Scales are among the most persistent and frustrating pests that orchid growers encounter. These tiny, sap-sucking insects can weaken plants, cause yellowing leaves, and even stunt flowering if left untreated.
Because they often hide beneath protective shells and blend into the plant’s surface, scale infestations are easy to overlook until they’ve spread.
Here, I will walk you through how to identify them accurately and share proven treatment methods to eliminate infestations. I’ll also share some essential prevention strategies to keep your orchids healthy and thriving for the long term!
Let’s start!
Table of Contents
Understanding Scales: Decoding the Tiny Invaders
Scales belong to the family of Hemiptera. They are tiny sap sucking insects that cling to stems, branches, leaves and even on roots or rhizomes.
Due to their appearance, they are often unnoticed. A small infestation is manageable, but a large infestation will severely damage the plants.
Adult scales have covers for protection, which can be white, red or brown in color. The size and color of scales vary with life stages. The adults have an average size of 3-5mm, while juvenile scales are around 1mm. Juvenile scales have a yellow or grey cover and can be spread by wind.
Once the cover is built, the adult scales do not move and stay in one position, but immature scales are motile. Adult scales have a flattened appearance with no visible legs.
When settled on an orchid, the scale inserts tiny threadlike styli in the plant to feed the cell contents. The adults secrete honeydew waste that attracts ants for food. A powdery white appearance on the plant indicates infestation of male scale.
Life Cycle
Scales have a short life cycle, which means they multiply rapidly. Their life cycle comprises three notable phases: egg, nymph or crawlers, to an adult.
The female adults develop hard scales and lay eggs under a covering. The hard brown shell is full of eggs and spills after the eggs have hatched. Few species produce eggs externally with white, waxy cotton coverings. The males have wings but do not have a hard covering. Their primary role is mating.
Scales do not wait for the adult phase to damage the plant. The crawler begins to feed on the plant sap after two days of its emergence and is motile. The life cycle completes within a month, and a colony of scales grows on an orchid in less than two months if the plant is left untreated.
Most scales reproduce by cloning, which means females can give birth to exact copies of themselves. The multiple generations within a year make it hard to manage them. A scale is easy to treat when in the nymph stage because they are mobile and have not developed their hard, waxy covering that makes them more vulnerable to chemical insecticides and other treatments.
Types of Scales
There are about 27 species of scales classified as soft and hard scales that cause severe damage to the plants. But only the soft scale or soft brown scale can survive indoors and in greenhouses. These are the most commonly reported orchid pests.
1. Boisduval Scale
Boisduval Scale (Diaspis boisduvali) is a common scale pest of orchids and tends to kill the plant if not controlled in time. These scales spread quickly and are difficult to control. The Boisduval scale can damage leaves, bark, pseudobulbs, roots and petioles of orchids.
- Female Boisduval scale is round, translucent, and light-colored or creamy white in appearance with a dark central part. The size ranges from 1.5 to 2.5mm. The female produces a slightly domed waxy covering to shield from predators and pesticides. A mature female can live for seven months and produce 200 eggs.
- On the other hand, Immature male Boisduval scales have long and narrow outer protective cover with brighter white color, which you might confuse with mealybugs. Males have a shorter life span of about 33 days from egg to adult.
- Crawlers (immature stages) are tiny nymphs 0.18 mm in length, which are difficult to see without magnification. Crawlers, which are yellowish to pinkish in color are active scales that move around the plant until they find a perfect site for feeding.
Almost 34 natural and hybrid orchid genera are particularly prone to Boisduval scale, including Phalaenopsis, Vanda, Paphiopedilum, Stanhopea, Angraecum, Zygopetalum, Cattleya and Cymbidium.
2. Brown Soft Scale
Brown soft scales (Coccus hesperidium) belonging to Coccoidea are also the culprit that damages the orchids of different genera.
Adult brown soft scales are pale brown to yellow in color with brown spots. Older scales become dark brown in color. The shape of the soft brown scale varies with different parts of the plant where it develops. They can be oval or flattened in shape and 4-5 mm in length.
Brown soft scale is commonly found in stems, petioles, undersides of leaves, and flower stalks. Sometimes they exist on pseudobulbs, roots and rhizomes. These scales specifically tend to cluster along stems and in leaf axils.
Honeydew Production and Sooty Mold
Brown soft scale is a prolific honeydew producer because it directly damages the cell content of the plant, i.e. phloem tissues. They feed on the sugar-rich sap of plants and excrete sticky, shiny residue known as honeydew. Significant production of honeydew is a serious nuisance for orchids as it leads to sooty mould growth, which is a black fungus. When this mold covers the leaves, it further stresses the plant by blocking sunlight and reducing photosynthesis.
How to Identify Scales on Orchids
Now that you know about scales, let’s move towards possible signs and symptoms your orchid will show during scale infestation. You will notice pale yellow, light brown to dark brown circular bumps on leaves, stems, pseudobulbs and sometimes on rhizomes. These are the first signs of scale infection.
1. Sticky Residue
Apart from hard bumps on the plant body, you will notice a shiny, sticky substance on them, which is basically a sugary waste on orchids infested with scales. Sugary waste or honeydew residue causes sooty mold growth, trails of ants, and leads to other stress signs in orchids.
2. Discoloration and Yellowing
Scales decrease the vigor of plants by continuously feeding on phloem tissues. Also, the edges of the flower may dry prematurely if infested with scales. Boisduval scales cause cell death, chlorosis, necrosis and overall decline of orchid plants. The infested area of leaves, stems, or pseudobulb turn pale and yellow. Severe infestation results in leaf dropping and deformed flower buds.
Areas to Inspect Closely
Scales are difficult to notice as they hide well underneath the leaves and foldings. To manage them early, spot them as soon as possible. Some of the key areas to examine for scale in the plant are listed:
- Undersides of leaves (especially along veins).
- Stem junctions and leaf axils (where leaves meet the stem).
- Pseudobulbs and rhizomes.
- Flower stalks and buds
- Under the old leaf sheaths
Similar Issues and Misdiagnosis
Some symptoms of scale infestation are similar to other pests, like honeydew, which is secreted by aphids, mealybugs and whiteflies. Therefore, do not solely rely on a single symptom before treatment.
- Bush snails living in the moist potting medium can cause damage by scraping the leaf cuticle, leading to desiccation.
- Sun damage, water quality and excessive use of heaters can mimic bush snail or scale damage.
- Mechanical damage (e.g., old scars) may resemble pest damage.
- Edema or fungal spots are usually within the leaf tissue and not raised or external bumps. But discoloration of leaves and stress symptoms in plants are quite similar to scale infestation.
Therefore, I recommend carefully checking the plants before any treatment. The area where scales are feeding appears yellow due to cell death, along with white powdery stuff, which is full of eggs.
How Scale Spreads:
Here are some common reasons:
- Infested plant purchases are the most common way scale is introduced. If you have recently purchased a new plant or been gifted one. If infested plants come in contact with healthy plants, crawlers can easily spread among other plants.
- Crowded plants allow crawlers to move between them and damage multiple plants.
- Airborne transmission: Furthermore, crawlers can spread through wind, animals or through humans indoors and in greenhouses. Therefore, even if only a single plant is infected, healthy plants nearby are prone to scale infestation.
Step-by-Step Treatment Methods
1. Physical Removal
Before any treatment, I advise you to remove as many scales as you can physically. For this, take a toothpick or a soft cloth and wear gloves, gently remove the scales from leaves, stems and other parts. It may take some time, but it is effective for successful treatment. Take off all the old lead sheaths because this is an ideal place for scales to hide.
2. Rubbing Alcohol
Rubbing alcohol is the first method gardeners used to treat pests, but it is less effective for established scale populations. Moreover, it does not work against eggs that are hiding under the hard shells of the scale. So, for heavy infestation of scale, using insecticides is a better approach.
For this treatment, you need cotton swabs, a soft toothbrush, rubbing alcohol (isopropyl alcohol), and water.
- A standard rule for the treatment of any pest or disease is to isolate the infested orchid.
- Prepare dilute rubbing alcohol with water (e.g., 70% alcohol diluted 1:1 or 1:2 with water.
- Dip a toothbrush or cotton swab in alcohol solution and gently wipe the scale insects from infected parts. Carefully wipe the undersides of leaves, stems and crevices.
- Monitor the orchid regularly, and it will need reapplication in 2-3 weeks.
- Alcohol evaporation may cause chilling of plants, especially soft and thin-leaved orchids.
An alternative to the swab method is misting. Just pour the diluted solution into a spray bottle and thoroughly mist the infected parts. Avoid using undiluted rubbing alcohol, ethanol or methanol as they can penetrate the cell, which can be too harsh for orchids.
3. Neem Oil
Neem oil is gardeners’ favorite choice to deal with pests because it is organic, derived from neem trees and has no side effects. Other horticultural or mineral oils are petroleum distillates.
Neem oil, mineral oil or horticultural oil kills the pests by smothering. Oil will clog the pores through which insects breathe. Generally, these oils are mixed with water or detergent for better spreading and sticking of the oil.
I recommend using a Natria ready-to-use neem oil spray. You can mix concentrated neem oil with water and a surfactant (soap) according to product instructions. But Natria is a ready-to-use spray, so convenient.
It’s an easy-to-use product, although I feel it has a strong smell which eventually fades after some time. Neem oil temporarily controls the population of scales but does not completely eradicate them.
Spray the oil on all parts of the orchid as the scales hide well under the leaves, in the sheaths and especially in infested areas. It needs reapplication every 7-10 days, or as per product instructions, for several weeks to disrupt the scale life cycle and complete removal.
An additional tip to remember is to apply neem oil in the evening or on cloudy days. This practice is recommended to avoid leaf burn in direct sunlight. If the temperature is greater than 80 degrees F, place the plant in a shaded area.
The horticultural oil application in high temperatures or in direct sunlight causes leaves to decay and form gummy blobs. Always patch test the product before using it, as you do not know how the plant reacts to the product.
Don’t spray on blooms or vegetative buds to avoid any deformities.
4. Insecticidal Soap
The subsequent recommended treatment for scale is using insecticidal soap. Some insecticidal soaps are basically potassium salts of fatty acids. Insecticidal soaps remove the waxy coating of pests, disrupt insect cell membranes, and cause dehydration and death of the pests.
Similar to the above two methods, it’s only effective against small infestations, soft-bodied insects like scale crawlers (juvenile, mobile stage) and adults if directly contacted. You need to manually remove the hard scales, as the eggs may be hiding under the scale covering.
I have used Garden Safe Insecticidal soap for flies on my outdoor plants before. This was quite effective against flies. You can spray all orchid surfaces thoroughly for direct contact with scale insects. It has no residual effect and does not harm plants, so repeat 3 applications every 7-10 days.
Use the product as per the instructions, but make sure you patch the test before using. Remember to place the plant in shade afterwards to avoid sunburn.
Personally, if I had a larger-scale infestation, I wouldn’t opt for DIY or traditional methods. Many gardeners are sensitive to using chemicals due to potential risks. Organic treatments are safe but time-consuming and need a lot of effort.
I recommend the insecticide solution of synthetic pyrethrin, a synergist: piperonyl butoxide and a plant-safe detergent. Typically, these are derived from natural sources, i.e chrysanthemum flowers. These are over-the-counter strong chemicals, and are more effective against heavy infestation.
5. Chemical Treatment (Systemic Insecticides)
For heavy infestation, quarantine the plant and do not go for traditional methods like, neem oil, insecticidal soap or alcohol rubbing. Organic methods cannot control heavy scale infestation.
Manually remove as many scales as you can and clean the leaves for better application of chemicals. But never use insecticides that are not labeled for ornamental plants, as they often cause phytotoxicity and severe damage to delicate leaves.
Systemic insecticides are absorbed by the plant and transported throughout the plant tissues and into sap. The scale pests that feed on the sap are killed by ingesting these toxic chemicals. Remember, using chemicals on orchids should be your last option due to the risk related to plant growth, potential environmental and health concerns.
- Types of Systemic Insecticides (Examples):
The most common and widely used systemic insecticides effective against scales are acephate, imidacloprid, dinotefuran. A mixture of acephate and miticide fenbutatin-oxide is really effective against orchid pests. Orthene, Malathion and Carbaryl are also effective to control heavy infestations.
Imidacloprid comes in the form of tiny light-weight granules, pre-mix spray or even as a concentrated form. I recommend using granules or Premix spray, as it is easy to use, just follow the manufacturer’s guidelines, but concentrated imidacloprid should be diluted before using.
For the granules, sprinkle some in the potting medium but not directly on the roots, water the medium slightly and it will dissolve in the potting mix. The roots will absorb the dissolved chemical and spread to the plant tissues. The population will decline in no time.
Additional Tips
- Use the chemical early in the morning.
- Keep the plant drier, in a shaded region.
- Monitor them for 1-2 weeks.
- Don’t water them the same day you spray chemicals.
- Apply another dose of chemical after 1-2 weeks.
Precautions and Safety:
Orchids are susceptible to chemicals, especially at high temperatures and in sunlight, so make sure to place the plants in shade during chemical treatment.
Avoid products of Cygon or Diazinon, although they are no longer available for commercial use. Avoid using the same chemical for an extended time period (more than 9 months), as the scale may become resistant to insecticides.
Always read and follow all label directions for safety precautions. Wear protective gloves and a mask when handling chemical insecticides in order to be safe from fumes. Some chemicals are respiratory irritants.
Apply the chemical spray in a well-ventilated area. Keep treated plants away from children and pets.
Repotting and Cleaning
I recommend repotting the orchid after persistent infection with scales. A heavy population of scales may settle on the roots and rhizomes. It can harbour eggs and crawlers so that the population may get out of control.
Dispose of the infected potting medium. Remove any dead and infected parts of the plant, clean it well, and if necessary, use a fine jet of water to remove scale from the plant and soil. Re-pot the plant in fresh potting media in a new container.
Treatment Difficulty Matrix
| Scale Severity | Recommended Treatments |
| Light: A light infestation of scales looks like a few scales on any part of one plant. The start of infection looks like fluffy white powdery stuff on the plant. | Rubbing alcohol, insecticidal soap, neem oil (less toxic, takes more time and effort) |
| Heavy: Heavy infestation means the scale population is out of control, and there are visible health effects on the plant. The plant vigor declines, chlorosis, and growth of sooty mold. | Systemic insecticide (last resort), Combined Methods are highly efficient, take less time and effort. |
Preventing Orchid Scale Infestations:
For future prevention of scale, check that your orchids are living in the right conditions.
1. Optimal Growing Conditions
Maintain the growing environment optimal for orchids, as healthy plants are unlikely to get pests. Keep a check on humidity, maintain good air circulation and provide proper light and water to orchids to keep them happy.
2. Regular Inspection Routines
I regularly inspect my plants to spot any disease or pests. Even if you have an extensive collection of plants, I advise you to monitor them weekly. Making inspection a habit will save you from a hazardous event in the future.
It’s better to use a magnifying glass for closer examination, as the majority of the pests are not visible to the naked eye. Moreover, using a magnifying glass will help to detect early-stage scale (crawlers) or tiny species.
Quarantine Practices
Quarantine or isolating your newly purchased orchid is essential for both the new plant and your present collection of plants. This practice will prevent scales, other pests or any disease in your existing collection.
- Isolate new orchids in a separate area for at least 4-6 weeks. Keep it away from your main collection of plants.
- Before purchasing any plant, inspect it for pests or diseases.
Quarantine prevents pests and diseases to your established orchid collection. Also, it allows early detection and treatment of any issues before they spread.
Even if the plant seems fine and healthy, sometimes eggs are hiding in the potting media. Eggs will hatch within a week if the plant is infected.
FAQs
Can I Spray Soapy Water On Orchids?
Mild dishwashing is an effective treatment against pests. Mix 1 tablespoon of liquid dishwashing detergent with half a gallon of water. Pour this into a spray bottle and reapply after a few days or as needed. Clean the plant with clean water after a few hours of application. This will disturb the pest’s ability to reproduce and feed on the plant. The remedy is effective against soft-bodied pests like mealybugs and aphids.
Can I Spray My Orchid With Vinegar?
Diluted Vinegar is used to clean orchid leaves and stems. But avoid concentrated vinegar on any part of the orchid, especially roots. Mix 1 part vinegar in 4 parts of distilled water to make a solution. Spray it on leaves to wipe off dust, mites, mineral buildup or any pests. Rinse the leaves with clean water after a few minutes. It is not recommended to use this frequently.
How Do You Get Rid Of Sticky Residue On Orchids?
To remove the sticky residue on orchids, gently wipe the orchid leaves or any part with a damp, warm cloth or paper towel. Make sure to identify the root cause of sticky residue, as pests can be the underlying issue. However, some orchid flowers or buds naturally secrete sap. In any case, wash the area with tepid water or use lemon juice. Dip the cotton or paper towel in lemon juice, wipe the sticky part and let it dry.
What Does Sugar Do To Orchids?
While sugar is essential for orchid health, it is naturally produced in the plant body. But some orchids benefit from sugar when the plant is not actively doing photosynthesis. Roots can absorb it, but you should be careful about the concentrations, as it may damage the roots.
How Often Should You Wash Orchids?
You should mist the orchids every 7-10 days. But the washing regime may vary. If you notice dust more often, gently wipe it off rather than running it under the water.
Final Thoughts
Dealing with pests is not easy, and when the pest is stubborn, like scale, it’s pretty frustrating. Early detection, consistent care, and the proper treatment methods are must to deal with orchid scales.
It’s better to take preventive measures to be on the safe side. You may get frustrated with time-consuming and ineffective control methods. Many houseplant owners do not want any harsh chemicals and rely on organic methods, but remember to change your strategy as per the situation.
You can only save the infested plant when you choose the proper treatment as per the pest population. Have you battled an orchid scale? Share your tips and experiences in the comments below to help fellow orchid lovers!
