Spider mites are among the most common pests of popular houseplants and garden plants, and hibiscus is no exception. They love hot, dry weather, they breed fast, and they are so small that most people notice the damage before they ever see a mite.
Hibiscus [hi-BIS-kus] is a genus of flowering plants in the Malvaceae, or mallow, family, prized for big, showy flowers. The tropical hibiscus (Hibiscus rosa-sinensis) sold in garden centers is thought to come from tropical Asia. Hardy hibiscus (Hibiscus moscheutos) and rose of Sharon (Hibiscus syriacus) are different plants with different care, so know which one you have.
Spider mites are among the sap-sucking pests of hibiscus, along with scale, mealybugs, aphids, whiteflies and thrips. The good news? Sap-sucking hibiscus pests such as aphids, whiteflies and mealybugs are easily controlled with insecticidal soaps or horticultural oils if caught early, and the same two tools are recommended for spider mites. Here’s how to spot spider mites, what they do, and how to get rid of them without making things worse.
What Are Spider Mites?
Spider mites aren’t insects. UC IPM says that although they are related to insects, mites are arachnids, like spiders and ticks. They belong to the mite family Tetranychidae. The species you are most likely to meet is the twospotted spider mite (Tetranychus urticae), which Colorado State University Extension calls the most important species on house plants and a prolific producer of webbing.
They are tiny. Adult females, the largest form, are less than 1/20 inch long, and the twospotted spider mite is about 1/50 inch long. To the naked eye they look like tiny moving dots, but you can see them easily with a 10X hand lens. Adults have eight legs and an oval body.
The webbing is their calling card. The silk webbing most species produce is an easy way to tell spider mites from other mites and small insects, and it gives the mites and their eggs some protection from natural enemies.
Why Spider Mite Numbers Explode So Fast
It comes down to a short life cycle and a lot of eggs:
- Eggs hatch in about three days. The eggs are attached to fine silk webbing.
- Egg to adult in 5 to 20 days. That’s the range under optimum conditions (about 80°F), and a generation can be completed in less than a week when temperature and food are favorable.
- Lots of eggs. The adult female lives two to four weeks and can lay several hundred eggs in her life. Mature females may produce a dozen eggs daily for a couple of weeks.
With many overlapping generations, a few mites can become a colony of hundreds in a hurry. That’s why early detection matters so much.
How To Spot Spider Mites on Hibiscus
You’ll usually notice plant damage, such as stippled or yellow leaves, before you spot the mites themselves. Watch for these signs:
- Stippling. Tiny light dots or speckles on the leaves, where mites have sucked out the contents of individual cells. These are the early signs of spider mites.
- A faded, bronzed or yellow look. As feeding continues, leaves can turn bronze, yellowish or reddish and drop off.
- Fine webbing. Dense webbing can cover leaves and twigs when numbers are high. True spider webs are often confused with mite webbing, so look closely.
Do the white paper test. Ohio State University Extension says to hold a piece of white paper or cardboard under some foliage and strike it. Dislodged mites can be seen walking slowly on the paper. Here’s a neat trick: smear one with your finger. Most plant-feeding mites leave a green streak; if they streak yellow or orange, they are likely beneficial predators.
Check the undersides of the leaves with a hand lens, too. Look there for mites, their eggs and webbing, and be sure mites are present before you treat. Sometimes the mites are already gone by the time you notice the damage.
Is it mites or the weather? Tropical hibiscus drops leaves for other reasons too. Tropical hibiscus is sensitive to cold, and the slightest cold wave can cause lower leaves to yellow and drop off. If a few yellow leaves show up after a cold snap and you find no stippling, webbing or mites, the weather is the likelier cause.
Related: More reasons why hibiscus leaves turn yellow
What Damage Do Spider Mites Cause to Hibiscus?
Spider mites feed by piercing plant tissue and sucking out the cell contents. A small chlorotic (pale) spot forms at each feeding site, and continued feeding leaves the leaf stippled and bleached, then yellow, gray or bronze. Mite damage to open flowers causes browning and withering of the petals that looks like spray burn.
How serious is it? That depends on how many mites there are. A small number usually isn’t a problem, and most woody plants can tolerate low to moderate mite populations. Heavy infestations are different. Complete defoliation may occur if the mites are not controlled, and if mites are left unchecked, leaves become bronzed or yellowed and the plant dies.
Hot, dry, dusty conditions make it worse. Damage is usually most severe in hot, dusty conditions and on water-stressed plants. Dry conditions greatly favor all spider mites: they feed more when humidity is low, many of their natural enemies struggle in dry air, and drought-stressed plants can become more nutritious to them.
How To Get Rid of Spider Mites on Hibiscus
Work from the gentlest fix up. Most of the time you won’t need anything stronger than water and an insecticidal soap or oil.
1. Isolate the Plant
If your hibiscus is indoors or in a container near other plants, move it away from them first. The first step in controlling a houseplant pest is to isolate any plant suspected of being infested and keep it separate until the pest is completely controlled, which may take several weeks or more.
2. Wash Them Off With Water
Water is your first tool. Regular, forceful spraying of plants with water often reduces spider mite numbers adequately in gardens, as long as you get good coverage on the undersides of the leaves. Regular syringing with a forceful jet from a hose can keep spider mites under control on most landscape ornamentals and helps conserve their natural predators. Hosing also removes the dust that interferes with mite predators and breaks up the webbing.
For a potted hibiscus, periodically hose small plants in the sink or shower and wipe the leaves of larger plants with a soft, damp cloth, repeating every one to two weeks while mites persist. Trim, bag and remove heavily infested leaves, too.
If plants are infested, go further: apply a water spray or mist to the undersides of the leaves at least once a day.
3. Use Insecticidal Soap or Horticultural Oil
If water alone isn’t enough, use selective materials, preferably insecticidal soap or insecticidal oil. That includes petroleum-based horticultural oil and plant-based oils such as neem, canola or cottonseed oil. Insecticidal soaps and oils are effective against mites and the least toxic to people, other non-target organisms and the environment.
Use a product made for plants, not a homemade mix. Clemson Extension says commercial insecticidal soaps are a highly refined version of liquid dish soap, and that homemade soap mixtures carry a substantially increased risk of plant injury. University of Minnesota Extension says plainly: don’t make a homemade soap solution, as this can burn and damage plants.
A few rules make these sprays work and keep your hibiscus safe:
- Coat the undersides. Oils and soaps must contact mites to kill them, so excellent coverage, especially on the undersides of leaves, is essential. Spray the tops of the leaves and the stems too.
- Mind the heat and sun. Don’t use soaps or oils on water-stressed plants or when temperatures exceed 90°F. Don’t apply soap in full sun either, and treat in the early morning or late in the day.
- Water first. Water plants thoroughly before spraying for spider mites, and spray in the early morning or early evening.
- Test first. Test soaps and oils on a portion of the foliage several days before a full treatment. A quick check is to spray a small area and wait 24 hours to see if any damage occurs, but symptoms of injury may take at least 48 hours to appear.
- Follow the label for the rate. Mix and apply exactly as your product’s label says. More is not better.
What about neem oil? Neem is on the list of acceptable plant-based oils for spider mites. But hibiscus gets a special note: neem oil insecticides have shown good plant safety, with some precautions for use on hibiscus, among a few other plants. So test it on a few leaves before you spray the whole plant.
Spraying a houseplant? Spraying houseplants is most safely done outdoors in the shade and during mild temperatures, and the plant can come back indoors once its foliage is completely dry. Wear whatever protective gear the product label lists.
4. Repeat Until the Mites Are Gone
One spray won’t do it. Soaps and oils only kill the mites they touch and have no residual activity, so repeat applications may be needed. It is often necessary to spray once a week for several weeks to control mites. Keep checking the leaf undersides between treatments for new stippling, webbing or moving specks.
Never Use Malathion on Hibiscus
This one matters. UF/IFAS Gardening Solutions says to read labels carefully, because you should never use the pesticide malathion on hibiscus. Its Hibiscus in Florida guide also says that hibiscus are sensitive to many pesticides and that this sensitivity can be increased by improper use.
It isn’t a good mite product anyway. Malathion can aggravate some spider mite problems, despite being advertised as effective for mites.
Why Broad-Spectrum Insecticides Can Make Mites Worse
Reaching for a strong all-purpose bug spray often backfires. Spider mites frequently become a problem after applying insecticides such as carbaryl, some organophosphates and some pyrethroids. These kill the mites’ natural enemies, and some can even stimulate mite reproduction. Long-lasting insecticides such as bifenthrin and permethrin kill natural enemies and could make infestations worse in the long run. Soil applications of the systemic insecticide imidacloprid have also contributed to some spider mite outbreaks.
Let Natural Predators Help Outdoors
Outdoors, spider mites have plenty of enemies. Predatory mites, sixspotted thrips, the spider mite destroyer lady beetle, minute pirate bugs, bigeyed bugs and lacewing larvae are among the important ones.
You can buy predatory mites, too. A good guideline is one predator for every 10 spider mites, and the best results come from creating favorable conditions for the predators already present, such as avoiding dusty conditions and insecticide sprays. Six species are commercially available, including Phytoseiulus persimilis, which can eat 20 eggs or five adults a day. These predators have been successful on interior plants, but effective use outdoors has not been demonstrated in Colorado, and they often need fairly high humidity.
If you release predators, skip the sprays. Nonselective insecticides kill the predators, so protect the helpers you paid for.
When To Use a Miticide
If water, soap and oil have not brought the mites under control, a product made for mites, called a miticide or acaricide, is the next step. Read the label to make sure it lists hibiscus and spider mites, and follow it exactly.
Two things to know. Most miticides do not affect eggs, so you’ll need more than one application. Recommended intervals vary, from about 10 to 14 days to five days in summer and seven days in winter. Spider mites can also develop resistance to pesticides, so don’t rely on the same product over and over. Use the interval your product’s label gives.
Bringing Hibiscus Indoors for Winter
If you grow tropical hibiscus in a pot and bring it in for winter, that move is a good time to get ahead of spider mites. Bring Chinese hibiscus (tropical hibiscus) indoors when nighttime temperatures fall into the lower 50s °F.
- Inspect before it comes in. Check the leaf undersides with a hand lens and do the white paper test.
- Hose it down outside. A good spray of water on the leaf undersides removes mites and dust before the plant moves in.
- Treat outside if needed. Spraying houseplants is safest outdoors in the shade during mild temperatures; bring the plant in once the foliage is dry.
- Keep it apart at first. Isolate new plants from plants already in the home for six weeks and examine them about once a week, paying attention to the undersides of leaves. The same habit works for a hibiscus coming back in.
Keep watching through winter. Spider mites are usually more of a problem on houseplants that remain indoors year-round, and plants placed outdoors during summer may have a reduced problem with them.
How To Prevent Spider Mites on Hibiscus
- Don’t let it dry out. Water plants enough so they are not drought stressed, which increases mites and mite damage. (Don’t overwater either, which can lead to root rot.)
- Keep the dust down. Dusty conditions often lead to mite outbreaks; mulch and regular irrigation help. Periodic hosing removes dust that interferes with mite predators.
- Check often in hot, dry weather. Twospotted spider mites prefer the hot, dry weather of summer and fall but may occur any time of year. Check garden plants every 3 to 5 days, especially during drought.
- Inspect instead of spraying on a schedule. Routine inspections instead of routine spray schedules may reduce the amount of pesticide needed on hibiscus.
- Protect the predators. Skip broad-spectrum insecticides when you can, so natural enemies keep mite numbers low.
Grow it well, too. A healthy, well-watered hibiscus bush in the right spot handles a few mites far better than a stressed one.
Have you battled spider mites on your hibiscus? What finally worked for you? Tell us in the comments!
Frequently Asked Questions
How do I know if my hibiscus has spider mites?
Look for leaves speckled with tiny light dots, then turn them over. Spider mites live mostly on leaf undersides and look like tiny moving dots, easy to see with a 10X hand lens. Dense webbing shows up when numbers are high. For a quick test, strike some foliage over white paper and watch for specks walking on it.
What is the best treatment for spider mites on hibiscus?
Start with a forceful water spray on the undersides of the leaves, which often reduces spider mites adequately in gardens. If more control is needed, use insecticidal soap or insecticidal oil, with complete coverage of leaf undersides. Don’t spray water-stressed plants or when it is above 90°F, and expect to repeat the treatment.
Can I use neem oil on hibiscus for spider mites?
Neem oil is one of the plant-based oils considered acceptable for spider mites, and like other oils it must touch the mites to kill them. Hibiscus gets a caution, though: neem oil insecticides have shown good plant safety, but there are some precautions for use on hibiscus. Test it on a few leaves first, as with any soap or oil.
Can I use malathion on hibiscus?
No. Read labels carefully, because you should never use the pesticide malathion on hibiscus. It is a poor fit for mites anyway: malathion can aggravate some spider mite problems, and some organophosphates and pyrethroids kill mite predators and can trigger spider mite outbreaks.
Will my hibiscus recover from spider mites?
Often, yes. Most woody plants can tolerate low to moderate mite populations, and plants often recover after the mites have left. Heavy infestations are another story: leaves become bronzed or yellowed and the plant can die if mites are left unchecked, so check the leaf undersides early and often.