Consider yourself something of a super plant parent? Houseplant pests will really test your mettle. Your favorite plant that has thrived for months or even years suddenly droops or yellows. Perhaps its new leaves unfurl puckered and deformed. A closer look might make you shiver. Not only is there something, well, kind of creepy about large populations of very tiny insects living in our midst, but these houseplant pests can do real damage and must be taken seriously.

An overwhelmed or inexperienced plant owner might think that the problem will go away on its own, but this is unlikely. Swift identification and treatment is crucial for catching an infestation before it gets out of hand (many of these insects reproduce rapidly, causing dramatic population booms). If you truly care for your plants, you will put any squeamishness aside tend to them through good times and bad.

To help you move through this unfortunate yet inevitable phase of plant parenthood, we’re posting a 3 part series called Dealing with Houseplant Pests. In this post, Part 1, you’ll find some background information about houseplant pests, preventative care tips to avoid them in the first place and an overview of the different treatment methods available for handling an infestation.

Mealybugs can often be found where leaves meet the stem. Can you spot the culprit in this photo?

Where Do Houseplant Pests Come From?

One of the most common questions we’re asked at Pistils is where houseplant pests come from. Pests come into your home a number of ways. They can find their way in through open windows (yes, many of them fly) and on people, pets, or even produce or flowers from your garden. They might hitch a ride on newly purchased plants from a nursery, or plants that have been enjoying a summer holiday on your patio. They can even find their way into open bags of soil and then into your home when you repot.

Any self-respecting wholesale or retail nursery checks their plants diligently and employs a wide arsenal of tools and products to keep plants pest-free by the time you take them home. However, sometimes sneaky stowaways or unhatched eggs evade detection. Some pests, like spider mites, are nearly invisible to the naked eye — especially when there’s only a few present — and so can be exceptionally difficult to spy at the early phases of an infestation. That said, whenever you bring new plants into your collection, whether from the nursery or from a friend, you’ll want to take some preventative care steps.

Houseplant Pest Prevention

Proper care

When it comes to houseplant pests, the best preventative measure is good regular care and a watchful eye.

Improper care or growing conditions can make a plant weak and more susceptible to pests. Over or under watering, insufficient light, lack of humidity, fertilizer misuse, and extreme temperature changes can all significantly weaken a plant.

Your first step to preventing pests (and keeping your plants healthy in general!) is to always identify your plants and do research to make sure you are providing the proper care. Good light and consistent watering are key.

Fresh soil and clean pots

Because pests often stowaway in soil, always use clean containers and sterilized potting mix. Watch closely for changes in appearance and growing habits.

Careful observation and early action

Very small and often difficult or impossible to see with the naked eye, it’s easy to miss a pest problem until it’s too late and your plant is in real danger, which is why frequent and careful inspection of your plants is so important. Consider getting a magnifying glass or lighted hand lens to better see and identify these very tiny creatures. Look closely at the junctions of stems and leaves, undersides of leaves, and any delicate new growth, which is a bug’s absolute favorite supper.

Remember to check roots for any abnormalities when repotting. Keep your tools clean and do not reuse the same cloth or duster to clean all of your plants, which can spread pests. Isolate any sick plants immediately by moving them outside (if temperatures allow), or as far as possible from healthy plants.

Isolate new plants and problem plants

If you have space, consider isolating any new plants for up to a month before adding them to your collection to make sure they’re not carrying any pests. If you don’t have space, consider a gentle insecticidal treatment just to be safe.

If, during your routine care, you do spot the beginning of a problem on a given plant, you’ll also want to isolate or quarantine it. When it comes to your precious plant collection, it’s much better to be safe than sorry!

Summer clean-up

If you’ve put your plants outdoors for summer, carefully inspect and wash these plants before bringing them back inside. There are a few insects that would prefer to live outdoors but may end up in your house for one reason or another. These insects will often seek refuge in the familiar territory of plant life and wind up nibbling on your houseplants to keep from starving. These are insects such as earwigs, pill bugs, ants and caterpillars. When moving plants back inside from any extended period of time, consider spraying foliage and/or soaking pots with a diluted insecticidal soap solution to avoid these bugs.

Houseplant Pest Treatment Methods

When pests are discovered, the best way to proceed is a two-pronged approach: first, physically removing as many pests as possible and second, treating with some form of insecticide.

Physical removal

For physical treatment, use a q-tip or even your fingers to simply remove (or smush) as many of the pests as possible. Some pests like aphids can be rinsed off en masse with the gentle spray of water from your sink hose sprayer. Clip away heavily infested leaves or stems, and dispose of them. For some pests like mealybugs and scale, it may be helpful to douse the q-tip in rubbing alcohol to aid in pest removal.

Aphids often congregate on the stems of plants. A cluster like this can be sprayed off with water.

Treating pests with household products

When you’re ready to move on to more generalized treatment of your plants, the most gentle things you can use to treat pests are household products you probably already have on hand like gentle Castile soap (not detergent), rubbing alcohol, and vegetable oil. Soap (household or insecticidal) is the least toxic way to treat the problem. Soap coats insects and breaks down their bodies with fatty acids. You may need to repeat several times to completely eradicate a problem, because the soap must touch the insects to be effective. Make sure to keep any plants treated with soap out of direct sun, as it can increase the likelihood of sunburn.

Natural houseplant pest treatments

Other natural products often used for houseplant pests are diatomaceous earth, beneficial parasites, and horticultural oils. Neem oil is a popular organic treatment. It is a complex plant-derived oil that makes insects’ hormones go haywire, interrupting maturation and appetite. It has a rather pungent odor and can cause allergic reactions in some people, but it is natural, effective, and happens to give foliage a beautiful shine!

A gentle insecticidal soap solution is widely available at nurseries and garden centers and is a great product to have on hand. This soap is specially formulated for use on plants and is therefore generally more gentle and effective than household soaps. Some brands include ingredients like neem oil and kelp extract to keep plants extra happy, lustrous, and safe from pests.

Although gentle, these soaps and oils can still harm some types of plants. Some known to be sensitive to soap or neem treatments are Begonias, ferns, jade plants, palms, Scheffleras, Alocasias and Euphorbias. Do your research and test on a small leaf before spraying the whole plant.

Systemic houseplant pest treatment

Systemics are stronger products that must be watered into the soil. The plant takes it in through the roots, becoming toxic to the insects. These chemicals can be potentially harmful, so always read labels carefully and follow directions for proper use. Unless you have a serious collection of houseplants and know what you’re getting into, it’s best to use gentler means of control.

Although it can be temping in a moment of haste or laziness, don’t be too heavy-handed with chemical pesticides; they can damage plants, introduce toxins into your home and the environment, and often do more harm than good. Save systemics for very special or mature plants you can’t bear to lose.

When to Throw In The Towel

That having been said, save your sentimentality for only your most treasured plants. If more than half a plant is damaged before you can treat it, it’s best to dispose of it before you risk pests spreading to your other plants. An entire collection can become infested before you know it.

If a beloved plant is too far gone, you can always look for even the smallest healthy leaves or stems and take cuttings to preserve the spirit of the specimen and start all over again. Plants are rather magical this way. 

This Jade Plant is infested with mealybugs, causing the new growth to shrivel and fall off. For heavy infestations like these, it might be worth throwing in the towel.

In Part 2 of our series, we’ll dive into the nitty gritty of treatment, detailing the seven most common houseplant pests and how to eradicate them. Be sure to subscribe to our mailing list to find out when the next piece is published!

October 02, 2018 — Pistils Nursery


Emerald said:

Very informative. Waiting with anticipation for part 2. I like the advise of keeping new plants away for at least a month from my collection. I have learnt that the hard way. These last couple of months I recognize that most of the plants purchased from nurseries have spider mites. Thanks for the information.

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