No, Scale Insects Don’t Live In Soil (Identification Guide)
Scale insects are one of the most interesting insect pests you’ll encounter in your yard. Since they don’t really look like insects, even experienced gardeners will miss their presence until plants begin to deteriorate.
If you’re trying to get rid of scale insects on your plants, you may be wondering if you should worry about the soil being infested.
Scale insects are only mobile for a couple of days after their eggs hatch. Within 2 days, many species must find a suitable plant host, insert their mouthparts to feed, and then they don’t move again. You might find scale insects crawling across the soil, but they can’t live in it!
While you don’t have to worry about your soil being infested, it is helpful to know where to look for scale insects so you can catch an infestation early.
It’s even better if you know how to identify scales so you can determine the best way to get rid of them. In this article, we’ll tell you where you’ll find scale insects, how to identify them, and what they prefer to eat.
Where Do Scale Insects Tend To Be?
There are more than 8,000 species of scale insects currently described, with new species being discovered as recently as 2022! It should come as no surprise then that they can be found in a variety of places. They can feed on just about any part of a plant from the trunk to the fruit.
If you are interested in learning more about scale, you can reference our article on Why Scale Can Spread To Other Plants. It even tells you what to do about them!
Scale Insects Love Woody Plant Parts!
Scale insects will feed on all woody parts of a plant from the tiniest twigs to the trunks of trees. Some will feed on individual plant cells, sucking out their contents and killing the cell, or tap into the phloem of the plant to feed on the nutrients it contains. Their feeding can lead to an overall decline in plant vigor, dieback of branches, and even plant death if infestations become large enough.
The San Jose scale (Quadraspidiotus perniciosus) is a major problem of fruit orchards and they are most commonly found feeding on the trunks. They will hide among the bark crevices making them even more difficult to control with pesticides. They can also feed on other parts of the trees including the fruit.
Plant Leaves Are A Buffet For Scale Insects
Many species of scale insects prefer to feed on leaves instead of woody plant parts. Most typically feed on the underside of the leaf which helps them remain undetected. Others, like the false oleander scale (Pseudaulacaspis cockerelli), will feed on the leaf surface and are easy to spot.
The feeding damage from scale insects on leaves can cause a variety of plant symptoms. Leaves may be stunted or distorted due to scales. They may also become discolored, usually turning yellow first and then brown as the plant tissue dies.
Scale Insects May Nibble On A Plant’s Fruit
Scale insects will also feed on the fruits of a plant. This has made them a major pest in fruit orchards. Even a few scales feeding on a piece of fruit will leave signs of damage making the fruit unmarketable.
Both the San Jose scale (Quadraspidiotus perniciosus) and European fruit lecanium (Parthenolecanium corni) are two serious pests of fruits in North America. They will feed on other plant parts until fruit appears then begin feeding on it. These scales can be difficult to control since they live on plants we eat which limits the types of pesticides that can be used on them.
Scale Insects Don’t Tend To Live In Soil
Scale insects actually can’t live in the soil long term. They are dependent on the sap from plants to survive. Without a plant to feed on, scale insects can only survive for a few days.
When scale insects hatch, they are known as crawlers. They have legs and eyes during this stage and can move around. Within a couple of days of hatching, they must find a suitable plant to feed on and insert their needlelike mouthparts to begin feeding.
Once they start feeding, they begin the transformation process of becoming mature adults. They will ultimately lose their legs and eyes which prevents them from moving. Due to their dependence on plants to survive, they cannot live in the soil.
How To Identify Scale Insects
It is important to determine which scale insect you are dealing with when it comes to getting rid of them. Due to their biology and life cycle, there are certain control methods that work for some groups that won’t work for others.
While scales can be extremely difficult to identify to the species level. Our hope with this guide is to give you enough information about scale insect identification so you can select the correct management strategies to get rid of them.
A useful tool for scale insect identification and scouting is a hand lens. We recommend this Illuminated Loupe Magnifier because it’s compact and has a light to improve visibility. It also has a low and high-magnification lens, comes with batteries, and has a carrying case!
Soft Scales Versus Armored Scales
Scale insects can be extremely difficult to identify down to the species level. However, most scale insects fit into one of two main groups, soft or armored.
The management techniques for soft scales don’t work as well for armored scales and vice versa. If you can at least identify whether you’re dealing with a soft scale or armored scale, you can choose the correct management techniques to get rid of them.
Two of the best characteristics to use for identification between soft and armored scales are their overall general appearance and whether or not they produce honeydew while feeding. The table below provides some of the main differences between soft scales and armored scales.
| Characteristics | Soft Scale | Armored Scale |
| Appearance | 1/4 to 1/8 inches long, round or oval in shape, dome-shaped, often white, cream, or light brown | 1/16 to 1/8 inches long, circular to elliptical in shape, slightly convex, color varies |
| Protective covering | Soft, composed of secretions that appear waxy, powdery, or cottony | Hard, composed of waste excretions |
| Protective covering attached to body | Yes | No |
| Generations per year | Usually only 1 | Usually more than 1 |
| Mobility | Females mobile until they begin laying eggs | Females immobile when once they reach maturity |
| Feeding habits | Feeds on vascular tissue that carries plant sap | Feeds on liquid from individual plant cells |
| Excretes honeydew | Yes | No |
Douglass Miller and John Davidson have a wonderful Identification Guide for Armored Scales. It has fantastic colored images and focuses only on species found in the U.S.
Now that you know the difference between soft and armored scales, you’ll need to know a little more about their general appearance so you can spot them on plants. Since scale insects are so small and cryptic, we’ll give you more details about their general appearance which will help you detect them.
Scale Insects Are Usually White, Tan, Or Brown
Scale insects are generally neutral colors such as white, tan, brown, or sometimes black. This is part of what can make them extremely difficult to detect. Detection is especially challenging when they blend in with the plant they’re feeding on.
There are a few species that have a bit more color to them. For instance, the green scale (Coccus viridis), an armored scale pest of citrus and other plants, has a pale green color to its covering. Some species can also be reddish, orangish, or yellowish in color.
Scale Insects Are Usually Circular Or Elliptical
Scale insects will have a round shape whether they’re soft or armored scales. Soft scales tend to look more plump or convex while hard scales tend to be more flattened. Either group can be perfectly circular or be an elongated oval shape.
Some scale insects can look more like a pear-shaped or oyster shell shape upon closer inspection. The oystershell scale (Lepidosaphes ulmi) is an armored scale that, as the common name suggests, looks like an oyster shell.
According to the University of Kentucky, this insect feeds on more than 130 different plant species and can cause severe plant damage… yikes!
Scale Looks Like Small Bumps On A Plant
Due to their protective covering and lack of movement, scale insects often just look like small bumps on plants. Their inconspicuous coloration is often similar to the plant tissue they feed on which also helps them blend in. They can often be confused with lenticels or galls.
Lenticels are pores and are present on woody parts of plants to allow for gas exchange. For example, prunus species such as black cherry trees have distinctive horizontal white lenticels and forsythia has raised white circular lenticels.
To determine if what you see is a lenticel or a scale insect, you can press on it with your fingernail. Scales will produce a liquid when squished whereas lenticels won’t. Similarly, you can try to gently scrape them off. A scale insect will come off the tree while a lenticel will not.
Galls are abnormal plant growths that can be a variety of shapes and some may resemble a bump on a plant just like scales do. Galls are typically caused by bacteria, fungi, or insects such as midges, mites, or wasps.
You can determine if the bump you’re looking at is a scale insect or a gall using the same technique described above for lenticels.
Your Plant May Feel Sticky If It Has Scale Insects!
Honeydew is produced by many sap-sucking insects that feed on plant sap (phloem). The sap is primarily sugar and water, so they must ingest a large amount of sap in order to consume enough of the proteins and nutrients for survival. The honeydew they excrete is composed of the excess sugar and water they consume while feeding.
Honeydew leaves a sticky, shiny residue left on plants that sap suckers have fed on. Only soft scales produce honeydew since they feed directly on the sap while armored scales feed on the liquids from individual plant cells.
Honeydew can be a nuisance when sap-feeding insects are present in large numbers. It can drip from trees onto cars leaving a sticky residue. Black sooty mold grows on honeydew which can be unsightly and reduces the ability of the plant to photosynthesize.
If you do find that you have scale insects on your plants, you can reference our guide on how often you should spray scale for more info!
What Plants Do Scale Insects Like?
That leads us to the next question, what plants are these insects drawn toward?
1. Broadleaf Trees
Both soft and armored scales will feed on broadleaf trees. They will feed on both the foliage and woody parts of the tree. According to the University of Minnesota, almost any broadleaf tree can be attacked by scales including elm, oak, maple, poplar, birch, ash, magnolia, linden, honeylocust, and willow.
Two common soft scales which feed on broadleaf trees are the Lecanium scale (Parthenolecanium spp.) and the European elm scale (Gossyparia spuria). While the Lecanium scale will feed primarily on oak and maple species along with a few others, the European elm scale only feeds on elm species. Both can cause branches and twigs to dieback, and their honeydew can grow sooty mold that turns limbs black.
Two common armored scales that will feed on broadleaf trees are the Oystershell scale.
(Lepidosaphes ulmi) and the Scurfy scale (Chionaspis furfura). Both species feed on a variety of broadleaf trees and other deciduous plants. Hard scales often do more damage than soft scales because their feeding kills the plant cells.
2. Conifers
Soft and armored scales also feed on conifers. They feed on the needles, buds, and woody parts. Many conifers can be attacked including pines, spruce, fir, hemlock, yew, and junipers.
The small spruce bud scale (Physokermes hemicryphus), Fletcher scale (Parthenolecanium fletcheri), and pine tortoise scale (Toumeyella parvicornis) are three common soft scales found on conifers. Their feeding damage can lead to discolored foliage and dieback of branches. In large numbers, their honeydew can lead to the growth of sooty mold which turns branches and foliage black.
The pine needle scale (Chionaspis pinifoliae) and the black pineleaf scale (Nuculaspis californica) are two common armored scales that feed on conifers. Pine need scales rarely kill trees but will cause the needles to turn yellow and fall off. Black pineleaf scale feeding damage can kill younger trees and cause reduced vigor in mature trees.
3. Any Plants With Fresh And Tender Growth
Some scale insects prefer to feed on the new growth that plants put out during the growing season. This new growth is easier for their mouthparts to penetrate and provides plenty of nutrients. It also provides new real estate on heavily infested plants where young crawlers won’t have to compete with others to find a place to settle down and feed.
Some scale species’ eggs have evolved to hatch at the same time of year when new growth appears on certain plants. The young growth often becomes distorted or discolored due to their feeding. This damage can be a good indicator of a scale problem and should be investigated to determine if scales are present on your plants.
4. Plants With Soft And Large Leaves
For scale insects that prefer to feed on leaves, soft large leaves can provide a great buffet. They provide plenty of feeding space and can handle higher populations per leaf. Some scales will feed on the large fronds of palm trees or the large leaves of the catalpa tree.
Soft scales on large leaves will tend to stay near the large leaf veins where they can easily access the phloem. Armored scales will feed on any part of the leaf since they feed on the individual leaf cells rather than the phloem.
5. Fruit Trees
As we’ve mentioned, some scale insects can also feed on fruits. Fruit trees make great hosts to some scale species which can feed not only on the fruit but on other parts of the tree as well. Since fruits are only available for a short time each year, many fruit tree scale insects have to be able to utilize other parts of the plant when fruits are present.
Pears and apples are two of the most commonly impacted fruit trees when it comes to scale insects. However, many other fruit trees are also impacted by scales. Prunus species, peaches, oranges, pecans, blueberries, and many more are all hosts of various scale insect species.
6. Houseplants
Scale insects are one of the top houseplant insect pests. Since scale insects can’t fly (except the adult males which don’t feed) and they don’t move very far, scale insects often get into your house when you bring home a new plant that is already infested. It’s extremely important to carefully inspect any new houseplant you bring home for scale insects.
Since these insects can be difficult to detect, it’s even better if you isolate your new houseplants for several weeks before putting them near existing plants in the home. This will ensure that you have time to see if a problem develops. If there are only a few scales present on the plant initially, they may go undetected and it will take a month or two for the problem to become noticeable.
That’s A Wrap!
Scale insects can be difficult to detect and can show up on many different plants both outdoors and indoors. They can appear on a plant’s trunk, stems, leaves, or fruits. They can impact broadleaf plants, conifers, fruit trees, ornamentals, and houseplants.
The first thing you need to do if you suspect your plant is infested with scale insects is to determine if their soft scales or armored scales.
Remember soft scales tend to be much more convex and have a soft covering made of a waxy or powdery-looking material. Hard scales tend to be flatter and have a hard covering over their bodies.
If you identify scales on your plants, you’ll want to get rid of them as quickly as possible. Our article on the Best Ways To Get Rid Of Scale Insects For Good is a great resource that will tell you everything you need to know about managing your scale insect problem.
References
Miller, D. R., Rung, A., & Parikh, G. (2014). Scale Insects, edition 2, a tool for the identification of potential pest scales at USA ports-of-entry (Hemiptera, Sternorrhyncha, Coccoidea). ZooKeys, (431), 61.
Takagi, S. (2022). Another mode of life in armoured scale insects (Sternorrhyncha: Coccoidea: Diaspididae). Insecta matsumurana. New series: Journal of the Research Faculty of Agriculture Hokkaido University, series entomology., 78, 27-56.
Unruh, C. M., & Gullan, P. J. (2008). Identification guide to species in the scale insect tribe Iceryini (Coccoidea: Monophlebidae). Zootaxa, 1803(1), 1-106.
