House Plants 101: Pest Control

House Plants 101: Pest Control

Chris
12 minute read

No one wants to talk about pests, but it is crucial that we do it for the sake of our house plants. Whether growing indoors or outdoors, all plants are susceptible to pests - no exceptions. But these pests can easily populate and wreak havoc on your beloved plant babies grown indoors due to the lack of outdoor environmental factors such as rainfall, wind, and harsh weather conditions that can naturally rid or help control pest populations. They also lack natural predators indoors that would otherwise eat them. It is important to keep in mind that no house, botanical garden, greenhouse, nursery, online retailer or boutique plant shop is guaranteed to be pest-free. The sooner you can accept that pests are going to be a natural part of owning house plants, the sooner you can learn the signs of an infestation and how to control any outbreaks. 



Common Houseplant Pests 

Aphids
Though they are most commonly an outdoor pest, they can very easily find their way into your homes by hitchhiking on herbs, produce, or on a person who spent time outdoors or in the garden. They will also be an issue if you like to grow your house plants outdoors in the spring and summer.

yellow aphids in a leafs A plant with distorted leaves due to aphid damage


Profile: Small, soft-bodied insects. Usually green, yellow, or white in colour. Adult aphids appear in large clusters on stems and undersides of leaves
Damage: Aphids suck the stems and leaves of plants causing them to weaken. They can also transmit viruses from plant to plant.
Signs: Misshapen, yellowed leaves
Treatment: Quarantine infested plant immediately to protect the rest of your collection. For small infestations, aphids can be easily wiped off with damp tissue. For larger infestations, strong blasts of water will easily wash a good amount of the aphids off. Follow up with insecticidal soap or diluted soapy water. In the summer, ladybugs (The aphids natural predator) can be purchased and released outdoors in your garden or in a large, ventilated container holding your affected plants indoors in your home.
Susceptible: Herbs and fruit trees are most susceptible to aphids, however, your house plants growing outdoors in the summer can come under attack by aphids too. They can also find their way into your home very easily. They have been known to take a liking to Anthuriums, Hoya and Peace Lilies.
Prevention: Frequent inspection. Apply insecticide, cayenne pepper-infused water spray or garlic-infused water spray. Neem oil is commonly used in the house plant community to prevent any sort of pest infestation. Neem oil is natural oil produced from the pressed leaves of the neem plant and work to get rid of pests in two ways: by making them feel full when they’re not which causes them to starve to death, and by disrupting regulatory hormones in larvae which disables them from transforming to the next growth stage.

 

Caterpillars
Although most people think that caterpillars aren’t a house plant pest, think again! It is not an uncommon occurrence that moths will fly into your home. Some moths love laying eggs in your house plants! 

a photo of a caterpillar on a leaf a photo of a caterpillar eating holes into a house plants leaves

Profile: Long, soft-bodied insects ranging in colour from green to brown. Can be smooth or hairy in appearance. They are typically moth caterpillars.

Damage: Adult moths and butterflies won’t do much damage to your house plants, however in their larval stage, they have big appetites and can munch on the leaves of your plants, causing pretty serious cosmetic damage.

Signs: Seeing egg clusters, large holes or chunks on leaves, webbing in between leaves, caterpillar droppings on leaves. 

Treatment: Quarantine infested plant immediately to protect the rest of your collection. Since caterpillars are bigger than other common pests, when spotted they can easily be removed and discarded outside. Otherwise, soapy water or insecticides can help rid caterpillars.

Susceptible: It is possible that any plant can come under attack by caterpillars, however, moths particularly love ferns.

Prevention: Frequent inspection, applying neem oil, insecticides, or cayenne pepper spray.



Fungus Gnats
Fungus gnats are more of an annoyance than they are a threat to your house plants. They breed and thrive in damp soil.

a close up image if a fungus gnat a photo of countless fungus gnats stuck to a yellow sticky trap

Profile: Tiny flies, grey to black in colour, often mistaken as fruit flies.

Damage: As mentioned, fungus gnats are more of a nuisance than they are harmful. They reproduce quickly (each female can lay up to 300 eggs) and constantly having them buzzing around your home can get rather annoying. Their larvae tend to feed on small roots, so they are a concern when growing seedlings, but not so much a concern to already established plants.

Signs: Discolouration of leaves in younger plants. Tiny insects fly up into the air when you water your plants.

Treatment: Yellow sticky traps are great at controlling fungus gnat populations and can be found online or at your local garden centre. You can also make your own apple cider vinegar trap, or water your plants with diluted hydrogen peroxide – don’t worry, hydrogen peroxide is safe to use around humans, pets, and plants!

Susceptible: Any tropicals planted in soil are susceptible to fungus gnats.

Prevention: Frequent inspection. Applying a thin layer of sand to the top of your soil can make it difficult for adult gnats to get into the soil to lay eggs. Neem oil and citronella sprays are helpful in deterring fungus gnats. Diatomaceous earth (DE) is also an effective way to control fungus gnats. DE is a naturally occurring soft and siliceous sedimentary rock that has been ground into a powder form. The tiny and sharp edges of DE cut into the body of small pests causing dehydration and ultimately death.



Mealybugs
Mealybugs are a family of scale insects that suck the sap from plants. Root mealies are harder to spot because they exist in the soil line and attack your plants' roots. They are attracted to moist, humid conditions.

a photo of an isolated mealybug on a leaf a colony of mealybugs attacking a dracaena house plant

Profile: Soft-bodied, white in colour, coated in powdery wax coating giving them a fuzzy appearance.

Damage: Weakened plants, stunted growth, wilting, sudden leaf drop.

Signs: Dense, white, fuzzy clusters often found in crevices and joints of plants.

Treatment: Quarantine immediately from the rest of your collection. Swab to remove any visible scale with a Q-tip and 99% alcohol. Apply insecticides, soapy water, predatory mites. Get rid of heavily infested growth or plants altogether. Apply neem oil.

Susceptible: Any tropical foliage plant is susceptible to mealybugs. However, they are particularly keen on succulents and cacti and often attack succulent roots.

Prevention: Frequent inspection, avoid overwatering your plants, apply neem oil or insecticidal soaps, use predatory mites.



Scale
Scale, just like mealybugs, feed by sucking the sap out of your plants. They are inconspicuous and much harder to spot because they don't move much and often look like a part of a plant. This is especially the case on plants that produce woody trunks or stems such as Fiddle Leaf Figs.

Two different species on scale attacking the same ficus plant a close up photo of  yellow scale on a leaf

Profile: Hard-bodied, usually beige or brown in colour. Look like little bumps. Can be shiny or matte in texture, depending on the species of scale. Did you know that there are over 6,000 species of scale in the world? 

Damage: Weakened plants, stunted growth, wilting, sudden leaf drop.

Signs: Look for small bumps in the veins of leaves or on the trunks and branches of your plant.

Treatment: Quarantine immediately from the rest of your collection. Swab to remove any visible scale with a Q-tip and 99% alcohol. Apply insecticides, soapy water, predatory mites. Get rid of heavily infested growth or plants altogether. Apply neem oil.

Susceptible: Any tropical plant is susceptible to scale.

Prevention: Frequent inspection, apply neem oil, insecticidal soaps, predatory mites.

 

Whiteflies

Unlike fungus gnats, adult whiteflies will feed on the sap of plants and can be difficult to get rid of for good. They are also very small and usually go unnoticed. Female whiteflies can lay 200-500 eggs. Due diligence and dedication will be required to end their life cycles.

a photo of the underside of a leaf infested with whiteflies a photo of a leaf infested with larval and adult whiteflies

Profile: Tiny soft-bodied, winged insects, white in colour and triangular in shape. Wings are coated in wax powder giving them a soft and powdery appearance.

Damage: Feed on the sap of plants and can transmit disease between plants.

Signs: Look for small bumps in the veins of leaves or on the trunks and branches of your plant.

Treatment: Quarantine immediately from the rest of your collection. Swab to remove any visible scale with a Q-tip and 99% alcohol. Apply insecticides, soapy water, predatory mites. Apply neem oil. 

Susceptible: Any tropical foliage plant is susceptible to whiteflies. 

Prevention: Frequent inspection, apply neem oil, insecticidal soaps, predatory mites. Do not over-fertilize your plants – whiteflies are very attracted to nitrogen.



Spider Mites
These tiny pests are incredibly hard to see with the naked eye unless you are really looking for them. Since they usually populate unnoticed, it is likely that an infestation will get worse before it is noticed. This makes them one of the more devastating houseplant pests. Spider mites love hot and dry environments.

a photo os a person holding a magnifying glass up to red spider mites a photo of a dead leaf covered with spider mites and webbing

Profile: Microscopic mites, usually black in colour but can also be red, white, or brown. They live in large colonies and are good at hiding in tiny crevices and new leaves of plants.

Damage: Spider mites feed on the sap of plants.

Signs: Tiny spotting on leaves that spread quickly, yellowing leaves, dense webbing.

Treatment: Quarantine infested plant immediately to protect the rest of your collection. Spray down your plant with water, apply soapy water spray or insecticide. Pay extra attention to joints, crevices, and new unfurling foliage – the love to hide in these spaces.

Susceptible: Spider mites are not picky about what they eat, leaving just about any plant susceptible to an infestation. They are particularly fond of palms, Alocasias, Cast Irons, Ivy, and Birds of Paradise

Prevention: Frequent inspection, showering plants, increasing humidity in your space, apply neem oil or insecticides.



Thrips
We saved the most diabolic pest for last. Thrips are not only very damaging to your plants, but they are incredibly hard to eradicate. They can reproduce asexually and lay their eggs inside foliage by cutting microscopic slits in your plants' leaves. This makes their eggs and soon-to-be larvae completely safe from any spray treatments. Eradicating these takes time and dedication to disrupt their growth cycle. They also travel very quickly to other plants so we will always recommend that you consider whether the infested plant is worth trying to save at the risk of spreading to your plant collection!

a photo of a thrip on the pistil of a flower a close up image of thrips on a leaf with thrip damage

Profile: Tiny soft-bodied insects. Can be black or beige in colour. Slender bodies with pointed ends.

Damage: Thrips feed in large populations to quickly suck the life out of plants. 

Signs: Weakened plants, distorted growth, mottling or dotting on foliage. The thrips themselves can be noticed. At first, they look like specks of dirt but you will notice them moving. Again, they are quite fast.

Susceptible: Thrips love tender tropical foliage plants.

Treatment: Quarantine infested plant immediately to protect the rest of your collection. The most effective systemic pesticides for treating thrips are not legal to use and cannot be found in Canada. The second best chemical option is Doktor Doom Total Release Fumigator Insecticide Spray (please read the label and use it with caution!). Predatory mites are widely preferred in treatments for thrips for those who prefer the natural way. Remember: if you plan to use both methods to combat thrips, make sure that the predatory mites are introduced at least two weeks after fumigation, as the chemicals will also kill the predatory mites.

Prevention: Thrips can hitch a ride into your home on your groceries but most commonly, they thrive feeding on flowers. Wash fruits and vegetables as soon as you get home and if you like keeping fresh cut flowers in your home, keep that far, far away from your house plants! Be extra cautious of plants that are sold in establishments that also sell cut flowers. Inspect plants frequently, apply neem oil, insecticidal soaps, or predatory mites.


Important note: When treating plants with any products or homemade sprays, make sure the treatments are done in the evenings or early morning when the sun is not at its strongest. Liquids on your plants during peak sun hours can cause burns on your plant. Inspect your plants frequently, apply neem oil, insecticidal soaps, or predatory mites.



Extra precautionary steps in preventing an infestation:

1. Always quarantine new plants

No matter where the plants came from, it is very important that you keep them separated from the rest of your collection until you are confident it is safe for them to hang out with the rest of your plant babies. We recommend keeping your new house plants in quarantine for at least a week. During this time, inspect your plants daily for any signs of pests.

2. Repot your new plants

Many bugs lay eggs or stay dormant, hiding in the plant's soil. An excellent precautionary step is to re-pot your plants in fresh, sterile soil once you’ve brought them home.

3. Sterilize your soil (optional)
Just like in the soil of your plants, bugs can lay dormant in the bags of soil that you purchased! Some collectors like to sterilize their soils before transferring them into air-tight containers. Sterilizing your soil will not only help kill any pests but will also help kill off any bad bacteria as well. Some easy ways your can sterilize your soil at home are as follows:

a) Place soil in an oven-safe container and bake the soil at 180°F for 20-30 minutes

b) Place soil into a microwaveable container and cover but leave an opening for ventilation. Zap in 30 to 60-second intervals until the temperature of the soil reaches 180°F.

 

a photo of a person inspecting a peperomia house plant with a magnifying glass for pests


In conclusion, it is always going to be significantly easier to take steps in preventing an outbreak than actually having to deal with an infestation. We cannot stress enough the importance of inspecting your house plants weekly. The sooner an outbreak is detected, the better your chances will be at containing and eradicating the pests. Plant parenthood isn’t always going to be glamorous, but your plant babies will thank you for taking the extra steps to help ensure they are safe!





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