When is a pest not a pest? That’s a question many of us might ask when faced with soil mites. Unlike most houseplant pests who cause destruction and devastation when they infest our precious houseplants, soil mites are incredibly beneficial organisms. In fact, their presence is usually a good omen, indicating healthy soil and a thriving plant.
Because soil mites are not necessarily ‘pests’ in the strictest sense of the word, many indoor gardeners are unsure how best to approach them. But worry not, this comprehensive guide to soil mites will teach you all you need to know about these magnificent but misunderstood micro-organisms, and how to deal with them (or not!).
What are Soil Mites?
Soil mites are microscopic arthropods, related to spiders and other invertebrate creatures with exoskeletons. There are over 20,000 known species of soil mite, of which Oribatid mites are the most common. They are sometimes called ‘Turtle Mites’ because of their very tough, shell-like exteriors. Soil mites are usually brown or white in color, and measure around a millimeter in length. They have a surprisingly long lifespan and can live for up to seven years, although most will only survive for around three to four.
Soil mites are the most abundantly found organisms in soil. They live both indoors and outdoors but prefer compost piles or areas of very rich soil with plenty of nutrients to feed on. Different species of soil mites favor different food sources. Some species eat fungus and bacteria, some species hunt smaller pests and their eggs, and some species scavenge the carcasses of other insects. Soil mites will pretty much devour any kind of decaying organic matter, including leaves, mosses, algae, fungi, and dead creatures. They break all this organic matter down and transform it into beneficial nutrients and energy.
What Causes Soil Mites?
Every species of plant which is grown in a soil-based substrate will be susceptible to soil mites. Soil mites love damp, dark conditions so are more prevalent on thirsty or shade-loving houseplants. They will be more likely to appear if you use potting soil which is rich in organic matter. Cacti, succulents, and orchids are less likely to harbor soil mites since they need drier and less nutritious substrates that are typically low in organic matter. Keeping your houseplants’ soil clear of any debris like fallen leaves will discourage soil mites since it removes their primary food source.
The most common way for soil mites to be introduced to your houseplants is through the potting mix that you use. They are often already present in soils and are transferred to your houseplants during the potting or repotting process. Using a sterile potting soil will reduce the chances of soil mites being introduced to your houseplants.
How to Identify Soil Mites
Because they are so microscopic, most soil mite populations are almost invisible to the naked eye. In some cases, when the population has had time grown to a considerable size, you may be able to see tiny white or brown flecks moving across the surface of the soil around your houseplants. These are soil mites. In most cases, however, you will probably need a magnifying glass or even a microscope to positively identify them.
Soil mites live exclusively in and on the soil, and won’t venture onto the plant, so they won’t be found amongst the foliage like other bugs. They only feed on decaying matter within the soil and don’t take any nutrients from the plant or cause it any harm at all. Whilst it’s a relief to know that soil mites won’t harm your plants, it does make them tricky to identify, since they won’t leave any telltale marks or damage on the host plant’s roots, stems, or foliage.
What Are the Benefits of Soil Mites?
Healthy soils are full of microscopic and macroscopic organisms which all work together to create and maintain a thriving, mutually beneficial ecosystem for both the plants and animals living in the soil. They are instrumental in the natural decomposition process of soil, acting as a miniature clean-up crew by breaking down decaying organic matter and turning it into energy and nutrients for plants and other organisms which depend on the soil.
Spider mites also consume bacteria, fungus, and harmful soil-dwelling creatures, which are then released back into the soil in the form of nutrient-rich excretions. By consuming these potentially harmful pathogens and pests, spider mites help to protect plants from fungal disease and harmful pest infestations.
What Are the Problems With Soil Mites?
Given that soil mites are the undisputed heroes of healthy soil, most people prefer to leave soil mite populations undisturbed, allowing them to continue their very important work. Having a soil mite population means that your soil, and by extension, your plants, are healthy and thriving.
Other people, however, find soil mites to be unsightly if their population becomes large enough that they can be seen crawling on the surface of the soil. Additionally, soil mites have been known to carry and transmit bacteria or parasites like tapeworms, which in very rare cases, can be passed on to humans or animals. So, whilst not posing any particular threat to your houseplants, you may still want to get rid of soil mites if their presence is bothering you.
How to Treat Soil Mites
The best course of action to take for a soil mite infestation is simply to do nothing! They will support a healthy soil ecosystem and deliver nutrients to your plants. However, if you really feel the need to get rid of them, there are several methods you can use.
Soil mites tend to stay localized to one pot rather than spreading prolifically, as they cannot jump or fly, so it is not usually necessary to isolate affected plants. Because soil mites live and feed exclusively in the soil, you won’t need to treat the foliage as you might with other pests. Any treatments should be applied only to the soil.
Repot and Replace Soil
The simplest way to get rid of soil mites is to get rid of the infested soil and replace it with fresh. Carefully remove the affected plant from its pot and gently shake the soil away. If you have a compost bin, you can put the old soil in there as the mites will give a much-needed boost to the natural composting process. You can use a steady stream of water to rinse all the remaining soil from the roots. Clean the pot thoroughly, or you could use a new one, and position the plant inside before filling it with fresh, sterile potting mix. You should also clean the area where the plant used to stand to eradicate any lingering mites.
Many insects, soil mites included, are averse to strong odors, so using organic ingredients with strong smells is a good way to deter them. Garlic is one of the most effective natural insect repellants. To create a garlic solution to deter soil mites, infuse four garlic cloves in a gallon of water, allowing the mixture to sit for around three to four days. Remove the garlic from the water and thoroughly soak the soil of affected houseplants. The soil mites will gradually migrate away from the now strong-smelling soil.
Cinnamon is another organic, non-toxic scent that is effective in repelling insects. Mix a heaped tablespoon of cinnamon with a gallon of water and soak the affected plants’ soil thoroughly. The cinnamon solution will work in the same way as the garlic solution. You could also decant either solution into a spray bottle and spray the soil periodically. Because neither solution is harmful to plants or the surrounding environment, you could incorporate these methods into your regular watering routine to provide a long-lasting deterrent against future soil mites and other pest infestations. Alternatively, you could simply place cloves of garlic or cinnamon powder within the soil, and they will have the same effect.
Many indoor gardeners prefer to use this method to tackle soil mites as it humanely encourages them to move on to a more appropriate place where they can continue to carry out their very important soil-enhancing work rather than killing them.
Hydrogen peroxide is a very efficient treatment for all manner of soil-borne pests. It will kill many adult pests, nymphs, and eggs on contact, without causing any harm to your plants. Hydrogen peroxide is available cheaply from most drugstores. To treat soil mites, mix a solution of one part hydrogen peroxide with four parts water. Soak the soil thoroughly and allow it to dry out.
You can repeat this treatment twice more over the course of a few weeks for best results, but don’t incorporate hydrogen peroxide into your regular watering routine, as overuse can be detrimental to the plants. Don’t worry if the solution fizzes and bubbles slightly when applied to the soil, this is normal. Make sure that you don’t use anything higher than three percent hydrogen peroxide solution, as this will be far too strong and may scorch or damage the plants’ roots.
Neem oil is a naturally occurring pesticide obtained from the Azadirachta indica tree. It won’t harm your plants but is very effective at getting rid of unwanted insects. It works by adhering to their exoskeletons and smothering them. Most neem oil is purchased as a concentrate, so dilute it in accordance with the instructions on the packaging, and mix in a little dish soap to help the solution adhere to the bugs. Pour the solution over the soil and allow it to soak thoroughly. Neem oil has a residual effect, so it will act as a preventative treatment deterring other, more sinister pest infestations from emerging in the future.
Diatomaceous Earth (DE) is a powdery substance made of the crushed up, fossilized remains of prehistoric organisms called diatoms. The powder feels fairly soft to human hands, but to tiny bugs and insects, it feels like millions of shards of broken glass which pierce their exoskeletons and cause them to bleed out when they crawl across it. DE can be sprinkled on the surface of the soil or mixed throughout the soil, causing no harm to the plant, but it will efficiently kill any creature with an exoskeleton, which includes soil mites.
Always use food-grade, rather than pool-grade DE to avoid damaging the plant, and wear gloves when handling the powder.
Frequently Asked Questions
Here are a few of the most common questions about soil mites:
Are soil mites harmful to humans and animals?
Whilst soil mites are not aggressive and do not bite or attack people or animals, they are known to carry some potentially harmful pathogens and parasites such as tapeworms. Because of this, you should always wash your hands after handling soil to minimize the likelihood of contracting any illnesses, although the chances of this happening are very rare indeed.
How long do soil mites live?
Soil mites have an impressively long lifespan, and have been known to live for up to seven years! They also reproduce fairly slowly, meaning that their populations aren’t prone to exponential expansion like some other more harmful pests. Because they reproduce so slowly, it often takes a long time for any visible signs of soil mites to be noticeable.
How can I encourage soil mites?
Many gardeners want to entice a helpful soil mite population to take up home amongst their houseplants. The best way to encourage them is to use a rich substrate, adding plenty of extra organic matter for the mites to feed on.