Two spotted spider mites are one of the most damaging pests of different field, fruit and vegetable crops, and ornamental plants. Two spotted spider mites feed by sucking cell sap (juice) from leaves and succulent twigs of their host plants. Feeding injuries caused by these mites generally give mottled and speckled (Photo 1) appearances to host leaves as well as affect the process of photosynthesis, which in turn reduces plant’s ability to make its own food. Heavy infestations of these mites generally result into leaf yellowing and desiccation, leaf drop, death of plant and yield loss of many crops like beans, canola, cotton, citrus, cucumber, eggplant, melon, peanut, pepper, strawberries, potato, soybean and tomato. While feeding, both adults and nymphs of this mite also produce webbing on the leaves and small branches with the fine strands (Photo 2) that reduces aesthetic value of many ornamental plants including azalea, camellia, hollies, ligustrum, roses and viburnum. The damage caused by two spotted spider mites can cause in millions of dollars loss to agricultural, horticultural and ornamental industries.
Adults: Adult mites are very tiny about 1/20 inch long, oval shaped with four pairs of legs and two red spots. Depending upon the species, mites can be brown, green, red or yellow in color. The color of mites may also change with the season.
Eggs: Mite eggs are translucent and spherical in shape and as large as the size of adult mites.
Larvae: Mite larvae resemble to their parents but they are comparatively very small with only three pairs of legs.
Nymphs: Nymphs also resemble to their but they are larger than larval stages and smaller than adult stages. There are two nymphal stages; first stage is called protonymph and second stage is deutonymph. Like their parents, they have four pairs of legs.
Pupae: Pupal stage is not present in the life cycle of spider mites.
Life cycle of two spotted mites consists of four stages including eggs, larvae, nymphs and adults. These mites overwinter as mated females (quiescent stages) under the tree bark and/or plant debris on the ground. Early in the spring, mated females lay hundreds of eggs on the leaves of host plants. Eggs hatch within 2-3 days into small larvae that molt into first nymphal stage called protonymph within next 2 days. The first nymphal stage then molt into second nyhmpal stage called deutonymph within 1-3 days. The deutonymphs then molt into adult stages within 2 day. Thus, under favorable climatic conditions, spider mites can complete their life cycle within 5- 20 days.
Currently several chemical acaricides (pesticides) are available for the control of pest mites but their use is restricted in organic gardens due to their detrimental effects on human and animal health, and the environment. Therefore, natural enemies such as predatory mites (Amblyseius swirskii, Neoseiulus californicus, Neoseiulus fallacis, Phytoseiulus persimilis, Stratiolaelaps scimitus (Hypoaspis miles, and Western predatory Mite, Galendromus occidentalisand) and predatory insects including gall midge (Feltiella acarisuga), minute pirate bug (Orius insidiosus) and predatory bug (Dicyphus hesperusare) are currently used as environment and human friendly biological control alternatives to chemical pesticides to control two spotted spider mites.
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The following beneficial organisms can control the plant feeding spider mites