Have you ever seen a web on your houseplants? Or how about weird black dots that wipe off? Or maybe little things fly around and bug you when you water?… Welcome to houseplant pests.
What are Houseplant Pests?
Houseplant pests are organisms that cause harm to your houseplant, or organisms that live off your houseplant and annoy you. Unlike garden pests which include animals such as rabbits, dear, moles, and mice, houseplant pests tend to be quite small and may not even be noticed unless their numbers get out of hand, or you go hunting for them. The most common pests you will find are:
- Scale Insects
- Fungus Gnats
For more information on pests and how to identify them go to: https://apps.extension.umn.edu/garden/diagnose/insect/?utm_source=custom%20block&utm_medium=ext&utm_term=diagnostic%20insect&utm_campaign=
As most houseplant pests are quite small the only way you may notice them is to scout (look) for them. Here are a few tips when scouting:
- Inspect all plant parts. Pests love to hide, so check hidden areas. You may need a hand magnifying lens to see some of them as they can be VERY small.
- Check for evidence of insect damage. This can include webbing from spider mites, holes from beetles and caterpillars, and stippling (discolored tiny dots on leaves) from piercing insects. Also look for “honeydew” a shiny, sticky substance excreted by many piecing insects (aphids, mealybugs, and scale insects). Honeydew can be found on the tops of leaves, or on surfaces surrounding your plant.
- Inspect the container. Some pests can be found along the edge/rim, or even the pot bottom or the saucer under a pot.
- Check for pests when you water. Some pests such as springtails and fungus gnats will move when disturbed.
- Yellow and blue sticky traps can be used to detect flying insects like whiteflies, fungus gnats, winged aphids, and thrips. Sticky traps will not catch them all, but will give you notice of what is present.
Integrated Pest Management Triangle
So you found something and even identified it. Now what? According to the Integrated Pest Management (IPM) triangle you have 5 options: Prevention, Cultural/Sanitation, Physical/Mechanical, Biological, and finally Chemical
At the base of the triangle, and what you should try first, is Prevention. First, if your plant is healthy it is less prone to pest infestations. If your plant is not healthy or highly infested the best option may be to toss it. Trying to save unhealthy and infected plants may not be worth it, especially if it puts your other plants at risk.
If you are bringing plants in from outside for the winter or acquired a new plant. You may want to put those plants in isolation for a week or two to see if any pests emerge and to protect your existing houseplant collection.
Prevention ties in well with cultural care and sanitation, which is the next step up on the IPM triangle. Are you growing your plant correctly? For trees outside the saying goes “Right Tree, Right Place”. Are you growing the right plant in the right environment? Does your house plant like full sun (direct light) in it’s native habitat, or is it an understory plant (indirect light)? Should it get regular watering or does it prefer to dry out between waterings? Not all plants like the same amount of water, at the same time. Nor do they all like the same lighting, potting media, humidity or even temperature. Research your plant and figure out what its needs are. Perhaps you should consider moving your fern that loves humid air into the bathroom or kitchen and away from the vent putting out hot, dry air.
Please note: It is possible to OVER WATER. Many plants, especially houseplants, die from over watering rather than under watering. Plant roots need oxygen, if the potting media is waterlogged, the water is taking up the space the oxygen would fill and the plant may succumb to root rot. Make sure plants are not sitting in drainage water.
So your plant is healthy with proper lighting, watering, temperature, humidity, and potting media, but you still have pests. Sometimes plants, like people, just need a bath. Place your plant in the sink or shower and give it a nice gentle rinse. Another option is a sponge bath. Wipe leaves with a damp paper towel. Just be sure to change out towels regularly. You don’t want to spread or relocate your pests to a different area of the plant. Or even worse a different plant completely.
Larger pests can be removed by hand, such a slugs and caterpillars. Scale insects can be carefully scraped off, while others can be removed with a cotton swab dipped in alcohol. If you have soil borne pests, repot your plant with clean potting media after washing as much of the old media off the roots as possible.
If the pest problem is isolated you may be able to prune out the infected area. Or if widespread, prune out the most infected area or, depending on the type of plant, cut it back. Removing as many pests as possible makes it easier to deal with the remaining pests. Be sure to watch new growth for pest issues as new growth is more susceptible to pests.
Biologicals are beneficial insects or natural predators that prey on unwanted pests. Unfortunately, unless you have a sizable green house this is not practical for most home owners. Especially as most home owners find the idea of any insects in their home to be unwelcome. Biological controls are typically used in large-scale production or interior-scape facilities.
At the top of the pyramid are chemicals. These should only be used when all other options have been eliminated.
Things to know before you go shopping.
- All chemicals are regulated by the EPA.
- If you use a chemical (this includes all pesticides such as: herbicides, insecticides, miticides, fungicides, etc.) you MUST follow ALL of the directions listed on the label.
- Not doing so is a violation of federal law.
The label will tell you:
- what pests the chemical will target
- where the chemical can be used
- when and how the chemical should be applied
- how to mix the chemical
- how to dispose of the chemical and its container
- what safety gear must be worn
- what types of plants can be treated
- plus much, much more!!!
There are a limited number of pesticides available for indoor use. Look for them at plant nurseries, garden centers, building supply stores, and online. BE SURE to keep them locked up and away from children and pets.
Please note, that some chemicals are labeled organic. This DOES NOT mean they are safe. One of the most common natural sources for organic pesticides is plants. Plants have been fighting pests for eons, and have adapted methods, including chemicals, to deal with pests. However, many of these plant chemicals are dangerous even poisonous. Treat all pesticides with care and FOLLOW the label!
If you are having issues determining what pest is bugging you and your plants, you can contact the Plant and Insect Diagnostic Clinic at Iowa State University https://hortnews.extension.iastate.edu/pidc.
Here are some additional resources with more information: