Two-Spotted Spider Mite

The two-spotted spider mite is one of the most widespread and economically significant plant-feeding mites in the world, found on nearly every continent except Antarctica. It belongs to the arachnid family Tetranychidae, the spider mites, so named for the fine silk webbing many species produce over leaves and stems.

At just a fraction of a millimeter long, individual mites are barely visible to the naked eye, but large colonies can be spotted as fine webbing and stippled, discolored patches on the undersides of leaves. The species gets its common name from two dark patches often visible through the body wall, though coloring can shift with diet and season.

Two-spotted spider mites feed on an extremely broad range of host plants, from garden vegetables and ornamentals to houseplants, making them one of the most frequently encountered plant pests in home gardens and greenhouses alike.

• Adults are oval, roughly 0.3-0.5 mm long, and have eight legs like all mites, distinguishing them from six-legged insects.
• Body color ranges from pale yellow-green to greenish with two darker spots visible on either side of the body, giving rise to the common name.
• Overwintering females often turn orange-red.
• Fine, silky webbing is often visible on the undersides of leaves and between stems during heavy infestations.
• Feeding damage appears as tiny pale or yellow speckles (stippling) on leaves, which can merge into larger bronzed or bleached patches.
• A hand lens or magnifier is usually needed to see individual mites clearly; without magnification, they may look like moving dust specks.

Two-spotted spider mites are found nearly worldwide, thriving especially in warm, dry conditions. They live on the undersides of leaves of an enormous range of host plants, including vegetables, fruit trees, ornamental flowers, and houseplants. Populations build fastest during hot, dry weather and can persist year-round in greenhouses and indoor growing environments.

These mites feed by piercing individual plant cells with their mouthparts and withdrawing the cell contents, which causes the characteristic stippled or bronzed appearance on leaves. Because of the rapid feeding and reproduction rate under warm conditions, two-spotted spider mites are considered a significant pest of many garden and greenhouse plants. They spin silk webbing that can cover leaves, provide protection from some predators, and aid in dispersal, since young mites can be carried on wind currents by ballooning on strands of silk. In natural and agricultural settings, predatory mites, lady beetles, and minute pirate bugs are among the natural enemies that feed on spider mite populations.

Females lay tiny spherical eggs on the underside of leaves, often within the protective webbing. Eggs hatch into a six-legged larval stage, which molts into two eight-legged nymphal stages (protonymph and deutonymph) before reaching adulthood. Development from egg to adult can take as little as one to two weeks in warm conditions, allowing many overlapping generations per growing season. In cooler regions, fertilized adult females overwinter in bark crevices or plant debris, emerging to resume feeding and reproduction when temperatures rise.