Houseplant bugs can be a letdown as a plant parent.
Unfortunately, no matter how diligent your care is, pests can find their way into your indoor jungle.
The truth is that some plants are more susceptible to bugs than others.
However, with the proper techniques and knowledge, these houseplant bugs can be identified and eliminated without harming your plant family.
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Where Do Houseplant Bugs Come From?
Houseplant bugs can come from many sources.
Sometimes they simply enter from the outside through doors and windows.
They can also be on fresh flowers, either from the grocery store or from the garden.
However, most often they arrive on new plants that come into your home.
How to Inspect Houseplants for Bugs Before Buying Them
It is critical to examine new plants thoroughly before purchasing them.
Especially look under leaves and at the new growth for bugs, spider webs, a sticky substance, ants, or black mold.
The webs could be from spider mites, which are difficult to see with the naked eye.
The sticky substance is called honeydew and it is excreted from various houseplant bugs.
It’s a sign that bugs are in the area, so although you may not see them, it is a warning.
Ants and the black mold on the leaves are also a by-product of this honeydew substance so they too are a signal that pests could be present.
Also, gently move the leaves and pick up the plant to see if insects fly away when the plant is disturbed.
If purchasing plants online, examine the plants the same way when they arrive at your home.
A 10x (or greater) magnifying lens is a valuable tool for spotting bugs in the early stages of development.
Sometimes it is difficult to see a few bugs with the naked eye, especially in low light.
A magnifying lens will give you an advantage in spotting and identifying houseplant bugs.
It can save a plant parent a lot of grief and hard work.
What to Do Once You Get a New Plant Home
Once you have a new plant baby home and it appears to be pest-free, it is wise to quarantine it from other plants in your home for 6 weeks.
This allows time for any eggs or immature bugs to develop that may have been difficult to initially detect.
During this quarantine period, it is always advantageous to be proactive to eliminate the development of any insects.
Rinsing the leaves (top and underside) and stems with a stream of lukewarm water every 2-3 weeks will dislodge any eggs or nymphs that may have developed.
This is an effective, natural method of pest removal.
Also, continue to visually inspect the plant with the magnifying lens weekly throughout the quarantine period.
If the houseplant is pest-free at the end of the quarantine period, it can then be added to your houseplant collection.
What If I Find Houseplant Bugs?
Unfortunately, it can happen.
A bug appears on one of your favorite plants.
Identifying the pest and attacking it appropriately is the key to eliminating an infestation while keeping the plant healthy and vibrant.
It may require several simultaneous approaches to kill the bugs that are in different stages of the reproductive life cycle.
Nature will always try to find a way to prevail, so repeated applications of the same treatment are a reality as well.
What are Fungus Gnats?
One of the most common houseplant bugs is fungus gnats.
They are flying gnats (1/8 to 1/16 inch) with gray or clear wings and black heads that are most noticeable when the plant is moved or the leaves are rustled.
The adult gnats don’t cause harm to plants as they feed on moisture in the soil.
They are certainly a nuisance.
However, the larvae (immature stage) live in the soil, feed on organic matter, and can consume plant roots.
When larval populations reach high levels, the severed roots will cause leaves to turn yellow and drop.
Fungus gnat larvae are approximately ¼ inch in length, have clear to white, legless bodies, and a dark, shiny head.
Fungus Gnat Life Cycle
Female fungus gnats lay whitish-yellow eggs in the top layer of the plant’s soil.
They prefer extremely moist conditions that have a lot of organic matter.
Eggs develop into larvae that feed in the soil and then emerge into adults.
This process takes about 3-4 weeks and is dependent on air temperature.
The warmer the environment, the faster the maturation process.
An adult fungus gnat lives approximately 8 days, but during that time a female can lay approximately 30-200 eggs.
Therefore, fungus gnat populations can swell exponentially within a short time.
How to Prevent Fungus Gnats
Overwatering is the number one reason for a fungus gnat infestation.
Fungus gnats thrive in moist soil conditions.
The best way to prevent fungus gnat populations is by allowing the top several inches of the soil to dry in between watering.
Without a moist environment, it is challenging for fungus gnats to live.
The adults won’t have a water source and the larvae won’t have enough moisture to complete their life cycle.
It’s also important to remove any dead leaves or other debris on the soil surface.
This can hold moisture and is an ideal place for a female to lay eggs.
How to Get Rid of Fungus Gnats
Once a plant has an established fungus gnat population, there are multiple methods of eliminating the infestation.
The first is to use yellow sticky cards to trap the adults.
When these are strategically placed near the soil surface, they can trap large quantities of adults.
Yellow sticky cards are also a great option for preventative measures as they can alert you to the presence of a few insects before they are noticeable.
Sprays to Kill Adult Fungus Gnats
There are natural sprays containing pyrethrin that will kill fungus gnat adults.
Pyrethrin is a substance derived from chrysanthemums that is a natural insecticide.
Horticultural oil is also an effective natural method for controlling a large fungus gnat population.
However, because of the quick life cycle, the plant will have to be sprayed regularly to eliminate the adults as they emerge.
How to Kill Fungus Gnat Larvae
There are both naturally derived and synthetic chemically derived methods for controlling fungus gnat larvae.
Products that contain Bacillus thuringiensis subspecies israelensis (Bti) are made from natural bacteria that will kill fungus gnat larvae.
These are soil additives that naturally kill larvae.
There are also beneficial nematodes (Steinerema feltiae) that can be added to the plant’s soil. These are harmless to plants and people, but deadly to fungus gnat larvae!
These are highly effective when used as directed.
There are also synthetic chemical pesticides available for extreme infestations.
However, these should be used with caution indoors, especially around pets and children.
What is this White Cottony Stuff on My Plants?
Mealybugs are another very common houseplant bug.
To the naked eye, it looks like white, waxy, cottony stuff on the plant.
They are often misidentified as a fungus.
However, when looking with a magnifying lens, it is clear that they are white, oval slow-moving pests with legs that congregate in masses.
Mealybugs are a pest that can be difficult to detect because they can hide in the nooks and crannies of a plant.
Mealybugs love a plant’s tender, soft new growth, so they can often be found right at the top of the plant where the new leaves are emerging.
However, they will feed along the plant’s main stem as well as the underside of leaves.
They have piercing-sucking mouthparts to remove sap from the plant.
This can create yellow speckling on leaves known as chlorosis.
Mealybugs secrete a clear, sticky, sugary substance called honeydew that grows a black fungus on it.
This can coat leaves and prevent the leaf from receiving light.
Plants with heavy mealybug infestations will often have wilted, yellow leaves with sooty black fungus on the leaves.
Ants are also attracted to the sugary honeydew, although generally harmless, they are seen around the plant.
Mealybug Life Cycle
Mealybugs lay small yellowish eggs on leaves.
They are visible with the naked eye, but not easy to detect.
An egg matures into an adult in about 6-8 weeks.
How to Get Rid of Mealybugs
One of the easiest ways to get rid of mealybugs is to use a cotton swab dipped in rubbing alcohol and wipe them away.
This process must be repeated every week or so to remove any new mealybugs that emerge, but over time, it is an effective control method.
These are highly refined, specialized oils and soaps that are designed specifically for indoor horticultural use.
Be sure to use these as directed so that there isn’t any damage to the plant.
What Are Aphids?
Aphids are another common houseplant bug that has piercing-sucking mouthparts that remove sap from a plant.
They are 1/8 to 1/16 inches long, pear-shaped, and usually green, but also orange, red, beige, brown, pink, yellow, or black.
Aphids are commonly found on a plant’s new growth or underside of leaves.
As aphids feed on the plant’s sap, they can cause new leaves to be deformed or distorted.
Similar to mealybugs, aphids excrete a clear, shiny, sticky, sugary substance known as honeydew.
Over time, this substance develops a black appearance as fungi grow on it.
Known as sooty mold, this black covering on the leaves weakens the plant and ultimately can cause leaves to wilt and drop.
Aphid Life Cycle
The types of aphids found on indoor plants generally do not lay eggs but give birth to live babies that begin feeding on plant tissue immediately.
As a young aphid develops, it molts leaving a dry skin casing.
This is a distinctive sign to help identify an aphid infestation.
A female is capable of giving birth to 3-6 young per day.
Female aphids also can produce young without mating.
This is known as parthenogenesis.
This can create a scenario in which populations can explode at a rapid rate.
Thus causing a lot of damage to a plant in a short time.
How to Get Rid of Aphids
Since aphids have soft bodies they can be easily removed from a plant with a strong stream of water.
Gently use your fingers to remove the aphids under the water (use a glove if you’re squeamish).
This is a highly effective method of removing and controlling a small number of aphids.
Another easy method of killing aphids is to dip a cotton swab in rubbing alcohol and wipe the aphids away.
Repeat this regularly to remove all hidden young that might be in the leaves nooks and crannies.
Sprays that are made with pyrethrin, a natural insecticide derived from plants, are also effective in treating aphids.
What Do Whiteflies Look Like?
Whiteflies are one of the most common houseplant bugs that can arrive on plants that are purchased from a greenhouse.
As the name implies, they are small (1/10-1/16 inch), white, moth-like flies that congregate on the underside of leaves.
Once the leaves are disturbed, the whiteflies take flight and create a noticeable white cloud.
Not only is this a nuisance, but they damage plants by sucking the sap from the leaves.
This creates yellow spots, can deform leaves, and ultimately weakens the plants.
Whiteflies also excrete a clear, shiny honeydew substance on which a black fungus will grow.
This creates a black sooty mold coating on the leaves.
When high populations of whitefly are present, it is not uncommon to find honeydew on surrounding surfaces such as floors and tables.
Whitefly Life Cycle
Whiteflies reproduce by laying eggs on the underside of the leaves.
Each female can lay several hundred eggs at a time.
Eggs hatch within a week and the crawlers begin feeding on the plant sap immediately.
The young undergo a metamorphosis to become adults, continually feeding on plant juices.
The life cycle process from egg to adult is approximately 18 days.
Therefore, whitefly populations can explode rapidly.
How to Get Rid of Whiteflies
This is one situation in which an ounce of prevention is worth a pound of cure.
Whitefly can be troublesome to eradicate and even seasoned greenhouse managers can battle this bug.
Vigilance when purchasing plants whether at a local greenhouse or online is critical to avoid introducing whiteflies into your home.
Poinsettias and tropical hibiscus are notoriously susceptible to whitefly infestations.
Implementing several approaches will be the best plan to eradicate whiteflies.
The use of yellow sticky traps within the foliage area is an effective organic method of eliminating adults.
Rustling the leaves will put them into flight and along the path of the traps.
Check the product label before spraying to ensure that it is safe for the particular plant.
What Are Spider Mites?
Another common houseplant bug is the spider mite.
Spider mites can be one of the most difficult to spot because they are so small (1/50 inch).
They cause damage by piercing the leaf and sucking the sap out for food.
This causes yellow, stippled leaves that have a dull appearance.
Over time the leaves can appear bronze and dried.
Spider mites create webbing that will be a calling card for their presence.
Usually, their damage and webbing are noticed before they are.
However, placing a white sheet of paper under the leaves while gently shaking them can be an effective way to scout for spider mites.
They will appear as moving specks on the paper.
If you can see them with a magnifying lens, they are generally yellow, orange, or red, have 8 legs, and 2 spots on either side of their body.
Spider Mite Life Cycle
Spider mites reproduce by laying eggs.
The eggs develop into larvae and then into adults.
This process takes approximately 1-2 weeks, so infestations can develop quickly.
How to Prevent Spider Mites
Spider mites thrive in dry, hot, arid environments.
They will prey on plants that have been underwatered or stressed in some way.
A room humidifier increases the amount of moisture in the air thus creating a less inviting environment for spider mites, especially on tropical plants.
How to Get Rid of Spider Mites
Because spider mites are so small one of the most effective ways to get rid of them is to use a strong stream of lukewarm water to wash them away.
They simply can’t overcome the force of the water and it removes both the webbing and mites.
To prevent mites or eggs from being washed into the soil, wrap the pot in plastic wrap while rinsing.
Several applications may be necessary since the spider mites are difficult to see and generally on the underside of the leaves.
Tips to Keep Houseplants Bug-Free
- Tailor each plant’s care (water, light, humidity, etc.) so that it doesn’t become stressed. Plants under stress are more susceptible to pests.
- Inspect and quarantine new plants vigilantly before introducing them around your existing plants.
- Invest in a minimum 10x magnifying lens. Most houseplant bugs are hard to see with the naked eye before populations become large.
- Regularly inspect all plants for signs of bugs. Look especially under leaves. in the leaf axils (the area where a leaf stem joins a branch) and the new growth.
- Remove all dead leaves and debris on the soil surface as this can be an ideal breeding area.