Spider mites (Phytoseiulus persimilis) is the primary predator of the spider mite and therefore the preferred predator species against spider mites.
When you use predatory mites against spider mites, you control them in an ecological way that is safe for the health of plants, animals and humans.
In addition, predatory spider mites are by far the most effective and natural way to control spider mites. You can read more about spider mite control here.
You can buy spider mites here.
Spider mites are larger and more active than spider mites
Release of spider mites
BuyMost retailers sell spider mites in small bottles containing 500, 1000 or 2000 individuals. The bottles are filled with granules or sawdust. In some places, they are also supplied on plant leaves.
Postponement: The spider mites should be exposed immediately upon receipt, but can be stored in the refrigerator at 6 - 8 degrees for a few days in case of emergency.
PlacementThe mites should always be released on dry leaves (i.e. do not use a nebulizer beforehand) and placed directly on the leaves of the plants. In practice, simply sprinkle the contents of the bottle onto the leaves and leave the bottle and cap hanging on the plant. Try to distribute the contents on all leaves, but mostly on the infested leaves.
The result: A few days after release, the spider mites begin to fight the spider mites and after 2 - 6 weeks the spider mites are usually controlled.
You can buy spider mites here.
Combat
If your plants are already infested with spider mites, you'll need 500 spider mites in an area the size of 2 A4 sheets. On cucumber and tomato plants, for example, you'll need 10 mites per plant plus 1-2 mites per leaf (but it can be difficult to control the release so precisely).
The more spider mites you release, the faster the spider mites will be controlled. You can estimate the number of spider mites on a plant by counting the mites on a leaf and multiplying by the number of leaves.
Rule of thumb: If you expose 1 spider predator mite to 20 - 25 spider mites, control is achieved in about 4 - 6 weeks. If you expose 1 predatory mite to 5 spider mites, control will take about 2 weeks.
However, this assumes that the temperature and humidity are optimal (see the 'Thriving' section below). The release can be repeated every 2-3 weeks until control is successful.
For heavy infestations, remove the most damaged leaves before releasing the mites. For very heavy infestations, you should apply insect soap on the plants two days before the mites are released.
Be aware that spider mites can return later in the year as a result of the predatory mites running out of food and ending up eating each other. Therefore, preventative application is often a good idea.
We recommend these insect soaps
Preventive application
If you want to use spider mites to prevent spider mite infestations, release 1 - 5 spider mites per square meter. The mites should be released once a week and should also be released on plants that have not been previously infested.
Description of the spider mite
Spider mites are very small (about 0.5 mm) but visible to the naked eye. However, you'll need a magnifying glass to identify them.
Like most other predatory mites, spider mites move around very quickly. Their bodies are tear-shaped with long legs and they are slightly larger than their prey (the spider mites). The adult spider mites are orange or orange-red, while the nymphs are a pale salmon color.
The eggs of spider mites are oval-shaped and about twice the size of spider mite eggs.
Keep in mind that in winter, spider mites develop a reddish color, which can make it harder to distinguish them from spider mites.
Wellbeing
Spider mites can control spider mites at 18 - 35°C, but thrive best at 18 - 27°C (especially 24 - 25°C because the spider mites reproduce faster than their prey). The temperature should be in these ranges for at least 8 - 12 hours per day.
The relative humidity should preferably be above 60%, with 70 - 80% being optimal. The development of mites stops completely at a humidity of 25 - 30%.
Sulphur also inhibits the activity and development of mites.
Prey of the spider mite
The spider mites are specialized predators that feed almost exclusively on spinning mites in the subfamily Tetranychinae. However, spider mites can also eat young thunderflies and even be cannibalistic if there is a food shortage.
Spider mites hunt their prey using specific odors found on plants infested with spider mites. When spider mites find spider mite webs, they intensify their hunt for prey.
Spider mites eat 5 adult mites or 20 eggs per day and reproduce faster than spider mites if the temperature is 28°C or above. Spider mites can rightly be described as voracious and will eat all spider mites in all their life stages (i.e. eggs, larvae, nymphs and adults).
You can buy spider mites here.
Lack of food
It's worth noting that spider mites need access to spider mites to survive. While they can eat young thunderflies and be cannibalistic, this is usually not a sustainable food source.
Because spider mites are such efficient hunters, it often happens that they completely exterminate their prey, eliminating their own livelihood. This is desirable on plants where you don't want mite damage at all (such as flowers), but on crops where a certain level of damage is acceptable (such as tomatoes and cucumbers), it's more optimal to have a stable balance between the predators and their prey.
When the spider mites eat all the spider mites in their environment, they starve to death. In these cases, the spider mites must be reintroduced if they become a problem again.
Life cycle
The life cycle of the spider mite is explained step by step below:
- Egg stage: At a temperature of 17 - 27°C, the adult female maggot lays up to 60 eggs. The eggs are light orange in color and darken shortly before hatching. The eggs are laid close to a food source (often among the eggs of spider mites) and hatch after 2-3 days.
- Larval stage: In the larval stage, the larva does not consume any kind of food.
- Nymfestadie: The nymph begins feeding on spider mites (and possibly other prey) immediately after molting. The nymph goes through two stages before reaching adulthood; protonymph and deutonymph.
- Adult spider miteAdult spider mites usually live for about 50 days and female mites lay eggs throughout their lifetime. Because spider mites originate from tropical climates, they are active all year round when indoors.
The period from egg to adult stage lasts from about 25 days at 15°C to about 5 days at 30°C. The minimum temperature for activity is 10°C. The optimal humidity is 70 – 80% (in the crown of the plant). The development of mites is inhibited if the humidity is below 70% and at 25 - 30% their development stops completely.
Other beneficials against spider mites
In addition to spider mites, you can also use the following beneficial insects to control spider mites:
- The tripsrovmid (Amblyseius cucumeris)
- The beaked tongue/Orius rove tongue (Orius majusculus)
- Netwing species Chrysopa pearl (in the family gold eyes)
Read more about these species in our article on predators against arachnids.