Have you noticed an ornate network of finely spun webs draped over the foliage of your houseplants? Perhaps it’s the handiwork of a cordial house spider who has chosen to set up a home among your plants. Or it could be the work of something much more sinister. Spider mites are tiny arachnids who like to devour the chlorophyll contained within our plants. Don’t be fooled by their minute size. These microscopic pests are capable of inflicting monumental damage to your houseplants.
If your plants are suffering from a spider mite infestation, this guide will help you to get rid of them for good!
About Spider Mites
Spider mites are microscopic creatures belonging to the Arachnida class of animals, which also contains spiders, scorpions, and ticks. There are over 1000 different species of spider mites, usually measuring less than a fiftieth of an inch. They live on the underside of leaves and weave fine silk webs around the foliage to protect their eggs. Spider mites have long mouthpieces which pierce the flesh of the host pant to feast on chlorophyll contained within it. They are prolific breeders and at optimum temperatures, some species can reach sexual maturity in as little as five days, so even a small infestation can quickly get out of hand.
Causes of Spider Mite Infestations
Spider mites love hot and dry conditions, meaning they are more prevalent during the summer months, and plants that live indoors are particularly vulnerable. Outdoors, spider mites become dormant over winter, but in the consistently warm home environment, they can be active all year round. Frustratingly, spider mites don’t have any natural predators indoors as they do outdoors, so they are much more likely to emerge and thrive on houseplants than on garden plants.
Under-watered plants are a paradise for these moisture-hating menaces, so make sure all of your plants are getting plenty to drink. Over-fertilized plants are especially appealing to certain spider mite species since they are attracted to the amino acids and proteins contained in plant foods.
How to Prevent Spider Mites
As with all plant pests, prevention is better than cure. Always inspect any new plants thoroughly for any signs of pest or disease before purchasing. You should quarantine any new plants for at least a month after bringing them home, giving plenty of time for any hidden problems to make themselves known before introducing them to the rest of your collection.
Regularly inspecting all of your houseplants for signs and symptoms of pests will help you to catch any budding infestations early, giving you a much better chance of salvaging any stricken plants. This is especially important with spider mites since they are capable of reproducing and spreading so quickly. Because spider mites are so tiny, their population may have gotten quite large before you even notice anything is amiss. To make it easier to spot them early, you can use a magnifying glass when inspecting your plants. Make sure you check the undersides of the leaves as this is where they like to congregate.
Spider mites like to live amongst dust particles, so spraying or wiping your plants’ leaves with water regularly will not only dislodge any mite-enticing dust, it will also increase the ambient humidity, which spider mites hate. Another way to increase humidity is to rest your plants on pebble trays filled with water, but only if the plants are humidity-lovers.
Healthy, happy plants will be better able to withstand a spider mite infestation, so make sure that you are consistently meeting the needs of each of your plants to minimize the potential damage should they fall victim to pests.
Symptoms of Spider Mite Infestations
Because of their microscopic size, it can be difficult to spot spider mites with the naked eye. Often, the first visible sign of an infestation will be the fine, silvery webs draped across the foliage of the host plant.
If you think you may have an infestation on your hands, you can use a piece of paper to help identify the mites. Shake a leaf over the paper, and if you do have a spider mite infestation, you will be able to see tiny dark specks moving across the paper. These specks are spider mites.
Infested plants may have tiny white dots or stippling on the leaves from where the spiders have pierced them with their long mouthpieces. If a spider mite infestation is left to exacerbate, they can inflict serious damage. Leaves will begin to fade and yellow as the mites siphon the chlorophyll, which is vital for photosynthesis. Over time, the plant will become weaker as it can no longer photosynthesize efficiently, leaving it susceptible to secondary diseases. The leaves will gradually curl, dry out, and drop. If left unchecked, a spider mite infestation will be fatal.
How to Get Rid of Spider Mites
Spider mite colonies can quickly adapt to become resistant to certain chemicals and pesticides, so natural, organic treatments are generally more effective. Spider mites are very stubborn, so you will almost certainly need to repeat any treatment a few times to make sure that you have successfully eradicated both the adults and the larvae. It may take a few weeks and several applications before all the spider mites are completely gone.
With any treatment for spider mites, you will want to pay special attention to the undersides of leaves, since this is where they like to congregate.
Always test any treatments on a small area of the plant first, and leave it to settle for a couple of days to observe whether it causes any damage before applying to the whole plant.
Always isolate your plant from your wider collection at the first sign of infestation, since spider mites can quickly spread by weaving webs between plants. They are also easily blown from one plant to another by even the slightest breeze, so try to keep the host plant away from away drafts. You should also thoroughly clean the area where the host plant stood to remove any lingering mites from the area.
If the infestation is caught early, you may be able to dislodge some of the spiders using a high-powered stream of water, like a shower or hose. Don’t try this method on very young or delicate plants, as the water pressure may damage them. You should prune the worst infested leaves and stems before carefully discarding the cuttings.
Neem oil is a highly effective natural, non-toxic insecticide. It kills spider mites by permeating their fragile exoskeletons and suffocating them. Neem oil is mostly available as a concentrate. You should dilute the oil according to the instructions on the packaging before you apply it using either a spray bottle to douse the plant thoroughly or by using a cloth to wipe over the stems and leaves. You will need to repeat the neem oil treatment periodically until all the bugs are gone, but the bonus with neem oil is that it has a residual effect, meaning it offers protection from future infestations. You can also use neem oil as a preventative measure, even when no mites are present.
Insecticidal soap is another non-toxic treatment for spider mites. You can either purchase ready-made soaps or make your own at home by mixing one tablespoon of fragrance-free dish soap, one tablespoon of vegetable oil, and one liter of water. Pour the mixture into a spray bottle and apply liberally to the plant. Let the solution rest on the plant for a few hours before rinsing thoroughly with running water. The soap will cling to the spider mites causing them to suffocate and die. It’s best to apply insecticidal soap in the early morning or evening when light levels are lower, as direct sunlight can cause the solution the scorch the foliage.
You can use a 70% rubbing alcohol to treat spider mites by soaking a cotton bud or cloth in the alcohol and wiping it over every part of the plant. You need to make sure that the alcohol comes into direct contact with all of the mites, removing them as you go. The alcohol will cause the mites to dehydrate and die. Rinse the whole plant with water afterward to prevent the alcohol from burning the foliage. This method is pretty time-consuming, so alternatively you can dilute the rubbing alcohol with water and spray it onto the plant, but remember to rinse it off afterward.
Essential oils are a good way to deal with any unwanted pests naturally. Not only do they repel a wide variety of pests with their strong aromas, but they also kill spider mites on contact. The essential oils which are most effective against spider mites are; chamomile, coriander, spearmint, and rosemary. Simply add a few drops of your chosen oil to a spray bottle full of water and apply liberally to your plant. The essential oil method has the added bonus of making your home smell positively beautiful!
Chilis are an excellent, natural, non-toxic treatment for spider mites. Hot peppers like jalapeños and cayenne have been scientifically proven to possess potent toxicity to certain species of spider mites. Capsaicin, the active chemical which gives chilis their heat, damages the nervous system of the mites, whilst simultaneously deterring other insects with its pungent aroma. You can make a homemade chili spray by mixing dried chilis or chili powder with water and spraying it directly onto the plant. Leave it to settle for a few hours before rinsing off thoroughly. Alternatively, you could add chili to insecticidal soap for an even more powerful pesticide.
Diatomaceous Earth (DE) is a powdery substance that is made from the fossilized remains of microscopic, prehistoric creatures called diatoms. Although it may feel relatively soft to us humans, for tiny bugs who crawl across it, DE feels like millions of shards of broken glass. It kills spider mites by piercing their exoskeleton, causing them to dehydrate as all of their internal fluids leak out. It is an incredibly effective, but rather fiddly way of treating spider mites.
Usually, DE is spread throughout the soil to treat infestations, but since spider mites live on the undersides of leaves, the DE will need to be applied there, which can be tricky. Sprinkle the powder over the foliage, and try to cover the spiders’ webs so it can catch them as they travel along. Gently rub it into the underside of the leaves, taking care not to damage them. You could also use a paintbrush to dust the leaves. You should repeat the application every few days, as the powder will be dislodged easily. Don’t allow the DE to become wet, as this nulls the razor-like quality of the powder. Always wear gloves when using DE as it can irritate your skin, and make sure you are using food-grade quality, as pool-grade will be far too abrasive.
Frequently Asked Questions
Here are a few of the most common questions that we get about spider mites:
Are spider mites arachnids or insects?
Spider mites belong to the Tetranychidae family of arachnids, so yes, they are microscopic spiders! Just like spiders, these miniature cousins also have eight legs and weave intricate webs.
Are spider mites harmful to humans and animals?
Although they may cause devastation to your houseplants, the good news is that spider mites don’t pose any threat to humans or animals living in your home.
How long do spider mites live?
The average lifespan of a spider mite is around two weeks to a month. Some species of spider mite can develop from a hatchling to a sexually mature adult in as little as three days. Adult females can lay up to 20 eggs per day, meaning their population can increase exponentially over a very short period of time.
What plants do spider mites infest?
Spider mites are known to feed on many hundreds of plant species, so the chances are, whatever houseplants you have in your collection, they’re probably vulnerable to a spider mite attack.