How to Identify and Control House Plant Pests

Common House Plant Pests

Pest attacks are much more common outdoors in the garden, but even the most seasoned house plant owner will eventually fall victim to an attack indoors. Close up photo of a Red Spider Mite on a plant leaf The trick is to be observant of your plant and then when problems arise act decisively. If you follow this rule your plants have a much better chance of making it out the battlefield with minimal or no lasting damage.

Organic v.s Chemical Control

Where possible we promote the most eco friendly method for pest eradication and control. But the truth is that having plants indoors severely limits or completely removes the option to use truly organic pest control, for example outside Aphids will eventually be eaten by ladybirds. So while we detail our favorite method, we also list a chemical option where appropriate.

The Common Pests

The most common ones are listed below, along with their identifying symptoms and suggested treatments. If you're having problems with something different let us know and we will try and help you out. Sometimes your plant will have a disease rather than a pest problem in which case you will need to head on over to our disease page.

Aphids / Greenfly / Blackfly
Mealybugs
Red Spider Mites
Scale Insect
Sciarid flies / Fungus gnats
Slugs / Snails
Springtails


Aphids / Greenfly / Blackfly

Aphids suck sap usually from the new soft plant growth, the tips, flowers etc, however they can attack any part of the plant. Aphid colony sucking sap from a ZZ plant leafNormally hidden from obvious sight, i.e. under the leaves, they are typically green, but can also be black or grey and arrive in small but quickly reproducing colonies. They can be seen easily with the human eye if you look closely.

Symptoms

They tend to mass together in large numbers making them easy to spot and identify. Look for sticky honeydew deposits on the plant and their white or grey "husks" littering the soil and sticking to the honeydew. Long term effected plants may become infected with disease or viruses, the leaves may also turn yellow in random patches. Growth may also become distorted.

Treatment

Control is really easy and in most cases doesn't require anything more than warm soapy water although theoretically a chemical treatment, in comparison to others it's very gentle.

  • One - You can reduce the numbers (or any strays) by simply squishing them with your fingers. If there are lots or you are too squeamish to do this then move to the following steps.
  • Two - Fill a spray mister with warm water and a small amount of liquid soap or washing up liquid. There should be enough that if you shake the bottle it foams up.
  • Three - Spray the plant liberally with the solution, make sure you target the Aphids themselves so this may involve moving the bottle or plant into different positions to reach everything. It's important you do this as Aphids must be covered in the solution for it to work.
  • Four - Most plants don't mind the occasional drench of soapy water, but if you don't want to risk it, hold the plant sideways as you are spraying or cover the soil to reduce the amount of liquid that soaks in.
  • Five - Wait five minutes before washing off the soapy mixture as best as you can. You can also water the plant well at this point to flush out any mixture that may have soaked into the soil (make sure you have drainage holes!).
  • Six - Sometimes one treatment is enough, but its possible you may have to repeat again a few weeks later.
  • Chemical: If you need something stronger look for permethrin, derris (banned in many countries due to human health concerns) or malathion containing products. Be careful if using chemical sprays on Ferns as they can be very sensitive.


Mealybugs

Mealybugs are related to Scale insects and cause damage by sucking sap from plants. They are reasonably large as far as pests go, resembling furry white woodlice. They cluster together and on first glance you might think you are looking at cotton wool. Mealybugs attacking the underside of a plant leaf If left untreated their damage will cause the leaves of the plant to yellow and eventually drop off.

Symptoms

It's very common to be able to spot the insects before you start noticing symptoms on the plant, colonies of mealybugs tend to group on the undersides of leaves and in the leaf joints of plants. The plant will show you it is infested by wilting and generally looking dehydrated, it may be losing leaves quite rapidly. Also look for sticky honeydew residue.

Treatment

  • Organic: You can often knock them off the plant with a shake, poke or spraying them with water.
  • Chemical: If the infestation is quite large follow the Aphid treatment technique.
  • Chemical: Use products containing natural fatty acids or those formulated with a surfactant.

Red Spider Mites

Of all the house plant pests you can come across the Red Spider Mite is arguably the most feared. The damage caused isn't necessarily the worst, but their prevalence and difficultly in removing can be quite trying and frustrating. Red Spider Mite's spinning webs over a house plantLike their name suggests they are arachnids and therefore related to normal spiders, however although they spin webs all over your plants they don't feed on flies, instead they eat the liquids found within plant leaves. The webbing is used to protect the colony and basically open up quick access "roads" to different parts of the plant, if allowed to get out of hand you will have a mini metropolis on your hands.

Symptoms

The sticky webbing is one of the most obvious signs these insects have set up home. However the most common symptom on the plant is mottled leaves with lots of little brown dots. This is caused by the spiders piercing the leaf cells with their mouthparts which then causes the cells they've pierced to die and in turns creates this brown speckling effect.

Treatment

  • Organic: These mites hate water and humid conditions. It can take a while to completely remove the pests, but if you pop your plant in the shower each week and give it a tepid shower you will help to wash off the webbing and gradually reduce the spider mite numbers. During the days between showers, mist the plant daily to help increase humidity. Check our Humidity Guide for other ideas you might like to try.
  • Organic: If multiple plants are effected, or you live in an area where they are a regular problem (perhaps also with your garden or yard plants) it might be worth purchasing the predatory mite Phytosieulus persimilis. They feed on Red spider mite and will quickly outnumber them if temperatures are above 18°C (64°F).
  • Chemical: Use products containing natural fatty acids or those formulated with a surfactant.


Scale Insects

Scale Insects sucking sap from an Umbrella PlantScale is a tricky pest to identify and can be difficult to eradicate. The insects have a hard outer brown shell that locks them in place a bit like barnacles on a beach at low tide. They are neatly camouflaged because even if you are looking at them directly to the untrained eye you may still think you are looking at a natural blemish on the plant leaf.

Symptoms

Quite simply, sticky honeydew everywhere. If the plant is near a window it will be filthy with it, if near fabric the honeydew will eventually turn black and create almost "sooty" like mould. Look closely at the underside of the leaves or on the stems and you will see them as small round or oblong brown discs.

Treatment

They are only formidable because of their protective shield, if you can get rid of that then you've almost won the battle already. Although it's rare to eradicate them in one go. Their offspring are very small and mobile therefore easy to miss, in a few weeks they will set up home where their parents once lived. Be prepared to treat the plant several times before they go completely.

  • Chemical: The Aphid spray method detailed above works well in softening the discs. After about five minutes you can pretty much wipe them off with a damp cloth.
  • Chemical: If you need something stronger look for permethrin, derris (banned in many countries due to human health concerns) or malathion containing products. Be careful if using chemical sprays on Ferns as they can be very sensitive so use only as a last resort.
  • Organic: If you have a small number you can pick or rub the scales to kill them.
  • Organic - Dab individual scales with alcohol. This basically dissolves them.

Sciarid flies / Fungus gnats

Close up photo of a Fungus Gnat / Sciarid FlyThere is nothing worse than having small annoying files zipping around. You bat them away to start with, but with their constant distraction you seek out where they are coming from and eventually find a small colony hovering or running around the base of your house plant(s). Fortunately although very common they tend not to harm indoor plants and are therefore more of a nuisance than anything.

Symptoms

Spotting small black flies around 2mm long either flying around near the plant, or running over the soil surface. The larvae are small worm like creatures, up to 1cm long, it's hard to spot them though as they tend to exist just under the soil surface.

Treatment

  • Organic: These pests need organic matter to feed off and moist upper soil conditions. Make sure you pick off any fallen plant material and try keeping the soil less moist until they leave. A good tip is to use the Bottom Watering Method, as long as you don't overwater this should help keep the soil surface drier and reduce the Fungus Gnat population.
  • Chemical: Pyrethroids and Pyrethrin containing products.

Slugs / Snails

In 95% of cases you will only have Slug or Snail problems on plants which you choose to put outside in the warmer months of the year, they can still set up shop in your home too though. Slugs and Snails can eat and damage entire sections of plants in a single night They are quite a big pest both in size and with the amount of damage they do in a short space of time, however they are also the simplest to deal with.

Symptoms

Identification is easy. The leaves will be drastically damaged, large holes, or entire leaves stripped clean. When morning comes they will be well hidden, but they will sometimes leave a slimy trail around the area, which is the smoking gun as to what the culprits are.

Treatment

  • Organic: If the plants are outdoors the easiest solution is to put them in a protected place. High up etc. Slugs and Snails have strong homing instincts returning to the same areas night after night, so another idea is to move the plant to a different place entirely.
  • Organic: Indoors / Outdoors, if you go on a "dusk pick" when they start to become active again you may catch them in the act and can therefore move them far away.
  • Organic / Chemical: If you have it in you, then you can also kill them. Either with a large boot or with slug pellets. As with all pests however they do play a vital role in the natural cycle of things, in particular making a delicious meal for birds and small animals like hedgehogs. So if you can't bring yourself to kill them something else will do the job for you eventually.

Springtails

Springtails Springtails living on the soil surface of a house plantare small, white or grey insects that live off the decaying organic matter found in soils. They are small (although can be seen easily with the human eye as they stand out against the dark compost) and best resemble fleas, they aren't really pests at all as they do no damage. However their presence often attracts attention because when you water and are consequently paying more attention to the plant than usual, the water triggers the Springtails to go wild with movement and thereby alerting you to their existence.

Symptoms

When you water the plant and it hits the soil, you will notice small white flea like insects jumping or moving around.

Treatment

As above there isn't really a need for a "treatment", but they can be frustrating.

  • Organic: The simplest way to reduce numbers and give control is, where possible, water your plants less. Springtails need water to survive and if there isn't their numbers will eventually decline. You have to be careful though as not many plants will survive long periods without water!

Also on OurHousePlants.com

Photo credit of the Red Spider Mite close up Gilles San Martin
Photo credit of the Mealybug Forest & Kim Starr
Photo credit of the Red Spider Mite Harald Hubich
Photo credit of the Fungus Gnat Erik Burton
Photo credit of the Springtails Marshal Hedin


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