How to Get Rid of Common Houseplant Pests
How to Get Rid of Common Houseplant Pests
- 1 How to Get Rid of Common Houseplant Pests
- 2 Aphid
- 3 Broad Mites
- 4 Fungus Gnat
- 5 Leafminer
- 6 Mealybug
- 7 Scale
- 8 Spider Mites
- 9 Springtail
- 10 Thrips
- 11 Whitefly
- 12 Controlling Pests Organically: Aphids, Whiteflies, and Thrips
- 13 Controlling Aphids in Indoor Growing
- 14 Controlling Whiteflies in Indoor Growing
- 15 Controlling Thrips in Indoor Growing
- 16 Aphids, scales, thrips
- 17 Managing insects on indoor plants
- 18 Quick facts
- 19 Healthy plants have fewer pest problems
- 20 Early detection is key to managing pests
- 21 How to identify common houseplant pests
- 22 Common houseplant pests
- 23 Best ways to prevent houseplant pest infestation
Your houseplants spend all their time indoors where the temperature, sunlight, and humidity may not be optimal. That makes them easy prey for plant pests that find their way indoors. Pests have no natural predators inside, and their population can increase rapidly. Don’t wait until your houseplants are struggling. Check your indoor plants regularly for signs that an insect has infested. Catching them early is your best chance of saving your houseplants.
Here are 10 of the most likely suspects and how to control them.
B. Borrell Casals / Getty Images
Aphids look like small green, white, yellow, or black spots that can appear on all parts of a plant. They weaken plants by sucking on the stems and leaves. Aphids can reproduce so quickly that an infestation will cover the plant in days.
Aphids are soft-bodied insects and can be killed quite easily by a strong blast of water in the shower or repeated sprays of insecticidal soap. But they are persistent and you will need to remain diligent to rid your houseplants of these pests.
Bruce Watt, University of Maine / Bugwood.org
Broad mites and cyclamen mites are less common pests, but they can do considerable damage to the growing tips of plants. They are too tiny to see with the eye, but if the tips of your houseplant start looking stunted, distorted, or the leaves start curling, you can suspect mites are there. Favorite plants include African violet, begonia, cyclamen, and several tropical houseplants.
Some cases can be treated with a miticide, insecticidal soap, or horticultural oil if you can completely cover the plant with the spray. Usually, it is best to simply dispose of the infested plant, so the mites do not spread.
Johnny N. Dell / Bugwood.org
Fungus gnats are tiny flies that hover around indoor plants and fly up in a cloud when disturbed. The adults do not do much damage, but the larval stage feeds on feeder roots along with organic debris and fungus in the potting soil. They favor damp soil and are a bigger problem with seedlings than with established houseplants.
You can catch the adults with yellow sticky traps, which will cut down on the population. Allow the soil to dry completely for several days, to kill any existing eggs and larvae. To deter the insects, try using dryer sheets.
PhotoStock-Israel / Getty Images
Squiggly lines running through a leaf are a sure sign of leafminer damage. These are generally more of a pest outdoors, but they can follow your plants inside. Leafminers are the larvae of small black flies. The fly lays its eggs in the leaf and the larvae feed their way through the leaves until they are mature enough to emerge.
Often the damage is just cosmetic. Leafminer damage on edible greens, like Swiss chard and spinach, can ruin a crop, but on a houseplant, they are just unsightly. You can trap the adults with blue sticky tape and remove any damaged leaves, to keep new flies from emerging. There are a few insecticides that will control leafminers, such as Spinosad, but they are not usually necessary indoors.
Bosca78 / Getty Images
Mealybugs look like small cottony white blobs, usually attached to the plant at the stem joints, but they may also be found along the stems. They make themselves at home and slowly feed off the plants by sucking. Plants infested with mealy bugs often look like they are drying out, even when they’ve been watered.
Mealybugs are very hard to get rid of. If you catch the problem early, cut out the infested branches. You can also dab the mealybugs with a cotton swab soaked in rubbing alcohol. If your plants become severely infested, it would be best to just get rid of them. The mealy bugs are only going to spread.
Sunniva Harte / Getty Images
Scales are small insects that attach themselves to the stem of a plant then cover themselves with a hard, oval-shaped shell. Like mealybugs, they slowly suck the sap from plants, leaving them too weak to sustain themselves.
A scale infestation is very hard to get rid of. Pesticides often don’t penetrate their hard shells. You may have some luck rubbing the scales off with your nail or a soft brush. Young scales have to crawl unprotected to a new location to set up shop and can be sprayed at this crawler stage with insecticidal soap. The soap has minimal effect on protected adults.
William Fountain / University of Kentucky / Bugwood.org
Spider Mites leave telltale webbing, especially on the inner joints of plants and in plants with lush foliage. The tiny mites are about the size of a pinhead and injure plants by sucking their juices. Attacked leaves will have yellow stippling. As the infestation gets worse, the leaves will turn totally yellow and brittle and quickly die.
To get rid of spider mites, thoroughly spray the affected plants with insecticidal soap. Repeat as recommended on the label.
Debbie Rigden Images / Getty Images
Springtails are tiny wingless insect-like creatures that can jump several inches in the air when disturbed. You probably won’t notice them unless there are several. In a cluster and they all spring upwards together, looking like a small cloud.
They favor damp areas, like moist potting soil. Although springtails can feed on roots, when they are in the soil, they don’t do much damage to plants. However, if the soil dries out, the springtails will look for moisture elsewhere, such as a basement or bathroom, where they can become an annoyance. You can vacuum them up or try using diatomaceous earth.
David Cappaert / Bugwood.org
These tiny insects (less than 1/25 inch) can do a lot of plant damage. They feed in groups, sucking on leaves, flowers, and even fruits. In addition to weakening plants and distorting growth, they also spread disease.
Since there are no natural predators indoors, you will need to use some type of contact insecticides, such as neem or insecticidal soap. Be sure to cover all sides of the leaves.
Ken Wilson / Getty Images
These tiny whiteflies tend to hide out on the underside of leaves and fly up in a puff when disturbed. They suck on leaves and stems, weakening plants and causing distortions and discolorations. Whiteflies reproduce very quickly, so catching them early will make eliminating them easier. You can catch them with yellow sticky traps and spray them with either insecticidal soap or horticultural oil. The spray must make contact with the insect to work.
Controlling Pests Organically: Aphids, Whiteflies, and Thrips
Takeaway: In this article, we look at aphids, whiteflies and thrips—three of the most common pests of indoor growing areas.
Most gardeners have had to fight off a pest infestation in their garden at one time or another. The good news is that there is a wide range of pest control options that allow you to deal with common plant pests without unleashing harmful chemicals and potentially exposing you, your family and your environment to harm. Mother Nature has already figured out how to deal with many of the pests that are bad for our gardens, we just need to let her be our guide. Read on to learn more about some of the most common plant pests out there and how you can effectively deal with them the natural way.
Controlling Aphids in Indoor Growing
Aphids, which are sometimes referred to as plant lice, damage plants by sucking out the sap from their leaves. Although they are large enough to be seen without magnification, their presence can go undetected until after significant damage has been done. There are many different kinds of aphids, but their modus operandi is generally the same.
Damage from aphids generally appears as a puckered or blister-like appearance on leaves, which can lead to leaf distortion or stunted growth. To add insult to injury, aphid frass (insect excrement), more commonly known as honeydew, attracts ants. Honeydew is a sweet substance made primarily of the sap aphids have consumed. Plants that have been contaminated with honeydew can develop a disease known as sooty mold, which creates a tar-like appearance on plant leaves that inhibits photosynthesis.
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Aphids are prolific reproducers. Female aphids are born pregnant and can start laying their own young within a week of their own birth. Due to their rapid population growth, multiple strategies often have to be employed to effectively control them.
Many different beneficial insects will either feed upon or parasitize aphids, or do both. One of the most effective biological controls that can be unleashed upon an aphid army is the common lady beetle, Hippodamia convergens. Lady beetles are carnivores that will seek out aphids and consume plenty of them every day. Lady beetle larvae will consume aphids and other pests in greater numbers than their adult counterparts.
Aphidoletes aphidimyza and Aphidius colemani are two parasitic wasps that seek out aphids in which to inject their eggs. Their eggs develop inside the aphids and feed on them from within. When they emerge as adult insects, they seek out other aphids to continue the cycle. The remaining hollow aphid carcass that these wasps leave in their wake is known as an aphid mummy.
If using beneficial insects makes you a bit queasy or sounds too much like science fiction, you can use a variety of liquid applications that are naturally derived from plants to effectively kill aphids by suffocating them or interfering with their body functions. Pyrethrins, not to be confused with the man-made pyrethroids, is an extract from the chrysanthemum plant. It is a common ingredient in many organic insecticides. It works by confusing the nervous system of the aphids, leading to paralysis and death.
Azadirachta indica, or the neem tree of India, is the source of another bio-pesticide, neem oil. Neem-based products can be applied to infested plants as either a foliar spray or as a soil drench.
Regardless of the method you have selected to control your aphid problem, multiple applications will be required. If you are using bio-controls such as lady beetles or parasitic wasps, it is important to release them on a regular basis to keep their populations sufficient for pest control. If you opt for a spray treatment, plan on applying the product two or three times every seven to 10 days, making sure to get thorough leaf coverage, both on the undersides as well as the tops and stems.
Controlling Whiteflies in Indoor Growing
Whiteflies, as their name implies, are white, flying insects. There are several species of whiteflies out there, all of which are closely related to aphids. Like aphids, whiteflies are visible without magnification. They damage plants by sucking the sap from them, but their damage appears differently than the damage from aphids. Leaves damaged during whitefly feeding will turn yellow or brown and drop off prematurely. They may get a speckled appearance before turning color.
Like aphids, whiteflies also secrete honeydew with the same potential results of attracting ants and fostering the development of black, sooty mold on leaves that may be below where the whiteflies are feeding. These pests are also prolific reproducers and each female whitefly can lay up to 400 eggs in her lifetime. Her nymphs will immediately begin sucking on leaves once they have hatched and can stay fixed in one spot, feeding for up to four weeks as they pupate into adult whiteflies. A heavy infestation of whiteflies will appear as a burst of smoke when disturbed. Care should be taken to not wear light-colored clothing when working around plants with whiteflies as they can easily be transported to other plants unknowingly.
Whiteflies can be controlled with beetles and parasitic wasps, like their aphid cousins, but different beneficial species are better at controlling them. A small, black beetle, known as delphastus pusillus, which is about the same size as the whiteflies themselves, will feed on all stages of whiteflies, but they prefer the eggs and nymphs. They are especially useful in high-infestation areas, as they require consuming up to 200 whitefly eggs per day in order to reproduce.
Whiteflies also can be controlled via the parasitic wasps found within the genus Encarsia. Encarsia formosa is the most prevalent beneficial wasp used to control greenhouse whiteflies. These tiny insects inject their eggs into the bodies of whiteflies in the same manner as the Aphidoletes aphidimyza and Aphidius colemani do with aphids. Whitefly hosts generally die 10 days after being parasitized. The adult Encarsia will emerge from the dead whitefly in about another 10 days.
To get a handle on whitefly infestations using sprays, pyrethrins and neem are two good options — insecticidal soap is another. For whitefly control, use a combination of different controls in successive sprays. It is nearly impossible to get full coverage in one application given the whitefly’s ability to spook easily and fly off. Plan on at least three applications, possibly more.
Controlling Thrips in Indoor Growing
Thrips are similar to aphids and whiteflies in that they cause their damage by sucking as opposed to chewing. These small flying insects can be anywhere from clear, to black, to reddish orange in color. Along with their black deposits of frass, they are often found on the undersides of leaves. Like the other pests described here, there are numerous thrip species out there, each with their preferred host plants.
Damage from thrips appears as a dappled, stippled or speckled leaf surface. Thrips will also feed on many fruits, which ends up causing damage to the entire crop. Thrips usually don’t kill their host plants; they often cause stunted growth or poor performance as a result of the plant’s cellular losses and reduced ability to photosynthesize.
Controlling thrips using beneficial insects depends on the species you’re tackling. There are actually predatory thrip species that can be released to control the pest thrips. A positive identification of the pest species should be made before deciding on a beneficial insect to release. Predators such as the green lacewing (Chrysoperla rufilabris) and the minute pirate bug (Macrotracheliella nigra) will generally feed on multiple species of thrips. However, you cannot expect stellar results if you are releasing beneficial insects to control thrips on outdoor plants. They are much more effective when used to control thrip infestations of indoor crops.
The most effective spray for controlling thrips is spinosad, a naturally occurring fermented bacterium. This is the active ingredient in many insecticides approved for organic gardening. Unlike many non-synthetic pesticides, spinosad penetrates the leaf surface to reach the undersides where the thrips are feeding.
Aphids, scales, thrips
These are all small, soft-bodied insects that feed by sucking plant sap. Damage may include leaf stippling, leaf bleaching, leaf curling and distortion, whitish waxy growth, or sticky honeydew (condensed sap) which may support the growth of sooty mold. Although most of these insects are related, thrips are classified in a different group.
Aphids, adelgids, and phylloxera
Adults of these tiny pests often lack wings. Aphids can produce copious amounts of sticky honeydew, which can lead to the growth of black sooty mold.
Hoppers, sharpshooters, and spittlebugs
These insects feed by sucking plant juices and may leave drops of sticky excrement. Damage includes stippled, bleached or brownish leaves.
Mealybugs often have waxy filaments radiating from their bodies. They are wingless, move slowly, and congregate in groups covered with whitish mealy or cottony wax.
Psyllids and whiteflies
Psyllids and whiteflies suck plant sap and excrete sticky honeydew. As adults, psyllids resemble miniature cicadas; whiteflies look like tiny flies with whitish wings.
Scales are immobile, wingless, and lack a separate head or other recognizable body parts, so many people donвЂ™t recognize them as insects.
Thrips are tiny, slender insects, with fringed wings and piercing mouth parts. They often leave tiny black dots of waste on leaves.
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Agriculture and Natural Resources, University of California
Managing insects on indoor plants
Healthy plants have fewer pest problems
Prevent, or at least minimize, pest issues on indoor plants by choosing the right plants and providing good overall plant care. Learn about basic care and growing needs for your plant.
Grow plants in the best possible conditions
- Select plants with growing requirements that match the indoor environment (humidity, light, temperature).
- Plants cannot fight off pests when they are struggling to grow in too little light, overly wet or dry soil, too hot or too cold air temperatures, etc.
Water plants properly
- Know how much water your plant needs.
- Water the soil at the base of the plant, not the leaves.
- Be sure the plant’s pot drains well.
- Avoid letting plants stand in water.
- Over-watering and poor drainage can cause root rot and encourage fungus gnats as well as other pest issues.
Understand your plant’s nutritional needs
- Apply fertilizer at half the recommended strength.
- Fertilize when the plant is actively growing.
Keep plants clean
- Keep soil surface free of dead leaves, stems and flowers.
- Wash plant leaves with a damp cloth as dust and grime can reduce plant health. Never use leaf shine products or milk.
- Prune out dead branches and stems.
Use new, sterile potting soil when potting plants
- Never pot indoor plants using soil from the garden.
- Avoid using soil from open bags of potting soil that have sat outside for potting indoor plants. Save it for your outside pots.
- Plant in clean pots and wash soil off of plant roots.
Early detection is key to managing pests
Finding pests before they become a problem is the best way to keep insects at bay.
- Thoroughly examine all plant parts and containers before bringing them home from the store or indoors for the winter.
- You may need to use a magnifying lens as some pests are very small.
- Inspect tops and undersides of leaves for insects, webbing, holes and eggs.
- Examine leaves that are discolored as this may be evidence of a pest problem.
- A ten-power hand magnifying lens is helpful when looking for pests. There are also magnifier apps for smart phones.
- Examine leaves that are discolored as this may be evidence of a pest problem.
How to identify common houseplant pests
As people became more aware of the plants that I was growing in my home, I noticed I would often get the question, «How do you deal with all the insects?»
«All the insects. » I thought. «What on earth do they mean?» I couldn’t quite pinpoint the root of their question. Did they assume that benign insects were just generally attracted to flower and foliage—or were they insinuating that I had an outbreak of insect pests? If the latter, I must admit that for the better part of six years I was blissfully unaware of any pesky insects in my home. Not because I’m out of tune with plant and bug (most friends know that I’ve been raising insects since I was 9 years old and ended up studying entomology in college), but largely because my plants didn’t have any noticeable pests.
All of that changed in 2016 when I began growing food in my home. I had converted my closet into a vegetable garden as an experiment and within weeks, the pest numbers exploded. I noticed scale, including mealybugs; whiteflies; thrips; and even the fungus gnat, (the latter which is more annoying than pest-like). As a prolific gardener in an indoor, closed environment, I didn’t have any desire to toss out plants or spray toxic insecticides indoors, so I opted for integrated pest management and natural techniques, which I’ll go over a little bit here and more in depth in a subsequent post. However, I wanted to use this time to go over some of the common pests that you may eventually get on your houseplants, and simple ways to prevent infestation from the onset.
Common houseplant pests
The list of seven insects and mites are by no means an exhaustive list of houseplant pests, but they are the most typical ones that you’ll likely see in the home.
Scale are primarily immobile insects that stick themselves to stems and leaves. They come in two families: Coccidae and Diaspididae. The brown soft scale (Coccus hesperidum L.) shown here is a common houseplant and greenhouse pest.
Common brown scale (Coccidae and Diaspididae families)
The first time I noticed a scale insect was on a jasmine plant that I had purchased at the farmers market. I didn’t see the insect at first, but I did notice that some of the bottom leaves of the plant were shiny and sticky. Upon closer inspection, I noticed brown nubs stuck to the woody stem and underside of leaves, closest to the central vein. This was scale.
There are different varieties of scale but by far the most common is the brown soft scale (Coccus hesperidum L.). They are rather inconspicuous—and don’t look like a typical insect—unless you know what to look out for. Firstly, they’re ovate, only about 3-4 mm long and about half as wide. They can range in color, but are most often brownish in appearance (hence the name), but I’ve also seen them in shades of yellow, amber, and even olivaceous. They’re called «scales» largely due to their scale-like appearance on a plant, due to waxy or armored coverings. They are often seen in clumps along a stem, sucking away at the plant’s juices with their spiky mouthpart.
They are only mobile when they are born. Soft scales, which are just one of the groups of scale insects, can reproduce both sexually or parthenogenetically, which means that they can produce young without fertilization. Quite unique in the insect world, the female scales are ovoviviparous, which means they give to birth to living young by hatching the eggs while they are still in their mother. This is the same in Madagascar hissing cockroaches, which are not a plant pest, but an insect that I raise, and I’ll be the first to say that it can be shocking that one day you’ll have 2 cockroaches and the next day 20X that amount. Same goes for the scale insects. I say this only because you can’t really get rid of the eggs unless you get rid of the adults. Once the young, which are called «crawlers» are born, they’ll disperse along the plant, find a place they like (usually around some new growth), and literally plant themselves there for the remainder of the time—reaching maturity at around 65 days.
Scale can be a real problem indoors because quite frankly, they have a good temperature year round, which means they’ll likely reproduce around the clock. Good news, however, is that scale are, as I shared, relatively immobile, so if they are contained to one plant, then you can control them. Most people choose to discard the plant. Though it was slightly stunted in growth, I decided to keep my jasmine to see if I could revive it. First, homemade soap sprays aren’t that effective on scale, partially because the scale on the outside of the insect acts like a shield. You’d want to get it under the cap of the insect.
What I did was as follows:
1. Place a plastic bag or some covering around the soil of your plant. This prevents any scale from falling into your soil.
2. Get a natural, rosemary-based insecticidal soap. Spray this on the plant so it’s nice and soapy.
3. Run your fingers along the stems and plant leaves, turning up the scale with your fingernails. If you don’t want to touch the insects, you can use an old toothbrush or even a toothpick, but I feel as if I have more control and accuracy with my fingernails. You may notice some scale fall onto the plastic bags; pick them up and discard them. Really be sure to look over the entire plant. My jasmine had a woody stem and the scale looked like part of the stem, so don’t be fooled! If helpful, get a pocket magnifier to look over the plant, including the creases of where the leaf meets the stem.
4. After you’ve sufficiently soaped and scraped the plant, give it a good, sharp spray with your hose or your shower. You’ll want to get all the soap off the plant so it doesn’t affect growth. Keeping a plant strong, healthy and growing, can often keep insects at bay.
5. Check the plant again for the next three days, making sure that you hadn’t missed any scales. If you did, you can repeat steps 1-4. Check again once a week for the two months, just to make certain you got all the little buggers.
Mealybugs are a type of cottony, mobile scale that often can be seen in clumps on your houseplants. They are generalists, and I’ve particularly found them on everything from my potato plants, succulents, Stromanthe and Plerandra.
Mealybugs (Pseudococcidae families)
I’m not quite sure how mealybugs first got into my home, but I first noticed them on my potato plants that I was growing in my closet garden. Potatoes, particularly the leaves and stems, grow incredibly fast, so I was monitoring them pretty closely. I first planted the potatoes from ones that I purchased in the farmers market and that started growing «eyes». Interesting enough, I had more potatoes that began growing eyes in my fruit basket, and mealybugs would just «show up» on them. Still to this day I’m befuddled by their spontaneous generation.
Mealybugs are an unarmored scale insect, and I personally think they are more difficult to control than the common brown scale. This is for a few reasons. First is the most obvious: mealybugs move. Though its slow movement, if any plant is touching another, there is a chance the mealybug will hitch a ride on a new leaf and spread. Secondly, though their soft, cottony white appearance is quite obvious on a plant, they have a tendency to hide out in the damnedest of places, like the crotch of a plant or in a leaf that has yet to unfurl. Additionally, they have waxy secretions, giving them their cotton-like appearance, which can serve as some basic protection. And lastly, they breed like rabbits of the insect world. Females can deposit around 600 eggs in loose cottony masses, often on the underside of leaves or along stems. The early instars will hatch in about a week and this often causes a population explosion.
As such, it’s important to get mealybug populations in control. Some will toss out a plant completely, but I did no such thing. Instead I did a three-pronged effort, involving the release of two beneficial insects—the green lacewing (Chrysoperla carnea) and highly effective, aptly named mealybug destroyer (Cryptolaemus montrouzieri), and also spot treatment using a q-tip and isopropyl alcohol. Dabbing the alcohol directly onto the mealybugs will easily kill them on the spot, but the upside to releasing the beneficial insects is that the insects can often get to places in a plant that you often cannot get, so I believe both methods—at least for me—have worked the best.
Aphids are another plant-sucking insect that often congregate in large numbers. I most often see them on my herbs and I take enjoyment in squishing them between my fingers, since they are full of plant juice. No wonder why some ants like to harvest the sweet goodness coming out of these globulous insects.
Aphids (Aphidoidea superfamily, Aphididae family)
Aphids may very well be the most commonly known unwanted houseplant pests. However, I’ve only ever seen aphids on the food crops that I grow in my home and never on my tropical houseplants. It may very well be a matter of preference of them, but I think what they’re really looking for is that gooey sap that they get from the plant by piercing it with their mouthparts. They also exude a sticky, sweet honeydew from their rear, which often attracts other pests, like ants—or provides a medium for sooty mold to grow on, which essentially spells disaster for a plant, particularly if it’s fruiting.
Aphids are a soft-bodied insect, so they’re very easy to squish between your fingers, which I typically do. Like scales, aphids are also viviparous, which means they give birth to live young. Aphids are born wingless, but if you see an aphid with wings, it’s a signal that the colony got too crowded and they are looking for a new houseplant for which to feed.
The best way to get rid of aphids naturally is as follows: on a warm day, early in the morning take your infected houseplant outside and spray it vigorously with a hose. Be careful not to break the plant if it’s delicate or newly growing. This can be done by spraying short, strong bursts. This should knock down the aphid population naturally. Once you’re finished, inspect the plant and crush any remaining ones with your fingers. Repeatedly do the hose-spray method for another few days until you see everything is under control. If you find aphids keep on coming back despite your best hosing efforts, I would then encourage bringing in some beneficial insects, particularly green lacewing larvae or ladybird larvae.
Whiteflies (Trialeurodes vaporariorum) closely resemble tiny white moths, but they are closely related to aphids and scales. Like aphids, they produce honeydew from sucking plant juices, which can then attract sooty mold, which can further harm plants.
Common whitefly (Trialeurodes vaporariorum)
At first whiteflies, which are more closely related to aphids and scale, can be mistaken for little white moths or even mealybugs. Unlike their fellow pesky counterparts, they will easily take flight if you disturb them. I first noticed whiteflies in my home when I started growing potatoes indoors (I mean seriously, potatoes indoors brought every pest imaginable!). Whiteflies are more or less generalists when it comes to plants. I noticed that they first were congregated in small numbers on potatoes, but they soon started to alight on my elephant ear plants, which were nearby.
Adults will lay eggs while they are eating (efficient little beasts, aren’t they?). Eggs will hatch in less than a week and then their nymphs, similarly to scale, will crawl a short distance, plant themselves, and suck the plant until they go into a resting stage at about the 3 week point. In about four, maybe five weeks, they begin to emerge as adults and the process repeats. As indicated, both the nymphs and adults of the whitefly use their mouthparts to suck juices from plants, which can cause leaves to yellow and fall off prematurely. Additionally, whiteflies, like aphids, exude honeydew, which becomes an attractant for sooty mold. If you allow whiteflies to multiply, then they can attack your plant enough to weaken it.
Whiteflies are attracted to the color yellow, so the best way to catch them is by having yellow sticky traps, blasting the leaves with short bursts of water from a hose, and also introducing a beneficial insect, like a green lacewing, ladybird beetle, or whitefly parasite (Encarsia formosa). All three techniques are highly recommended, in that order.
Red spider mites (Tetranychus sp.)
Mites are technically not insects but they, like insects, are Arthropods. They are probably some of the most feared of the common household insect pests, largely because they are so difficult to get rid of.
Spider mites are nearly naked to the eye. You often need a magnifying lens to spot them, or you may just notice a reddish film across the bottom of the leaves, some webbing, or even some leaf damage, which usually results in reddish-brown spots on the leaf.
Earlier in the year I was gifted an Alocasia micholitaiana ‘Frydek’, which is a gorgeous velvety green alocasia. I typically always check my houseplants before bringing them indoors, which is a proactive way to make sure no pesky insects are in tow, but you can’t always rely on eyesight. Within about three weeks, I noticed some webbing and the start of brown dots on some of the mature leaves. Before mites could spread to the other plants, I took the Alocasia and washed it thoroughly in the shower and made sure the humidifier was on daily. Mites prefer dry conditions, so keeping the air humid and the plant on the wet side (something an Alocasia prefers anyway), was able to save the plant, although it still bears the battle wounds of the mites.
Spider mites also have a range of natural predators, including other mites like Phytoseiulus sp. and generalist predators like minute pirate bugs and lacewing larvae.
Fungus gnats (Bradysia sp.)
I’m including fungus gnats as a common houseplant pest, only because they are common and more of an annoyance to people versus plants. Fungus gnats look similar to fruit flies, and are often mistaken as such. They are pretty feeble fliers and can often be seen circling around soil, particularly if it’s fresh, damp compost. Their larvae, which are really the more cause for concern here, prefer to feed on fungi in the soil, which you can only get in moist conditions. They technically can eat plant material, but if the fungi levels are high, they often won’t.
I ended up getting quite a few fungus gnats when I started to grow microgreens in a nice bed of compost. The adult gnats will often hang around the soil because that’s where they like to lay eggs, but adults are harmless. I basically got some BTI, or Bacillus thuringiensis, which is a natural and safe bacteria that you can sprinkle in the soil and some yellow sticky traps to catch the adults. The problem was solved within three days. Additionally, you can bring in a natural fungus gnat predator, such as Stratiolaelaps scimitus, which is a type of mite.
Thrips (Order: Thysanoptera)
Thrips are technically a less common insect pest, but I’ve found that they are most prevalent in my household. I believe they first came into my home through either my herbs or one of my friend’s plants, and they quickly spread, as thrips are typically generalists, puncturing the outer layer of a plant and creating a silvery discoloration on the plant leaf. You’ll also notice tiny little bits of black frass, which is a nice way of saying «insect poop». One of my most prized possessions, an African blue basil (Ocimum kilimandscharicum × basilicum), which is particularly hardy and difficult to find, had been almost fully ravaged by thrips. I had saved a couple cuttings, which have now almost entirely bounced back thanks to the help of some natural predators, including Thrips Predators (Neoseiulus cucumeris) and Minute Pirate Bugs (Orius insidiosus), which I released in tandem with much success. Additionally, adult thrips are attracted to the color blue, so you can also affix blue sticky traps around your plants to curtail the population.
When you first bring home a houseplant, you may want to take a few precautions to make sure that it has no pests that will spread to your other plants. Pictured here, an Alocasia reginula.
Best ways to prevent houseplant pest infestation
There are a number of best practices that you can do to reduce or eliminate the potential for pest infestation in the home. They are by no means «no-fail» solutions, as many plant pests can easily go undetected by the eye, but they are typically sufficient and proactive approaches to help ensure your plants stay healthy.
Inspect a plant before you buy it. There have been a number of occasions where I noticed insects on a plant. If you can and do identify insects, you should tell the plant shop owner or greenhouse owner so that they can quarantine the plant and ensure it doesn’t get sold to anyone else.
Use clean pots and potting soil. If you’re bringing home a new plant and are putting it in a new pot, make sure that pot was cleaned thoroughly with a diluted soap or bleach solution to ensure there were no disease-carrying agents. Same goes for soil: I typically always get new soil for my plants because there is no telling if there are any leftover eggs overwintering in the soil from previous pests.
Remove any potential pests from the actual soil ball of the plant. Sometimes the plant you bought will have some interesting Arthropods within its own soil. I’ve often seeing pillbugs (called roly-polys), sowbugs, and millipedes, all which prefer damp, dark, moist environments. These generally won’t harm plants, as they largely eat decaying organic material, but in the case of millipedes, they may eat bulbs and tubers. A long while ago, I bought a plant from the flower district in Manhattan and it was infested with millipedes. A natural way to reduce millipede population, if you think it is a problem, is spreading Diatomaceous earth on the soil, which are fossilized diatoms that actually cut the millipedes, or by using nematodes, which over time, breed and replicate within the millipede, eventually killing it. I would say that if you have a few millipedes in your soil, no biggie, but if you see them, you can capture them and set them loose outside.
Isolate your plant from other plants for a few days to a couple weeks. If you want to be extra careful, be sure to isolate your plant for a few days from your other plants, inspecting its leaves and stems everyday. If you think everything checks out, then move it into your intended space.
Don’t let other plant’s leaves touch the leaves of your new plant. This one is the hardest to do—particularly in my home—if not next to impossible. However, some pests, like scale, can’t spread unless they have a «bridge» to get across to the next leaf.
Don’t forget I have a YouTube Channel as well, with some more great insights into plant pests and beneficial predators. Here are two such videos below, and if you haven’t yet, subscribe to the channel, as «Plant One On Me» comes out every week!