Tetranychus urticae (common names include red spider mite and twospotted spider mite) is one of many species of plant-feeding mites found in dry environments across the world, and generally considered a pest. It is the most widely known member of the family Tetranychidae or spider mites. Its genome was fully sequenced in 2011^[1], becoming the first one for an Arachnida.

Distribution

Tetranychus urticae was originally native only to Eurasia, but has acquired a cosmopolitan distribution.^[2]

Description

Colony of Red Spider Mites.

Tetranychus urticae is extremely small, barely visible with the naked eye as reddish or greenish spots on leaves and stems; the adult females measure about 0.4 mm long.^[3] The red spider mite, which can be seen in greenhouses and tropical and temperate zones, spins a fine web on and under leaves.^[3]

Ecology

Tetranychus urticae is extremely polyphagous. It can feed on hundreds of plants, including most vegetables and food crops including peppers, tomatoes, potatoes, beans, corn, strawberries; and ornamentals such as roses.^[3] It lays its eggs on the leaves, and it poses a threat to host plants by sucking cell contents from the leaves cell by cell, leaving tiny pale spots or scars where the green epidermal cells have been destroyed.^[3] Although the individual lesions are very small, attack by hundreds or thousands of spider mites can cause thousands of lesions and thus can significantly reduce the photosynthetic capability of plants.^[3]

The mite's natural predator, Phytoseiulus persimilis, commonly used as a biological control method, is one of many predatory mites which prey mainly or exclusively on spider mites.^[3]

Life cycle

The egg of T. urticae is translucent and pearl-like.^[2] It hatches into a nymph, which in turn develops into a protonymph, and then a deutonymph, which may display quiescent stages. The adults are typically pale green in colour for most of the year, but later generations are red in colour; mated females survive the winter in diapause.^[2]

References