Spider mites
Pest mite
- Dozens of small white or yellow spots on leaves
- Fine dust on the undersides of leaves
- Fine webs on the leaves and stems
- Curled leaves
- Yellowed and dried leaves
| Difficulty Medium |
| Frquency High |
| Reproductive rate Up to 100x |
| Lifecycle Up to 65 days |
Two-spotted spider mites, commonly known as Spider Mites or Red Spider Mites, are small mites belonging to the same family as ticks. These tiny spiders are barely visible to the naked eye and cause damage to plants by feeding on the sap of their leaves.
Host plants
Spider mites are highly polyphagous, meaning they feed on a wide variety of vegetable and ornamental plants. They are less commonly found on cacti and succulents, although some species with soft foliage can also be attacked.
Screening
Spider mite infestations cause the appearance of small white or yellow spots on pierced leaves. Eggs, nymphs, and biological waste produced resemble fine dust and are particularly noticeable on the undersides of leaves. The most attentive gardeners might spot tiny spiders.
Spider mite webs have a very different appearance from those of domestic spiders. These webs are much finer, and no threads can be distinguished, giving them the appearance of a veil.
These mites are extremely prolific pests, and their reproduction is exponential. Under the most favorable conditions, their population can multiply by 70 in less than six days. It is strongly recommended to start treatment at the first signs of their appearance.
Prevention
Spider mites are most often introduced inadvertently when purchasing new plants or using contaminated gardening equipment. However, they are naturally present outdoors, during the summer in continental climates. Amblyseius Californicus is an excellent choice of natural predator to prevent spider mite appearance or control an initial infestation.
Treatment
Treating a spider mite infestation may involve removing certain leaves, thorough cleaning, and applying foliar insecticides such as black soap or horticultural oil. Introducing Phytoseiulus persimilis or Stethorus punctillum is recommended to eliminate remaining individuals and prevent reinfestation.
Products
Morphology
Adults measure nearly one millimeter long and are oval in shape. They have four pairs of legs and are hairy on the back. They are yellowish with a black dot on each side of the abdomen, hence their name "two-spotted" spider mites. Red eyes are present at all growth stages. The color of spider mites can vary depending on the host plant, ranging from pale yellow to brown, red, or black. Females turn a reddish-purple color in autumn.
The two spots on the backs of spider mites are accumulations of body waste. Older specimens have them, but younger adults and nymphs are translucent yellow, without spots.
Behaviour
Originating from Eurasia, spider mites are now present worldwide, including in continental climates. They are particularly comfortable and prolific in dry, warm environments, causing indoor infestations to accelerate in winter when indoor air is very dry.
Outdoors, winter is a hibernation period where spider mites hide until spring and can withstand temperature drops of up to -24°C. Females turn purple in response to temperature variations in autumn. This phenomenon also occurs indoors, even if the growing conditions remain relatively stable.
Lifecycle
The spider mite life cycle consists of four stages: egg, larva, nymph, and adult. Under optimal conditions, the adult stage can be reached in as little as three days. Females reach sexual maturity in five days and lay around twenty eggs per day for one to three weeks. Spider mites primarily reproduce through parthenogenesis, an asexual mode of reproduction that does not require the intervention of male individuals. In other words, a single female can be sufficient to trigger an infestation.