Common Houseplant Pests
Keeping your plants healthy means giving them the water, light, nutrients, and environment they need. And it also means preventing and treating pests if they happen to find your plants and make a problematic home for themselves.
This guide to five common plant pests will help you spot, treat, and conquer spider mites, scale, mealybugs, thrips, and fungus gnats. After reading, you’ll be a pest control pro and the hero of your plant collection!
Spider mites are tiny and hard to spot, but they leave silk-like web material on the underside of your plant’s leaves. Here are some fast facts about these fast-spreading pests:
- Spider mites can travel from plant to plant easily by swinging on webs, so quarantine any affected plants right away
- Female spider mites can lay 300 eggs in a two week period!
- Spider mites can grow from egg to adult in under a week, so it’s best to act fast
Signs of Spider Mites
- Web material on the underside of leaves
- Feeding spots - pale spots left behind when spider mites bite in and drain the cells
- Shrinking - If your plant looks like it’s getting smaller, check those leaves for evidence of spider mites
How to Treat Spider Mites
- Start by removing affected leaves and stems and throwing them away in the garbage
- Wash leaves with insecticidal soap and spray the leaves well to knock off any remaining mites
- Use neem oil to the soil and leaves every few days
- Release ladybugs or lacewings to your quarantined plant area to eat the pests
Scale insects are round, flat insects that stick themselves in one spot on your plant and feed on the sap from inside. They barely move, so they can be hard to spot unless you take a close look.
- Scale looks like small scab-like spots, usually around the joints between stems
- Scale is usually brown or tan but can also be light in color
- The full life cycle of scale can take up to ten weeks from egg to adult
- Eggs and nymphs are very tiny, so it’s hard to spot scale until you have a larger infestation
Signs of Scale
- Leaf damage, discoloration, and dropping on foliage
- Dents and marks on succulents
How to Treat Scale
- Scale can be hard to treat with topical pesticides because these insects have a tough exterior
- Soak a cotton swab in rubbing alcohol and use it to remove scale from the plant
- Check the plant from multiple angles, including under leaves and the joints of stems
- After removing the bugs with the swab, treat the plant with insecticidal soap or a solution of 1 teaspoon mild liquid soap to one quart of water
Mealybugs are the soft, fuzzy alternative to scale. That is, they’re also scale insects but without the tough exoskeleton. Mealies find a place to latch on and feed, and they stay put for most of their life in that prime spot.
- Mealybug eggs look like sacs on the underside of leaves, so check plants regularly for signs of eggs or other pest symptoms
- Mealybugs are attracted to high nitrogen levels in the soil, so they may pop up if your plant is over-fertilized
Signs of Mealybugs
- Mealybugs have a flat or rounded scab-like appearance like scale but are white and fuzzy-looking instead of brown
- Mealybugs secrete a sticky substance known as honeydew as they feed, so sticky spots on your plant are a sign to look for mealies
- Ants eat the honeydew, so if you notice ants hanging around a plant, check for their mealybug partners in crime
How to Treat Mealybugs
- Use a cotton swab soaked in rubbing alcohol to remove the insects from the plant
- After removing the mealybugs, treat the plant with insecticidal soap, diluted liquid soap, or neem oil
- If you have a quarantined space where you can release beneficial insects, ladybugs, lacewings, and mealybug destroyer mites to eat the mealybugs
Thrips are tiny flying insects that suck plant sap like other pests, but they are hard to spot since they are just a millimeter long!
- The life cycle of thrips depends on the environment; they hatch more quickly in warm weather but in cold temperatures it may take them weeks or months to hatch
- There are thousands of species of thrips and they can infest furniture, bedding, and electronics - but we are just talking about the ones that like plants
Signs of Thrips
- Thrips feed in groups, so approaching your plant will make them jump or fly away
- Look for slits in leaves and stalks, where adults make a place to lay eggs
- Silvery leaves that drop off the plant are a sign of thrip damage
- Plant material becomes scarred and twisted from feeding on sap
How to Treat Thrips
- Use blue sticky traps to catch adult thrips
- Wash off the plant with running water to remove eggs and larvae
- Introduce beneficial insects like ladybugs, lacewings, pirate bugs, and thrip predator mites
- Treat the plant and soil with diluted neem oil
Different from fruit flies, fungus gnats lay eggs in the soil of your houseplants and their larvae eat away at your roots!
- Fungus gnats have a fast life cycle, creating a new generation every few weeks
- You’ll need to treat for fungus gnats consistently until they are all gone
Signs of Fungus Gnats
- Fungus gnats look like small mosquitoes with transparent wings, and they will likely fly away from the plant when you water it
- The larvae have white-to-transparent bodies and black heads
- Sudden wilting of your plant may indicate fungus gnats, as well as poor growth overall due to root damage
How to Treat Fungus Gnats
- Allow your soil to dry and don’t overwater - fungus gnats lay eggs in damp soil
- Use a yellow sticky trap to attract and catch adults
- Apply a peroxide drench treatment to kill eggs and larvae (dilute one part 3% hydrogen peroxide to four parts water and thoroughly water the plant with this mixture)
- Use neem oil on leaves and stems or as a drench treatment
Natural Remedies for Plant Pests
We know that keeping things natural is important to many households, especially if you have pets or children in the house as well as your houseplants! These natural remedies are easy on plants but tough on pests. Do you already have any on hand?
- Neem Oil: Neem oil is available at most garden centers and home improvement stores, because its uses in the garden and on houseplants are amazing. It helps treat and prevent pests and fungus, and it’s food safe and non-toxic to animals and people. Dilute it and use it to spray down or drench plants to prevent reinfestation.
- Eucalyptus or Peppermint Oil: These oils smell like childhood memories of having a bad cold, but they help to prevent pests! Watch out for pets and small children though, as essential oils can be harmful if placed on skin undiluted, and the oil can also be harmful to pets if inhaled. It’s best to use outdoors during treatment. Mix a teaspoon of eucalyptus or peppermint oil with one quart of water, along with ½ a teaspoon of mild soap like castile soap. This mixture can be used to coat affected plants and kill off pests.
- Peroxide: As mentioned above, peroxide can be diluted and used as a drench treatment to soak through the soil and treat pest infestations.
- Diatomaceous Earth: Diatomaceous earth, or DE, is a powder made of crushed silica-based rock. Its microscopic texture kills insects by cutting into their exoskeleton and causing dehydration. It seems a little graphic, but it works. Food-grade DE is safe for human and animal consumption and won’t hurt us, just the bugs! Just don’t breathe it in, because it’s a fine dust and can cause coughing. DE can be found at most local garden or home improvement stores. To use this natural pest control, sprinkle it on top of dry soil and reapply after watering because it has to be dry to work.
There you have it, you’ve got the basics down to treat these five common houseplant pests! Let us know if you have any questions, and you can always DM us a photo of your plant on social media for a helpful diagnosis.