This guide is for ornamental house plants only. If you plan to eat it do not follow this guide. It is a work in progress and will be updated regularly.

Common Pesticide Terms Defined


Systemic

A pesticide that is absorbed into the plant either through the roots or the leaves where it then works its way through the rest of the plant. Typically provides long term residual protection.

Translaminar –

Pesticides in which the material (spray solution) penetrates leaf tissues and forms a reservoir of active ingredient within the leaf and provides residual protection.

The pesticide will work its way from top side to bottom side of a treated leaf but unlike systemics they will not be transported to other parts of the plant.

Control

Effectively reducing the population to 0 or near zero.

Suppress

Reduce numbers enough to prevent the pests from killing the plant but not eradicating the pest completely.

Insecticidal soap –

Real soap made from fat and lye which has the necessary potassium salts of fatty acids for insecticidal activity. Dr. Bronner’s or Safer insecticidal soap are two examples.

Spider Mites

Spider mites are one of the most damaging pests and can destroy plants quickly. Under ideal conditions (hot, dry) spider mites can complete their lifecycle from egg -> adult -> more eggs in 3 DAYS.

Because of this ability to multiply rapidly they can seemingly come out of nowhere but the worst part is it allows them to develop resistance quicker than most pests.

If you try and fail to kill mites all you are doing is breeding super mites with resistance to whatever you just used. This chart shows the activity of many commercially available pesticides: Miticide Activity

The first sign of spider mite damage is fine stippling on leaves that looks like many small holes poked with a needle which is clustered around the veins, especially the central vein.

Severely damaged leaves will take on a whitish or greyish appearance. Severe infestations of mites will show up as visible webbing on the bottoms of leaves and covering the growth tips.

Spider mite webbing has no pattern and is just a mess of silk. You will be able to clearly see the mites moving on it if it has progressed to that point.

Spider mites are true arachnids and so like most spiders they are not susceptible to most insecticides and are controlled better by using pesticides designed specifically for them.

There are a few non-pesticide options that can control light infestations if caught early but once they have established themselves you should use miticides designed specifically for spider mites or you are in for an uphill battle.

Non pesticide options:

Horticultural oil / dormant oil

This is a mechanical pesticide. It kills mites by suffocating them and so there is no way to develop resistance to it.

It is effective if applied routinely several days apart since it only suffocates the mobile stages and not the eggs. It can also be mixed with many other pesticides to increase their effectiveness. It is direct contact only and has no residual effects.

Horticultural oil and other oil-based pesticides can damage leaves.

They can cause burning or other damage to leaves if applied when temperatures are high (80-85F or higher) or if the leaves are sensitive.

Always test it on a couple leaves first before spraying a whole plant.

Soapy water & peroxide – Real soap like dr. Bronner’s or safer insecticidal soap + 3-4 TBSP of 3% hydrogen peroxide per cup of water.

Spray on and then use a soft, damp cloth to physically wipe the mites off the leaves.

Rinse with plain water. Direct contact only with no residual effect.

Miticides:

Avid (Abamectin) – Avid is one of the most popular commercially available miticides. It will control mites and leaf miners as well as suppress aphids, thrips & whiteflies. It is active on larvae, nymphs and adults but is not active on eggs.

It is both translaminar and active on contact. Translaminar pesticides are those in which the material (spray solution) penetrates leaf tissues and forms a reservoir of active ingredient within the leaf.

It is semi-systemic and works its way through the leaf but is not transported throughout the plant. Avid retails for around $95-100 for an 8oz bottle.

Forbid (Spiromesifen) – Forbid is a newer miticide and ovacide that has a unique mode of action that works against mites that have developed resistance to other more common miticides. It is active on eggs, larvae, and nymphs but not adults. Like avid it is both contact and translaminar and will provide resistance for 30-45 days. It is quite expensive normally around $220-240 for an 8oz bottle.

Floramite SC (Bifenazate) – Floramite is active on a wide range of mites and provides quick knockdown with 28 day residual suppression. It is active on all lifecycle stages from egg through adult. It is contact only and not translaminar so you must make sure to thoroughly cover the bottoms of the leaves with this one. Floramite retails for around $85-120 for an 8oz bottle.

You can find a 3-pack of 0.5 oz bottles of all 3 of these for sale here. They also sell each one individually in 0.5 oz to 1oz bottles: 0.5 oz is a lot more than it sounds like. 0.6ml makes a quart so each bottle makes almost 25 quarts. This will last you a LONG time since its rare you have to spray them more than once to eradicate mites.

Insecticides

The only insecticide I recommend for mites is Bifenthrin. It is effective for suppressing but not controlling spider mites on its own but is very effective when used in conjunction with the miticides listed above. It will kill almost anything else too and is not very expensive, only $22 for 16oz bottle

Mealybugs

Mealybugs are soft-bodied insects that feed by sucking sap from plants. They also excrete honeydew like aphids which leaves a sticky residue and can lead to black sooty mold.

The mealybug lifecycle takes approximately 2 months from egg to maturity. Once mature a female can lay hundreds of eggs that hatch within a few days. They are most mobile shortly after hatching.

Mealybugs can infest both the foliage and the soil so if they seem to keep coming back after treating them you probably need to treat the soil too.

They are frequently found hiding in new growth when there are only a few of them. In larger numbers they can cause plants to shed leaves or even die.

Non pesticide options:

  • Rubbing alcohol – For small infestations you can treat mealybugs by applying rubbing alcohol directly to the individual pests with a cotton swab. You can also dilute the alcohol to 25%-50% and apply it as a spray but you need to test this on a small portion of the plant first since it is possible to burn the leaves. Alcohol only kills on direct contact and has no residual action.
  • Insecticidal soap – Also kills on direct contact with no residual action but less effective than alcohol.

Insecticides:

  • Bifenthrin – a synthetic pyrethroid with a broad range of controlled pests including termites and spiders. One of my favorites, bifenthrin is effective at controlling most common pests and even suppresses spider mites. In addition to plant applications it makes a good barrier spray for around the home.
  • Permethrin – another synthetic pyrethroid with a smaller range of controlled pests. It is the active ingredient in dog flea collars and human lice medicine but it is a neurotoxin to cats so if you have cats keep them away from treated areas until dry (~12 hr). It can be found at home depot or lowes under the brand name Bonide eight in a 32oz container for about $20
  • Imidacloprid – Imidacloprid is a pesticide that works too well for its own good. If you have heard of neonicotinoids killing bees that’s this stuff. By 1999 it was the most widely used pesticide in the world but has since been banned in the EU. However, used correctly it is one of the safest and most effective systemics available. It is labeled for use on greenhouse plants or indoor plants, neither of which will harm bees. Never use it on an outdoor plant that will be flowering in the next 3 months although it is good for treating outdoor plants when you bring them inside for the winter to kill any hitchhikers.
    It is available in granular form which is applied to the soil then watered in. It kills EVERYTHING except for hard scale and spider mites, including soil borne pests like thrips, fungus gnats and mealybugs and lasts for 90 days between applications. Since it is applied via the roots it isn’t instant and is better as a preventative than to treat heavy infestations. I use this on all my indoor plants and cannot recommend it highly enough.
    It is available from amazon sold as Bonide systemic houseplant insect control in an 8oz container for about $20.
    If you have a lot of plants, I recommend purchasing Marathon instead. It is more expensive up front but much cheaper per application. 

Thrips

Thrips are very small insects which are only slightly larger than spider mites and hard to see with the naked eye. They are elongated and typically a tan or yellowish color although some species are darker brown or black. Thrips feed by scraping the outside of the leaves off and cause irregular silvery spots.

They also damage young leaves as they are forming causing them to be distorted as they grow.

They cause similar damage to flowers, infesting flower buds and damaging petals or even causing the flower to abort. In addition to damage from feeding they are also disease carriers and one of the most common vectors for many plant viruses.

Some strains of thrips have developed resistance to many pesticides while others are still more easily treatable.

Thrips can be annoying to eradicate because they can lay eggs inside of plant parts and some stages of the lifecycle are spent in the soil.

Typically it will require several treatments to eradicate them all.

Non pesticide options (not recommended):

  • Horticultural oil / dormant oil – This is a mechanical pesticide. It kills thrips by suffocating them and is only active on the exposed stages. It does not kill eggs and cannot be used to treat soil borne stages. It requires direct contact and has no residual action.
    Horticultural oil and other oil-based pesticides can damage leaves. They can cause burning or other damage to leaves if applied when temperatures are high (80-85F or higher) or if the leaves are sensitive. Always test it on a couple leaves first before spraying a whole plant.
  • Soapy water & peroxide – Real soap like dr. Bronner’s or safer insecticidal soap + 3-4 TBSP of 3% hydrogen peroxide per cup of water. Spray on and then use a soft, damp cloth to physically wipe the thrips off the leaves. Rinse with plain water. Direct contact only no residual effect.
  • Blue sticky traps – These will provide early warning of thrips but don’t do anything to control or suppress them.

Insecticides:

  • Spinosad – Spinosad is an insecticide based on chemical compounds found in the bacterial species Saccharopolyspora spinosa. It is highly active on most species of thrips and kills on contact as well as ingestion so there is some residual effect. It should be applied to the tops and bottoms of leaves taking care to get it down inside young leaves. The same concentration used for spraying leaves should be applied to the roots as a soil drench.
    Spinosad is widely available including from home depot and lowes sold as either Monterey garden insect spray concentrate in a quart for $33 or as Captain Jack’s Dead Bug Brew concentrate in a 16 oz container for about $20.
    Spinosad can also be tank mixed with abamectin (avid miticide), if your thrips are resistant to just spinosad this should nuke them. It is most common 2-part tank mixture used by nurseries for treating thrips: Tank mixing abamectin and spinosad
  • Abamectin – Abamectin is sold as Avid and is a miticide designed for spider mites. It also controls thrips and can be tank mixed with spinosad for dealing with resistant strains. See “Avid” in spider mite section for more info.
  • Azadirachtin – Azadirachtin is a limonoid chemical derived from neem seeds that acts as an antifeedant and insect growth regulator (IGR). It is significantly more effective as a pesticide than cold pressed neem oil. Since it is oil based it should be applied early morning or late evening to avoid burning leaves plus it is safe for pollinators once dried. It has a short-term residual effect.
    Azadirachtin is sold in the US under the brand name Azamax from General Hydroponics. You can find it on amazon in a 4oz bottle for about $27.
  • Imidacloprid – Imidacloprid is a systemic neonicotinoid that kills everything except for spider mites and hard scale. It is available in granular form that is applied to the soil and provides protection for 90 days. I highly recommend this for all indoor plants. See “Imidacloprid” in the mealybug section for more information.

Aphids

Aphids are small insects that feed by sucking sap. They come in many colors although common ones are green, yellow, or black. They produce a lot of sticky honeydew which ants feed on. 9/10 times if you see ants on a plant, they are not there to hurt the plant, they are there to farm aphids. Aphids are an easy pest to treat and only cause a lot of damage if they are present in high numbers. They have an interesting reproductive strategy where the females can give birth to live nymphs who are already pregnant themselves.Non pesticide options:

  • Water pressure – Aphids tend to cluster together and it is easy to blast most of them off with a water hose. Works great for minor infestations.
  • Horticultural oil / dormant oil – This is a mechanical pesticide. It kills aphids by suffocating them and so there is no way to develop resistance to it. It is direct contact only and has no residual effects.
    Horticultural oil and other oil-based pesticides can damage leaves. They can cause burning or other damage if applied when temperatures are high (80-85F or higher) or if the leaves are sensitive. Always test it on a couple leaves first before spraying a whole plant.
    Horticultural oil can also be mixed with many other pesticides to increase their effectiveness.
  • Soapy water – Real soap like dr. Bronner’s or safer insecticidal soap. Follow directions on the label for dilution ratio. Only kills on direct contact with no residual effect.
  • Blue sticky traps – These will not control or suppress aphids but provide early warning.

Insecticides

  • Azadirachtin – Derived from neem seeds, acts as an antifeedant and insect growth regulator. Absolutely destroys aphids and is organic and safe for food crops. See “Azadirachtin” in thrips section for more information.
  • Bifenthrin – a synthetic pyrethroid with a broad range of controlled pests including termites and spiders. One of my favorites, bifenthrin is effective at controlling most common pests and even suppresses spider mites. In addition to plant applications it makes a good barrier spray for around the home. It is inexpensive too, you can buy it as Bifen I/T in a 16oz bottle for about $22.
  • Permethrin – another synthetic pyrethroid with a smaller range of controlled pests. It is the active ingredient in dog flea collars and human lice medicine but it is a neurotoxin to cats so if you have cats keep them away from treated areas until dry (~12 hr). It can be found at home depot or lowes under the brand name Bonide eight in a 32oz container for about $20
  • Imidacloprid – Imidacloprid is a systemic neonicotinoid that kills everything except for spider mites and hard scale. It is available in granular form that is applied to the soil and provides protection for 90 days. I highly recommend this for all indoor plants. See “Imidacloprid” in the mealybug section for more info.
  • Almost any other insecticide – Aphids are susceptible to most contact and systemic pesticides you would have on hand to control other pests.

Fungus gnats

Fungus gnats are generally harmless but can be quite annoying. They are small, dark colored flies that hang out around the surface of the soil and fly around when disturbed. They lay their eggs in the top couple inches of soil and the maggots feed on decaying organic matter. They can also feed on root hairs which can reduce vigor. Once they turn into adults they only live for a couple of days.Non pesticide options:

  • Impermeable layer – Fungus gnats lay their eggs in the top couple inches of soil. If you exclude access to the soil with an impermeable layer of something like a half-inch of sand they will be unable to lay eggs.
  • Bottom watering – If you carefully water from the bottom and avoid wetting the top inch or two of soil fungus gnats will not lay eggs.
  • Yellow sticky traps – These will help control some of the adults but mostly act as an early warning system before infestations become noticeable.

Insecticides

  • BTI – BTI is a live culture of Bacillus thuringiensis israelensis, a bacterium that selectively targets the larval stage of certain dipterans like fungus gnats and mosquitos. It will not kill adult fungus gnats but they have very short lifecycles and will die off soon on their own.
    BTI is commonly available for control of mosquitos sold as mosquito bits or mosquito dunks at home depot or lowes. Sold in a 30 oz container of bits for $15 or a 6-pack of dunks for $9
    It is also available online in a more concentrated form specifically for fungus gnats called Gnatrol. You can buy it by the oz from this site but note that since it is a live bacterium it does have an expiration date. The expiration date is listed on the site. As of posting this the current batch expires on 1-31-2022. I recommend this over mosquito bits or dunks.
    0.5 oz for $8, 1 oz for $10, 2 oz for $15, or 4 oz for $23
  • Imidacloprid – Imidacloprid is a systemic neonicotinoid that kills everything except for spider mites and hard scale, including soil borne pests like fungus gnats. It is available in granular form that is applied to the soil and provides protection for 90 days. I highly recommend this for all indoor plants. See “Imidacloprid” in the mealybug section for more info.

Whiteflies

Whiteflies are small, white flies that cluster in large numbers on the bottom sides of leaves and fly around the plants when disturbed. They feed by sucking sap from the plant and heavy infestations can cause plants to shed leaves. They also excrete honeydew and can cause black sooty mold. Adult whiteflies will lay eggs on the bottoms of leaves which will hatch in three to seven days. The nymphs are responsible for most of the damage.Non pesticide options

  • Vacuum – You can knock down the number of adult whiteflies quickly by using the hose on a vacuum to catch them. Don’t try to vacuum them directly off of the plants but they’re easy to catch since they just fly right around the plants when disturbed.
  • Horticultural oil – This is a mechanical pesticide. It kills whiteflies by suffocating them and is only active on the nymph stage. It does not kill eggs or adults. It requires direct contact and has no residual action.
    Horticultural oil and other oil-based pesticides can damage leaves. They can cause burning or other damage if applied when temperatures are high (80-85F or higher) or if the leaves are sensitive. Always test it on a couple leaves first before spraying a whole plant.
    Horticultural oil can also be mixed with many other pesticides to increase their effectiveness.
  • Insecticidal soap – Kills nymphs on contact but has no residual effect.
  • Yellow sticky traps – Adult whiteflies are attracted to yellow sticky traps. These can reduce the populations somewhat but they are more of an early warning system.

Insecticides

  • Bifenthrin – Bifenthrin – a synthetic pyrethroid with a broad range of controlled pests including termites and spiders. Pyrethroid pesticides are excellent for controlling adult whiteflies. One of my favorites, bifenthrin is effective at controlling most common pests and even suppresses spider mites. In addition to plant applications it makes a good barrier spray for around the home. It is inexpensive too, you can buy it as Bifen I/T in a 16oz bottle for about $22.
  • Permethrin – another synthetic pyrethroid with a smaller range of controlled pests. It is the active ingredient in dog flea collars and human lice medicine but it is a neurotoxin to cats so if you have cats keep them away from treated areas until dry (~12 hr). It can be found at home depot or lowes under the brand name Bonide eight in a 32oz container for about $20
  • Azadirachtin – Azadirachtin is a limonoid chemical derived from neem seeds that acts as an antifeedant and insect growth regulator (IGR). It is significantly more effective as a pesticide than cold pressed neem oil. Since it is oil based it should be applied early morning or late evening to avoid burning leaves plus it is safe for pollinators once dried. It has a short-term residual effect. It is effective on both adult and larval stages of whitefly.
    Azadirachtin is sold in the US under the brand name Azamax from General Hydroponics. You can find it on amazon in a 4oz bottle for about $27.
  • Imidacloprid – Imidacloprid is a systemic neonicotinoid that kills everything except for spider mites and hard scale. It is the most extremely effective against whiteflies but since it is a systemic it takes some time to start working and is best used as a preventative or in conjunction with a knockdown pesticide. It is available in granular form that is applied to the soil and provides protection for 90 days. I highly recommend this for all indoor plants. See “Imidacloprid” in the mealybug section for more information.

Soft scales

There are several kinds of soft scales that attack houseplants, but they all have a few similar characteristics that easily differentiate them from hard scales. Soft scales produce large amounts of honeydew which can lead to black sooty mold, hard scales do not produce honeydew. If you try to remove a scale from the plant by prying up the protective covering you will find that the covering is part of the body of soft scales while hard scales are small, soft bodied insects separate from their armored shields.

Eggs hatch for a period of several weeks under the protective cover of the mother scale. After hatching the crawler stage is mobile and typically moves a short distance looking for feeding sites. After they settle in, they begin to form the armored covering and start to excrete honeydew. They continue to grow for the next two to four months.Non pesticide options

  • Manual removal – When there is only a small infestation soft scales are easily removed by rubbing or picking them off. Any disturbance of the scale can break its fragile mouthparts causing it to starve. Scales killed this way may appear the same as live scales.
  • Insecticidal soap – kills crawler stages but not very effective on adults.
  • Horticultural oil – This is a mechanical pesticide. It kills scales by suffocating them and is active on both the crawler and adult stages. It requires direct contact and has no residual action.
    Horticultural oil and other oil-based pesticides can damage leaves. They can cause burning or other damage if applied when temperatures are high (80-85F or higher) or if the leaves are sensitive. Always test it on a couple leaves first before spraying a whole plant.
    Horticultural oil can also be mixed with many other pesticides to increase their effectiveness.

Insecticides

  • Bifenthrin – Bifenthrin – a synthetic pyrethroid with a broad range of controlled pests including termites and spiders. Pyrethroids are effective for controlling soft scales but coverage must be maintained for the entire 2-4 month lifecycle to prevent further infestations. Bifenthrin is an excellent choice because it has very long residual activity. One of my favorites, bifenthrin is effective at controlling most common pests and even suppresses spider mites. In addition to plant applications it makes a good barrier spray for around the home. It is inexpensive too, you can buy it as Bifen I/T in a 16oz bottle for about $22.
  • Permethrin – another synthetic pyrethroid with a smaller range of controlled pests and shorter residual activity. It is the active ingredient in dog flea collars and human lice medicine but it is a neurotoxin to cats so if you have cats keep them away from treated areas until dry (~12 hr). It can be found at home depot or lowes under the brand name Bonide eight in a 32oz container for about $20
  • Azadirachtin – Azadirachtin is a limonoid chemical derived from neem seeds that acts as an antifeedant and insect growth regulator (IGR). It is significantly more effective as a pesticide than cold pressed neem oil. Since it is oil based it should be applied early morning or late evening to avoid burning leaves plus it is safe for pollinators once dried. It has a short-term residual effect. It is effective on both adult and crawler stages of soft scales.
    Azadirachtin is sold in the US under the brand name Azamax from General Hydroponics. You can find it on amazon in a 4oz bottle for about $27.
  • Imidacloprid – Imidacloprid is a systemic neonicotinoid that kills everything except for spider mites and hard scale. It is the most extremely effective against soft scales but since it is a systemic it takes some time to start working and is best used as a preventative or in conjunction with a knockdown pesticide. It is available in granular form that is applied to the soil and provides protection for 90 days. I highly recommend this for all indoor plants. See “Imidacloprid” in the mealybug section for more information.

Armored scales

These are uncommon on houseplants. Unlike soft scales, armored scales do not produce any honeydew and the protective shield is not attached to their body. If you pry up one of the scales, you will find a small soft bodied insect underneath.

The only effective method of controlling armored scale is horticultural oil. Both contact and systemic insecticides are largely ineffective at controlling them.

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