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Smiting The Spidermite – Hydro Harvest Pest Control

If you know what spidermites are capable of then they really need very little introduction. If you don’t know (or are just finding out) you’ll want to get straight to the bit where we tell you how to unleash a spidermite extinction-level event that would make Old Testament God blush.

Fear not, we will get there. But it is worth making sure you’ve chosen the right pest for eternal damnation. Getting it wrong can be costly and destructive. For the purposes of this guide we’ll  assume the worst case scenario – that you’ve got two-spotted spidermites.

In the event that it is a less resistant, less voracious, less altogether evil type of spidermite then the suggested approaches should wipe them out too, albeit more easily.

The Pest

Spidermites – specifically two-spotted, known in certain circles as ‘The Borg’

Distinguishing Features

Oval. Larvae have 6 legs, adults have 8 legs. 0.5-1mm in size when mature.


Most commonly a translucent off-white or greenish-yellow, can also range to brown or brick-red. Two spotted variety (unsurprisingly) have two spots on their back – even if the spots are unclear it’s best to assume the worst.

What they do

Sucking the sap like it was ancient Rome, spidermites have a prodigious ability to feed on your plants. Drawing out the life leads to leaf discolouration in the form of white speckles on the topside, quickly followed by leaf death and, if unchecked, plant death.

As if the appetite of spidermites wasn’t bad enough you can be sure there are more hungry mouths on their way. The females lay in abundance, the eggs hatch fast, and the newborns are straight out of the traps, well on their way to reproducing in a matter of days.

By this point they’ll be getting visible, in terms of leaf damage and their webs. Spidermite webs are a triple threat in that they allow the mites to scoot about more easily, give them cover from treatments such as sprays, and start to suffocate your plants.

You’re going absolutely gangbusters on treatments by now but nothing is working. Why? Because spidermites are capable of evolving to develop immunity to your pesticides. So you go and blow it all up, kill the harvest, and clear the room. And so they’re gone. Except they’re not, they’re hibernating for up to a year, even on hard surfaces, without eating or reproducing again. Ready to appear when you set up afresh. Why? Because they can, because they are bugs, with no notion of ‘gentleman’s code’.


The greatest trick the Devil ever pulled was convincing the world he didn’t exist. So it goes with spidermites. These pests tiny size gives them a huge advantage in gaining a foothold. Even vigilant growers can miss the 1mm bugs until suddenly they’re facing an infestation.

That’s not to say it’s not worth checking. Spidermites can be spotted with a simple, inexpensive magnifying glass, allowing you to intervene early which can make all the difference. As spidermites can hatch, mature and be reproducing within 7 days it is well worth timing your inspections for every 5 days to keep ahead of any developments.

Needless to say something so small can very easily get into your grow room unnoticed. The usual precautions in terms of bug blockers, disposable suits, and room seals are so cheap that it’s really just daft/lazy not to use them.

More of a dilemma are cuttings and young plants brought from outside. Whilst these are an inevitable part of indoor growing it is worth thinking very carefully before introducing them, and always quarantine.

The good news is that a healthy grow room environment with good air circulation, nice humidity levels, and plenty of natural predators can really slow spidermites down. They’ll struggle to reproduce, will have difficulty moving, and will be more easily picked off by your beneficial bugs.

Environmental Countermeasures

Even if spidermites are active on your plants you can still adjust growing conditions to slow them up. Circulation fans directed across the leaves will pin the mites down and prevent them from reproducing as quickly. It may be too late for natural predators to have an impact but it’s worth giving them a go. Ladybirds, predatory mites, and their ilk are all strong choices.

Physically washing and cleaning plants by hand can help hold back the tide too. Such techniques are time-consuming and won’t necessarily win the war. But washing and cleaning have bought many a grower the time required to save their crop with more advanced applications.

Direct Attack

Spidermites can be directly attacked in a number of ways. Treatments such as A.R.T.S Spired hit the webs and eggs, denying the mites mobility, cover, and a future generation.

Another favoured point of attack is the respiratory system. This is a key area in which spidermites cannot develop immunity. SMC+ and Guard Aid Spidermite are both excellent, natural choices for this job that rely on plant extracted oils. As well as hitting the spidermites on plants they’ll kill them on hard surfaces. All of the above are plant/crop safe, have negligible effect on crop taste or flavour, and are generally not harmful to beneficial bugs.

The near-nuclear options are treatments such as Killermite by Plant Vitality. These Abamectin-based insecticides will really go to work on spidermites and are capable of eradicating colonies. They are a little more abrasive towards the surrounding environment and should be used with care.

The nuclear option is a Smokebomb, although by this time the party is well and truly over, it’s just you and the mites. If you’ve had to cut your losses and kill the crop then a fumigation canister is one way to clean-slate the room. On a more positive note these can simply be used between crops to refresh your growing space.