Common Houseplant Pests: Identify, Control And Prevent

Houseplants let us bring the beauty of Nature indoors – even the parts we don't want. In this article, we'll explore common houseplant pests and the most effective treatments, and explain how to prevent future invasions.

How to Identify, Control and Prevent Common Houseplant Pests: Treatment begins with identifying pests by their appearance and effects on our plants. There are many natural, environmentally safe treatment options, but synthetic chemicals are available too. Prevention starts with healthy plants, along with regular observation and precautions.

Common Houseplant Pests Overview

There's no need to panic when faced with a pest invasion. Those alarming critters may look alien, but each is well known and can be addressed with specific treatments. Houseplant pests won't hurt you, either: it's your plant they are after.

Our houseplants know it, too. Research is showing that plants send distress signals to other leaves to mobilize defenses when under a pest attack. There is even evidence that stressed plants alert their neighbors of the situation. This may invite other pests who thrive on weakened plants … but it also calls local predators to save them from the invaders. Plant-lovers already know houseplants are amazing—and the deeper we look, the more incredible things we find out.

There are basically two kinds of pests that damage houseplants—those that suck their juices, and those that eat vegetation outright. There are also nuisance pests that typically bother humans more than plants.

Types Of Common Houseplant Pests

Juice-Sucking Insects

The most common and troublesome pests are the little plant vampires that multiply quickly and literally drink the life-force right out of your prized green babies. They're small enough to escape casual notice, so an infestation can be a sudden surprise.

This destructive group includes:

• Aphids
• Mealyworms
• Scale
• Spider Mites
• Thrips
• Whitefly

Nuisance Bugs

These pests are more irritating to the human side of the aisle. They can fly into food and buzz up orifices and generally become a maddening presence in what is supposed to be a gentle hobby.

These are the main nuisance pests:

• Fungus gnats
• Ants
• Fruit flies
• Springtails

Plant Eaters

Chewing pests aren't usually as big of a problem for houseplants as they can be for outdoor landscaping. This is a good thing, because they can decimate foliage in short order.

Here's the roundup:

• Caterpillars
• Slugs
• Black Vine Weevils

Where Do Houseplant Pests Come From?

You might wonder where an isolated indoor houseplant gets its pests. Sometimes bugs seem to come out of nowhere. People even believed insects spontaneously reproduced before experiments by Pasteur in 1859 helped prove otherwise.

Some crawl through cracks or drift by on a breeze, but most indoor pests come in with other plants – which is why inspection is so important before bringing a plant inside.

Contaminated soil can be another pest source: unseen eggs and larvae can develop after months of dormancy.

Treating Common Houseplant Pests

Before delving into the life of each pest – and how to end it – let's examine the available treatments and the strategy for using them.

First, realize that the goal is pest control, not pest elimination. It would be overly toxic to attempt eradication of every pest, and the plant doesn't need that anyway … a reasonable insect presence is natural. Pest control is about limiting pest populations to the point your plants remain healthy.

If the problem does tip over into infestation, consider isolating affected plants for treatment. A weakened plant's infestation can spread to healthy neighbors that would otherwise resist the pests. Pay close attention to your nearby plants and consider extra prevention efforts.

Chemical pesticides may seem the most direct solution, but many natural treatments are just as effective and have less toxic effects on the environment. Recent years have seen increased development of organic methods that result in better long-term pest management.

Organic doesn't automatically mean safe, however. You can wipe out pollinators and predators of the very pests you're trying to eliminate. The best strategy is to use the lightest effective method of control that solves the problem.

Organic Pest Control

These treatments use products derived from biological sources:

Physical Removal: Hosing Off

Surprisingly, one of the most effective treatments for common houseplant pests is giving your plants a thorough hosing. Use a strong stream to knock off clinging pests: apply to both sides of the leaves and all around the stems. This won't dislodge all the tiny invaders, but it will reduce their numbers.

Avoid overwatering in your anti-pest efforts. Tilt the plant and spray upwards to avoid soaking the medium. Consider placing plastic or other covering over the soil.

It's best to spray first thing in the morning. This lets plants dry off during the day to avoid fungal or other moisture-related disease.

Also, physical removal is a highly effective “organic” tactic against larger pests like caterpillars and beetles.

Sprays That Suffocate: Horticultural Oils

Horticultural oils are an eco-friendly general treatment that's useful against most common houseplant pests. They're made from either petroleum or vegetable products. These oils are sprayed on plants: the viscous liquid clogs the oxygen-exchange spiracles of insects and mites and interferes with feeding and metabolism.

Horticultural oils must contact the pests directly to be effective. They work better against young or soft-bodied critters than mature specimens.

Proper oils for houseplants are lightweight to allow the plant to breathe. They may be labeled light or summer oil. Avoid dormant oil: it was developed to spray fruit trees during dormancy.

Light horticultural oil evaporates and wears away quickly, so it must be reapplied every few days. These oils don't leave a toxic residue and are safe for pets larger than an aphid.

To avoid burning and stress, don't apply horticultural oils to plants in direct sun or when temperatures are above 100°F (38°C). Spraying is ineffective in wet or freezing conditions.

A few plants are sensitive to the oil, so check on your variety before use. Spraying plants in the fall seems to increase cold-weather damage. Also, avoid putting it on plants that have received sulphur fertilizer or pesticides in the past 30 days—it's a bad combination for plants.

Insecticidal Soap

Another eco-friendly option is insecticidal soap. It contains potassium salts or a mixture of sodium and fatty acids to dry insects out.

You must spray the solution directly on the pest for it to work, and it has to be re-applied because it doesn't have a residual effect. It's more effective on soft-bodied critters.

This is actually an old control method that fell out of favor as industrial pesticides were developed in the early 20th century. Fresh attention to organic products has brought them renewed attention. Insecticidal soaps are generally non-toxic and eco-friendly.

Most plants tolerate soap solutions, but check your specific plant to be sure. Don't use in direct sun or in high heat, and stop if you notice poor effects on the plant.

There are many retail versions, but it's easy and inexpensive to make an insecticidal soap at home. Use only pure soaps like Ivory or Dr. Bronner's … avoid detergents like dish washing “soap” that can strip a plant's protective oily coating. A simple recipe is to add 3 or 4 tablespoons of soap to a gallon of water—mix and use immediately.

Alcohol

70% Isopropyl alcohol can be effective. Use by dabbing directly, or by mixing one part alcohol to three parts water as a spray or wash. African violets and others can be sensitive to burning, so test a discrete area first.

Botanical Pesticides

Many plants produce their own chemical defenses against pests, and these botanical pesticides can be highly effective treatments against juice-suckers and foliage eaters. While they are usually safer and more eco-friendly than conventional insecticides, don't underestimate them. Plants can pack a wallop.

Pyrethrum

This is one of the most popular botanical treatments for common houseplant pests. It's made from Pyrethrum daisies (Chrysanthemum cinerariifolium), and comes as a spray or a powder for dusting on leaves.

The active substance, Pyrethrin, acts broadly on many insects. It has a rapid “knockdown” effect – flying insects fall on contact – but paralyzes pests rather than killing them. For this reason, Pyrethrum is often combined with another insecticide to finish the job.

Pyrethrins are considered safe for mammals, but are toxic to fish and amphibians. Once sprayed, they quickly degrade within a few days. Most plants aren't affected by their application.

Essential Oils

Plant substances can be extracted and concentrated into essential oils that work as pesticides. Oils of cedar, clove, garlic, mint, and citronella are examples.

Essential oils work on contact by disrupting insect neurotransmitters. They stop working quickly and must be reapplied. They're safe most plants and vertebrates, but a highly concentrated form may cause irritation.

Neem Oil

One of the newest and most useful botanical pesticides, this product comes from Neem tree seeds. Its active ingredient, Azadirachtin, interferes with insect reproduction and molting. The oily base works against juice-sucking pests, while the Azadirachtin compound is more effective against chewing insects.

Because it isn't a contact killer and takes effect over a week or more, some growers apply Neem oil regularly for continued protection. It persists for about three weeks.

Neem oil is environmentally friendly: it's only mildly toxic to honeybees and other pollinators, and is well tolerated by plants. It's safe for mammals, birds and fish … but it's still recommended to wear a mask when using. Inhaling Neem oil can cause respiratory irritation and headaches.

Be aware there are two Neem oil products on the market: cold-pressed oils that contain Azadirachtin, and hydrophobic Neem oil that has been stripped of the active ingredient. The second type is actually a Neem derivative that acts as any horticultural oil while using the whole-product's name for marketing.

Sabadilla

This product from the Sabadilla lily is one of the least toxic botanical insecticides. It affects the nerve cell membrane of insects and causes death through paralysis.

Sabadilla breaks down quickly in sunlight and is a legal organic pesticide. It has low toxicity to mammals but can cause significant eye irritation and allergic reaction. It may be absorbed through skin contact.

Nicotine

Nicotine sulfate from tobacco plants was one of the first botanical insecticides. It kills insects by disrupting their nerve transmitters. Used correctly, it is generally safe for warm-blooded animals, but it can be absorbed through unprotected skin.

Nicotine breaks down quickly and is legal to use on organically grown crops. It's safe for most plants other than roses.

Limonene/Linanool

These naturally-occurring substances are common in citrus. The action of these effective contact insecticides isn't well understood and is currently receiving significant research.

Both Limonene and Linanool are considered eco-friendly and have low toxicity to birds, fish and most mammals – but they may have a damaging effect on cats. Both are common in cosmetic products.

Rotenone

Rotenone is highly toxic – more poisonous than most available synthetic pesticides. It's found in several plants and works through cell inhibition that deprives insects of oxygen.

The substance is deadly to a broad spectrum of insects and highly poisonous to fish. Because of its toxicity, Rotenone is only marginally permitted in organic farming.

Rotenone breaks down in about a week in sunlight and leaves little residual effect in the environment. It's mildly toxic to humans and other animals if inhaled.

Ryania

This shrub extract is typically sold in powder form as part of a combination formula. Its poison acts by contact or consumption. Many beneficial insects are unaffected by Ryania, making it useful as a targeted treatment.

Ryania persists in the environment longer than most other botanical pesticides. It's considered safe for most mammals, but is toxic to dogs … and fish.

Biocontrol

Another natural approach is the use of beneficial organisms to prey on common houseplant pests. (The term “beneficial” is obviously the grower's point of view.) It's one of the most ecologically friendly methods.

Because some predators target a specific pest, biocontrol agents may allow a very targeted response. They tirelessly hunt down their prey in hiding spots you miss.

Biocontrol isn't cheapest solution, however; and, being animals, they don't necessarily stay where you want them. They aren't always the best indoor solution. Also, you must avoid insecticides that would kill them, and they have to be periodically replenished.

Here are common biocontrol methods:

Lacewings – These insects are harmless to humans but they eat aphids like candy. Also called “Aphid Lions,” they eat other pests, too. They are available in egg, larva, or adult form ready to be released on plants.

Lady bugs – Perhaps the most well known form of biocontrol, ladybugs eat aphids and other pests. Buy their hungry larva: you need a lot of adults to make a dent in the population. They have a tendency to roam: refrigerate them before releasing them at the plant's base at dusk, and don't wear white or have strong light sources around.

Parasitic wasps, Predator mites, Aphid midges, Pirate bugs – There are many predator species recommended for specific infestations. Many partake of plant-sucking mites, whitefly, scale, and thrips. They tend to disappear as they grow older or the food supply dwindles, so they may need to be replenished.

Nematodes – These parasitic roundworms patrol the soil, each primed to attack one of more than 200 pest species. You may not see them working, but they can be very effective. They're harmless to people, pets, and the environment.

Nematodes come in packs to be mixed with water and poured into soil. They require moist conditions. Different species may need a specific temperature range.

Bacillus thuringiensis (Bt) – This non-pathogenic soil bacteria kills a variety of pests—including the dreaded fungus gnat. It causes insects to stop eating and requires time to take effect.

There are thousands of Bt species keyed to specific hosts. They are environmentally harmless and safe for humans and other animals that aren't susceptible. Resistance is an issue, however, so new strains are continually being developed. These microbes are one of the GMOs that cause concerns.

Beauveria bassiana (Bb) – This fungi causes disease in aphids, thrips, whiteflies, and other pests. Their spores enter the insect's body and kill it.

Though a soil organism, Bb is typically used as a spray because many soil-living pests have a natural resistance. It's a reduced risk pesticide that's generally non-toxic to mammals, but it's quite poisonous to fish and can affect honeybees. Wear long-sleeved shirts, pants, and a mask when applying.

Trapping

Sticky traps are cards covered with a gluey substance. Placed near infected plants, they work like flypaper. Most are pesticide-free.

Sticky traps can help control flying insects like whitefly, thrips, and soil gnats. They won't eliminate every bug, but they're another weapon in the fight.

Traps are also useful indicators of pest populations. Yellow traps attract whiteflies and gnats; blue traps attract thrips. They are eco-safe and easy to use.

Organic Systemic Pesticides

Systemic pesticides are absorbed by the plant. These broad-spectrum toxins are convenient but contentious, as they also harm pollinators and other beneficial insects.

There are only a few organic options:

Spinosad

This bacteria-made natural insecticide works against thrips, spider mites, ants, and fruit flies. It's effective as either a fast-acting contact or systemic toxin. It causes hyperactivity that exhausts the pest.

Spinosad is eco-friendly and minimally toxic to mammals. It can be harmful to pollinators and so isn't recommended during flowering.

Garlic

This safe garden remedy is better as a repellent than an insecticide, but it can be fatal to pests if they come into contact with a concentrated source. A sprayed garlic solution is the typical use.

Garlic may be absorbed by the plant to help repel thrips and aphids, and can promote beneficial fungi. Garlic discourages pollinators, however, so don't spray flowers you want visited. Direct contact may also kill bees.

Diatomaceous Earth (DE)

Another unique entry in the anti-pest catalog is deadly dirt. Diatomaceous Earth (DE) is powdered silica made of fossilized marine phytoplankton. It lacerates and dries up a pest's oily protective coating.

DE is added to soil or dusted over the plant—wear a mask to avoid inhalation. DE is non-toxic and environmentally safe: silica is a common soil element, so there's no worry of contamination. Avoid putting DE on flowers pollinators visit.

Note: DE doesn’t work well in wet conditions.

Boric Acid

This treatment is most useful for ants, but it's a good one to know about. Though toxic to insects, it has low toxicity to humans—less than table salt (still, don't inhale it). It's environmentally safe in small doses.

The powder can be mixed into bait, but it's also effective as a powder scattered over surfaces where the insect travels. A thin coating is best—they often simply avoid deep powder.

Boric acid works by sticking to tiny hairs on the insects' legs: it is ingested when cleaning. Bugs also take it to their nest and share it.

Mix Boric acid with bait or dust it lightly over places where insects walk. Incidentally, boric acid kills roaches, too.

Synthetic Pesticides

There are a lot of organic choices – so why use synthetic chemicals?

First, synthetic pesticides can be used responsibly and have good outcomes. Many are analogs of substances plants naturally use for defense. Also, organic doesn't always mean safe. Both types can be dangerous to your health and the environment.

Theoretically, houseplant treatments don't impact the environment so much – though they may enter the larger ecosystem eventually. Inside the home, the immediate consideration is what harm a pesticide might do to residents behind the pest-battle lines.

To make the best possible choice, it's important to know the major synthetic classes … especially if you have older pesticides in storage.

Organochlorines (OC)

The poster pesticide for hazardous outcomes, most organochlorine products have been banned for agricultural use. DDT, Dieldrin, and Chlordane were prohibited after widespread environmental effects became apparent. PCBs were banned in 1977. Most remaining substances in this class are being phased out globally.

The effectiveness of these chemicals has never been denied, however, and they were popular before being curtailed. They are very persistent in the environment and accumulate in animal tissue: they will be with us for some time. Stockpiles are still being used in developing countries.

Organophosphates (OP)

One step down the toxicity ladder, Organophosphates were mostly banned by the EPA in 2001 for residential use. They are still used in agriculture to a limited degree. Examples are Malathion, Diazinon, Dichlorvos, and Parathion.

Toxic to humans and other animals, they degrade faster than Organochlorines but persist in groundwater. Significant exposure has been proven to cause a host of health problems including cardiovascular disease and cancer.

Carbamates

Carbamates are similar to Organophosphates but have even less environmental persistence. One of the family, Carbaryl (Sevin), is a very popular pesticide in the US. They kill insects directly upon contact or ingestion, and can be absorbed through roots systemically.

Less toxic to birds than Organophosphates, Carbamates can penetrate skin and are poisonous to humans, other mammals, earthworms, bees, and fish. The chemical is relatively short-lived in the body but can cause both long- and short-term health issues. It isn't recommended for in-home use.

Pyrethroids

Based on naturally-sourced Pyrethrin, Pyrethroids are manufactured to increase the toxicity and lengthen the residual staying power of the natural product. Pyrethroids are the most common ingredient in commercial household insecticides.

Pyrethroids are highly toxic to fish and insects, including pollinators. The chemical will breakdown in sunlight after a few days and have been labeled as moderately safe for the environment … but they are highly toxic to cats.

These insecticides are sometimes erroneously labeled as made from chrysanthemum flowers, implying they are natural. Take note of which form you are using.

Synthetic Systemics

Systemic pesticides used on houseplants are sold as granules or stakes. These absorbed pesticides are convenient because they don't require frequent reapplications … but there are some caveats.

The main systemic pesticides are from the Neonicotinoid chemical class. Neonics – Imidacloprid, Thiamethoxam, Clothianidin, and Dinotefuran—are the most widely used insecticides worldwide. Unfortunately they are bad news for pollinators. They've been linked to honeybee colony collapse and other adverse environmental effects and were banned by the European Union in 2018.

How To Use Pesticides

Here are some tips … and precautions:

• Read the label – make sure the pesticide is for use on houseplants and not only yards and gardens.
• Follow the instructions!
• Don't treat plants in extreme temperature conditions or if the plant is highly stressed.
• Spray the plant outside if possible.
• Apply in the evening when pollinators aren't active.
• Stand back. Don't spray closer than 18 inches from the plant.
• Thoroughly spray the undersides of the leaves – the main hiding place for bugs.
• Be careful of runoff if you're using a soil pesticide. Excess water can carry toxins. Empty caches so pets don't drink from them.

Common Houseplant Pests And Recommended Treatment

Considering the list of weapons at our disposal, one could almost start to feel sorry for the pests. A brief meet-and-greet session with our insect overlords will remind you why we're fighting.

Aphids

These soft-bodied juice-suckers are only about 1/8th of an inch long, but an infestation can disable a plant in short order. Aphids typically congregate on new, tender growth. They can transmit disease, and their sugary honeydew excretions are a calling card to ants and fungal mold.

There are thousands of aphid species: they come in shades of green, yellow, red, brown, and black. Woolly aphids are a bit larger and tend to cause less harm.

A few won't do any damage; but, if they're massed in colonies causing curled or yellowing leaves, you have a problem.

The challenge with aphids is their incredible ability to multiply. They usually reproduce asexually. Males are only produced at the end of the year to fertilize eggs that can survive the dormant season. Aphids can also develop wings: there's no such thing as permanently eradicating them from your plants. They will find your beloved greenery again and again.

Prune and safely discard leaves that have a heavy aphid accumulation, and hose off the rest. Rub the aphids away as you wash (wear gloves if you're squeamish).

The next step up is to use insecticidal soap. Spray the aphids directly. The soap stops working once it's dried, so repeat as needed.  If this doesn't cut their numbers down to size, here are other effective treatments:

• Horticultural Oil. Cover the plant thoroughly and reapply as needed.
• Neem Oil. The stripped-down horticultural oil form performs in that duty, and/or you can apply an Azadirachtin-containing product weekly as a proactive measure.
• Diatomaceous earth (DE). Works best when dusted over the plant.
• Biocontrol predators will be more effective if you've cut the aphids back before release … wash off the pre-treatment before adding them! Aphid midges are effective at higher temperatures but go dormant in the winter without supplemental lighting.
• Beauveria bassiana fungus.
• A fast-acting botanical or synthetic insecticide works, but it's likely to wipe out any biocontrol insects you've added.
• The controversial long-lasting systemic pesticide Imidacloprid is particularly effective.

Mealybugs

Mealybug females are similar to aphids in size and feeding choices. They're covered in a white powdery wax layer—the expendable males have wings but no mouths. Young nymphs are smooth and active: they become sedentary as they mature and start building up wax (and sucking plants).

Females lay masses of eggs in a small cottony mess on stems or under leaves. Larvae hatch in about a week, which often means a population explosion. Mealybugs hide well in leave joints and crevices.

A light infestation can be handled by dabbing them with Isopropyl alcohol or Hydrogen peroxide. A soaked Q-tip gets into tight spaces.

Many aphid treatments apply to mealybugs:

• Horticultural oils, Diatomaceous earth, and insecticidal soap
• Biocontrol … add Mealybug Destroyer (Cryptolaemus montrouzieri) to the list.
• Beauveria bassiana fungus. Lecanicillium lecanii is another good anti-mealybug fungus.
• Botanical pesticides. Repeat weekly as needed.

Scale

Another juice-sucking pest that gathers in clumps. Scale doesn't look like a regular insect: they appear to be small nubs or colored bumps. They are squat, oval and legless, and measure from 1/16 to almost 1/2 inches wide. Stationary scale inhabits stems and the underside of leaves, often near the central vein.

Moderate indoor temperatures year-round allows scale to constantly reproduce. The females harbor their eggs until the larvae swarm forth. The young travel around the plant before attaching themselves to one spot to start sucking. They secrete honeydew: an infestation looks like shiny, sticky areas which are typically located on the lower leaves.

Scale comes in soft- and hard-bodied varieties. (Mealybugs are actually scale insects.) Soft-bodied brown scale—which can come in shades of yellow and amber—has an attached shell. An armored scale has a hard but separable covering and doesn't excrete honeydew: these types consume plants rather than suck their sap.

The adults can be tough to conquer. Soapy solutions and contact pesticides kill the mobile young but don't penetrate a mature scale's outer covering. Still, with some extra effort, insecticidal soap can be effective with these steps:

1) Cover the soil with plastic to catch any scale that falls.

2) Thoroughly spray the plant with soapy solution.

3) Scrape the scale patches with a brush, fingernail, or other tool. Physical rubbing is effective as it breaks their delicate mouthparts. <em>Pro Tip: Mildly abrasive cosmetic facial sponges work well on tender plants.</em>

4) Rinse the plant under a brisk stream.

It's often best to prune heavily infested leaves and stems. Wrapping double-sided sticky tape on stems can help monitor and control the crawlers.

Whichever solution you use, repeat every few days to kill succeeding generations of these common houseplant pests. Here are other treatments for scale:

• Horticultural oil. Note: Smothered scale won't change appearance.
• Alcohol dabbed on individual scale can kill them.
• Diatomaceous earth can affect young, mobile scale.
• Neem oil with Azadirachtin controls both larvae and adults.
• Biocontrol agents.
• A more toxic treatment is spraying the plant with a mixture of two tablespoons of Canola Oil and 1/2 teaspoon of Pyrethrin in a gallon of water.

Root Aphids

Root aphids live under the soil line. They're harder to detect because they are small and colored similarly to the roots they eat. They may be detected by white, waxy secretions which are chalkier than typical honeydew.

These aphids cause an overall lack of plant vigor similar to underfertilization. Many growers discard plants heavily infested with root aphids because of the difficulty in treating them. (Always sterilize or discard any soil these aphids have been in!)

Horticultural oils can keep the infestation from spreading up the plant, but they aren't useful in soil. DE doesn't work in damp soil, either, and most biocontrols are only marginally effective.

Here are things to try:

• Submerge the soil in an insecticidal soap solution for 15 minutes (flush with fresh water afterwards).
• Beauveria bassiana fungus is often effective.
• Nematodes can help. They also help spread B. bassiana spores through the soil.
• Neem with Azadirachtin can be applied routinely as a preventative soil drench.

Thrips

These slender, active little plant eaters are only 1/25th of an inch long, making them hard to detect without a hand lens. Signs of their activity are pale, splotchy, or silver-colored damaged leaves. Thrips can also spread plant diseases. They feed in groups on the undersides and in the joints of leaves, and will jump or fly away when disturbed.

Thrips feed on the plant itself rather than suck its juices. They don't usually kill a plant but instead maim the foliage and flowers—they are so mobile that they can move on before their damage becomes apparent.

There are over 4000 known thrip varieties, some of which are beneficial predators instead of plant-damaging hooligans. Specific biocontrol targeting is difficult.

Thrips can be hard to control. Hosing off infected areas and applying insecticidal soap will knock down the numbers. Blue-colored sticky traps are useful for monitoring.

Here are other anti-thrip treatments:

• Horticultural oils.
• Diatomaceous earth deters but is unlikely to control them.
• Biocontrol agents like Pirate bugs, Predatory mites and Lacewings can reduce numbers.
• Beauveria bassiana fungus may reduce the population.
• Botanical pesticides can be effective. Spinosad works particularly well.

Whitefly

These frustrating little bad guys can be hard to get rid of. The 1/16-inch, moth-like insects crowd under leaves and fly away in clouds to resettle elsewhere when disturbed.

They're a lot like flying aphids: they suck plant juices and excrete honeydew, causing yellow leaves and stunted growth. Worse, whiteflies inject harmful saliva and spread disease. They can quickly overwhelm a plant. They also develop resistance to chemical pesticides quickly.

Eggs will hatch in less than a week. The nymphs crawl a short distance, plant themselves, and suck the plant until they go into a resting stage three weeks later. In about five weeks they emerge as flying adults.

While winged adults congregate near the top of the plant, the translucent, immature crawlers that cause the actual damage travel all over the plant and are harder to spot.

Hosing off the leaves and applying insecticidal soap or horticultural oil is the first line of defense. Discard damaged or highly infected leaves. Yellow sticky traps help monitor their levels.

Here are other treatments:

• Insecticidal soap.
• Horticultural oil.
• Biocontrol includes Ladybugs, Lacewing, and the Whitefly Parasite.
• Beauveria bassiana fungus
• Botanical pesticides. Resistance can develop from long-term use.

Spider Mites

These difficult-to-control pests are almost invisible; a magnifying lens is the best way to see them. Other giveaways are a reddish film along the leaves, tiny webbing, or reddish-brown spots.

These common houseplant pests are arachnids rather than insects. They live in colonies underneath leaves. Red Spider mites are common, but they can come in different colors.

Spider mite damage often looks like light dots on leaves. They can also be detected by their telltale webbing. Severely affected leaves eventually yellow and dry up.

They are prolific pests that can suddenly show up in masses. They can drift in with the wind. They prefer hot, dry, dusty conditions, and warm weather shortens their life cycle and explodes their population. They're great.

Chemical pesticides have limited success because spider mites adapt rapidly … they often take advantage of the absence of predators killed by the toxins. Natural methods are more effective. Note that treatments must be thorough enough to cover the whole plant, because it's hard to see the actual infestation.

The best proactive solution is to give your plant a weekly shower. This raises humidity and washes away webs and dust as it reduces the mite population.

Here are additional treatments:

• Horticultural oil.
• Insecticidal soap.
• Diatomaceous earth.
• Biocontrol includes Ladybugs, Lacewing, and Predatory mites.
• Beauveria bassiana fungus.

Fungus Gnats

These 1/8-inch gnats are less plant pests than people pests, but houseplants are the vector. They inhabit damp soil areas and rise in spasmodic clouds whenever disturbed. Fungus gnats fly feebly around the room looking like mosquitoes – but they don't bite.

It’s the root-chewing larvae that irritate houseplants. Fungus gnat larvae stress seedlings, cuttings, and young growth. In large numbers they can damage a mature plant. There are six related families – the Sciaridae can spread disease.

The entire life cycle takes place in about a month. Eggs, larvae, and pupae live together in your plants' pot. They thrive in moisture and feed from decay: fungus gnats are a probably a signal something is wrong with your watering routine.

The real solution for these common houseplant pests is to eliminate all dead/decaying material and avoid soggy soil. Always let the top of your soil dry out the recommended amount for your plant variety. Consider adding a thin layer of sand on top: it dries out quickly and discourages hovering adults.

Placing yellow sticky traps near the soil can reduce adult numbers and help you monitor their presence.

One easy treatment is to water the plant with one part of 3% Hydrogen peroxide to four parts water. Let it drain out the holes. This kills larvae on contact, though it doesn't affect the flying adults: an organic pesticide spray can clear the air.

Note that Hydrogen peroxide disturbs the beneficial bacteria in your soil, as can other pesticide drenches.

Other treatments include:

• Neem oil with Azadirachtin as a weekly soil drench.
• Beneficial nematodes.
• Bacillus thuringiensis var. israelensis.
• Biocontrol: the Fungus Gnat Predator.

Russet Mites

These teeny-tiny mites are an encouragement to keep new plants quarantined. They don't leave webbing or honeydew and do damage at the cellular level starting from the bottom of the plant. In later stages, they particularly like swarming on flowers.

With russet mites, you're battling an unseen enemy for the most part. It's hard to know when they arrive—they can blow in with the wind—or when they're truly gone. They form resistance to chemicals quickly.

The best control is prevention. Don't overfertilize, which causes vulnerable lush growth. If you do get an infection, don't wait between treatments to see if it works—keep it going. Once the infestation spreads high up the plant, the game is lost.

The following treatments can be effective:

• Insecticidal soap. Be sure to thoroughly cover the plant and wash the soap off after it dries.
• Horticultural oil. Again, cover the plant thoroughly. You can't target their population with precision as russet mites are essentially invisible.
• Isopropyl alcohol kills the mites on contact.
• Diatomaceous earth.
• Several species of predator mites feed on spider mites.
• Neem oil with Azadirachtin can control their numbers over time.
• Botanical pesticides work until resistance develops. Repeat every three to five days.

Black Vine Weevils

These are usually outdoor pests that hitchhike inside on a houseplant. They reproduce asexually, and both their 1/2-inch long grub-like white larva and the adult 3/4-inch six-legged black beetles can damage your plant. They're most prevalent on Cyclamens but also enjoy destroying Azaleas, Primulas, Begonias, and succulents. They are prone to developing chemical resistance.

The soil-dwelling larva's damage is worse than an adult's, and their hidden natures makes them hard to diagnose. The long-lived larva feed on the roots and cause wilting of top growth.

Adults feed at night, leaving riddled leaf edges in their wake. These beetles can be picked off easily: using a flashlight at night is a good way to catch them.

Start by removing leaf litter and other debris that may provide hiding places. Here are effective treatments:

• Diatomaceous earth in soil.
• Beneficial nematodes, particularly the Steinernematidae and Heterorhabditidae families.
• Beauveria bassiana
• Though more toxic, Pyethroid pesticides are effective in soil or when sprayed on the plant and surrounding crevices.

Ants

Ants are often attracted to the honeydew secreted by plant-sucking pests. They are not only bothersome in the home, but ants can actively protect pests and prolong your struggle. They can colonize the soil, too.

Here are ways to minimize their presence:

• Boric acid traps or thinly scattered powder.
• A layer of Diatomaceous earth on the soil.
• Wrap the container base with a sticky tape or paste product to trap visiting ants.
• Ant bait placed along their trails.
• Soak the container in insecticidal soap for 15 minutes. Flush the soil afterwards with clean water.

Springtails

Springtails are harmless to plants, people, or pets—but they can be annoying. Measuring less than 1/8th inches long, they jump and can be mistaken for fleas, but they don't bite or carry disease.

Springtails are often a signal conditions are too moist … sometimes peat can hold moisture and attract them. They respond to insecticides, but simply keeping your soil properly dry works best. You can vacuum them up while you're letting the situation improve.

Once the topsoil has dried, you can sprinkle on a layer of DE to seal the deal.

Caterpillars, Beetles And Slugs

The good thing about these pests is that they're easy to spot. They don't mass in huge colonies and don't madly reproduce.

There are many plant-chewing varieties, but the best means of indoor control for all caterpillars, beetles and slugs is to simply pick them off. Otherwise, they're susceptible to a synthetic pesticide with residual staying power on the foliage.

The main time you'll have issues with these larger pests is when bringing outdoor-summering houseplants inside. It's smart to treat them first. Once indoors, keep a watchful eye out for holes or other leaf damage that indicates stragglers that were missed.

Identifying A Pest Problem

Identification of a pest issue starts by regularly checking plants for symptoms. Take extra care when adding a new houseplant … and remain observant. You can't see the eggs or larvae that may be in the soil, and it's better to catch the situation before it becomes serious.

Sometimes a pest problem is obvious, especially if things are getting out of hand. Often, however, the first signs are vague and easily mistaken for something else. Diagnosing the problem can become a process of elimination.

Yellowing, spotted leaves, holes, or changes in leaf texture can mean insect problems. Carefully check out misshapen, curled or pinched-looking foliage. Look for tiny webs or cottony areas—these spell trouble. Be sure to examine underneath leaves and in leaf joints.

Also be on the lookout for shiny, sticky leaves caused by honeydew secretions, or for sooty mold that grows from the sugary buildup.

A magnifying glass is useful for checking out any crawlies or bumps … for small mites, it's a necessity.

Also check your plant pots for pests along pot bottoms, rims, saucers, and crevices.

Prevention Of Common Houseplant Pests

There's a gardener's saying: “The best pesticide is the gardener's shadow.” Prevention is the main safeguard against pests, and it begins with careful attention.

You can't keep your plants entirely pest-free all the time, but you can tilt the odds. Here are precautions that help make sure an infestation doesn't run away with your plant:

• Only buy from reputable sources.
• Check for pests with a magnifying glass before bringing a plant inside. Examine stems, leaf undersides, and nodes where pests like to hide.
• Isolate new plants after purchasing. Quarantining a plant for a few weeks is the surest way to avoid spreading unwanted guests.
• Regularly inspect your houseplants for pests. It's a good habit to make a visual check each time you water.
• Sterilize pots before use.
• Use only pasteurized potting mixes.
• Don't let plants touch each other, and make sure they have adequate air circulation.
• A healthy plant is more resistant to pests. Find out and supply the specific needs of each plant. Don't overwater or let them suffer a drought.
• Use the appropriate amount of fertilizer, and don’t overdo the nitrogen. Rank overgrowth attracts insects.
• Clean your plants regularly. Dust can harbor eggs or tiny insects. Spray down or wipe leaves with a damp sponge. Don't use a duster—it can spread pests.
• Regular showers help prevent spider mites and give the plant a refreshing cleanse of webs, dust, pollen, and other clogging debris.
• Regularly prune and remove dead flowers and leaves.
• Consider regular preventative treatments like Neem oil or biocontrol.
• Isolate plants suffering an infection. Don't leave them as a home base for pests to invade others.
• If one of your plants does get an infestation, keep an eye on your other plants to detect any problems early.
• Be diligent and repeat treatments until an infestation is under control.
• Consider disposing of a heavily infested plant. It can be easier for you and better for the other plants to replace it with a healthier specimen.