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A spider mite infestation can rapidly get out of hand, causing significant damage to your plants. It can even end up killing your plant, so it’s important to take action as soon as possible!
Spider mites are tiny arachnids. They are one of the groups of mites that feed off plants. Spider mites varies in both size and color depending on what species it is and environmental factors, seasons, and the host plant. Their size are ranging from microscopical, barely visible to the naked eye, up to just around 1 mm big. Colors can be light green, yellow, white, red, brown, black and even patterned.
One of the most common species are the two spotted spider mite, Tetranychus urticae. As the name makes pretty clear, it has 2 spots, sometimes 4, on its otherwise light colored body. But it can also turn orange to orange-red. Especially females during their dormancy period.
Spider mites feed on the sap of the plant. They use their mouth parts and suck out the sap from each one the cells they're feeding from. Leaving tiny necrotic spots. Eventually the leaf looks pale and mottled due to the increasing amount of dead cells.
SYMPTOMS & IDENTIFICATION
Some of the first signs of spider mites are:
Dust-like particles on the leaves
Tiny specks moving around on the plant
Mottled/stippled-bleached discoloration of the leaves
Curled edges of the leaves
Spider mites will also create fine strands of webbing. Mostly found at the edges of the leaves, on the undersides, in crevices of the plant and on new growth. In severe cases the webbing can cover the entire plant. Especially visible when misting a plant with water.
Note that the webbing is often confused with spider webs, dust or mold. The webs spun by spider mites are small, cling close to the plant, is dense and only found on the plant.
If you notice a lot off debris on your plant or you see discoloration but are unsure if there are any spider mites that's causing it, you can either use a magnifying glass to be able to look closer or you can take a sheet of plain paper and try to dust/scrape of the debris from the leaves onto the paper. It will be easier to see if the debris are moving around on the paper.
1. Isolate the infected plant
Spider mites feed on many different types of plants and spread easily so keep infected plants away from others
2. Prune off severely damaged parts of the plant
Damaged parts of the plant won't recover. If it's possible you should consider pruning off severely damaged parts of the plant. This will also result in having less of the plant to treat or places spider mites might hide.
3. Shower the plant with cold water
Spider mites dislike cold temperatures so try using cold water
The force of the water should be enough to dislodge most of the mites from the plant
4. Use a suitable pest control method - Note that some plants, especially their flowers, can react badly to pesticides or soaps so test it on a smaller area of the plant first and treat your plant carefully. Always avoid direct sunlight after application as it can burn the plant.
Insecticidal soap, neem oil or chemical pesticides are effective against spider mites and will help prevent future infestations
5. Keep treating your plants
Repeat the treating your plant with the pesticide, soap, or solution of your choice, about once a week for the upcoming 4-6 weeks. Then repeat it about once a month for a couple of months. After that you can repeat the treatment only if necessary.
Continue to remove any visible mites on your plant between the treatments to speed up the process. You can shower the plant with a jet of water or using masking tape or a lint roller.
6. Increase the humidity around the plant
You can do this by misting your plant often or placing a humidifier close by
Spider mites prefer dry conditions, so this will help make the environment less hospitable for them, as well as keeping your plants free of dust (which they also like!)
7. Consider using biological control
Spider mites can be controlled biologically by introducing natural predators such as different types of predatory mites, Phytoseiulus persimilis for example. Biological control is very effective when used in combination with the other treatments.
Note that these beneficial insects will also be harmed by pesticides used on the plant. Add them when you're done with the repeated initial weekly treatments or you think the mties are mostly gone on the plant.
HOW CAN I PREVENT THIS IN THE FUTURE?
Examine your plants regularly for early signs of an ongoing spider mite infestation. This is especially important during hot and/or dry conditions. Stressed plants are extra vulnerable to Spider mites. Avoid sensitive plants to be exposed to excessive drought. If you bring plants back in during colder periods in can be wise to clean them up and keep them quarantined.
QUESTIONS ABOUT SPIDER MITES
WHICH PLANTS ARE MORE LIKELY TO BE INFESTED WITH SPIDER MITES? Spider mites can spread and infest most plants in your collection. Some plants are however more prone to get infested than others. Calatheas, Alocasias, Hydrangeas, Ficuses and Palm trees are example of plants that's often reported with being infested with mites. Plants being overwintered, such as Citruses, are also often infested and needs to be regularly examined.
WHAT DO THEY LOOK LIKE? Spider mites are tiny oval-shaped arachnids that varies in both color and size. But they are barely visible to the naked eye.
HOW CAN I SPOT IF THEY HAVE DAMAGED MY PLANT? Spider mites are sap-sucking pests. As a result of this, your plant’s leaves will be dotted with feeding marks, which show up as little light-coloured dots (stippling). If the infestation and damage is severe enough the leaves will start to look pale and then turn yellow and eventually fall off. The plant may stop growing altogether.
CAN THEY FLY? No, luckily not! Spider mites do not have wings. However, they are ‘wind surfers’, meaning that they can be carried by the breeze on their webs. Therefore, it’s important to carefully dispose of any infected material and remove all webbing to avoid the spread of mites to other plants. Put any infected plant parts in the trash - don’t try to compost them.
HOW LONG DO THEY LIVE? When conditions are ideal for spider mites (i.e. warm and dry), eggs are laid almost continuously. It’s necessary to apply multiple treatments to be sure you get them all. Otherwise, you risk only removing the adults and not eliminating future generations. There are many different types of spider mites, so the length of their life cycle can vary greatly: anything from just 5 days to a month. However, the treatment for each type is the same, so it’s not necessary to try to identify the exact type of spider mite on your plant.
DO ALL MITES PRODUCE WEBS? All spider mites produce webs on their host plant. But there are other groups of mites that doesn't produce any webs. They aren't as common as spider mites on house plants, but all types of mites respond well to the same treatment.