Going up against an almost invisible enemy is not just fan fiction but a reality with spider mites during the cold months. Often they remain undetected for a long time. If you discover the first signs, usually a tiny colony has already grown up – ready to conquer the apartment.
Against the tiny red spiders, you can arm yourself with biological means, home remedies but also chemical pesticides. In this article, you will find out what these are, how you can recognize spider mites, and how you can prevent them!
Recognize spider mites
Unlike what is often assumed, spider mites are not insects. The pests belong to the arachnids (Tetranychidae). Thus, they are closely related to ticks and spiders. That can be recognized, among other things, by their eight legs.
However, depending on the stage of development, they can also have only six legs.
The exact identification of spider mites is not always easy. Also, recognition is challenging for some species.
Depending on species and developmental stage, spider mites are between 0.1 mm and 0.8 mm in size. The spider mite colour also varies depending on the season, host plant, and species.
In total, there are over 1,200 known species of spider mites. But don’t worry. Most pose no threat to your houseplants. In the next paragraph, I’ll introduce you to the six most crucial spider mite species.
Portrait of the essential spider mite species
Common spider mite (Tetranychus urticae)
The common spider mite, up to 0.6 mm long, is probably the most widespread, and it is found all over the globe.
Depending on the stage, it is transparent or light to brown-green. Over the winter, females turn bright red to orange. Both females and males retain their red eyes throughout their life cycle.
Another distinctive feature is the two dark spots on the mite’s back. Because of this feature, the mite is also known as the two-spotted mite.
Greenhouse spider mite (Brevipalpus obovatus)
With a size of 0.4 mm in length, the greenhouse spider mite is slightly smaller than the common spider mite. It is more ovoid, and its scarlet colour makes it easy to spot on plants, even without tools.
It prefers a warmer environment and is often found in greenhouses. The greenhouse control method, which I will present later, does not work well on this species.
Cactus spider mite (Brevipalpus russulus)
Cacti, as well as succulents, are the preferred target of the cactus spider mite. Infestation is more challenging to detect because it does not spin webs.
Depending on their sex, the pests are between 0.2 mm and 0.6 mm in size. Mature specimens can be detected with the naked eye.
Coniferous spider mite (Oligonychus ununguis)
The coniferous spider mite is only 0.1 mm to 0.4 mm in size and is greenish to brownish. Thus, it isn’t easy to detect on plants by colour and size.
It mainly attacks conifers. In the home, therefore, they are found if only on houseplants such as the indoor fir. Sporadically they can also nest in Christmas trees.
Fruit tree spider mite (Panonychus ulmi)
Better known as the “red spider”, the fruit tree spider mite prefers to infest fruit trees and berry plants. Occasionally, however, they can also be found on houseplants. Infestation is relatively inconspicuous, as only a few webs are produced.
It is recognizable by its conspicuous red colour and white bristles. With a length of 0.5 mm, it is one of the somewhat larger specimens.
Orchid spider mite (Tenuipalpus pacificus)
The orchid spider mite is probably the most challenging spider mite to recognize. It is just 0.1 mm long and does not form webs. Due to the lack of nets, it is classified as a “false spider mite”.
As its name suggests, it mainly attacks orchids. However, citrus and other houseplants can also fall victim to infestation.
The pattern of damage and general signs
The most common sign of a spider mite infestation is web-like formations on the leaves and in the leaf axils. Depending on the type and extent of the infestation, these are visible and cover large parts of the houseplant.
Infested leaves initially show small yellow dots. As these ages, they turn brown. The lack of chlorophyll causes the colouration.
If the infestation is not treated, the leaves turn yellow. A limp and grayish appearance may also be signs. Affected leaves feel dry and sandy.
After they turn yellow, they wilt until they turn brown and fall off.
If the spider mites can reproduce unhindered, the host plant is almost guaranteed to die in the foreseeable future.
Finding spider mites on the plant
Most spider mite species prefer to infest young shoots and mainly sit around young shoots. In addition to shoots, they also find shelter from predators and environmental effects on the undersides of the leaves.
There and in leaf axils, you can also find a large part of their net-like structures.
In addition to the locations described, spider mites can also be found in shaded and hard-to-reach areas of the plant.
Conditions that spider mites love
Just like your houseplants, spider mites have preferred living conditions and habitats. The pests thrive in warm and dry air. Under suitable conditions, a generation can be sexually mature in as little as a week.
High humidity of about 75 % causes problems for many species and can help to contain an infestation.
Due to the dry heating air in winter, spider mite infestations frequently occur, especially during the cold season.
Here you can find different methods to increase the humidity.
The life cycle of a spider mite
The life of a spider mite begins with an egg. The eggs are located on the underside of the leaf. They are yellow to red and have a round to onion shape. After a few days, the first larvae hatch.
After hatching, the six-legged larvae are still transparent. But they have the typical red eyes of the adult spider mite. Depending on the host plant, the colour of the larva changes as it feeds. Colours in different shades of yellow, brown, and green are possible.
Next comes two resting phases (protochrysalis) and moulting (protonymph). After the first moult, the larva is called a deutonymph, and after the second moult, it is called an adult.
Spider mites live between 21 and 35 days, and females are sexually mature after about two weeks. In their lifetime, they lay up to 125 eggs.
Adults conquer new host plants either on foot or by having a piece of spun thread blown by the wind to a new location. That allows them to cover great distances quickly.
Here is a video showing the life cycle of a spider mite:
Controlling spider mites
Before we get into what methods are available to you for controlling spider mites, here are a few essential tips. They will help prevent pests and contain any spread.
- Isolate infested plants
Spider mites are incredibly good at quickly gaining soil, or in this case, plants. Therefore, you should isolate the infested plant if possible. This way, you prevent the spider mites from invading other plants. - Check nearby plants for infestation
As mentioned, spider mites spread to other plants quite quickly. Therefore, be sure to check your other plants as well. It is quite possible that you will not control the core of the infestation or that spider mites will attack other plants during the control. - Rinse the plant
Rinsing the affected plant with a hard spray can remove most spider mites. That will save you time controlling the spider mites and may even save on pesticides. - Remove shoots
If the size of your plant allows it, you can also remove affected shoots if the infestation is severe. That way, you can be sure to have directly removed a part of the spider mites and their eggs. Although this may seem a hindrance initially, it can pay off in the long run. - Reduce ambient temperature
Spider mites reproduce particularly well at higher temperatures. The reproduction slows considerably if you reduce the ambient temperature to 15 °C (59 °F). However, make sure your plant is suitable for these temperatures. - Create a greenhouse climate
The opposite can also work. Create a greenhouse climate around your plant using a clear bag. Many spider mites will perish due to the high humidity and temperature, and the reproduction rate will decrease due to poor conditions.
Home remedies for spider mites
In addition to pesticides and beneficial insects, you can use a wide variety of home remedies. The choice of these remedies can be overwhelming at first. Therefore, I have compiled the most effective home remedies in my experience.
An exception is tobacco decoction and cigarette ash. You should not use these under any circumstances. You’ll find out in a moment why you’ll most likely kill your houseplant if you use them.
Alcohol soap suds
Alcohol soap suds are easy to make and suitable for small to medium infestations. Simply mix the following ingredients:
- No products found.
- 1.77 Fl Oz (50 ml) soft soap*
- 1.67 liq.gal (1 l) water
Spray the whole plant dripping wet with the lye weekly. However, before you apply the home remedy to the entire plant, you should test its compatibility on one leaf.
Oils
Water-rapeseed oil mixture
Canola oil has proven to be effective in pest control in the past. Canola oil is extracted from the rapeseed plant. Pure, however, it is too strong for many plants because it can close the pores.
To make 1.67 liq.gal (1 l) of the mixture, mix 4.37 Fl Oz (125 ml) canola oil with 31.22 Fl Oz (875 ml) of water. Mix the two ingredients until a cloudy mixture is formed.
Apply the mixture to a leaf first as a test to check compatibility. This home remedy for spider mites is unsuitable for some plants, such as orchids.
Neem oil
Neem oil is a popular home remedy that is often used as a preventative. However, use it only in diluted form. You can also buy pre-mixed No products found..
Spray the oil weekly on the plant. Be sure to spray hard-to-reach areas, such as the undersides of leaves.
Tea tree oil
Tea tree oil is an excellent alternative to neem oil. However, it must be dosed much lower. Just 0.4 teaspoon (2 ml) of tea tree oil* is added to 1.67 liq.gal (1 l) water. Larger quantities can harm the plant.
Tea tree oil is also applied every one to two weeks until the infestation is repelled.
Tea and decoction
Onion decoction
An onion decoction is quick to make and works great against spider mites. Simply steep a handful of onion skins in hot water for an hour. Then filter the decoction and mix 3.5 Fl Oz (100 ml) of decoction with 1.67 liq.gal (1 l) of water.
You can then apply this mixture to the affected plant. The easiest way to do this is to use a spray bottle.
Field horsetail tea
To prepare the tea, pour 3.65 ounces (100 g) of crushed field horsetail with 1.67 liq.gal (1 l) water of hot water. After one hour, you can filter the tea. Use the cold tea in a ratio of 1:20 with water.
Apply it weekly to the infested plant using a spray bottle.
Tobacco Brew & Cigarette Ash
Again and again, I hear or read about tobacco decoction or pest control with the help of cigarette ash. These home remedies work because they contain the nerve poison nicotine, which kills pests reliably.
What is rarely talked about, however, is that the plant also absorbs the nicotine. Here it has the same effect as on the pests.
Some plants can resist the nerve agent and survive the treatment. However, many plants suffer more damage than from pests.
Also, I can imagine that the smell of cold cigarettes in the apartment is not very pleasing for many. Therefore, I advise you not to use the home remedies tobacco decoction and cigarette ash.
Pesticides against spider mites
If you’re more skeptical about home remedies and don’t want beneficial insects in your home, you can use pesticides. Again, there are several options you can choose from:
Plant sprays
No products found. are ready-mixed pest control products. They are usually sold already in a spray bottle. So you don’t have to prepare anything and can use the product directly.
Usually, the sprays are effective against a selection of pests.
Mixing agents
Mixing agents come in concentrated form. Before use, they are measured out and usually mixed in water. The mixture is then used either for watering or spraying the leaves.
A mixing agent makes sense if you want to have control over the amount you need yourself. You can make different amounts of pesticide, large or small, as you like.
Sticks and granules
Pest control without sprays is also possible. You can control spider mites with sticks in the soil and pest granules placed on top of the potting mix. Both release the protective agent in the root ball when you water your plant. There it is absorbed by the roots and distributed throughout the plant.
If a pest sucks sap from the houseplant, it absorbs the pesticide contained in the plant and dies.
This method of spider mite control is especially suitable for people who do not want to have unpleasant odours in the apartment or have concerns about using sprays. Since many of the offered sticks also contain fertilizer, they can strengthen the plant.
Keep in mind that it takes some time for agents to be absorbed via roots and spread throughout the plant.
Pest sprays
Many pest sprays are not explicitly intended for use on plants. However, many collectors and plant lovers consider vermin spray a secret weapon. I also learned about them only after a few years of keeping houseplants.
Since then, I always have had some on hand if an infestation occurs.
My tip is the pest spray from ARDAP. It is one of the few pest sprays used commercially and in households. But only use it in small doses because it can damage the leaves if you use too much.
Beneficial insects against spider mites
Beneficial insects are probably the most sustainable form of pest control. Here, Spider mites can develop resistance more improbably. Most of the beneficial insects described here can also be found in our garden.
Therefore, you can put your infested plant outside if the weather permits. With a bit of luck, the beneficial insects will find their way to your houseplant on their own.
Ladybugs against spider mites
The black ball ladybug (Coccinellidae) and its larvae specialize in spider mites. They can be purchased and used even in small quantities.
Gall midges against spider mites
The predatory gall midge (Feltiella acarisuga) is mainly used for spider mite control. It is most effective against the common spider mite and the fruit tree spider mite. It does not matter in which stage of development the spider mites are.
One gall midge can kill up to 30 spider mites daily.
Try to keep the temperature between 19 °C and 26 °C (66 °F-79 °F) during the application period. Humidity above 60 % is beneficial but not essential.
Don’t worry if you don’t see the gall midges in their stakes. They are only 5/64th inch (2 mm) in size and mostly travel at night.
It is often recommended to control spider mites in parallel with predatory mites.
Predatory mites against spider mites
With predatory mites, you usually have the choice between PP mites (Phytoseiulus persimilis) and AC mites (Amblyseiulus californicus). Both have the same condition for practical application.
Try to keep the temperature at about 25 °C (77 °F). At the same time, the humidity should be around 75 %.
If no spider mites are left, the blind predatory mites will die.
Lacewing larvae against spider mites
Lacewing larvae can also be used to some extent against spider mites. However, they are suitable only for the early stage of development. Beyond that, they lose their effect.
Beneficial insects against spider mites – an overview
| Name | Bot. Name | Temperature | Humidity | Effectiveness |
|---|---|---|---|---|
| AC predatory mite | Amblyseiulus californicus | 23 °C-29 °C (73 °F-84 °F) | ~ 75 % | All stages |
| PP predatory mite | Phytoseiulus persimilis | 18 °C-29 °C (64 °F-84 °F) | ~ 75 % | All stages |
| Gall midge | Feltiella acarisuga | 19 °C-26 °C (66 °F-79 °F) | 60 % | All stages |
| Ladybug | Coccinellidae | min. 15 °C (59 °F) | 60 % | All stages |
| Common green lacewing | Chrysopa carnea | min. 12 °C (54 °F) | 35 % | Early stages |
Preventing spider mites
To avoid an infestation in the first place, you can already prevent an infestation. Here you will find various measures and tips that can prevent an infestation. Many can be combined into a care routine.
- Quarantine new arrivals
- Whenever you bring a new houseplant into your home, you should not place it near other plants at first. Even if it looked pest-free in the store, there might still be pests on it. If no infestation is visible after two weeks, you can move the plant to its final location.
- Regular dusting
Regular dusting or wiping off the leaves not only supports photosynthesis. In addition to dust, it also removes potential spider mites. A good routine is to wipe the leaves every two weeks with a damp cloth. - Regular pest control
You can discover many things if you keep a regular eye on your plants. You’ll notice how well or poorly they’re growing, get an indication of their health, and spot problems like pests or root rot early. This inspection can easily be combined with leaf dusting. - Use neem oil
Neem oil doesn’t have to be used after you discover an infestation. You can also apply it to the leaves beforehand. This will reduce the likelihood of pests settling on your houseplant. Try to find a rhythm of two to three weeks. - Increase the humidity
Spider mites love low humidity. Especially during the cold season, the humidity in your home is literally in the basement. Therefore, spider mites often appear during this time. So, try to increase the humidity. Many tropical houseplants also benefit from this.
What to do in case of recurring spider mite infestations?
If spider mites keep returning, the leading cause of their occurrence has not been addressed.
The following causes are often overlooked:
- Nutrient deficiencies weaken plants
- Wrong locations weaken plants
- Humidity is too low
- You overlooked infestation on another plant
- You did not fully treat the previous infestation (treatment ended too early)
Commonly infested houseplants
Spider mites also have their preferences. Thus, they prefer to infest some plants than others. The red spider most frequently plagues the following houseplants:
- Banana plant
- Bird of paradise
- Cyprus grass
- Finger aralia
- Philodendron melanochrysum
- Philodendron verrucosum
- Rubber trees
- Various palms
Conclusion
To control spider mites, you have a wide variety of options to choose from. Whether rapeseed oil, pest spray, or predatory mites – you can use many means against the pests. Dare to try new standards!
I wish you much success in fighting spider mites and other pests! If you have questions or suggestions, I am available in the comments!
More pests
- Aphids
- Fungus gnats (Sciarid flies)
- Leaf lice (Nematodes)
- Leaf miner
- Lily chicken
- Mealybugs
- Root mites
- Scale insects
- Spider mites
- Thick-mouthed weevil
- Thrips (Thunderbug)
- Whiteflies
Let me answer your questions!
How do spider mites get to houseplants?
Some species of spider mites travel great distances by being carried by a piece of thread and the wind. That is how they can enter the home during the airing. But we can also act as carriers.
Don’t miss!
Sources
(2021, July 5). Spinnmilben. Wikipedia. Retrieved February 11, 2022, from https://de.wikipedia.org/wiki/Spinnmilben
(2022, September 18). Gemeine Spinnmilbe. Wikipedia. Retrieved February 11, 2022, from https://de.wikipedia.org/wiki/Gemeine_Spinnmilbe
(2022, August 3). Spider mite. Wikipedia. Retrieved February 11, 2022, from https://en.wikipedia.org/wiki/Spider_mite
(n.d.). Managing Spider Mites on Houseplants. University of Minnesota Extension. Retrieved February 11, 2022, from https://extension.umn.edu/news/managing-spider-mites-houseplants
(n.d.). Brevipalpus russulus (Boisduval, 1867). GBIF | Global Biodiversity Information Facility. Retrieved February 11, 2022, from https://www.gbif.org/species/2131035
(n.d.). Brevipalpus obovatus (scarlet tea mite). CABI Invasive Species Compendium. Retrieved February 11, 2022, from https://www.gbif.org/species/2131035
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