red spider mites
Oh scary! You were just about to devote yourself to your indoor plants and suddenly discover fine webs on the leaves and leaf axes: spider mites. The annoying pests of the Tetranychidae family are primarily a nuisance during the winter and can lead to the death of the plants within a short period of time. In order to remove the mites, not only home remedies but also measures to prevent an infestation are extremely important. The good thing: an infestation by spider mites can be effectively combated.
Recognize
Before taking any remedy or action, you must be sure that it really is a spider mite infestation. Due to their way of life, the insects are not difficult to distinguish from other pests such as scale insects or weeping flies. The time is particularly important, because the animals attack indoor plants from late autumn to spring. Especially in the height of winter, when there is dry heating air, the parasites feel comfortable. The following points will help you analyze whether the infestation is spider mite:
- "Cobwebs" under leaves and between leaf axils
- light spots on the upper side of the leaf
- plant weakens increasingly; stunted growth
- webs on the upper side of the leaves in the case of severe infestation
- Leaves turn light to dull green
- leaves dry up
- Plant parts die off
- - prone to disease
An infestation by spider mites is usually only noticed once they have populated the plant. They reach a maximum size of 0.8 millimeters, which is difficult to see with the naked eye. The eggs, of which the females lay up to 100 pieces, are only 0.1 millimeters in size and, despite their light green color, can only be recognized through the webs. Note that other taxa besides the common spider mite (Tetranychus urticae) do not form webs. Especially the orchid spider mite (Brevipalpus californicus), which likes to attack orchids (bot. Orchidaceae) and citrus plants (bot. Citrus). Other plants that are particularly susceptible to mites:
- Ornamental ivy (bot. Hedera helix)
- Fuchsias (bot. Fuchsia)
- Cyprus grasses (bot. Cyperus)
- Rubber tree (bot. Ficus elastica)
- Room azalea (bot. Rhododendron simsii)
- Finger Aralia (bot. Schefflera)
- Flowering Maple (bot. Abutilon)
- numerous palm species
However, the infestation of these plants can be prevented.
tip: The insects also attack plants over the summer, but these are mostly plants that have been planted outdoors.
Prevent
Believe it or not, spider mites on houseplants are easy to prevent with the right preparation. Since the animals need a very specific habitat, you must ensure that this does not arise. Your houseplants are a found food if the location, especially the winter quarters, is as follows:
- Temperature 22°C - 28°C
- low humidity
- high sun exposure
The insects like it warm and dry, which is a typical problem over the winter. For this reason, indoor plants in Central Europe are attacked over the winter, since the dry heating air and mostly high "feel-good temperatures" offer the perfect conditions for a suitable breeding ground. The insects, on the other hand, do not tolerate the weather, moisture and cool temperatures at all. Already at 16 °C they stop moving and don't even reproduce anymore.
The following points will help you keep Tetranychidae away from your crops:
humidity
Make sure that you do not keep the humidity too low, especially in winter. The dry air suits the animals extremely well and they continue to multiply rapidly. To keep the humidity at an appropriate level, there are three different methods:
- spray bottle
- wide coasters filled with water
- humidifier
The spray bottle is particularly useful for individual plants or those that do not tolerate waterlogging. With this you spray either the plant or the immediate surroundings regularly. If you opt for wide coasters, they should always be filled with a little water. This evaporates and ensures good humidity. With a humidifier, you can regulate the humidity level down to the percent. This is a good method for you if you don't have much time to spray or change coasters.
temperature
If possible, place the plants in a spot where the temperature is below 22°C. Of course, this is not possible for many plants, for example tropical plants. Nevertheless, the temperature drop in winter works well against the pests, especially below 16 °C.
maintenance
Take care of the plant as much as possible. If the specimens move weakly to their winter quarters, they are at the mercy of spider mites and are therefore the ideal buffet.
Strengthen
If you keep sensitive plants in your living space, it is recommended to use them with plant extracts to strengthen. A good protection against Tetranychidae are extracts based on field horsetail (bot. Equisetum arvense), as these strengthen the leaf tissue and are thus armed against the bites of insects. You create this in the following way:
- 1 liter of water
- 150 g fresh or 15 g dried field horsetail
- 1 head of garlic
- 1 onion (large)
- Splash of rapeseed oil
- Chop garlic and onions
- put all the ingredients in the water
- Boil for 15 minutes
- let cool down
- pour off
- fill in spray bottle
- use from spring to early fall
- administer weekly
If your plants are already infested, you can easily use this brew to kill the animals. To do this, wipe the plant thoroughly with the broth over a period of one week until the insects have disappeared.
Preventing the pests does not require much work and saves you from a nasty surprise. The houseplants can easily overwinter in this winter quarters without being chosen as a food source by the Tetranychidae. Of course, this is the case all year round, but spider mites that sting houseplants are mainly found in winter.
Spider mites close-up
Fight
To remove spider mites, there are numerous measures that you can use effectively and promise great success. As described above, it is particularly important to make the location of the plant uninhabitable for the animals. It's not just home remedies that are available. However, these are necessary in the case of a severe infestation, when clear water is no longer sufficient. In any case, after using these methods and home remedies, you should remove infested parts of the plant with a clean, sharp knife or scissors. This will help you maintain the vitality of the plant.
tip: Many people use cigarette ash to combat spider mites because the nicotine it contains blocks the animals' airways. However, nicotine is harmful to many indoor plants, which should therefore be avoided.
take a shower
Douching the plant is a good way to control the insects when it's still an early stage. The fewer mites have populated the houseplant, the more effective this measure is. All you need is a waterproof plastic bag for this, as this will protect the substrate from flooding. Pack the planter's tub or pot and make sure it is tightly closed. Now carefully rinse the plant with the shower head. You can repeat this step multiple times to shower off more spider mites. Above all, take your time with the undersides of the leaves and the stems of the shoots.
Temporarily increase humidity
This method basically works in the same way as showering, but afterwards creates a microclimate in which leftover mites cannot reproduce or feed on the plant. This method is particularly suitable for smaller plants, since suitable plastic bags can rarely be found for larger specimens. Proceed as follows:
- Rinse the plant gently
- the pot should not be covered
- Substrate must not be under water
- place whole plant in a clear plastic bag
- leave a gap open
Leave the plant in the bag for up to a week. The humidity in this increases so quickly that all spider mites are killed. In the meantime, the location of the plant should be adjusted so that the pests do not infest again.
Spider mite close-up
rapeseed oil
An effective home remedy for spider mites is the use of rapeseed oil. The oil clogs the mites' respiratory organs, causing them to suffocate and allowing them to be removed easily. Best of all, only two ingredients are required:
- 1 liter of water
- 250 ml canola oil
Mix these ingredients in a spray bottle and shake well. You now have an effective spray at hand that can be sprayed directly onto the affected areas twice a week in the case of a mild infestation. If the infestation is worse, you can apply the spray directly to the affected areas with a cloth. Be careful not to injure the plant. Since rapeseed oil does not have an aggressive effect on numerous plants, you can use it without any problems.
predatory mites
If home remedies don't help, you should rely on predatory mites. This is particularly suitable for conservatories or large rooms. These insects are natural predators of Tetranychidae, listed on maps under the name Phytoseiulus persimilis. In the event of a spider mite infestation, simply spread these over the plant and the predatory mites will get to work. A single predatory mite can consume up to 50 mites and more than 200 eggs. At the same time, they continue to multiply, which maintains the natural balance. Predatory mites are also not harmful to your indoor plants. Depending on the provider, you can get these for free or for ten to 15 euros.