Spider Mites: Proven tips to protect your harvest
Spider mites are one of the most dangerous pests a grower can encounter. These tiny arachnids, almost invisible to the naked eye, can cause enormous damage and, if not stopped, can destroy an entire crop within a few weeks. In this article, we will look at how to recognise spider mites, why they thrive on your plants, and how to deal with them effectively.
What are spider mites and why are they so dangerous?
Spider mites are tiny arachnids from the spider mite family, whose most common representative in indoor growing rooms and gardens is the two-spotted spider mite (Tetranychus urticae). These microscopic insect pests grow to just 0.4 mm, have four pairs of legs, and vary in colour depending on the species and environment – from green and yellow to red.
Spider mites reproduce incredibly quickly and, under ideal conditions (warmth and dryness), can cover an entire plant within a few weeks. In addition to their rapid reproduction, spider mites are also tricky because they can easily hide in folds between leaves. Females create shelters in the tops of plants or between leaves, where they lay eggs. Larvae hatch from these after 3–15 days, mature over the next few days, and continue colonising. At high temperatures and low humidity, this cycle speeds up dramatically. That is why spider mites are such a common problem in enclosed indoor spaces or greenhouses.
How to tell if you are dealing with spider mites
It is difficult to spot spider mites on plants, as you often will not see them with the naked eye. However, you should certainly not overlook the warning signs that accompany a spider mite infestation:
- Tiny yellow-white spots on the leaves, especially on the underside, where spider mites most like to suck sap.
- Fine webbing between leaves, on stems, and on the tops of plants. A typical sign of a severe spider mite infestation.
- Wilting and premature drying of leaves, even though the plants have enough water.
Natural methods of fighting spider mites
If you have spotted spider mites on your plants, before reaching for chemicals, try proven natural methods. They are gentle on the environment and often very effective:
- Changing the climate: Spider mites like dryness and warmth. If you grow indoors, lower the temperature below 25 °C and increase the relative humidity to 60-70%, which will slow their reproduction. Better air circulation will also help, making it harder for the pests to move around the plants.
- Mechanical cleaning: Spider mites can be removed from leaves mechanically, most easily with a damp cloth or a vacuum cleaner set to low power. If possible, try showering the plants.
- Biological protection: Predatory mites persimilis, californicus, A. andersonii, N. fallacis and G. occidentalis are also effective against spider mites, as is the predatory gall midge Feltiella acarisuga, as well as Stethorus punctillium and Oius insidiosus.
Products against spider mites
In the case of a severe spider mite infestation, you need to use sprays – but even then, you can choose between gentler and more radical solutions.
Natural sprays and soaps against spider mites
These products are gentle on the environment and, in addition to spider mites, also protect plants against pathogens and other insects. Proven natural products against spider mites include:
- Neem oil: Biocont NeemAzal
- Oil emulsions: Rock Effect
- Biological sprays: BioBizz Leaf Coat, Canna Cure, NATURA, BHB MM, Spider Plant
Chemical sprays against spider mites – acaricides
Products designed specifically against sucking insects such as spider mites are called acaricides. However, when using them on plants intended for consumption, be cautious. These products require a safety interval and may harm your health.
- Biocont PREV-GUARD
- AgroBio Karate
- SmC Spidermite Control
- Agro Sviluška STOP
- Spruzit Pest Free
- Nissorun
You may also be interested in: How to get rid of slugs
For more advice on how to fight pests and other tips and tricks for indoor and outdoor growers, visit our Higarden blog.