An infestation of spider mites can cause major damage to both your garden and indoor plants.
That’s why it’s important to diagnose this problem early and deal with it immediately.
What are spider mites?
Spider mites (Tetranychus urticae) are tiny insect-like creatures that are very closely related to spiders. In fact, they belong to the same family (Arachnida).
These common pests suck the sap out of soft plant tissue.
They also create tiny silk-like webs on the underside of leaves. They use these to help themselves move around the plant.
Once they infect your plants, they can multiply rapidly. Each female mite can lay around 10 to 20 eggs per day.
It takes around 3 to 15 days for the eggs to hatch.
The tiny larvae have six legs and are colourless except for their bright red eyes.
What do spider mites look like?
Spider mites are tiny and red. They have eight legs as nymphs and adults but the newly hatched larvae only have six legs.
These tiny pests are difficult to see with the naked eye and you need a magnifying glass to see them clearly.
Early signs of spider mites
The first signs that you’ll see are small, necrotic spots on the leaves.
These will be most visible around the veins and the midrib of the leaf.
If you turn the leaf over and look at the underside, you’ll notice small white silk webs.
Amongst these webs, you’ll be able to see the tiny red mites.
As the mites continue to feast on your plant, the necrotic spots will merge with others until the whole leaf is damaged.
Eventually, the leaves will turn yellow and fall off the plant.
How to get rid of spider mites
Once you spot the tiny mites, it’s important to remove the infected leaves and throw them in the trash. This will help to break the breeding cycle.
Then, you’ll need to spray the entire plant with a mixture of isopropyl alcohol and soap.
The soap will help the mixture to adhere to the plant and the alcohol will kill the mites.
You can also spray your plants with wettable sulphur which is an organic insecticide. This treatment needs to be repeated a few times a week to get the infestation under control.
If your affected plants are outside, spider mites have a number of natural predators including ladybirds and lacewings.
There’s also a predatory mite (Persimilis) that has been produced and bred in Australia for more than 25 years.
This predatory mite is highly effective in reducing the spider mite population.
How to prevent a spider mite infestation
Spider mites thrive in warm to hot conditions that have low humidity.
Therefore, they’re not as big a problem in the northern parts of the country where the humidity is relatively high.
Here are a few ways that you can prevent a spider mite infestation:
- Increase the humidity around your plants. While this may not be possible for all of your plants, it’s an ideal solution for houseplants. By simply placing a few saucers of water around your plants, you can easily increase the humidity of the air. Or, you might want to consider getting a humidifier.
- If you have plants growing in a glasshouse or igloo, wet the ground around the plants periodically as this will help to increase the humidity.
- Keep your growing areas clean and remove any leaf litter from around plants that have had problems with spider mites.
What causes a spider mite infestation?
Primarily, spider mites thrive in warm to hot climates with low humidity.
Can plants recover from spider mites?
Yes, as long as not all the leaves have been infected, your plants will recover if you deal with the infestation as soon as you notice it.
Do spider mites live in soil?
Yes, spider mites can live in soils that are dry for a long period of time.