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When I first got into houseplants, I got almost all of my information from YouTube. I barely touched Facebook at all.
And then when I finally got around to joining a load of houseplant Facebook groups, I was struck by how often people recommended systemic pesticides. I don’t think I know of any YouTubers that recommend using them.
I don't use systemic pesticides. Mainly because they're tricky to get hold/banned of in the UK, but also because they don't discern between good and bad bugs and I like my soil to have a bit of life in it. I'm trying to create an ecosystem here!
What are systemic pesticides?
Systemic pesticides are chemicals that you can put in the soil of your plant. The granules will dissolve and the chemicals will be absorbed by your plant’s roots.
The chemicals will then be delivered to all the cells of your plant. When a pest like a thrips, scale, or spider mite ingests plant matter, they’ll die.
The most common chemical used in systemic pesticides is imidacloprid, which is banned in the EU due to its harmful effects on pollinators. If you live somewhere where you can get it, please don’t use it outside!
Neonicotinoids (of which imidacloprid is a type) are banned in the EU, but are approved for use in the UK. I don't think they're readily available though and...I don't think it's a step in the right direction. On the same day parliament approved the use of them (after they'd been banned in 2018) a study was published about the plummeting levels of bees in the USA directly linked to use of neonicotinoids.
How long does it take systemic pesticides to work?
Once applied, systemic pesticides can take about two weeks to start working.
How often do you need to use systemic pesticides?
Most systemic pesticides will last a minimum of two months, which should be ample time to eliminate your pest problem. However, the effects can last for up to a year.
Manufacturers usually recommend that you don’t reapply more frequently than once a year, which is interesting because Bonide are happy for you to whack it on every 8 weeks.
Do different systemic work on different pests?
No, but some pests are more resilient than others. One of the major problems with thrips is that they’re incredibly good at building up a tolerance to pesticides. So you might get rid of 99% of them, but the 1% that remain will be immune, so you’ll have to switch tactics.
There is also a TONNE of anecdotal evidence that systemic pet control treatments only serve to make spider mites stronger, so bear this in mind if spider mites are your issue.
Are systemic pesticides harmful to humans or pets?
They’re toxic to ingest, but not to touch. In fact, imidacloprid is the active ingredient in American flea treatments. Here in the UK we’re not allowed it, so we use fipronil.
It can be a problem if your pets are likely to eat your plants, but it’s not SUPER toxic. It’s no more harmful than, say, the calcium oxalate crystals in Monstera leaves. Unless your pet eats a whole plant it’s unlikely to be an issue.
I personally wouldn’t risk it, but a lot of people with well-behaved pets have no problems when using systemic pesticides.
Will systemic pesticides damage my plants?
No, the active ingredients in systemic pesticides don’t seem to have any negative impact on the plants.
This makes sense – these products were designed for protecting crops from insects BUT it is NOT recommended that you treat plants with fruit you intend to eat with systemic pesticides.
I tried to find out why they recommend that when presumably there are people eating commercially grown, imidacloprid-treated crops every day, but I couldn’t find an answer.
Maybe they can test produce to see if there are pesticides present?
Which systemic pesticide should I use?
I’ve tried one that was available in the UK and it didn’t work, so I wouldn’t waste your money unless you can get hold of imidacloprid.
Bonide is the only one I see being routinely recommended. I have seen people claim that it doesn’t work, so don’t think it’s some kind of silver bullet.
Pros of systemic pesticides
- They’re easy to apply
To use systemic pesticides you just sprinkle them on the soil and then water them in. Easy. Do don’t have to wipe the leaves, or go around with rubbing alcohol and a cotton bud.
- They can be effective
I mean, not the ones I’ve tried, but the guys in the Facebook groups are extremely passionate about systemic pesticides.
- They don’t require multiple applications
One of the main reasons traditional pest control is a massive ballache is the consistency required to make any headway with pest eradication. Systemic pesticides are potentially a one and done solution.
Cons of systemic pesticides
- They’re terrible for the environment
Insects are having a terrible time of it at the moment, and I don’t like using products that could make things even worse for them. I actively attract pollinators – I have a wildflower garden AND a lot of pollinator-friendly pots in my garden. I don’t want them to accidentally get into my house, eat a plant and die. The poison is present in flowers and nectar, so it can be an issue.
There are other cons I’ve mentioned, such as thrips building up resistance, but if I’m honest, there are few cons about systemic pesticides that don’t also apply to other methods of houseplant pest control.
Thrips are just a nightmare to get rid of – the only truly effective measure is to introduce predatory mites, but they can be really expensive so it’s not an option for everyone.
I find systemic pesticides a bit icky, but if you want to give them a go, I totally see the appeal.