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Spider mites can develop into gardens and greenhouses very quickly to an unpleasant and hardly to get to grips, among other things, because they are easily transmitted due to their low weight by draft, wind or fans.
In the house, the pests like to settle on all types of indoor plants, where they are particularly active by the dry heating air during the autumn and winter months. For greenhouses, it does not look better: Here they settle in the radiant area of the heating pipes and near doors and ventilation openings.
Why do spider mites occur so often?
Dry, warm air and the absence of natural enemies are an invitation for the spider mites to settle andto spread - and they multiply at a rapid pace:
- It takes 10-20 days for a spider mite to develop into an adult spider mite.
- She prefers young, soft leaves, but is not limited to these. There she quickly forms colonies under suitable conditions.
- A single, adult female produces about 50 to 100 eggs during its two to five-week life.
- The spider mite females hibernate in colonies in sheltered places such as fallen leaves and under the bark of woody host plants.
- You can easily survive at temperatures of -15° C for a few weeks.
- If conditions improve again after low temperature and high humidity, sudden mass infestations can occur.
Signs of spider mite infestation
In the case of infestation, small, yellowish-white spots first appear on the leaves, and in places a silvery sheen. The spider mite infests first the underside of leaves, but also the shoots, where it forms delicate webs, in which it resides and multiplies. More struck leaves change color from green to gray or copper brown and eventually fall off.
Best by naturalization of natural enemies such as predatory mites and robber bugs. Also useful: ladybugs and larvae of the lacewing (larvae can be ordered from specialist dealers) and their promotion by species-rich greening with regular flowering: Leave in the flower beds individual basket and Umbelliferae - these offer many beneficials whose larvae parasitic or predatory life, Refuge and food.
- Thorough watering of the garden - especially on hot days.
- Spray indoor plants with lime-free water in winter, also to increase the humidity.
- Use of beneficial acaricides (pesticides or biocides for the control of mites and ticks, available from gardeners).
Combating spider mites
Before any control measure that goes beyond the use of beneficial organisms, it should be thoroughly informed whether the plant tolerates this well. The sooner one detects the infestation of a plant by the spider mite, the greater the chance to limit the infestation in the same year! Therefore, you should pay close attention to signs such as silver gloss and bright spots on the leaves. To determine whether it is a spider mite, wipe with a white paper tissue over the underside of the leaves: In case of infestation red or green dots or streaks are seen on the handkerchief. Spraying the undersides of the leaves with water makes the weaves of the animals visible at an early stage.
- Isolate individual infested plants.
- Apply the treatment described to neighboring plants.
- Intense spraying removes spider mites from the plant and can prevent mass propagation of the animals.
Caution: Submerging potted plants does not help - the animals then surround themselves with protective air bags!
- For potted plants wipe leaves and rinse.
- Then pour and put a transparent plastic bag over the plant for a few days...
- ... and attach the lower edge to the pot with a rubber band.
It is advisable to repeat this procedure more often and to combine it with the use of predatory mites. If the predatory mites have eradicated their prey, they die after a while. In the garden, the plants are rinsed thoroughly with a very hard jet of water, whereby the undersides of the leaves should not be forgotten. After that, the most promising method is the combination of an increase in humidity through abundant watering, along with the use of predatory mites.
Young predatory mites depend on the intake of water droplets, so spraying the plants and moisturizing the paths will benefit them. In the event of a lack of food, the adult predatory mites migrate away, the young animals remain on the plants and completely eradicate the spider mite infestation. If the infestation is still moderate, proceed as follows:
Repeated spraying with garlic water (500 g garlic briefly boil on 10 liters of water and leave to draw)
- Or spray extra strong basil tea.
- A brew from field horsetail, with which one sprayed after rinsing affected plants and neighboring plants, can remedy the situation. (Repeat this treatment for a long time.)
The following mixture of essential oils was successfully used:15 drops of lavender, 15 drops of tea tree oil, 5 drops of thyme in 1/2 liter of water. This should be especially the leaf underside edit, since the spiders sit here.
- Niembaumprodukte (available in organic garden trade) can be used both in already infected plants, as well as preventive.
They contain the active ingredient azadirachtin from the Indian neem tree, which hinders the development of the animals. Stop this, stop eating, do not mate and no longer lay eggs. A treatment with Niemprodukten should not be combined with the use of beneficials, as they try to feed on the spider mites and can be harmed!
- Insecticides are not particularly suitable for combating spider mites because they are arachnids.
For pesticides generally applies: hardly any group of pests develops faster resistance to toxins than the spider mite - often after two applications no effectiveness can be determined, so would have to be worked with several means!
- Treatment of hard-leaved plants with certain oils (white oil, paraffin or rapeseed oil). They stick the respiratory openings of the animals so that they enter.
- Use-friendly sprays based on natural fatty acids and potassium salts are also helpful.
- The specialist retailer offers a range of non-toxic spray sprays based on rapeseed or mineral oil. Splashed during the expulsion, spider mites are thereby combated.
Worth knowing about the fight against spider mites shortly
Since spider mites are resistant to poisons much faster than their natural counterparts due to their rapid life and multiplication cycle, the use of toxic sprays quickly gives them the advantage of being able to spread unhindered while their predators are rigorously eradicated.
- Especially in hot, dry summers, but also in the dry air heated rooms and in greenhouses, the common spider mite spreads quickly.
- The tiny, yellowish or reddish spider sits mainly on the underside of the leaves. Starting with the older leaves up to the shoot tips, they gradually cover the whole plant with their fine silky web and suck the juice from the leaves. The affected buds and shoots are severely restricted in their development, the leaves wither and die.
- Spider mite infestation is always a sign of drought. Water treatments in any form are therefore the most important immediate measure. Potted plants are conveniently placed in the shower.
Procedures for potted and garden plants
- Potted plants can be sprayed with water, put in a plastic bag and tie. The plants survive this procedure for a few days, the spiders do not. Similarly, garden plants can be kept moist by frequent spraying or spraying.
- For fruit trees, nettle has also proven successful. Add 1 kg of fresh nettles to 10 liters of water and let it ferment for a few days (stir daily!). This broth is diluted 1:50 and sprayed on the infected parts of the plant.
- In the greenhouse can be used as natural enemies predatory mites or flower bugs. They prefer to eat spider mites and other pests and otherwise do no damage to the plants.
- Even if there are many ways and means: In the case of very strong infestation, only chemical sprays or, to prevent at least spread, strong cutting back or destruction of the affected plant.
Anyone who manages to provide his plants with the best possible conditions in the long run will no longer have the problem of spider mites in the future.