Common Coleus Pests, Damage Signs, and How to Stop Them

Coleus is prized for its vibrant foliage and easy care, but if you’ve noticed chewed leaves, holes, or sticky residue on your plant—something’s definitely not right. The question is: What’s Eating Your Coleus?

The truth is, Coleus is susceptible to a handful of common garden pests, especially when grown in warm, humid conditions or shady areas. But don’t worry—most of these problems are easy to diagnose and fix with a few simple tools and tricks. In this guide, we’ll cover all the top culprits, how to identify them, and what to do about it—naturally or with safe pesticides.

By: Reggie Meehan (8/11/25)

Quick Answer: What’s Eating My Coleus?

Here’s a fast breakdown of the most likely pests:

How to Diagnose What’s Eating Your Coleus

Identifying pest problems often starts with recognizing the unique signs of damage they leave behind. Many pests hide during the day, so heading into the garden at night with a flashlight can help you spot slugs, caterpillars, and other nocturnal feeders in action. During the day, take time to inspect the undersides of leaves and the joints where stems meet, as these protected spots are common hiding places for eggs, mites, aphids, and mealybugs. If the pests are too small to see clearly, use your phone camera or a magnifying glass to zoom in on tiny insects and their damage. 

Clues can also be indirect—trails of sooty mold may point to sap-sucking insects like aphids or whiteflies, cast skins (molting) may reveal an aphid or thrip problem, and frass (droppings) often signals caterpillars or beetles. By learning to recognize the specific patterns and signs of damage, you equip yourself to identify the pest more accurately and choose the most effective control method, saving time, effort, and the health of your garden.

Slugs & Snails: The #1 Coleus Culprit

Slugs and snails are especially attracted to shade-grown Coleus in moist conditions. If your plant looks like something’s been munching random holes in the leaves and you spot a shiny slime trail, you’ve found your culprit.

Signs of Slug or Snail Infestation

Signs of a slug or snail infestation include irregular holes with ragged edges in foliage, caused by these pests chewing through leaves with their rasping tongues (radula), which leave uneven, torn margins. Silvery, slimy trails on leaves or soil are another unmistakable clue, often most visible in the early morning or after rain. Since slugs and snails are nocturnal feeders, most of the damage occurs overnight, when they emerge in cool, moist conditions to cause sudden and severe harm to plants.

How to Control Slugs and Snails

To control slugs and snails, apply pet-safe iron phosphate pellets such as Sluggo for effective protection. Beer traps are another option—bury a shallow dish filled with beer near plants to lure and drown the pests. Wrapping copper tape around containers or garden beds can create a barrier they won’t cross. Additionally, watering plants in the morning rather than the evening helps reduce overnight moisture, making the environment less inviting for these pests.

Aphids: Small Bugs, Big Problem

Aphids are small, soft-bodied insects that love to cluster on the tender new growth of Coleus. They suck sap from the plant and secrete a sticky residue known as honeydew, which can attract ants and encourage mildew. Honeydew often coats leaves and stems, creating a shiny surface that can attract ants or lead to the growth of sooty mold, which further stresses the plant. Spotting honeydew means aphids are actively feeding and multiplying, and immediate control measures may be needed to prevent damage.

Signs of Aphids Infestation

The telltale sign of an aphid infestation include molting strips on lower leaves, as aphids shed their exoskeletons three to four times before reaching maturity, leaving behind translucent cast skins that often collect just below feeding sites. Clusters of live aphids are frequently found on new growth, where these soft-bodied insects gather on tender stems and buds in dense colonies that distort plant tissue as they feed. A sticky honeydew coating on leaves and stems is another common sign; this sugary excretion from mature aphids attracts ants and encourages the growth of sooty mold. Sustained feeding can also cause curled, yellowed, or stunted foliage, as aphids disrupt nutrient flow and weaken overall plant health.

How to Treat Aphids (Organic)

• Spray with insecticidal soap combined with neem oil every 3-5 days

• Introduce beneficial insects like ladybugs or lacewings

• Pinch off and dispose of heavily infested buds/blooms/stems

• Use streams of water to blast aphids off infected foliage and flowers.

Mealybugs: The Cotton-Like Invader

Mealybugs are sneaky pests that look like bits of cotton wedged between leaf stems. They feed on plant sap and can weaken Coleus quickly if left untreated. Over time, their honeydew secretions can attract ants and encourage sooty mold, further harming the plant’s health.

Signs of Mealybug Infestation

• White, fluffy blobs on stems, leaves, and leaf joints

• Wilting, yellowing, or stunted growth

• Sticky leaves from honeydew leading to sooty mold

How to Get Rid of Mealybugs

To get rid of mealybugs, an effective organic option is to dab visible pests with rubbing alcohol, which kills them on contact. Going one step further, synthetic treatments such as Acephate are highly effective for targeting pests you can’t see, and the plant should be saturated on leaf tops and bottoms, stems, and even containers, with two treatments recommended for complete eradication. Imidacloprid can both prevent and eliminate mealybugs but should only be used on non-blooming plants; remove Coleus blooms before spraying or during active treatment. Always isolate affected plants to prevent the pests from spreading to healthy ones.

Caterpillars: Hungry Leaf-Munchers

If you see large, irregular holes or chewed edges on your Coleus, a caterpillar could be the culprit. Moth or butterfly larvae may hatch and start feeding rapidly, especially in late summer.

Signs of Caterpillar Infestation

Signs of a caterpillar infestation include chunky holes or large missing portions of leaves, often leaving plants with a ragged appearance. Small, round droppings may be visible on the leaves themselves or on the table, soil, or ground beneath the plants. You may also spot the larvae directly, typically hiding on the undersides of leaves or along the plant stalks.

How to Control Caterpillars (Organic)

During peak caterpillar season, inspect plants daily and remove any caterpillars by hand, dropping them into a container of soapy water to kill them. For a quick reduction in numbers, give infested foliage a firm shake to dislodge the pests. You can also apply Bt (Bacillus thuringiensis), a natural and targeted treatment that is highly effective against worms and caterpillars while being safe for beneficial insects.

Spider Mites: Tiny But Destructive

These nearly invisible pests can be a nightmare in hot, dry conditions, multiplying rapidly when humidity is low and temperatures are high. Spider mites feed by piercing leaf tissue and sucking out chlorophyll, which robs the plant of its ability to photosynthesize efficiently. If left unchecked, spider mites can spread quickly from one plant to another, causing widespread damage in a short period.

Signs of Spider Mites Infestation

Stage 1: Tiny, pale speckles or stippling on the upper surface of leaves—this is where mites pierce cells to feed, draining chlorophyll and leaves begin to appear mottled.

Stage 2: If left uncontrolled, leaves become more mottled and grey. Fine webbing appears on the undersides of leaves.

Stage 3: Yellowing or bronzing of foliage and leaves begin to drop.

How to Stop Spider Mites

To stop spider mites organically, start by performing a simple test: vigorously shake plant foliage over a sheet of white paper to dislodge any mites. These pests will appear as tiny, pinhead-sized moving specks, and even spotting one indicates a growing population. Treat affected plants by spraying with neem oil, making sure to coat the undersides of leaves thoroughly, and repeat the application after seven days to catch any newly hatched mites. Increase humidity around the plant by misting the undersides of leaves, as spider mites thrive in dry conditions. You can also gently wipe the undersides of leaves with a damp cloth to physically remove mites and their webbing.

If all else fails, synthetic miticides can provide a fast and effective solution for controlling spider mites once their presence is confirmed through a spider mite test. Choose a product specifically labeled for spider mites and follow all application instructions carefully to ensure thorough coverage, especially on the undersides of leaves where they hide. Rotate between different miticides if repeat treatments are necessary, as spider mites can develop resistance quickly.

Whiteflies: Persistent and Annoying

Whiteflies are tiny winged insects that scatter into the air when a plant is disturbed. While they don’t usually kill Coleus, they can weaken it over time and cause yellowing. They also excrete sticky honeydew, which can lead to sooty mold and attract other pests.

Signs of a Whitefly Infestation

• Clouds of tiny white bugs when touched

• Yellowed or curled leaves

• Sticky honeydew and potential sooty mold

Whitefly Control Tips

For organic whitefly control, start by spraying plants with neem oil, followed by insecticidal soap, and then pyrethrins for a layered approach that disrupts their life cycle. Encouraging natural predators such as parasitic wasps can also help keep populations in check over time. For synthetic control, systemic insecticides like Imidacloprid or Acephate can be highly effective, providing longer-lasting protection by targeting whiteflies both on the plant surface and within the plant tissue.

Less Common Coleus Pests

In addition to common pests mentioned above, Coleus can also fall victim to smaller, less noticeable insects that cause significant damage if left unchecked. Fungus gnats thrive in moist soil, and while the adults are mostly a nuisance, their larvae can damage plant roots. To control them, allow the soil to dry between waterings, use sticky traps to capture adults, or add Bacillus thuringiensis israelensis (BTI) to the soil to target larvae. 

Thrips, on the other hand, are thin, elongated insects in shades of black, brown, tan, or yellow that leave silvery or streaked damage on leaves. Detect them by shaking foliage over white paper—these fast-moving insects will be visible as tiny, slender specks. Even finding one indicates a population is forming, so treat with Spinosad and use yellow sticky traps to monitor and reduce their numbers.

Other Causes of Leaf Damage

Not every hole or blemish is caused by bugs:

• Sunscald – leaves may look crispy or faded if sun exposure is too high
  
  

• Cold and wind damage – especially on tender young leaves
  
  

• Fungal leaf spot – irregular brown or black blotches
  
  

• Nutrient deficiency – yellowing between veins; faded, non-vibrant leaf color; leaf drop
  
  

If you see damage but no bugs, consider environmental or cultural causes.

Prevention Tips to Keep Your Coleus Pest-Free

Avoid overwatering, as consistently wet soil creates the perfect environment for fungus gnats, slugs, and other moisture-loving pests. Good watering habits not only help prevent infestations but also promote stronger root systems and healthier plants overall. Equally important is proper plant spacing—crowded plants can trap humidity and reduce airflow, which encourages fungal problems like powdery mildew. By giving each plant room to breathe, you reduce the likelihood of disease and make it harder for pests to spread from one plant to another.

Before adding any new plants to your garden, take time to thoroughly inspect them for signs of insects, eggs, or disease. This simple step can save you from introducing an entire pest population to your healthy plants. Keep your garden tidy by removing dead leaves and pruning back excessive growth, as decaying plant matter and dense foliage can shelter pests. Finally, feed your plants with balanced nutrition, but avoid overdoing it—too much nitrogen leads to soft, tender growth that aphids find especially attractive. By combining these practices, you create an environment that’s less inviting to pests and more supportive of long-term plant health.

Identify Early, Act Fast, and Grow Beautiful Coleus

If your Coleus is under attack, don’t panic. Most pest problems can be reversed quickly if caught early. By matching damage symptoms to the right pest and choosing the right treatment—whether physical, organic or synthetic chemical—you can restore your Coleus to its full, colorful glory. Stay observant, water wisely, and inspect regularly. Your Coleus will thank you with lush, vibrant foliage all season long.