Spider mites are the most common mite that attacks woody plants and are especially active in drier climates. These pests suck on plant sap by penetrating cell walls and tissue with sharp mouthparts, causing injury. A speckled appearance, alongside yellowing or greying of leaves, develop as a result.
Infestations are exacerbated by aggressive reproduction. Female spider mites are known to lay hundreds of eggs at once at just a few days old. Because of this, rescuing your plant is usually a fight against the clock.
Thankfully there are several solutions in your quest to rid your plants of spider mites, including natural home remedies. However, the most effective solution is to use an insecticidal soap spray.
Learn more about identifying if you have a spider mite infestation, why they are detrimental and how to get rid of them for good!
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What are spider mites?
Spider mites are not technically insects but arachnids, which means they have eight legs instead of six like other common pests such as fungus gnats or aphids. They are related to scorpions, spiders and ticks (yuck).
There are several different varieties of spider mites that come in reds, blacks and greens. However, the most common is the two-spotted spider mite (Tetranychus urticae Koch). They have one dark spot on either side of their bodies, giving this mite its nickname.
Contrary to popular belief, the bodies of two-spotted spider mites are usually very light greenish-yellow, appearing almost translucent. Orange-red coloured bodies are less common.
However, you’d struggle to identify the exact type without using a microscope, as spider mites are only about 1/50 inch long (smaller than a grain of sand).
Why are spider mites harmful to plants?
Unlike soil mites, spider mites are extremely harmful to your plant. They appear on the undersides of leaves, using sharp mouthparts to pierce and draw out plant sap. This causes injury to the plant’s cell walls and tissues, resulting in the “dotted” appearance of the leaves called stippling.
Some types of spider mites also attack fruit in the same way, causing stippling on the damaged parts. As more plant tissues are damaged, the spots enlarge and merge; leaves fade in colour, curl, and eventually die.
They also use the surfaces of leaves to lay eggs and spin webs to protect the eggs.
When do spider mites attack?
Spider mites are particularly active in dry and hot summer months and are attracted to dehydrated and stressed plants. Tetranychus urticae Koch is known to attack over 200 plant species, including:
- Ornamental plants: evergreens, roses, azalea, citrus, hollies
- Trees including maple, elm, redbud
- Fruit crops: blackberries, strawberries, blueberries
- Vegetables: tomatoes, eggplant, cucumber
Spider mites are also attracted to over-fertilised plants. This is because excess nitrogen (found in fertilisers) isn’t used to help the plant grow; instead causes plant sap to become sweeter. Sweet sap is more attractive to spider mites.
Spider mite reproduction
Unfortunately for gardeners, spider mites reproduce aggressively and rapidly. So it is essential to act swiftly to get of these pests!
A female spider mite will start laying up to three hundred eggs over two weeks at just five days old. Once hatched, it only takes a few days for the eggs to mature into adults, ready for the whole cycle to start again.
How to identify a spider mite infestation
Here are some signs that you have a spider mite attack on your hands:
- There is webbing on and around the underside of leaves and along stems. This is a tell-tale sign as all spider mites uniquely spin fine silk webbing to protect their eggs, and what gives these mites their name!
- There are small yellow, brown or white specks on the leaves, and the leaves are also faded or greyish.
- If you tap on the stem while placing a white sheet of paper underneath, you can see mites falling off the leaves and moving around.
How to get rid of spider mites on plants
The good news is that if the infestation is confined to a few leaves, your plant is likely able to recover from spider mite attacks if you act quickly.
You may read of several different natural home remedies or pesticides that get rid of spider mites. A home solution of or store-bought neem oil spray can be effective for less severe cases, as the layer of oil smothers mite eggs and breathing holes. However, if you have a widespread infection on hand we prefer to go straight for the most effective option: Insecticidal Soap spray.
According to the University of Florida, insecticidal soaps are “effective against mites and the least toxic to people, other non-target organisms and the environment”, and “the effectiveness of laundry soaps, washing detergents, and vegetable oils is less consistent”.
Common pesticides are often ineffective against spider mites and may kill off beneficial insects. Use only insecticide soap sprays that specifically call out their efficacy for killing spider mites. Our favourite is this one.
We also do not recommend using natural predators like ladybugs to kill off spider mites, as this takes time. And we’ve learnt that quick reproduction means we don’t have time to waste!
How to use Insecticidal Soap Spray
- Using clean garden shears, remove all dead and heavily infested leaves.
- Shake the insecticidal soap spray before use. Liberally spray on all parts of your plant, ensuring you cover each leaf and stem until wet.
- Repeat the treatment every 4-7 days, depending on the type of plant. The Bonide instructions sheet will list the types of plants and appropriate treatment frequency for each type.
It’s also important to note that spider mites can disperse through the wind. Webbing can be caught in the wind and disperse these pests far and wide.
For this reason, you must dispose of any infested leaves carefully to avoid contaminating other areas of your garden or home. Do not use infected dead leaves as compost!!
How to prevent spider mites from harming your plants
The best prevention for spider mites is to ensure your plants are healthy. Use our plant guides for advice on keeping your plants thriving in your home or garden.
Spider mites, in particular, target dehydrated plants, so ensuring your plants are sufficiently watered is one way to prevent these pests from attacking. Regularly misting your plants or using a humidifier is also a way to deter these pests.
Recall that spider mites are especially attracted to over fertilised plants. Follow our plant guides to ensure you are not inadvertently setting your plant up to be attacked!
Another way to prevent spider mites is to incorporate neem oil as part of routine plant maintenance. This article show you how to use neem oil as a preventative measure.
FAQ: What are the first signs of spider mites?
The first signs are small dots or specks on the leaves, called stippling. Over time, the foliage will lack vibrancy and fade.
FAQ: Will spraying water on the plant dislodge and kill spider mites?
Spraying water will help wash away any spider mites, but this is a temporary solution. Given its aggressive reproduction, chances are that a large number of tiny eggs and larvae are sitting on your infected plant, and it is challenging for all of these to be eradicated using water. Your spider mites will likely reappear as you have not tackled the underlying problem.
FAQ: What are the main ways to control spider mites?
There are three main ways to get rid of spider mites: biological, physical and chemical.
- Biological. Introducing spider mites’ natural predators such as ladybugs or predatory mites to reduce the spider mite population. The downside of this is that this usually takes a while to work.
- Physical: Using water to spray, dislodge and wash away spider mites. This is a way to remove some spider mites, but given its small size and presence of hundreds of eggs, it is not as effective as chemical controls. Another example of Physical control is pruning off infected leaves. This is best in the very early stages of spider mite infestations.
- Chemical: Using chemicals to deter or kill off spider mites. Neem oil is an example of this, as is insecticidal soap spray.
FAQ: Do spider mites live on humans?
No, they do not. Spider mites need plant material to eat and thrive. They cannot live far from their food source.
Deborah is a plant enthusiast and founder of Gardening Collective.