How To Get Rid of Scale on Plants

Are your beloved plants looking sickly, or have you noticed strange bumps on them? They may have fallen victim to a scale infestation that’s literally sucking the life out of them. These stealthy little pests can even infest resilient houseplants such as succulents and snake plants, and different types of scale insects can harm both indoor and outdoor plants.

So, it’s vital to eradicate scale insects to prevent them from weakening and even killing your plants. Below learn exactly what these pests are, why your plants are prone to them, and how to get rid of scale on plants with our expert tips. 

What Is Scale on Plants?

“Armored scale are the secret agents of the insect world,” Nathan Heinrich, horticulturist and botanical designer, says. “They are masters of disguise, and it’s very common for them to infest plants in your home or garden for weeks or months before you even know that they’re there.”

He continues, “Protected by a ‘scale’ or outer shell that ranges in color from light brown to green, these sneaky pests fall into a category of parasitic insects that suck nutrients directly out of the leaves and stems of your plants.”

Samuel Davis, a horticulturist and the CEO of London Gardeners, says that scale can appear as tiny bumps or scales, often blending in with the plant’s natural surface. These insects can cause significant damage by draining vital nutrients, leading to weakened plants, yellowing leaves, and stunted growth.

There isn’t just one type of scale insect you need to worry about either, and they can attack an array of plants, including fruit trees, woody plants, flowering plants, vegetables, and various houseplants.

Julia Omelchenko, resident botany expert at Plantum, says there are over 8,000 species of scales, each varying in color and shape. Their size can fall between 0.04 and 0.4 inches (1 mm to 1 cm) in diameter.  

Why Do Plants Get Scale?

So what causes these little plant suckers to show up in the first place? Davis says that scale insects are attracted to plants for their sap, which serves as their primary food source.

“They often infest plants that are already stressed or weakened, but they can also spread to healthy plants,” he says. “Common reasons for scale infestations include poor plant health, environmental stress, and the introduction of infested plants to your garden or indoor space.”

Heinrich says that ants on plants are a common sign of a scale infestation. “Ants feed off of the sweet discharge left behind by scale and aphids, so even if you don’t notice any insects on your plants, when the ants move in, it’s time for a closer inspection,” Davis informs.

Another sign that you have a scale problem on outdoor plants, he explains, is sticky drips on sidewalks, decks, pavement, or on cars parked under infested trees.

If you’re wondering how scale is able to infest your indoor plants, Omelchenko shines some light on the subject. She says that scales can get indoors by hitching a ride on infested plants. They’re attracted to weakened plants that grow in improper conditions, so struggling houseplants can easily become infected. 

How to Get Rid of Scale on Indoor Plants

There are a couple of methods you can utilize to get rid of these insects. Omelchenko says you can start by removing adult scales off your plant. “Use a sponge dipped in a weak soapy solution to wipe them off the branches and leaves,” she says. “If this doesn’t help, use an old toothbrush. However, make sure to avoid damaging the plant.”

She continues, “Prepare the solution by using a mild liquid soap, preferably unscented. After removing the insects, rinse your plant to wash away the soap. Use a sprayer filled with clean water for this. Alternatively, you can wipe the foliage with a damp sponge soaked in clean water.”

She says that in cases of severe or repeat infestations, you’ll need to treat the plant with an insecticide afterward, which can be either organic or synthetic in origin.

Heinrich provides another effective strategy for ridding indoor plants of scale. “One of my favorite tried-and-true organic treatments for getting rid of scale on houseplants and outdoor plants is neem oil,” he says. “Just add 2 teaspoons of dish soap and 2 teaspoons of neem oil to a gallon of water, mix gently, and then spray it generously onto the leaves and stems of your plants two or three times each week until the infestation is killed.”

He continues, “Scale can also be removed by hand before and after you spray with neem oil, but it’s almost impossible to remove each manually. Spraying with oil will suffocate the insects and keep them from spreading.”

How to Get Rid of Scale on Outdoor Plants

“To curb a scale infestation on an outdoor plant, you’ll also need to start by manually removing the pests from it,” Omelchenko says. “If there aren’t too many of them and they’re attached mostly to leaves or young branches, wipe the scales off using a soft sponge.”

She continues, “If they’re present on older, woody branches, use a soft brush instead. However, if the infestation is severe, pruning the most affected shoots will work best to reduce pest numbers.”

Omelchenko and Davis both say that introducing and encouraging natural enemies, like ladybugs, parasitoid wasps, or lacewings that feed on scale insects can help keep the population in check.

“Some of them are even available commercially, though not all may be native to your area,” Omelchenko says. “Take note that insecticides will kill beneficial insects along with the scale. It’s also important to refrain from using these products while plants are flowering to protect pollinators.”

Heinrichs says that you can also use Neem Oil on your outdoor plants, especially fruit trees, like lemons and other citrus trees, that are susceptible to scale.

“For non-edible plants and trees, you can use a very effective systemic treatment such as the Bonide Insect Control Systemic Granules,” he advises. “It’s water resistant and perfect for trees and shrubs that are dripping a sticky mess from scale.”

5 Top Tips to Help Prevent Scale Infestations

You know what they say: An ounce of prevention is worth a pound of cure. Although scale is common, there are a few things you can do to help prevent infestations from starting. Here are the top tips from the experts on what can help stop scale from infiltrating your indoor and outdoor plants:

Regularly Inspect Your Plants

Omelchenko says to prevent repeat scale infestations, you should regularly inspect your plants for signs of the insects’ presence. “Those include sticky spots of their excreted honeydew, or a black coating where sooty mold has established on said honeydew,” she informs.

Davis also advises regularly inspecting your plants for scale and other pests to ensure you can treat the infestation as soon as possible.

Keep Plants Healthy

“Keeping plants healthy is another major factor in scale prevention, as the pests have a harder time infesting them over weak and sickly ones,” says Omelchenko.

Davis says you can maintain plant health through proper watering, fertilizing, and pruning to reduce stress and make plants less attractive to pests. So, research the plants you have to ensure you give them the proper care they need to keep them happy and healthy.

Quarantine New Plants

It’s easy to get excited about a new plant and want to bring it inside or add it to your flower bed right away. But if that plant happens to have scale, it can swiftly spread to other plants, which is why you want to wait before you introduce it to your home or garden.

“Quarantine any new plants that you bring to your home or garden,” Omelchenko says. “Keeping them apart for a few weeks before placing them next to your established ones will allow you to tell if they’re infested or not.”

Clean Your Garden Tools

To prevent the spread of scale and other bacteria or fungi, it’s vital that you clean your garden tools after use, especially after pruning an infested plant. Davis says regularly cleaning garden tools can help prevent the spread of pests and diseases. You can disinfect your tools with bleach water before you store them.

Practice Plant Hygiene

“Finally, practicing good hygiene in your plant care will also reduce the chances of a scale infestation,” Omelchenko advises. “Regularly wipe the dust off the foliage of your houseplants, and take care to remove dried leaves and shoots in a timely manner. Clean up any litter under the plants in your garden and aim to keep it weed-free.”