them a few more times over the next few months. I had to discard many of them. My advice is to really take a close look at your plants on a regular basis. Pests make a living from hiding and they are very good at it! I believe the scale insects were brought in on orchids that were passed to me from friends after their flowers faded. Years later, I had a bay tree (Laurus nobilis) in a pot in the greenhouse that I neglected to pay much attention to. When I was cleaning up in the fall, I discovered it was covered in soft scale insects, top to bottom! Nothing else in the greenhouse had this particular scale, luckily. I isolated it out of doors and let the freezing weather kill the scale.

    • Constant daily scanning is the only way to get rid of pests, I agree. But a lot of the times life can get in the way and we can miss the little clues that our plants are being infested! Happened to me many a time 🙂

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