Knowing and successfully fighting spider mites

the essentials in brief

• The first measure against spider mites is to shower the affected leaves. Killing sprays from household products help to capture all pests. Chemical agents should only be used in the event of severe spread.
• To prevent an infestation, the living conditions for spider mites should be made unfavorable. In some cases, the pests keep coming, so clarifying the cause is important.
• The most common species include the red spider and the fruit tree spider mite. There are almost 100 species in Germany that attack various ornamental and useful plants.

What helps against spider mites

Spider mites are annoying pests that appear again and again on some indoor plants or in the greenhouse. With crops in particular, it is important to combat the sap suckers naturally. Injections leave residues that can get into the food. Indoor plants should only be controlled with drastic means if they are severely infested.

also read

• Fight spider mites on the palm successfully
• Recognize and fight spider mites on ivy
• Identifying and combating spider mites on orchids - this is how it works

First aid for spider mites:

1. Thoroughly rinse the plant 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 ball of the earth
5. Leave the plant like this for the next two weeks

This method improves the microclimate between the leaves. The humidity rises sharply, so that the spider mites die off over time. Eggs that have already been laid can survive this procedure, so you have 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 become very hot, damaging the leaves.

Beneficial against spider mites

Many beneficial insects can be used specifically to combat sucking pests. Spider mites can be combated biologically with these insects, which means that no spraying is required in fruit growing. You can use predatory mites against spider mites in the greenhouse or on indoor plants if an adjustment of the temperature and humidity has not been successful.

	Art	temperature	humidity
Phytoseiulus persimilis	Predatory mite	17 to 28 degrees Celsius	at least 60 percent
Amblyseius californicus	Predatory mite	at least 23 degrees Celsius	not less than 60 percent
Feltiella acarisuga	Gall mosquito	20 to 26 degrees Celsius	60 percent is optimal

Take cutting measures

If perennials such as hemp or shrubs and trees are heavily infested with spider mites, pruning measures are recommended. With hemp, you remove individual leaves to stop the pests from spreading further. If the oleander is infested with spider mites, pruning the infested leaves consistently helps. The poplar fig can be cut back to the stump if it is heavily infested. It then drives out again.

Getting rid of spider mites with home remedies

The list of home remedies for spider mites is long and ranges from milk and horsetail broth to dish soap 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 long period of time for lasting success.

nicotine

A tobacco brew is a proven means of killing pests because nicotine is a powerful neurotoxin. It is precisely for this reason that you should definitely not use nicotine to control pests. This is because parts of the poison are absorbed by the plant and - provided it is a cultivated plant - ends up on your table. In the 1970s, the use of nicotine for pest control on plants in agriculture was banned.

Broths, teas and manure

When making brews, teas and liquid manure, you can use a rule of thumb as a guide: one kilogram of fresh or 200 grams of dried herbs for ten liters of water. While liquid manure is made with cold water and ferment for several days, brews and teas are made with boiling water.

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

• Splash tea : wormwood and tansy leaves, sprigs of lavender
• Brew to pour : worm fern and bracken
• Broth for pouring : onions and garlic

Canola oil and neem oil

The neem tree oil contains azadirachtin, which stops the spider mites from laying their eggs. Since the active ingredient does not act selectively and also harms beneficial insects, you should not use neem oil when predatory mites are used. An aqueous solution with rapeseed oil is gentler. When the leaves are sprayed, it forms an oily film under which the spider mites are trapped. You can no longer breathe and die.

Soapy water

A self-made agent consisting of 15 milliliters of potash soap and alcohol in one liter of water is ideal for spraying in the early stages, when the infestation is not yet very advanced. Make sure to spray the colonies directly on the underside of the leaves. The measure must be repeated every four to five days. Detergent is suitable to a limited extent, as it is usually not biodegradable.

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

Chemical agents against spider mites

Before you reach for the chemical club, you should weigh the benefits against possible harm. In most cases, chemical pesticides do more harm to plants than they do to clear the spider mite fall. You will 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 are not selective, but kill spider mites as well as beneficial insects. Since not all pests are detected during the first spraying, the treatment must be repeated at regular intervals. Spray the undersides of the leaves generously so that the pests come into direct contact with the poison.

When pesticides make sense

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 infected by spider mites. This also applies to persistent pest infestations or very large populations. The agents are often used against spider mites on orchids. Even the undemanding cactus or the warmth-loving palm can be freed from spider mites by sprays.

Acaricides are preferred 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 also work 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 carefully check the underside of the leaves for spider mite infestation. If the leaves have already settled, the pests can multiply rapidly over the next few weeks. So that it doesn't come to that, you should make the living conditions for the mites suboptimal.

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Constantly spider mites: find out the cause

The arachnids need warm and dry weather in order to develop. Wet conditions and cool temperatures severely limit the 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.

House plants are often attacked by spider mites in winter when they are on the windowsill directly above the heater. Weakened plants are also found food for the pests, because the plant tissue is particularly easy to pierce and suck out.

What to do to get rid of spider mites permanently

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, a change of location can help. If the room air is very dry overall, you should place a small bowl of water on the heater. You can also moisten a towel and place it over the radiator.

No spider mites in the greenhouse

A natural measure against spider mites in greenhouses is the right mix of plants. Monocultures are generally more susceptible to pests than mixed cultures. They can multiply faster in a one-sided crop. Mix vegetables with herbs, making 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 uniformity and ventilate regularly
• Temperature : Avoid a rise by protecting the greenhouse from the blazing midday sun
• Humidity : large-leaved plants prevent heavy waste

When action doesn't help

Experience reports repeatedly show that all measures to combat it have no effect. If so, 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 prove to be extremely resilient.

Beneficial insects are ineffective

Predatory mites are efficient pest fighters, but require different conditions for their development than spider mites. You are dependent on a humidity of at least 60 percent. If the spider mite infestation does not subside despite the use of predatory mites, the beneficial insects have probably perished due to the suboptimal living conditions.

No improvement despite high humidity

If measures are taken to improve the indoor air and the temperature has been lowered, but the plants are still plagued by spider mites, the health of the plant may be weakened. Spider mites can survive well despite adverse living conditions if they can easily get 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 occur. Weakened plants are attacked again and again. Repot the affected plants and provide them with fresh soil. Herbal brews support vitality and strengthen the plant.

	effect	preparation	fitness
Comfrey	supplies potassium, silica and tannins	Pour hot water over the leaves and let them steep	undiluted for watering
Nettle	strengthens the plant tissue	Pour warm water over the leaves and let them ferment	1:20 for pouring and 1:50 for spraying
Field horsetail	Silicic acid to strengthen the 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 the herbs and let them steep for 24 hours	undiluted for spraying

Recognize spider mites

Spider mites are a suborder and, with around 1,200 species, belong to the mites. They live on the underside of the leaves on different plants and form fine nets to protect themselves. Their food consists exclusively of the sap of the plants. To do this, they prick 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 specializes in ivy
• Brevipalpus californicus is the name of the orchid spider mite

Their coloration varies depending on the color of the ingested plant sap and can range from yellow to green to orange. Small red spider mites are typical of house 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 to brown-green in color. The two blurred spots on both sides are noticeable. Females overwinter and can survive temperatures down to -15 degrees Celsius. During the winter they are colored orange-red. In Germany, the common spider mite attacks around 90 cultivated and ornamental plants, including frangipani, beans and vines, potatoes and sunflowers, or fruit trees and shrubs.

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 grow to half a millimeter long and are brick-red in color. 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 subordination have this ability. Only the representatives from the subfamily of the Tetranychinae have a large gland. This produces a secretion that 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

Plants often affected

Spider mites are not picky about their food crops. They attack 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 normally do not fall into the usual prey schedule can also be attacked.

What helps against common spider mites:

• Fight boxwood spider mites with potash soap solution
• Treat spider mites on ivy with aqueous tea tree oil solution
• First remove spider mites from hemp by cutting off the leaves, then injecting essential oils
• Strengthen bonsai with rock flour (14.95 € at Amazon *) and prevent spider mite infestation with onion stock

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. You must not forget the rolled edges at the tip of the leaf, because this is where spider mites linger unnoticed.

Manufacture of sprays:

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

Do not use cold water or fertilizer during the treatment. Algan can be given to weakened plants as a growth aid. It is an organic source of potassium that helps build cell walls. In order for the banana plant to recover quickly, you should cut off the lowest leaves. Make sure to cut horizontally to reduce the leakage of juice.

Roses and cucumbers

In the warm summer months there are more prolonged dry periods, in which spider mites also find optimal living conditions. They colonize open-range and cold frame cucumbers equally and do not stop at rose bushes. Spider mites on cucumbers and roses are often caused by an excessively high nitrogen content.

Pay particular attention to moist 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 frees roses from spider mites and at the same time protects against powdery mildew. Sulfur is harmless to bees, but it damages beneficial organisms such as predatory mites and ladybugs.

Tips

Sulfur also helps against pests that have already spread. Dust 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 orchards and in private gardens. Not only is the apple tree infested, but the lemon tree is also often home to spider mites. Strong trees can tolerate an infestation of 40 percent. If the infestation continues to increase, you should fight the pest.

When it comes to crops, do without chemical acaricides. As soon as you observe the pest on the underside of the leaves, start with an oil treatment in warm weather. Inject the undersides of the leaves with a neem oil preparation and wet the shrubs and trees with water.

This helps preventively:

• Mulching tree grate
• fertilize little, an annual addition of 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 a lot of draft reduces spider mites drastically. Once the infestation has progressed, you can use a rapeseed oil-based spray and spray the plants dripping wet. Sprays with pyrethrins or abamectin are suitable for ornamental plants. Do this on a cloudy day or in the evening.

Tips

In order to prevent spider mites from spreading under ornamental plants, you should clear the garden of French herbs. This is often first attacked by the pests, which then spread to ornamental and useful plants.

frequently asked Questions

How do I get rid of spider mites?

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

Do spider mites overwinter in the greenhouse?

Common spider mites overwinter in the form of red winter females. They form dense colonies in protected hiding places such as piles of leaves, holes in the ground or under bark scales. Once the pests have spread in the greenhouse, they can overwinter there in niches and cracks. The common spider mite does not mind temperatures of -15 degrees Celsius. In contrast, the fruit tree spider mite usually overwinters in the ice 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. Your mouthparts are unable to penetrate your skin. They can quickly develop into annoying subtenants, and fighting them takes the last nerve. If spider mites have developed into a plague, often only drastic measures such as radical pruning or the use of pesticides can help.

What damage patterns do spider mites leave on plants?

Spider mites prefer to live on the underside of the leaf near the leaf veins. A single insect can stab the epidermis of the cells more than 20 times per minute and suck out the sap. Yellow spots form first, which make the leaf look speckled. If the infestation is severe, the leaves turn completely brown and wither. Webbing is the first sign of spider mite infestation.

Exceptions that do not form webs:

• some greenhouse spider mites
• Orchid spider mites
• Cactus spider mites

What is the life cycle of spider mites?

The common spider mite develops into an adult animal over four developmental stages. From the egg, which is usually located on the underside of the leaf, hatches a transparent larva that appears white. This first develops into a protonymph and finally into a deutonymph before it turns into a full-grown mite.

In the larval and nymph stages, there are active periods, which alternate 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.