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Predatory mites are slowly becoming the go-to when it comes to house plant pest control. Legends like Summer Rayne Oakes have been singing the praises of using integrated pest management for years, but it’s taken a while for it to catch on.
There are definitely pros and cons to using predatory bugs to deal with your house plant pests (which obvs we’ll discuss) BUT often the things people worry about (which can be broadly encompassed by the phrase ‘bugs? EW’) aren’t often that big of a deal.
There are some seriously tiny insects out there (as in, naked to the human eye) that have no issue with chowing down on an entire thrips larvae.
In short, don’t knock it till you try it.
Benefits of using predatory mites on house plants
This is the biggie.
The problem with pests is that they are incredibly resistant. Scientists that make pesticides will likely never be out of a job because over time, pests (especially thirps, ofc) build up resistence to pests.
They’re constantly trying to tread the fine line between killing the pest and harming the host and the surrounding environment. There’s no point killing the carrot pest if the carrot (and the eater) is going to be harmed too.
Pests don’t build up resistance. Sure, they might get full, but they’re gonna get hungry again. Also if you’ve ever watched ladybirds and/or their larvae munch their way through aphids, it’s impressive/terrifying in equal measure.
They’re also super loud. Like, you can hear them crunching.
They’re easy to use
Most predatory mites that you buy come in little packets that you simply hang on your plant. There’s usually a hole you can perforate, and then…that’s it. No spraying, no checking for the next few months that they’re all gone.
Even if the infestation isn’t completely removed, they won’t be able to build up significant numbers in the presence of a predator.
They won’t cause any damage
Gardening enthusiasts, whether it’s indoor or outdoor are becoming increasingly aware of how they affect the environment. Recent research has discovered that using phosphorus in fertiliser, whilst benefiting the plants short term, can damage the soil and cause long-term damage.
And that’s fertiliser, something that’s mean to benefit the soil. Imagine the damage insecticide can do. Even relatively gentle pesticides, like castile soap, can cause build-up of salt in the soil.
Commercial insecticides can’t distinguish between good bugs and bad bugs, so as well as killing pests, they’re killing beneficial bugs like isopods and springtails, as well as tiny microbes that can benefit your plant.
The easiest way to grow big, beautiful house plants is to replicate their natural environment, so by adding life to the soil, rather than decimating it, we can help out plants with very little effort.
They’re super hands off
This is what I LOVE about predatory mites.
If used correctly, most house plant pest eradication tips work. Even just using plain water works, if (big if) you’re consistent with your application and you don’t stop until all the pests are gone.
Simple, but not easy.
Predatory mites just do their thing. They know what they’re after and they’re happy to do it. No rinsing, checking leaves, masking up to spray chemicals. Just little bugs you can’t even see.
Problems with using predatory mites on house plants
This is the biggest issue – prices do vary, but you’re looking at about £10 for a sachet of mites.
If you don’t have the cash, then this is really the end of that conversation. Get yourself some spray bottles of castille soap and remember to send everyone links so you can get some mites for your birthday.
However, if you’re happy to spend that, then they can be value for money. If, for example, you have a TONNE of plants and a lot of pests, then that money can be considered an investment. It’ll take you hours of care to spray for pests and you might not get them all, whereas the mites will be far more effective.
If you’re busy, or the infestation is weighing on your mind and making you hate your plants, throwing cash at the issue can sometimes help.
You need to get the right types
There are different mites that target specific pests and specific stages of that pest’s lifecycle. There are pests that will eat everything, but they will also be more than happy to eat each other.
The mite that eats adult thrips is very voracious and undiscerning (you’d have to be, to eat a thrips) so can’t be used in conjunction with any other pests. You might be better off getting ones that eat the thrips larvae and getting all the adult ones yourself.
It can be hard to establish a decent population
If you have a veritable jungle at home, then you probably won’t have an issue keeping a decent population of mites alive. However, if you only have a few plants, then you won’t be able to sustain the mites, and they’ll die when their food source is gone.
Some people like this, because they don’t like the idea of a house full of bugs (understandable, but they are teeny tiny) BUT for soft-hearted people like me, open the windows when your pests are gone and the predators will fly away, and look for other sources of food.
Which predatory mites are available?
Phytoseiidae are a family of predatory mites. They’re small arthropods with a very predatory nature.
Different species of phytoseidae target different mites, and the main ones we see are:
These little mites are best used to target red spider mites (which are, you, know, normal spider mites). Yes, they’re both mites, so there’s a bit of casual cannibalism going on, but you know? We’re not here to judge.
For one so angry, they are TINY. You buy in literal thousands, and a pot smaller than a jam jar holds about 2000. They’re too small to see, so don’t worry if you’re a bit bug-phobic*.
Bear in mind that you’ll need around 100 per plant, so buy as many as you think you’ll need BUT Phytoseiulus persimilis will eat spider mites in all of their life cycle stages AND their lifecycle is faster than that of spider mites.
If you have a lot of spider mites, then put all your infested plants together – over time, the population of Phytoseiulus persimilis will exceed that of the spider mites and the battle will be in the bag.
*Apologies, if you’re super bug phobic and the idea of microscopic bugs being in your house, is worse than ones you can see, but I’m kind of assuming you wouldn’t have made it this far through the article.
Another spider mite assassin, basically the same as above BUT there is a key different. Phytoseiulus persimilis are most effective in humid conditions. If the air is too dry they’ll retreat into soil.
Neoseiulus fallacis thrive in hot, dry conditions, so if that’s what you’re dealing with, use these.
This is a good ‘will eat anything’ mite, but they’ll be most effective on spider mites. They’ll eat thrips if that’s what’s available, but they won’t reproduce as quickly.
They’re also pretty happy with a range of conditions and temperatures.
These will eat thrips larvae. They also eat pollen, so a lot of commercial greenhouses (or anyone will pollen available) use them as a preventative measure, rather than a treatment.
These bad boys are thrips killers. They’ll eat a thrips in any stage BUT they’re only effective in temperatures above 20oC (68oF).
They’ll also eat spider mites, aphids and whitefly. They will also eat each other (well, the adults will eat the babies) should they lack another food source.
These eat adult thrips. They’re very effective but they do a lot better in warmer temps (like Amblyseius Swirskii) and they really benefit from having a source of pollen.
These are for mealybug control. They look a bit like a ladybird when they’re adults, but the babies looks like big, fluffy mealybugs. They are VORACIOUS mealybug eaters.
They’ll also eat other scale insects, but not as quickly (I assume they’re not as tasty??)
These are expensive and difficult to get hold of. They’re also grim – parasitic wasps that lay their eggs in mealybugs. No ta.
What’s the best all-round predatory mite for house plants?
Like most things, if you want to tackle a specific problem, you’ll need a specific solution.
However, if you want to try predatory mites and have a few spider mites, a few thrips, and a couple of aphids here and there, you’re best off with Amblyseius Swirskii BUT you’ll need to ensure you keep your temperatures up.
Another great option is Neoseiulus californicus – they’re not as voracious, but they’re pretty chill about conditions.
This is one of those things that I can only help so much with – the best approach is to try a few different things and see what works for you.
As far as I’m aware, mealybugs need a specific mealybug predator. For one thing, the others will all be too small to manage a full mealybug.
How to tell the difference between predatory mites and house plant pests
Sometimes, you can’t. Phytoseiulus persimilis look practically identical to spider mites, by the way, but they’re very effective and die if they have no spider mites to eat, so should Phytoseiulus persimilis just turn up (unlikely), you probably won’t even notice you ever had spider mites
Predatory bugs rarely just show up, unless we’re talking ladybirds or spiders. that would be too easy.
If you can see spiders on your plants, then it’s probably just…spiders. Spider mites (the bad ones) are very difficult to see without a magnifying glass – you’re more likely to see the damage they do or their webs.
If you see a spider web on your plant, check it isn’t just a regular spider. Spider mites are teeny tiny and red and most importantly if you can see webbing, you will already see damage to your plant.
If you’re still unsure if you have spider mites or good mites, spray the plant with water. This won’t kill them but it will ruin their plans. Check for damage to the plant and if there isn’t any, leave them alone.
Also, if you’re in the UK, predatory mites are highly unlikely to just rock up, unless you’ve been to a botanical garden or something.
Do predatory mites live in the soil?
Sometimes they retreat to the soil if the conditions don’t suit them, but usually, they live on the plant leaves and stem. That being said, the soil can still be full of beneficial bugs that are aerating your soil and eating any rotting matter or fungus that they can find.
How long do predatory mites live for?
It varies depending on the species and how big of a population you have. The bigger the pest infestation, the more food they have, the more chance they have of establishing a breeding colony. It also depends on whether they have other food sources – some mites can eat things like pollen, so if you have that available they’ll live longer.
Often, the lifecycle of the mite is shorter than that of the pest, so numbers increase faster than their prey. The individuals may only live a few dozen days, but they keep replacing themselves.
Are predatory mites harmful to humans or pets?
No. Even the more general ones only really do damage to other insects.
Will predatory mites reproduce?
Yes, if given the right conditions. However, unless you have a lot of plants and a constant supply of food for them, then they will starve over time unless they get ones that can be supplementarily fed.
Dragonfli is a great UK-based seller of predatory mites
ARBICO sells them in the US.