You’ve no doubt heard of spider mites and probably seen them without knowing what they were.
You often discover them when watering your indoor plants. You notice the leaves are turning yellow and covered in webbing.
Unfortunately, this means your plant has become infested with perhaps the most dangerous pest imaginable, and it’s likely any nearby plants are also under attack.
Holding a sheet of paper under a leaf and tapping it may result in red specks falling off the leaf, a sure sign that you’ve got spider mites.
What Are Spider Mites?
Spider mites are a type of arachnid related to ticks and spiders that are barely visible but can damage your plants.
They can vary in size but are as small as 1/50” inch long and come in various colors.
The most common species is Tetranychus urticae, commonly referred to as the red spider mite or two-spotted spider mite, although there are over 1200 different species out there.
Some other common species include:
- Citrus mite
- European spider mite
- Southern red mite
- Spruce mite
The name will often give away the preferred food for a species, such as citrus mites, which feed on citrus trees.
Southern red mites go a step further than regular red spider mites, eating both the plant and its fruit.
Meanwhile, spruce mites prefer evergreens and can devastate pine and spruce trees.
Under a magnifying glass, a two-spotted spider mite will appear yellow-orange and have a dark spot on either side of the body.
Different species tend to prefer specific plants, but they will infest a wide range of fauna, including but not limited to:
- Annuals and perennials (ex. azalea. lantana, marigolds, roses, salvia, spruce, viola)
- Berries (blackberry, blueberry, strawberry)
- Fruit-bearing plants (apple, apricot, cherry, ficus, peach, plum, tomato)
- Grasses and grains (chickweed, clover, hemp, hops)
- Vegetables (cucumbers, legumes, lettuce)
A distinctive feature of spider mites is their ability to produce webs that are chemically different from spiders, which they use to create bridges between the leaves.
Most spider mite species require warmer weather, but the spruce spider mite prefers cold temperatures and dry conditions.
In ideal conditions and depending on the species, adult spider mites will live up to two months and lay hundreds of eggs to increase the spider mite population.
What Damage Do Spider Mites Do To Indoor Plants?
If you’re lucky, the first sign of spider mites will be barely visible dots scurrying around on your plant.
If you’re unlucky, the first sign will be the densely packed webbing, which signals an established, multigenerational infestation on your house plants.
Like scale insects, aphids, and the sap sucker mealybug, spider mites have piercing/sucking mouthparts.
Spider mites pierce stems and the underside of leaves to suck out the chlorophyll, causing your plant to slowly starve.
The leaves will dry out, turning yellow and eventually darkening as the plant loses more and more vital fluids.
As spider mites tend to begin at the base of the plant and work upwards, it’s often easy to miss the damage being caused on dense plants until it’s already severely injured.
The lesions leave behind white sticky sap that attracts other pests and encourages bacterial and fungal infections.
In short, if you have spider mites, you have a plant-threatening problem.
How To Control Spider Mites On Indoor Houseplants
There are a lot of important things to consider when dealing with spider mites.
Understanding how to prevent them as well as what options are available once they attack is equally important.
Here are some useful tips on ensuring your plants remain free of spider mites.
A Note on Diapause
One of the biggest problems with spider mites is the diapause stage many species go through as nymphs.
This is when spider mites change from green to brighter colors, and it’s during this period, they become more resistant to chemical pesticides.
Thankfully, they won’t lay eggs during this phase. Multiple treatments allow you to kill the eggs, larvae, and adults, then return to get the rest as they exit the diapause stage.
As soon as you notice a spider mite infestation, you need to isolate the infected plant for others nearby.
Be careful to avoid cross-contamination, washing any tools used, as well. Thoroughly wash your hands to kill any mites trying to hitch a ride.
Always inspect newly acquired plants before putting them near other bits of greenery. Adoptees from garden centers and friends can often turn out to be a leafy Trojan horse.
Natural Remedies To Get Rid Of Spider Mites
Unless you plan to stick your infested plant outdoors for a while, natural predators such as Feltiella acarisuga aren‘t much help.
There are organic spider mite control options or biological control such as making use of predatory mites, introducing beneficial insects, other predators, horticultural oil, organic insecticides, and pesticides to solve the spider mite infestation.
There are plenty of other tricks Mother Nature has provided that work indoors.
Spider mites rely on certain environmental conditions for reproduction and longevity.
Tweaking those conditions indoors can slow a population explosion and may even help kill some of these pests.
Try to isolate your plant in a room or small greenhouse (you can buy them for seedlings at many garden centers) and crank the humidity up to 65% or higher. They hate a humid environment.
The ambient temperature should be kept under 80° degrees Fahrenheit.
This will affect most spider mite species, but be sure your plant is capable of surviving these conditions, or you’ll end up killing the plant yourself.
Neem Oil, Rubbing Alcohol, and Insecticidal Soap
Plants, like people, enjoy a good bath now and then.
You can use any of these three options on a soft cloth or paper towel to give your plants a thorough bath, making sure to get every nook and cranny. This includes the undersides of leaves.
Repeat the process every other day for 10 days or until all traces of the spider mites are gone.
Note that you can give periodic wipedowns with neem oil or alcohol as both a preventative method. This removes dust from the leaves and plant tissue. It also allows the plant to breathe and feed more efficiently while making any variegation more visible.
Many essential oils, such as cinnamon, clove, mint, rosemary, or garlic extract, are also great options that can leave a pleasant (or not) scent behind.
There are a lot of pesticides out there, but many won’t work against spider mites.
Always use caution when using any form of pesticide or poison. They can harm children or pets who come in contact with a treated plant and may contaminate the air.
Anti-Spider Mite Options
Aim for a broad-spectrum pesticide that lists spider mites on the label or stick with a miticide.
Avid, a brand of abamectin, is a miticide that’s applied with a spray bottle to the tops of leaves and soaks through, killing adults and nymphs on both sides of the treated leaf, although it won’t kill eggs.
Another common brand is Worry Free, an insecticidal and miticidal spray that’s safe for use on edible plants.
Spray on all plant parts, including under the leaves. Only use the spray outdoors to avoid contaminating anything in the home.
This chemical is present in many pesticides and has been found to encourage spider mite reproduction.
Some pyrethroids and organophosphates have also had unwanted effects on spider mite populations.
Give your plants a regular health check to help ensure they’re not sick or infested.
Look at any leaves with unusual spots, specks, or white sticky stuff using a magnifying glass.
Be sure to also check the undersides for webbing, discolorations, or other signs of a problem.
Do the tap test with a piece of paper in different plant areas to see if anything drops from the branch or leaves.
Finally, pay attention to people who come in contact with your plants. If they’re itchy when the plant normally doesn’t cause irritation, it’s a good sign there’s something wrong with the plant.