Ask a Plant Pro: Spider Mites
Welcome to Our New Series - Ask a Plant Pro
Every month on our Instagram account we will open up a question box for you to submit your plant questions. Think of it like Dear Abby column but for plant-related questions. If we select your question, we'll send a treat to your Instagram inbox.
Dear Plant Pro: I have spider mites on one of my plants and I've tried everything. What's the best way to treat spider mites? - Exasperated in Echo Park
If you've been keeping plants for awhile, you've likely encountered Spider Mites (even if you don't know it yet). A very common plant pest, Spider Mites are a teeny-tiny type of arachnid (so small you can't really make out their shape with the naked eye), which can range in color, but what you'll usually notice first is one of these tell-tale signs.
5 signs your plant may have Spider Mites:
- A patch of what looks like dust, which may on closer inspection, start moving - often on the backside of the leaves, but not always.
- Very fine webbing (so fine it's almost hard to see, not as obvious as spider webs) near where plant leaves join the stems, or at the sinus of the leaf (the kind of 'v' shape near where the leaves join the stem on certain plants.
- Yellow or bronze discoloration of leaves.
- Leaves looking almost bleached out or dull.
- Deformed leaves, especially in combination with the other symptoms above.
If you've identified your plant problem as Spider Mites, the first thing you'll want to do is isolate the plant from any other plants (ideally in another room), as well as check all nearby plants for signs the mites have spread. While Spider Mites can be treated, be prepared for several rounds of your chosen treatment - Spider Mites can be tenacious and aren't usually wiped out quickly.
How to treat a plant that has Spider Mites:
- Start by removing as many of the mites as possible with a strong stream of water from a hose or shower sprayer, making sure to spray the whole plant (leaves, stems, trunk, etc). You can also use a lint roller or tape (credit to Darryl from Houseplant Journal for this tip) to remove them if you aren't able to spray the leaves down.
- Next wipe down or thoroughly spray all plant parts (front and back of leaves, stems, trunk, etc) with neem oil or other horticultural oil, OR treat with a miticide or insecticidal soap (follow package directions). If you do this outdoors in warm months, do it first thing in the morning or later in the evening in order to avoid damaging the plant tissue.
- Spider mites thrive in dry conditions, so raising the humidity level around affected plants can aid in recovery. The best way to do this is with a humidifier.
- Check on affected plants once a week. If you spot new Spider Mites, follow these treatment steps again until the plant appears mite-free for at least two weeks in a row.
- Other methods, such as predatory beneficial insects like predatory mites, spider mite destroyer lady beetles, or lacewing larvae can also be used to control Spider Mites, but aren't as practical a solution for indoor plants.
Now, you might be wondering - "how can I avoid Spider Mites to begin with?". Sometimes it can be hard to escape Spider Mites, especially if you keep plants like Calathea or Alocasia species which are very susceptible to them, but there are a few things you can do to help prevent this annoying pest.
Steps to take to avoid Spider Mites:
- Inspect plants very well before bringing them home. We like to use our phone flashlight to slowly go over the leaves - Spider Mites and their webbing will usually be more obvious with the light reflecting off them. If you can't tell if a residue is Spider Mites or just dust, try rubbing it between your fingers - dust will feel gritty, whereas Spider Mites will be almost imperceptible between your fingers. If that method grosses you out, you can also watch very carefully for movement, you'll often be able to see the tiny mites moving around across the leaf or webbing.
- Once plants are home, keep them isolated from the rest of your plants for a week or two. This is a good practice in general, since many pests can be hidden when you first purchase a plant, but become more obvious as the plant adjusts to life in your home.
- Keep your plants in appropriate humidity levels. If you live in a dry area (like we do here in southern California) and you keep plants with high humidity needs, it's best to either run a humidifier or keep the plants in an enclosure like a greenhouse cabinet, vivarium, or terrarium.
- Ensure plants are not water-stressed, which makes them more susceptible to Spider Mites.
- Regularly clean/dust your plant leaves. This will make it more obvious if Spider Mites do gather, and dusty conditions seem to lead to outbreaks.
- Use your watering time to check in with your plants and look over their leaves for any signs of trouble. Catching any plant problem early will improve the odds of a full recovery.
Spider Mites can certainly be frustrating, but with a little persistence, victory over these tiny nuisances is possible.