Spider mites are one of those annoying pests that every plant lover has to struggle with. They seem to appear out of nowhere and spread en masse within a short period of time. The desperation is great when the mites reappear after successful control.

Spider mites are fairly easy to spot by their spidery webs

Table of Contents

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  1. the essentials in brief
  2. Fight spider mites
  3. Fight spider mites - home remedies
  4. Chemicals
  5. Prevent
  6. Negative experiences
  7. Identify spider mites
  8. Commonly Affected Plants
  9. frequently asked Questions

    10. the essentials in brief

    • The first measure against spider mites is to shower off the affected leaves. Killing sprays from household products help to capture all pests. Chemical agents should only be used if the spread is widespread.
    • In order to prevent an infestation, the living conditions for spider mites should be designed unfavorably. In some cases, the pests keep coming back, so it is important to clarify the cause.
    • The most common species include the red spider and the fruit tree spider mite. There are almost 100 species in Germany that attack different ornamental and crop plants.

    What helps against spider mites

    Spider mites are annoying pests that appear again and again on some indoor plants or in the greenhouse. Especially with crops, it is important to combat the plant sap suckers naturally. Sprays leave residues that can get into the food. Houseplants should only be combated with drastic measures if they are severely infested.

    Rinsing the plants can be a good remedy for a light infestation

    First aid for spider mites:

    1. Rinse the plant thoroughly in the shower
    2. Remove eggs with a damp cloth
    3. put a transparent plastic bag over the plant
    4. Tie the bag over the soil
    5. Leave the plant like this for the next two weeks

    This method improves the microclimate between the leaves. The humidity rises sharply, so the spider mites die off over time. However, eggs that have already been laid can survive this procedure, so you need to check the plant for a relapse in the near future. Do not place the plant on a south-facing window sill, but choose a shady location. In the sun, the temperature under the plastic bag can increase significantly, damaging the leaves.

    Beneficial insects against spider mites

    Many beneficial insects can be used specifically to combat the sucking pests. Spider mites can be controlled biologically with these insects, which means that spraying can be almost completely dispensed with in orchards. In the greenhouse or on indoor plants, you can use predatory mites against spider mites if adjusting the temperature and humidity has not been successful.

    kind temperature humidity
    Phytoseiulus persimilis predatory mite 17 to 28 degrees Celsius at least 60 percent
    Amblyseius californicus predatory mite at least 23 degrees Celsius no less than 60 percent
    Feltiella acarisuga gall midge 20 to 26 degrees Celsius 60 percent is ideal

    take cutting action

    If perennials such as hemp or shrubs and woody plants are heavily infested with spider mites, pruning measures are recommended. With hemp, remove individual leaves to stop the pests from spreading further. If the oleander is infested with spider mites, a consistent pruning of the infested leaves helps. In the event of a severe infestation, the poplar fig can be cut back to the stump. It then drives out again.

    Get rid of spider mites with home remedies

    The list of home remedies for spider mites is long and ranges from milk to field horsetail broth to washing-up liquid and vinegar. There is no best way to get rid of the pests in one fell swoop. Each remedy has its advantages and disadvantages and sprays must be used over a longer period of time for lasting success.

    nicotine

    A tobacco decoction is a proven means of killing pests, since nicotine is a powerful neurotoxin. This is precisely why you should never use nicotine to combat pests. Parts of the toxin are absorbed by the plant and - if it is a cultivated plant - ends up on your table. In the 1970s, the use of nicotine to combat pests on plants in agriculture was banned.

    Broths, teas and manure

    You can follow a rule of thumb for the preparation of brews, teas and manure: for ten liters of water there are one kilogram of fresh or 200 grams of dried herbs. While liquid manure is prepared with cold water and ferments over several days, brews and teas are prepared with boiling water.

    Lukewarm water is suitable for broths, as the herbs steep for 24 hours. Before pouring, the batches are diluted with water in a ratio of 1:10. If you use the agent for spraying, a dilution of 1:20 to 1:50 is recommended.

    • tea for squirting: wormwood and tansy leaves, sprigs of lavender
    • Broth for pouring: Male Fern and Bracken
    • broth for pouring: onions and garlic

    canola oil and neem oil

    Neem oil and rapeseed oil are powerful helpers in the fight against spider mites

    Neem oil contains azadirachtin, which stops spider mites from laying eggs. Since the active ingredient is not selective and also damages useful insects, you should not use neem oil when using predatory mites. A watery solution with rapeseed oil is gentler. When sprayed on the leaves, it forms an oily film under which the spider mites are trapped. They can no longer breathe and die.

    soapy water

    A self-made remedy made from 15 milliliters of potash soap and spirit in one liter of water is ideal for spraying in the early stages when the infestation is not very advanced. Be sure to spray directly onto the colonies on the undersides of leaves. The measure must be repeated at intervals of four to five days. Dishwashing liquid is suitable to a limited extent, as it is usually not biodegradable.

    There are numerous home remedies for spider mites. The most effective are solutions with oil or soap.

    Chemicals against spider mites

    Before you reach for the chemical club, you should weigh the benefits against possible harm. In most cases, chemical control agents do more damage to the plants than they eliminate the spider mite case. They achieve the greatest possible success when most of the animals have already hatched from their winter eggs and this first generation of mites has not yet laid any summer eggs.

    Biological alternative to chemistry

    If the infestation is still limited, you can use sprays based on rapeseed oil with added pyrethrins. Such biological agents do not act selectively, but kill spider mites as well as beneficial insects. Since the first spray often does not capture all pests, the treatment must be repeated at regular intervals. Spray the undersides of the leaves liberally so that the pests come into direct contact with the poison.

    When are pesticides useful?

    Plants that generally need a location on the windowsill and cannot be cultivated on the balcony or terrace should be treated with a pesticide if they are infested with spider mites. This also applies to a stubborn pest infestation or very extensive populations. The funds are often used against spider mites on orchids. Even the undemanding cactus or the warmth-loving palm tree can be freed from spider mites with sprays.

    Acaricides are preferably used against spider mites. They are effective against various arachnids and may only be used on ornamental plants. They contain around 15 different active ingredients, some of which are based on sulfur and tin compounds.

    Worth knowing and hints:

    • some acaricides are also effective against biting insects and house dust mites
    • not harmful to wild bees, butterflies and bumblebees
    • Optimal effect when sprayed directly on spider mite colonies

    Prevent an infestation

    If you transport potted plants to their winter quarters in autumn, you should meticulously check the undersides of the leaves for spider mite infestation. If the leaves are already colonized, the pests can multiply rapidly over the next few weeks. To prevent this from happening, you should make the living conditions for the mites suboptimal.

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    Constant spider mites: find out the cause

    The arachnids need warm and dry weather to develop. Wet conditions and cool temperatures severely limit populations. The pests find ideal conditions at temperatures around 30 degrees Celsius and dry air. Under these conditions, the development time of the mites is greatly reduced, so that they can develop large populations within a very short time.

    Indoor plants are often attacked by spider mites in winter when they are on the window sill directly above the heater. Even weakened plants are good food for the pests, because the plant tissue is particularly easy to pierce and suck out.

    What to do to permanently get rid of spider mites?

    If you want to get rid of spider mites permanently, you need to identify and eliminate the causes of the infestation. If your indoor plants on the windowsill are infested in winter, changing the location can help. If the air in the room is very dry overall, you should place a bowl of water on the heater. You can also dampen a towel and place it over the radiator.

    No spider mites in the greenhouse

    A natural measure against spider mites in the greenhouse is the right mix of plants. Monocultures are generally more susceptible to pests than mixed cultures. They can multiply faster in a one-sided plant stand. Mix vegetables with herbs and make sure that the plants do not belong to the same family. Sufficient space between the plants ensures optimal growth and supports vitality.

    No chance of survival in the greenhouse:

    • conditions: pay attention to evenness and air regularly
    • temperature: Avoid rise by protecting greenhouse from the blazing midday sun
    • humidity: large-leaved plants prevent heavy dropping

    When action doesn't help

    If the infestation cannot be brought under control with the best will in the world, it may be because the cause has not been eliminated

    Experience reports show again and again that all countermeasures have no effect. If this is the case, the correct cause of the spider mite infestation has probably not been identified. In some cases, the pests can multiply despite increased humidity and moderate temperatures. Despite their small size, spider mites are extremely resilient.

    Beneficiaries are useless

    Although predatory mites are efficient pest controllers, they require different conditions than spider mites for their development. They need a humidity level of at least 60 percent. If the spider mite infestation does not subside despite the use of predatory mites, the beneficial insects have probably died due to the suboptimal living conditions.

    No improvement despite high humidity

    If measures have been taken to improve the indoor air and the temperature has been reduced, but the plants are still plagued by spider mites, the plant's health may be weakened. Despite adverse living conditions, spider mites can survive well if they can easily get hold of the coveted plant sap.

    If the ornamental plants grow in the same substrate for several years, the nutrients can be used up and deficiency symptoms can occur. Weakened plants are attacked again and again. Replant the affected plants and provide them with fresh soil. Brews made from herbs support vitality and strengthen the plant.

    effect preparation fitness
    Comfrey supplies potassium, silicic acid and tannins Pour hot water over leaves and let steep undiluted for pouring
    nettle strengthens the plant tissue Pour warm water over the leaves and leave to ferment 1:20 for watering and 1:50 for spraying
    field horsetail Silicic acid to strengthen cell walls Soak plants in water for 24 hours and then simmer for 30 minutes 1:20 for spraying
    yarrow prevents sucking pests Pour cold water over herbs and let steep for 24 hours undiluted for spraying

    Identify spider mites

    Spider mites are a suborder and belong to the mites with about 1,200 species. They live on the underside of leaves on different plants and form fine webs to protect themselves. Their diet consists exclusively of the sap of the plants. To do this, they pierce the epidermis with their mouthparts and suck up the liquid. Some species are more common on certain plants:

    • Schizotetranychus celarius occurs on bamboo
    • Panonychus ulmi is considered a fruit tree spider mite
    • Bryobia kissophylla has specialized in ivy
    • Brevipalpus californicus refers to the orchid spider mite

    Their coloring varies depending on the color of the plant juices they absorb and can range from yellowish to greenish to orange. Small red spider mites are typical for indoor plants. White spider mites are still in the larval stage.

    Common spider mite (Tetranychus urticae)

    This species is characterized by a translucent body that is light green to brown in color. The two blurred spots on both sides are striking. Females hibernate and can survive temperatures down to -15 degrees Celsius. During the winter they are colored orange-red. In Germany, the common spider mite affects around 90 cultivated and ornamental plants, including frangipani, beans and vines, potatoes and sunflowers or fruit trees and perennials.

    Red spider (Panonychus ulmi)

    If you find red spider mites on fruit bushes, it is usually the red spider. It is also known as the fruit tree spider mite because of its preferred food spectrum and is found on apples and pears, gooseberries and currants or grapevines. It can also affect indoor plants such as calathea. Females are half a millimeter long and are colored brick red. The white bristles on the back are characteristic. This species usually overwinters in the egg stage on fruit trees.

    digression

    cobwebs

    Spider mites owe their German name to the property of producing spider threads. However, not all species from this suborder have this ability. Only the representatives of the Tetranychinae subfamily have a large gland. This produces a secretion, which is spun into a double thread with two hollow bristles. Orchid and cactus spider mites do not produce webs.

    form webs:

    • Common spider mites
    • Linden and hawthorn spider mites
    • fruit tree spider mites

    Commonly Affected Plants

    Spider mites infest cultivated and ornamental plants alike

    Spider mites are not picky about their food plants. They infest a wide variety of plants from different families such as hibiscus, Hawaiian palm or dipladenia. However, there are some plants whose living conditions are ideally suited to the needs of the pests. Weakened plants that do not normally fall into the usual prey pattern can also be affected.

    What helps against common spider mites:

    • Combat boxwood spider mites with a potash-soap solution
    • Treat spider mites on ivy with an aqueous solution of tea tree oil
    • Eliminate spider mites on hemp first by cutting off the leaves, then spray essential oils
    • Strengthen bonsai with rock flour (€14.13) and prevent spider mite infestation with onion broth

    banana plant

    The large leaves of the Musa are popular with spider mites. After successful control, the sucking pests reappear. To get the plant pest-free, you should treat the leaves at least three times a day with a suitable spray. Don't forget the curled edges at the tip of the leaf, because spider mites linger here unnoticed.

    Make sprays:

    1. Pour 500 milliliters of distilled water into a container
    2. Dissolve 2.5 grams of potash soap in it
    3. Add 2.5 grams of denatured alcohol

    Avoid cold water and fertilizer during treatment. Algan can be given to weakened plants as a growth aid. It is an organic supplier of potassium that supports the construction of cell walls.In order for the banana plant to recover quickly, you should cut off the bottom leaves. Be sure to cut horizontally to reduce juice leakage.

    roses and cucumbers

    Too much nitrogen attracts spider mites to roses and cucumbers

    In the warm summer months, there are often long periods of drought, in which spider mites also find optimal living conditions. They colonize outdoor and cold frame cucumbers alike and don't stop at rose bushes. Spider mites on cucumbers and roses are also often due to excessive nitrogen levels.

    Pay special attention to humid air by regularly watering the substrate in the immediate vicinity. Dusting the leaves with ground sulfur has proven to be a preventive measure. This method rids roses of spider mites and at the same time protects against powdery mildew. Sulfur is harmless to bees, but damages beneficial insects such as predatory mites and ladybugs.

    tips

    Sulfur also helps against an already widespread pest infestation. Pollinate the plants at temperatures above 20 degrees Celsius and repeat the procedure after rainfall.

    fruit trees and fruit bushes

    The fruit tree spider mite is a feared pest on meadow orchards and in private gardens. Not only the apple tree is attacked, but often the lemon tree is also home to spider mites. Strong trees can tolerate an infestation of 40 percent. If the infestation continues to increase, you should fight the pest.

    If they are crops, do not use chemical acaricides. As soon as you observe the pest on the underside of leaves, start with an oil treatment in warm weather. Spray undersides of leaves with a neem oil preparation and mist shrubs and shrubs with water.

    This helps preventively:

    • Mulch tree disc
    • fertilize little, an annual compost is sufficient
    • water regularly

    hydrangeas and oleanders

    Spider mites on hydrangeas are a problem in outdoor cultivation when the climate is dry and warm. The pests prefer high temperatures and low humidity just like the oleander. An airy location with plenty of draft reduces spider mites drastically. If the infestation is advanced, you can use a rapeseed oil-based spray and spray the plants until dripping wet. Sprays with pyrethrins or abamectin are suitable for ornamental plants. Carry out this measure on a cloudy day or in the evening.

    tips

    To prevent spider mites from spreading under ornamental plants, you should free the garden of French herb. This is often the first to be attacked by the pests, which then spread to ornamental and crop plants.

    frequently asked Questions

    How do I get rid of spider mites?

    First, you should spray visible colonies with a hard jet of water. Then wipe eggs with a damp cloth. Since the pests like to hide under curled leaf edges or in leaf axils, spray the entire plant with an aqueous solution of neem or canola oil. Treatment with a spray made from potash soap and alcohol is also effective.

    Do spider mites overwinter in the greenhouse?

    Spider mites survive even harsh winters

    Common spider mites overwinter in the form of red winter females. They form dense colonies in sheltered hiding places such as piles of leaves, burrows or under bark scales. If the pests have spread in the greenhouse, they can also spend the winter there in niches and cracks. Temperatures of -15 degrees Celsius do not bother the common spider mite. In contrast, the fruit tree spider mite usually overwinters in the egg stage on the bark of infested trees.

    Are spider mites dangerous to humans?

    From a medical point of view, spider mites are not dangerous to humans. Their mouthparts are unable to penetrate the skin. They can quickly develop into annoying subtenants that it takes the last nerve to fight. If spider mites have developed into a plague, only drastic measures such as radical pruning or the use of pesticides often help.

    What kind of damage do spider mites leave on plants?

    Spider mites prefer to live on the underside of leaves near the leaf veins. A single insect can prick the epidermis of cells more than 20 times per minute and suck out the juice. Yellow spots appear first, giving the leaf a mottled appearance. With a severe infestation, the leaves turn completely brown and wither. Webs are a first sign of a spider mite infestation.

    Exceptions that do not form webs:

    • some greenhouse spider mites
    • Orchid spider mites
    • cactus spider mites

    What life cycle do spider mites go through?

    The common spider mite develops into an adult animal through four stages of development. A transparent and white larva hatches from the egg, which is usually located on the underside of the leaf. This first develops into a protonymph and finally into a deutonymph before turning into an adult mite.

    In the larval and nymphal stages there are active periods alternating with long periods of rest. Adult spider mites are colored light yellow, orange, light or dark green depending on the food they eat. They can appear red, brown or almost black and have two dark spots.

Category:

Animals in the garden