Host plants and damage
The two species of spider mites: The two-spotted spider mite Tetranychus urticae and the red spider mite Tetranychus cinnabarinus - are major pests of a wide range of ornamental and vegetable plants as well as fruit trees throughout the world. The mites feed on cell chloroplasts, producing characteristic minute, yellowish feeding marks that may coalesce, causing leaves to shrivel and die. When in excessive numbers, the mites produce dense silken webs to protect their colonies, using the webs also as an aid in transportation within and between the host plants.
Basic biology
The spider mite has five developmental stages: egg, larva, two nymphal stages and adult. Females lay spherical eggs (about 0.15 mm diameter) on the underside of leaves. The small whitish larva has three pairs of legs while the nymphs and adults have eight legs. Adults of the two-spotted spider mite are very small, oval-shaped and yellowish or greenish except for two dark spots on the back. Adults of the red spider mite are plum red in color. At 20ºc and low humidity (ca. 35% RH) a female will lay about 7 eggs/day while at high humidity (95% RH) about 5 eggs/day. At temperatures 32, 21, 18 and
15.5 ºc - the spider mite completes its life cycle within 3.5, 14.5, 21 and 30 days, respectively. |
