Top 5 Most Common Houseplant Pests and How to Overcome Them

It happens to all Houseplant Addicts eventually, no matter how hard we may try to prevent it. One day you’re admiring your beautiful houseplants over a hot cup of coffee when suddenly a tiny fungus gnat flies right into your cup – GROSS! But don’t panic yet, we’re here to help you learn how to identify, eliminate and control the 5 most common houseplant pests.

FUNGUS GNATS.

What do they look like? Fungus gnats are small blackish-gray flies (1/8 inch long), they are non-biting soft bodied insects with long dangling legs and clear wings.

Most often you’ll first notice the presence of these pests in their adult form, (described above) harmlessly flying and skirting around your home near your plants or walking nearby along your countertops. These houseplant pests can be a nuisance, often ending up in your food or drinks but they will not harm you.

The damage this insect causes is done while these pests are still in their larval stage. In their larval stage they can be found in the top soil of your houseplant chowing down on organic matter in the soil, stealing nutrients and harming tender plant roots. The larva are very small (1/4 inch) with a shiny black head and an elongated, whitish almost transparent body.

Some symptoms you may notice in your plants that are caused by a fungus gnat infestation are sudden wilting, loss of foliage, poor growth and yellowing.

Where do they come from? There are several different ways you could end up with a fungus gnat infestation; they came in on a new houseplant, they flew inside when you opened the door, they overwintered in the soil, eggs or larvae were present in new soil you just purchased or so many other ways.

To better understand how an infestation gets started once they’ve made it inside your home, lets talk about their life cycle. These pests have four life stages: egg, larva, pupa and adult.

Adult fungus gnats lay their eggs in dark moist decaying organic matter. After about 3-5 days, the larvae will hatch and begin feeding immediately. They primarily feed on fungi growing in the soil and other organic matter but as we’ve already discussed they will also feed on your plants new growth, root hairs and small immature roots. This feeding frenzy will last for roughly 10 days.

Once feeding ends, the larva will pupate for about 4 days before turning into adult fungus gnats. Adults live about 7-10 days, plenty of time to carry out their new mission – to mate and find another suitable media source in which to lay their eggs. Females can lay up to 300 eggs in batches of 2 to 30 each so it is easy to see how quickly these pests can reproduce and infest an entire houseplant collection or greenhouse!

How do I get rid of them? There are many methods of control and elimination for fungus gnats. Finding what works best for you can be a journey all it’s own!

The first thing you’ll want to consider regardless of pest is if you’d like to use an organic method or not. If you have pets or small children, we highly recommend sticking with organic options as they’re safer should accidental ingestion or contact occur.

Here are some tips and tricks for eliminating and controlling fungus gnats:

• Frequently check your plants for dead or dying foliage and remove immediately.
• Use a well draining soil mix and water your plants from the bottom when possible, this will prevent the top layer of soil from becoming overly moist. Remember, fungus gnats must have moist and shaded areas in which to breed.
• If you’re a habitual overwaterer, consider purchasing a soil moisture meter!
• Thoroughly inspect your plants for larva to find the breeding ground of the gnats. Remove that top soil and/or allow the soil to dry out completely preventing breeding. You can also repot your plants entirely with new soil.
• Purchase sticky traps or fly tape and strategically place them in or around affected plants. Replace with new traps at least weekly.
• Using common craft sand, cover the top soil of the houseplant in a smooth half inch layer. Water will drain quickly leaving the top layer drier and will help prevent egg laying and further breeding.
• Get yourself some Food-Grade Diatomaceous Earth! This organic powdery substance can be mixed with the top layer of your soil to help control larva. DE is made up of microscopic shards of silica that cut and tear into larvae as they crawl through it.
• Infestation too bad? Consider using a chemical solution such as mosquito bits, microbe-lift BMC, gnatnix, or other commercially available products.
• Neem oil applied regularly can be used for prevention and control. Dilute the oil with water according to your packages directions then drench the soil with the solution.

SPIDER MITES.

What do they look like? Spider mites are a common pest that feast on plants by sucking nutrients from plant cells in the leaves and stems. These spider like pests are in fact not a type of insect, but are classed as an arachnid. This means spider mites are close relatives of spiders, horseshoe crabs and ticks!

Adults can range in color from red to orange to brown, their bodies are oval-shaped and incredibly small (1/50 inch). In fact spider mites are so small that to truly see them you would need a magnifying glass!

Spider mites often infest a houseplant without us noticing until we see their signature spider-like webs appear on the plants stems and underneath foliage. These webs are what distinguish spider mites from other type of mites and microscopic pests.

When webs and leaf damage are present this is a signal that the infestation is out of control, though small infestations can easily slip by unnoticed, large infestations will always leave visible damage that can decimate a plant and spread quickly.

Some symptoms of spider mite damage are patterns of tiny spots or stripes in the plants leaves, yellow or brown leaves leaf drop and leaves curling/crisping.

Where do they come from? These pests spread quickly and most commonly through the wind. Though they can sneak into our home in many different ways! Often they’ll make it indoors when you bring a houseplant in from summering outside or on a new houseplant. They can even get in by hitching a ride on your clothing or on your pets!

Spider mites thrive in hot and dry environments where their populations can grow rapidly. They have five life cycle stages; egg, larva, two nymph stages and finally an adult stage.

Spider mites can reproduce sexually or asexually and lay between 100-300 eggs (which can overwinter in your plants) on the underside of leaves or on the bark of plants over the course of about three weeks. If the eggs were not fertilized, the spider mite egg will become male, while fertilized eggs become female. The length of time for a spider mite to go from egg to adult once hatched is roughly 14 days though it can be as little as 5 in optimal conditions.

As temperatures start to warm, the larvae begin hatching and feed for a few days before they temporarily become inactive and begin to molt into the first nymphal stage called a protonymph. Now finished with it’s first molt the newly eight-legged protonymph will again start to feed and rest.

Once sufficient feeding has occured it will begin a second molt where it then becomes a deutonymph. The deutonymph continues to feed and after a short rest from all that munching will molt again. The adult spider mite will emerge from its prior skin and is now ready to begin laying eggs to restart the cycle. All stages of spider mite with the exception of larva and egg can form webs.

How do I get rid of them? There are many methods of control and elimination for spider mites. As always you’ll first want to decide if you’d like to use an organic method or not. If you have pets or small children, we highly recommend sticking with organic options as they’re safer should accidental ingestion or contact occur.

Here are some tips and tricks for eliminating and controlling spider mites:

• Neem oil and other horticultural oils are a common solution and preventive for spider mites. The idea behind these oils is to smother the mites or their eggs and discourages laying new eggs.
• Take your plants outside and turn your hose up to it’s highest setting. (Tip* you can purchase a “bug blaster” attachment for your hose online!) Use the hard spray of the water to wash off as many of the mites, nymphs, and larvae as you can. You may elect to try this method alone or do this as a step in treatment before applying oil, soap or chemical solutions.
• Prune leaves, stems and other affected parts of your plant well past any webbing. Do NOT compost infested plants or plant parts.
• Practice proper watering. Both under watering and over watering can make plants more susceptible to spider mite infestations.
• Treat infested areas with insecticidal soaps. You can do this for prevention as well.
• Dust on leaves and branches encourages mites. Clean your leaves every few weeks to help discourage mites.
• Consider a chemical solution such like mite-x, nuke em, take down or “worry free” brand insecticides.

MEALYBUGS.

What do they look like? Mealybugs are the bane of every houseplant addicts existence. Mealybugs are small (1/16 inch) soft-bodied wingless insects that are covered with a white, waxy, fluffy material.

They appear as tiny white cottony spots on plants, usually in crevices near the stems, leaf junctures and in compact new growth. Mealybugs move slowly searching for a suitable location on the plant and once found they often become immobile and form clusters.

These pests feed by sucking sap out of the plants tissues. If caught early then the damage is not often significant and they can usually be easily eliminated. However, at higher numbers an infestation can cause, stunted growth, yellowing and leaf curling.

Feeding is usually accompanied by honeydew (other pests like aphids and scale also leave behind this substance), which makes the plant sticky to the touch and can attract ants and encourage mold growth.

Where do they come from? This is a tricky question. There are 275 species of mealybugs known to occur throughout the United States so you could have gotten them almost anywhere. Most commonly mealybugs are brought into our home through infected plants. They can also come in on our shoes, our pets, in fresh flowers or produce, through air currents or even on the backs of ants.

Mealybugs reproduce quicky and generations can overlap so it’s vital that you treat your plant for mealybugs on first site. The mealybugs life cycle consists of three main stages; egg, nymph and adult. Female mealybugs will undergo three instars (an instar is the growth that occurs between molting) as nymphs while male nymphs undergo four instars.

Males do not feed after the first two instars and exist solely to fertilize the females after their final molt. After the male nymphs second instar they settle and spin an elongated, white waxy cocoon. Adult males that emerge from their cocoons are tiny and winged and only live a few days. 

Females lay between 300 to 600 eggs in waxy sacs similar to the males cocoon which are affixed to the plants stems or leaves. A new generation develops every one to three months depending on environmental factors. Shortly after laying her eggs the female dies and eggs begin to hatch in 7 to 10 days.

Once hatched tiny yellow nymphs emerge. At this first instar stage both male and female nymphs appear identical. As the second instar begins, the nymphs will begin to form the white fluffy coating characteristics that we recognize in mealybugs. Female nymphs continue to feed and increase greatly in size between the second and third instars before molting into their adult form.

How do I get rid of them? There are many methods of control and elimination for mealybugs. As always you’ll first want to decide if you’d like to use an organic method or not. If you have pets or small children, we highly recommend sticking with organic options as they’re safer should accidental ingestion or contact occur.

Here are some tips and tricks for eliminating and controlling mealybugs:

• Inspect your plants weekly for signs of mealybugs. Catching an infestation early is key with this pest.
• Using a Q-tip dipped in common household rubbing alcohol, directly apply it to the mealybug on your houseplant. This will kill the pest on contact. Keep going until there are none visible, repeat treatment over the next few days until all signs of pest are gone.
• Prune off and destroy affected areas of the plant if infestation is severe. Do NOT compost infested plants or plant parts.
• Mealybugs tend to wedge themselves anywhere they can fit such as leaf folds, in blooms and on new growth. Make sure to inspect all new houseplants before introducing them to your home, and keep the new houseplant separate from other plants for a week or so if possible.
• Insecticidal soap can be effective, but must be carefully applied to get to hard-to-reach places that mealybugs inhabit.
• Neem oil and other horticultural oils sprayed on plants or mixed into the soil are a common solution and preventive.
• Take your plants outside and turn your hose up to it’s highest setting. Use the hard spray of the water to wash off as many of the mealybugs as you can. Alternatively wash plants foliage and stems under lukewarm water in your sink brushing off pests with a soft toothbrush. Follow this treatment with rubbing alcohol on a q-tip to destroy any remaining pests.
• Chemical solutions are not recommended for mealybug treatment and have been shown to be nearly as effective as spot treatments, soaps and oils. Systemic insecticide dinotefuran may reduce mealybug numbers on houseplants.
• If your plant is having frequent outbreaks of mealybugs, consider repotting the plant. Thoroughly wash the pot with soap and water and use fresh soil.

APHIDS. 

What do they look like? Aphids are small (1/8 inch long), soft bodied, pear-shaped insects with long legs that may be green, yellow, brown, red or black in color depending on species and food source.

There are more than 4000 species of aphids. The majority of aphids are wingless, but many aphids can also have winged forms, especially when an infection is at its height. The ability to produce wings provides the pest with a way to disperse to other plants when their current food source becomes scarce.

These pests tend to group together toward the base of the plant and on the underside of leafs where they feed and cause damage by sucking sap from your plants. During this feeding the aphids secrete a a sticky fluid called honeydew. This fluid drips onto plants, attracting ants and promoting mold growth on leaves. 

Signs of aphid damage may include may stunt plant growth, yellowing, mold, leaf drop and deformation of leaves, buds, and flowers.

Where do they come from? Many times aphids are brought in on an infected plant but like other pests they can be introduced through wind, fly inside or may be carried in on your clothings or pets.

The life cycle of the aphid is quite different from other insects. These pests may or may not have wings depending upon their circumstances and species. Wingless females are called stem mothers. Stem mothers can reproduce without fertilization throughout the entirety of the summer or even year round in tropical environments. These female aphids are unique from other insects because they produce live young as opposed to eggs. They will give birth to many generations until finally one day the host plant becomes overcrowded and it’s time to move on.

When this occurs, some of the offspring will become adults with wings after their molt. These winged adults will then fly to nearby plants and begin the cycle over. In late summer as temperatures begin to drop there will often be both males and females produced. Mating occurs and the female lays eggs that survive the winter and hatch in the spring. In tropical climates where temperature drops are mild to moderate, there may be no need for this egg stage and generations continue as normal.

How do I get rid of them? As always you’ll first want to decide if you’d like to use an organic method or not. If you have pets or small children, we highly recommend sticking with organic options as they’re safer should accidental ingestion or contact occur.

Here are some tips and tricks for eliminating and controlling aphids:

• Pruning off affected areas of the houseplant is an effective removal method if you’ve found them before the infestation has gotten bad. Do NOT compost infested plants or plant parts.
• Another effective method is to turn your hose to its strongest setting and blast the plants with water, follow up with a soap spray or neem oil solution and repeat as necessary every few days.
• Check your plants regularly for aphids, at least twice a week when plants are in active growth.
• Control ant populations. These pests go hand in hand as ants love to feed on honeydew. If many ants are present near your garden or plants, it is likely aphids are as well.
• Neem oil, insecticidal soaps, and horticultural oils work well against aphid infestations.
• Avoid over fertilizing, especially with fertilizers high in nitrogen. Nitrogen encourages rapid foliage growth and this new growth is something aphids love.
• Chemical solutions should only be used for extreme infestations and sparingly. Using pesticides can lead to pesticide-resistant aphid populations.

SCALE.

What do they look like? Scale insects are small (1/8-1/2 inch) oval shaped immobile insects that fix themselves to our plants to feed on their sap and nutrients. There are over 1000 different species of scale insects, they come in a wide variety of shapes, sizes and colors. This pests appearance is more like that of a shell or dark bump on the plant than an insect so many times they can sneak by feeding on your houseplant unnoticed.

Scale insects can be divided into two main categories – armored and soft. Armored scales have a hard protective covering that is not attached to the body – this covering is called a test. This waxy covering seals tightly against the branch or leaf the scale insect is feeding on, making the insect essentially waterproof. They are immobile and live their life under their protective covering (armor/test) feeding on the plant they are attached to. Unlike their soft counterparts armored scales do not secret honeydew but they are much harder to control when mature.

Soft scales are covered in a smooth waxy film instead of having a test. They are larger and their bodies are often more rounded and flatter than armored scales. Soft scales excrete large amounts of honeydew, which as we discussed previously will drip on plants and promotes the growth of blackish sooty mold while also attracting ants. Some varieties of soft scare are able to move though they rare will.

Signs of scale damage you may notice are poor or slow growth, a withered or sickly appearance, leaf drop and yellowing foliage. If left unchecked, an infested plant may become so weak that it dies, if the infestation is large this may happen very quickly.

Where do they come from? These small pests are sneaky, like other pests they often get inside by hitching a ride on a new houseplant or are carried in by humans and pets. The scales life cycle may be different depending upon the species but generally all are similar consisting of three main stages and a few instars, the main stages of the scale life cycle are egg, nymph and adult.

Mature female scales lay eggs hidden underneath their protective covering, although some species lay their eggs externally where they are covered in a cotton like substance. These eggs will hatch between 1 and 4 weeks depending upon environmental conditions. Once the eggs hatch, tiny yellowish orange nymphs begin crawling around the plant until a suitable feeding site is found – this nymph stage is when the majority of movement occurs giving them the nickname “crawlers”.

Once the nymph finds a suitable feeding spot they typically do not move again and will spend the rest of their life in that spot. Male nymphs typically have two instars before maturing into adults but because the scale insect changes to much in appearance as it matures, many species can appear to have more than two instar stages. Female nymphs usually have three to four instars before their adult stage. During these instars scales will lose their legs and begin to develop their outer coating or their test/armor, depending upon if they’re soft or scales.

Although in many species of scale insects females reproduce asexually, there are some species of scales where male will retain their legs and even develop wings for the purpose of seeking females and reproducing. These winged males look like tiny gnats and do not feed on plants. Most species of scales have several generations a year making them especially difficult to control. They may also overwinter as nymphs and adults.

How do I get rid of them? Many houseplant addicts agree that these pests are one of the hardest to eliminate once they’re established. There are many methods of control and elimination for scale insects.

As always you’ll first want to decide if you’d like to use an organic method or not. If you have pets or small children, we highly recommend sticking with organic options as they’re safer should accidental ingestion or contact occur.

Here are some tips and tricks for eliminating and controlling scale:

• The best method for control and elimination is to remove and destroy infested branches and plant parts, since these pests are immobile this is a very effective removal method. This will also prevent them spreading to your other plants. Do NOT compost infested plants or plant parts.
• Try removing them manually. Using a metal icing spreader, butter knife or the tip of a pocketknife attempt to flip the armor off the branch. If you are able to successfully remove the armor you should be able to now see the insect’s body and destroy it – if you see the body this means you have armored scales. If you are dealing with soft scales the whole insect will come off when you try to remove it. Soft scales are easier to remove manually and you may be able to even rub them off by hand or with a soft toothbrush.
• Remember how we said armored scales are virtually waterproof? Well because of this most direct contact insecticides will not affect the scale insect outside of its nymphal stage. If you are using a chemical solution carefully read the package and make sure it says it can be used for scale insects. We recommend a solution containing acetamiprid, dinotefuran, thiamethoxam or others in the same family.
• Systemic insecticides are also effective if they are the type that work by being absorbed into the plant (making it toxic to feed on) after they’re applied, again thoroughly read the label.
• Horticultural oils work well on scale. Oils kill scales by disrupting their cell membranes and blocking off the pores on their bodies in which they use to breathe. Oils kill on contact if the scale is in its nymph stage.
• Insecticidal soaps are excellent for prevention and while they won’t affect adult armored scales very much they will help eliminate soft scales.
• Neem oil or chemical solutions containing azadirachtin, a key ingredient in neem oil, are an excellent way to prevent scale. This will also will kill mature insects over time and kill nymphs on contact.
• Food-Grade Diatomaceous Earth is an excellent preventive.
• The cotton swab and alcohol method mentioned in our mealybug section is also effective in smaller infestations.

Have any of these top 5 most common houseplant pests ever affected you? What houseplant pests are you interested in learning about? Do you have any special methods to combat these pests that have worked well for you in the past to share with us? Let us know in the comment section and keep an eye out for our next article on beneficial insects!

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