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Hoya aren’t too bad when it comes to pest management.
Their leaves are a bit too thick to attract thrips – they definitely do get them but thrips tend to abandon them in favour of other plants if they can. They do get spider mites, and can suffer damage from them, but they recover really well.
Mealybugs can be a devil but *touch wood* any I’ve had don’t tend to stick around.
Flat mites are quite new pests, which is exciting! They’re also frequently named as the worst pest, which is not!
Ok, they’re not actually new, but they don’t seem to have really plagued casual house plant people until about a year ago, and then suddenly they were wiping out people’s entire collections.
Am I blaming the sudden explosion in Hoya popularity? I’m not not blaming that.
What are flat mites?
Flat mites are teeny tiny red mites that often turn up on Hoya. I’ve never heard of them on other plants, but obvs let me know if you have.
Spider mites are visible to the naked eye if you have decent eyesight, but they are VERY small.
Another name for flat mites is ‘false spider mite’ but I don’t really like that because it suggests they’re less of an issue than spider mites. They’re both arseholes.
Flat mites look very similar but are MUCH smaller. You’ll need a very good magnifying glass OR you can get cheap USB microscopes from Amazon for about £20.
By the way, if you’re having issues with your Hoya not producing new growth, but producing a load of nubby stems you might have white/broad mites, which are microscopic. They’re different to flat and spider mites in that they tend to stay on the stems rather than the leaves.
What does flat mite damage look like on a Hoya?
I don’t have any, so I can’t show you, but it looks similar to spider mite damage – a bit like someone’s taken sand paper to the backs of your plants.
Hopefully I can never update this section, but I assure you that if i ever get them, I’ll post a picture of the damage here!
How to get rid of flat mites on Hoya
The first step to take when you discover you have any pests is to take it either outside or to the shower and hose it off with water. Preferably warm water.
This will knock off any adult mites but it’s unlikely to touch any of the eggs, and larvae can be a little sticky too so don’t make this your only treatment.
If you do only want to use water for mites, you can either hose the plant down every couple of days OR submerge the plant (taken out of the soil) in a bowl of water that’s 45˚C/115˚F for fifteen minutes.
The bathing method works on most plants and will eradicate, er, most pests – it’s great for thrips and aphids. It doesn’t work 100% on flat mites so you’ll need to try something else.
The next step is to try either pesticides or predatory mites. If you use pesticides, find they don’t work and want to switch to predatory mites, leave 30 days between otherwise you’ll kill your mites.
Neem oil is a great option, as is mineral oil or castile soap. Spray the plant down thoroughly one a week for eight weeks. If you miss a week, start again and do another eight.
If you want to use a store-bought pesticide, look for one that contains sulphur – both flat mites and spider mites can build up a tolerance to pesticides unless they have sulphur in them.
Predatory mites are a favourite way to get rid of spider mites because there are a few options to choose from and they’re very quick and efficient. The only issue is they’re definitely pricier than other options.
I have an article that goes into more detail on predatory mites here, but Betsy Begonia had success wit Amblyseius californicus.
There doesn’t seem to be too much information on flat mites outside of Hoya-specific social media, so if you’re having issues with your Hoyas not growing and you can’t see any spider mites, it might be worth investing in a microscope of magnifying glass to check for false spider mites.