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There are three main types of Soil Mites, each digesting different sections below the soil line. The most common Mites you'll find in houseplant composts are Oribatids, which will feed off rotten roots, bits of bark and other dead mites. Their speciality to reproduce is in moist, organic matter-rich compost that rarely sees periods of droughts.
Soil Mites are completely harmless to both indoor and outdoor plants, feeding only off the compost's properties and avoiding the plant's healthy tissue. Indoor gardeners often remove the infestation purely on a visible aspect, as seeing small white or brown critters rambling across the soil isn't a pretty sight. Keep scrolling to learn more about these Mites and how to eradicate them!
As the Mites aren't detrimental to the plant itself, you won't see any symptoms arise on its foliage. Instead, have a scan across the soil's top surface for small white or brown critters that'll parade across the dirt. If you're not fully satisfied with just searching its surface, be sure to gently take the plant out of its pot and check the base. Be sure you don't over-touch the root system or pull soil from them as it'll only result in 'Transplant Shock' and potential death.
Soil Mites will occur solely along and beneath the compost line. If you find small white critters roaming the foliage of your plant, you may be looking at a Spider Mites infestation.
Plants - All species are susceptible to Soil Mites, including plants that require moist soil. Like Cacti and Succulents, arid dwellers are less likely prone to an attack due to the drier conditions that may not support a large infestation.
1. Before sifting through the soil, the first step to do is hydrate the plant. Fingering the dry roots will bring nothing but grief in the form of Transplant Shock, which will only add to the misery.
2. A few hours after irrigation, take the plant out of its pot and inspect the outer surfaces of the rootball - crush each bug or colony as they become visible.
3. Gently remove the soil's bottom quarter by shaking the plant to loosen off the dirt. As it's essential to respect the plant, refrain from unearthing ALL of its root system, or readily snapping its roots. Have a look at the image below to learn more about how much soil you can safely remove without causing Transplant Shock.
4. Before placing the plant back into its original container, have a scan over the pot, too. As you can see on the next image, borrowed from the Root Mealybugs article, the Mites may even attach themselves to the nooks on the pot's inside, potentially reigniting the infestation. Wash the pot using warm water and dish soap to destroy any remaining inhabitants for several minutes.
5. Place an inch of the appropriate potting-mix into the pot's base and place the rootball on top. Pour more compost over the plant's soil to fill the remaining gaps between the rootball and its pot. If you need help choosing the right mix for your plant, send us a message to be pointed in the right direction.
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6. Once the plant is back in its pot, don't tinker with the roots again unless the symptoms progressively worsen. The final step to eradicate Soil Mites is to choose between using either an organic or chemical-based pesticide.
Cinnamon Solution is the first organic pesticide that we'll discuss, which can be created by mixing 1 tsp. of cinnamon to 200ml of tap water. When the plant next needs a water, which could be in a couple of days, pour the dilution into the plant's compost to administer the pesticide. If necessary, replace this once every two weeks (or every three waters) to help eradicate the infestation - a total of three applications can be made, before waiting eight weeks to see if the infestation arises again. If it does return, we'd recommend opting for DE which can be applied by applying a thin layer onto the soil's surface.
Insecticidal or Horticultural Soap is a well-known organic pesticide on the market, with two versions to consider. Although most garden centres will stock this, it's far more economical to purchase the second option - concentrated bottles. This method comes with pros and cons but is far cheaper to use if you have a large infestation. It's self-explanatory and highly beneficial for the outbreak as long as you use the correct levels of dilution - the only downside is its availability in local centres. It's best to buy this option online as there are many different companies to choose from, with some being cheaper than others. The second and most affordable way is by making it yourself.
There are three ingredients in creating your own Horticultural Soap - a vegetable, tree or nut-based oil, non-fragrant dishwashing soap and tap water. Most oils are acceptable, with the most successful being vegetable, sunflower, neem and olive oil. Add two parts oil, one part dishwashing soap and eight parts water to create the dilution. Although it's best to fresh bottled water, tap water that has been allowed to sit for 24hrs is also excellent.
For both variants of Horticultural Soap, dilute it down to the recommended strength and hydrate the plant using the newly-created liquid. Continue to care for the plant in the same way as before, hydrating the specimen every week or so with normal water. Applying Horticultural Soap should only be performed every two weeks, or after three waters (whichever comes first) to avoid burning the roots. We would only recommend using this pesticide on four occasions in total, and if the infestation continues to develop after four applications of the Soap, we would move on to using DE.
Diatomaceous Earth (D.E. or DE) is grounded diatom mantels (skeletons) that can be highly abrasive to many arthropods, including Soil Mites. Although the white powder may be soft to the human touch, the sharp tooth-like edges off each grain will begin to cut its way into the pests' eco-skeleton, causing significant discomfort and weakened health. After a period of several days, the infestation will decrease as the mature mothers won't be able sufficiently to lay their eggs. Equally sprinkle a thin layer of DE across the soil's surface to create a protective barrier against the Mites rising to the top.
As you have followed the first six steps mentioned in the previous section, you may not see any signs of an infestation for several weeks. We'd recommend waiting eight weeks before deeming the specimen pest-free, as relapses of later-hatching larvae could occur. DE is considered safe to both pets and humans and has no links to the development of illness. You can safely remove the powder (and a bit of the soil) once you feel that the infestation has subsided.
As the first method will take several weeks to eradicate, you may want to consider spending some money on 'hydrogen peroxide'. Now, before you rush to your local garden centre, this chemical is mostly found online, so have a shop around for the best deal here. For every three irrigations, incorporate a splash of the peroxide into its with to administer the pesticide. You'll have to do this for at least three times to stop the chance of a relapse thoroughly. Always follow the manufacturer's recommended dosages as Hydrogen peroxide may become detrimental to the plant when over-used. If you're worried about killing your plant, use DE!
At the local plant shop or garden centre, inspect the soil of any plants that you wish to buy. Most infestations come from already-affected plants, so always keep this in mind when increasing your plant-collection.
Regularly check for pests on your plants. Although this may sound patronising, many gardeners forget to inspect their indoor specimens. As soon as you see a symptom in the soil, keep it quarantined and follow the steps above!
Store your bags of compost well by keeping them tight and enclosed, out of dry or damp areas. Never use soil that has been left outside for any length of time, due to the very high risk of contamination.
Need realtime advice for your Soil Mite situation? Book a video or message consultation with expert Joe Bagley, THE HOUSEPLANT DOCTOR™ (author or ukhouseplants.com). Choose between a ten or thirty-minute session & a platform of your choice (WhatsApp, FaceTime, Facebook Messenger or Zoom). Ask unlimited questions in one session, including queries on your dying/challenging plants, pests eradication, terrariums, repotting advice & everything in between! Available worldwide.