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House plant pests, like house plants themselves, seem to have a preference when it comes to the environments they like, so you may find that one type is harder to eradicate than others.
I think I’ve had most of the house plant pests, but only the thrips were really clingers on (although if I keep Calathea in low light they always end up with spider mites, so now I keep them in the terrarium).
Pests/bugs common to Monstera
Thrips are my main issue with Monstera. My main Monstera has had them for YEARS and I can’t eradicate them. The population is under control, but if I don’t treat it for a week or two, larvae appear.
Thrips are a PAIN to get rid of. A PAIN. The only reliable way to get rid of them quickly is to buy predatory Amblyseius cucumeris mites, that will eat the larvae. Amblyseius swirskii eat the adults as well, but you need warmer temperatures (over 20oC/68oF) otherwise they’ll die.
Yes, you can use systemic pesticides if you can get hold of them (they get absorbed by the plant and make the leaves poisonous) BUT we can’t get good ones in the UK and more importantly, thrips can build up a resistance to almost anything over time, except for being washed off (my preferred method of eradication) or eaten.
Scale come in a variety of forms, but usually look something like this:
You can either pick them all off or dab them with a cotton bud dipped in rubbing alcohol. They build in numbers quickly so keep an eye out for them. Not to be confused with corking.
You can also get predatory mites to deal with spider mites, Phytoseiulus persimilis. Be careful when buying spider mites predators because one of them (can’t remember which one, so I haven’t mentioned it) will also eat any other predatory mites you have, and is a cannibal. So you’ll end up with one big fat one at the end (jokes – predatory mites are so teeny tiny you can’t really see them).
Mealybugs are a type of scale, and usually prefer juicy plants like succulents, but if allowed to breed unhindered they’ll make a quick meal of your Monstera.
Interestingly, there’s a predatory mite you can get for mealybugs that looks like a giant mealybug (a wolf in sheep’s clothing, if you will) BUT it moves faster – which isn’t hard because mealybugs basically don’t move at all.
Killing the adults is easy, but they can lay their eggs in the tiniest crevices so total eradication can tae weeks of treatment. Like with all pests, I just painstakingly wash the leaves with diluted castile soap and/or neem oil twice a week until we’re clear.
I HATE aphids. They’re a pain to get rid of. They don’t like Monstera, but will eat them if there’s nothing else.
They’re easy to get rid of in summer – if you put your plant outside predators will come and eat them (baby blackbirds are extremely efficient at removing aphids, and super cute!)
Bugs in Monstera soil
There are a few different bugs that live in Monstera soil. I actually have worms in mine (no idea where they came from, but free worm castings in exchange for shelter seems like an awesome deal) but you can also get springtails and millipedes.
None of these critters will do your plant any harm, and will actually help you out by aerating the soil and eating rotting matter.
Bacteria/fungus common to Monstera
Root rot is by the far the most common bacterial infection in Monstera, and it’s usually caused by user error.
Root rot happens when the soil around the roots becomes oxygen-starved. This environment is the perfect place for certain bacteria (usually some form of Phytophthora) to multiply to unsafe levels and cause issues.
I have a whole article on how to save an overwatered Monstera, which will guide you through the causes and solutions to root rot in Monstera.
Bacterial leaf infection
I have an article on bacterial leaf infection, BUT it’s one of those things that isn’t as common as we might think, and it can often be cured by taking better care of your plant. Like root rot, it doesn’t just turn up one day.
The bacteria are usually present in small amounts and it’s environmental issues that cause them to proliferate.
Rust, unlike a lot of other bacterial infections, likes very hot, humid conditions, so be vigilant in summer. It rarely just shows up, so it’s more common for people that have a lot of indoor and outdoor plants.
Once you have rust, it’s almost impossible to completely eradicate, so you either need to destroy the plant or keep it isolated from other plants.
Like most bacterial infections, prevention is better than cure, so make sure to keep your plant healthy.
Warm weather benefits Monstera, so don’t try to control rust by keeping the temperature low. Focus on improving air flow and making sure that you’re keeping the leaves of your Monstera dry.
Powdery mildew likes cold, damp conditions, so be vigilant in winter. It’s nowhere near as damaging as rust fungus and rarely kills plants unless they’re compromised in some way (though it will be more attracted to plants in a weakened state).
Make sure you have plenty of air flow in winter, and consider a dehumidifier (for your own health as well as that of your plants). High humidity is great, but if the humidity is high and temperatures are low then you can create more problems than if the air was drier.
Obvs a heater would be awesome, but we’re in a cost of living crisis. A dehumidifier is a great investment because they don’t use a lot of power and by removing the moisture in the air they can make your heating more efficient (because it’s easier to heat dry air).
Mosiac virus isn’t really a specific thing – it’s any virus that gives plant leaves a mottled appearance.
Mosaic disease is very rare in Monstera, so don’t worry about it unduly. I see a lot of people posting pictures of suspected mosaic disease and it’s always been either chlorotic leaves (so in need of fertilising) or thrips damage:
Currently there’s no cure for Mosaic virus – you just have to burn your plant and start again. Yay!
In my experience, Monstera are pretty good at dealing with pests due to their pretty thick leaves and invasive nature. Their leaves may suffer, and they may stop growing, but as long as you keep on top of treating and keep pest populations small they should bounce back.
There’s little you can do to prevent pests – they come in clothes and shoes, not just plants, so we’ll all get them at some point. The best way to reduce the damage they do is to keep your plants healthy so they can fight them off and recover as quickly as they can.