How do I control spider mites?

Brown or yellow spots on the leaves of your green houseplant? That may well mean your houseplant is suffering from a plant disease or pest. When spider mites have settled on your houseplant, you'll see brown or yellow speckles that can grow much larger over time. Eventually the whole leaf can turn brown.

When you bring a houseplant into your home, it helps to know which plant diseases exist, how to recognise them and how to control pests. Spider mites aren't insects but relatives of the spider. You can't see these little creatures with the naked eye, but under a microscope they show up clearly. You don't need a microscope to work out that your houseplant has a disease or pest, though. Usually you can tell from discoloured leaves or stems.

What exactly are spider mites?

Spider mites aren't the same as aphids: this is an infestation of tiny mites that settle on your houseplant. They usually sit on the underside of the leaves and are white, green or yellow. Spider mites live on the sap from the leaves: by piercing tiny holes in them they can suck the nutrients out. They effectively drain all the life out of the leaves of your houseplant, which over time causes small brown or yellow spots. The longer the spider mites get their chance, the more of these spots you'll see. Eventually they spin fine webs that you can see between the leaf tips and stems of your houseplant.

The mites are hard to spot with the naked eye because they are extremely small. Spider mites have a round or oval body that is usually less than 1 millimetre long. They can be red, brown, white or transparent. With a magnifying glass you can often see more clearly which pest is on your houseplant, and identify the eggs and young mites more easily.

What you need to know about spider mites

Spider mites thrive at higher temperatures. At 30°C it takes just 7 days for an egg to develop into an adult spider mite, which then starts reproducing. At 20°C that cycle stretches considerably to around 17 days. Below 12°C the eggs stop developing altogether. That doesn't mean they'll never hatch, though; they simply wait for the temperature to rise.

Spider mites love dry conditions and don't do well in a humid environment. That's why it's a good idea to mist the leaves regularly with a plant mister, especially the undersides, when you're dealing with a spider mite infestation.

How do you prevent spider mites on your houseplant?

A spider mite infestation is hard to prevent because the mites are so small and always find a way to crawl onto new leaves via our hands, our clothes or the wind. But preventing them altogether isn't impossible! There are a few conditions that make it extra tempting for spider mites to settle in your home. By keeping these factors in mind, you can help stop them from making themselves comfortable in your space.

Spider mites thrive in dry, warm conditions. During warm, dry spells it's wise to always have a plant mister at hand. The fine mist from a plant mister is unpleasant for spider mites, which makes your houseplants less attractive for the mites to settle on. Make sure you spray the undersides of the leaves well too!

Mites love old, nutrient-poor potting soil. Make sure you repot your houseplants at least every 2 to 3 years. No time to repot right away? Then add a fresh layer of potting soil for now. Fresh potting soil puts spider mites off.

Make sure your houseplants are healthy! A healthy houseplant is more resilient and can even make spider mites disappear by themselves. It may sound surprising, but it really works.

What can you do about spider mites?

Have spider mites managed to settle in anyway, and do you want to know how to get rid of them? Controlling spider mites can be tricky at times, but we've collected a few effective tips for you!

First, grab your secateurs and cut away all the affected parts of your houseplant. Bear in mind that your hands, clothes and secateurs can carry the mites, potentially spreading them to other spots in your home.

Wait until evening and fill a plant mister with cold water. Then add 2% hand soap and 1% methylated spirits and shake well. Spray your houseplant thoroughly with this mixture, especially the undersides of the leaves. Why in the evening? That's when the eggs hatch, so by misting at that moment you poison the very first, youngest mites.

Repeat the misting a few times until you feel the spider mites have effectively stopped reproducing.

If you find these methods aren't doing enough against the spider mites, you can consider bringing in predatory mites. These natural enemies feed on spider mites and make sure you no longer need to worry about the infestation.

What are the consequences of a spider mite infestation?

Don't worry if you have, or have had, spider mites on your houseplant. Houseplants usually survive this pest, especially if you act quickly and use our tips to stop it spreading further. When the mites are also on other large houseplants, getting rid of the infestation becomes harder.