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House Plant Pest Profile: Spider Mites

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I couldn’t find a free image of a spider mite (no one’s surprised) so I was going to go with a picture of a regular spider. Then I realised that

  1. That’s super mean to all the arachnophobic people that came here wanting to look at nice plants and got whacked in the face with a photo of a spider and
  2. I didn’t want to confuse people and have them spraying their resident spiders with soap spray. Spiders eat a lot of plant pests, and we love them.

So I went with a nice picture of a rubber plant. I currently love my rubber plant. We’re in the depths of December and it’s just chucked out a new leaf. We all very happy and proud.

Anyway, this is about spider mites. I don’t think I’ve ever had an issue with them since my house errs on the side of cold and damp, which really isn’t their cup of tea.

Still, you never know what summer will bring, so it’s best to be prepared and to be prepared you must first know your enemy…

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What do spider mites look like?

Not really like spiders.

They look like tiny weeny red bugs – like, smaller than a millimetre in length. There are over 1200 species, which sounds like a lot, but scale insects boast a whopping 8000 species.

Up your game, spider mites.

They’re called spider mites because some of those species spin a protective webbing, which looks like a spider web.

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What plants do spider mites prefer?

They’re known to snack on hundreds of species of plants, but if you grow cannabis, prepare to meet your worst enemy. They also like potato and corn plants.

I only have house plants, so potato and corn aren’t really in my remit, and if I decided to casually grow cannabis the police would whisk me off to jail and if I were ever let out my mother would kill me.

Still, they do love a house plant, and if you provide them with the right conditions, they’ll soon show up.

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Where would I find spider mites on my plant?

You can, if you put your best eyes in, see them running around on the undersides of leaves. You’re best off looking for their webs though, and any sign of damage.

If you have webs but no damage, then maybe a little spider has moved in – a great first line of defence against loads of pests.

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How did I get spider mites?

Apparently one of the leading causes of spider mite infestations is plant swaps, or being given plants by friends.

You see, spider mites can go dormant if they’re not in the right conditions, so your friend may not realise they’re passing on a plant with a monstrous secret.

They can also be carried on the wind because they’re so small. This also means you can bring them into your house on your clothes and hair.

Close your windows on any windy days in summer, folks.

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What damage do spider mites cause?

Oh, lots.

Spider mites pierce holes in the leaf in order to extract sap and moisture. The plant can sense that it’s losing too much water and closes its stomata.

Unfortunately, the spider mite has created thousands of holes itself, and the plant will, frightening quickly, lose too much moisture and die.

According to this website, the plant begins to taste better when it’s under attack, which causes the spider mites to feast even more, and more to show up. FFS.

Spider plants hatch in 3 days and reach maturity in 5, so you can have a pretty big problem in a short space of time.

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What conditions do spider mites thrive in?

Spider mites love hot, dry conditions, and HATE any kind of cold and humidity.

If they don’t like the conditions then reproduction rates will slow considerably, and they have the ability to do dormant, so keep treating your plant for a couple of weeks, even if you don’t see any mites.

If you’re using a mild insecticide, then it shouldn’t harm your plant.

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How to control and eliminate spider mites

Neem oil is your friend. Neem oil is your friend against most plant pests. Get yourself some. There are links to the one I buy on my resource page.

You can also take your plant outside and hose it down. Not only will the water blast off the mites, but the wet soil also will make them less likely to call your plant home.

Wash your plant with insecticidal soap, such as washing up liquid.

You can get a naturally occurring pesticide called Harpin Alpha Beta which helps your plant to boost its immune system and fight of predation by bugs.

I’m assuming that it stops the plant tasting so delicious to the mites when they’re halfway through eating it? Google could neither confirm nor deny this.

You can get predatory mites to eat them, and ladybirds will eat them if there are no aphids around.

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Preventative measures to discourage spider mites

  • Keep your plant healthy

  • Clean the leaves with neem oil

  • Mist the top of your soil to keep it moist

  • Check your plants regularly. Look for sad-looking, wilted leaves.
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Notes

  • Spider mites are at their best in temperatures of 27 degrees C (80F). That’s when they can really thrive and produce the most offspring. So if you can, keep your house cooler than this. Obvs my house will NEVER be 27C – 24C is probably my absolute limit here in North Yorkshire, so yay for that.

  • Don’t spray beneficial insects with insecticidal soap. You’ll kill ’em.

  • Get yourself a humidifier if you have very dry air – it’ll give your plants a boost and discourage pests like spider mites.

  • No word on asexual production, so shall we assume we need male and female spider mites to make baby spider mites?

  • Don’t confuse spiders with spider mites. Spiders good, spider mites bad.
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And so concludes my expose on spider mites. I also have articles on mealybugs, thrips, aphids and scale if that’s the content that really speaks to you.

I think those are the main bugs that people complain about in the house plant world, but if there is some other pest you want me to cover, then leave me a comment.

Any weird and wonderful pest repelling tricks would be greatly appreciated too.

Actually, I’ve never lost a plant to bugs (although it’s currently touch and go with my pink Syngonium), but my rabbit did eat half an Orbifolia leaf the other night.

We accidentally left her pen open and she monched through the Orbifolia, a maranta leaf, a phone charger cable, and 2 sets of Christmas lights.

Ta Isobel.

(She was absolutely fine, btw, and loved her little adventure).

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