The twospotted spider mite is approximately 1/50th of an inch in length, oval, and varies in color from orange-red or brown to green or greenish-yellow. Females are approximately 0.4 mm. in length with 12 dorsal hairs. Overwintering females may be orange to orange-red in color. Overwintering occurs in the leaf litter or beneath the bark crevices of their host plants. As the common name suggests, twospotted spider mites often possess (but not always) two dark spots on their dorsal side. The spots may vary depending upon when the last molt occurred. Twospotted spider mites feed and reproduce as soon as warm temperatures allow, from early in the spring through the fall. Eggs are attached to fine silk webbing and hatch in approximately 3 days. The life cycle includes an egg, larva, two nymphal stages, and the adult. Adult females can live for 2-4 weeks and lay 100-300 eggs. Temperatures impact the length of time it takes the twospotted spider mite to develop from egg to an adult. Warm or hot conditions favor their development, increased feeding, and reproduction. At approximately 80°F, these mites may complete their development in 5-20 days. Many overlapping generations can occur per year (Johnson and Lyon, 1991). The twospotted spider mite was originally described from specimens originating in Europe, however it is considered widespread in temperate and subtropical locations.
Twospotted spider mites prefer hot, dry conditions in the summer and fall. Population increases and subsequent plant damage can occur under these conditions. Using piercing-sucking mouthparts, twospotted spider mites feed primarily on the underside of host plant leaves and remove fluids. This feeding causes graying or yellowing of the leaves. Necrotic spots can also occur in advanced stages of leaf damage. This may lead to a stippled/bleached appearance of the leaves; on occasion, complete defoliation due to spider mite activity is possible under high populations. Twospotted spider mites also create a fine webbing which can be found on infested plants. Over 200 species of host plants are known for the twospotted spider mite, including many deciduous shrubs and trees. Other species of spider mite can be found on some overlapping host plants as well. Species discussed elsewhere in this Guide include: clover mite (Bryobia praetiosa), European red mite (Panonychus ulmi), honeylocust spider mite (Platytetranychus multidigituli), oak spider mite (Oligonychus bicolor), southern red mite (Oligonychus ilicis), and the spruce spider mite (Oligonychus ununguis).
Magnification is needed to visually detect twospotted spider mites. At least a 10-15X hand lens is required. The undersides of host plant leaves can be examined for the mites themselves or their shed or cast skins, as well as the fine webbing left behind by spider mites. However, it may be easier to view twospotted spider mites when a branch that is suspected to be infested is shaken or struck over a white piece of paper. This will dislodge the mites, causing them to fall onto the piece of white paper where they will be easier to see. For other spider mites, such as the spruce spider mite (Oligonychus ununguis) it is suggested that chemical management options be considered if the stippling (feeding) damage from the spruce spider mite exceeds 10% of the green foliage. Another metric suggested is if more than 10 spider mites (on average) are found when sampling (tapping onto a white piece of paper) each branch. However, if predatory mites (natural enemies) are present on the foliage, take caution when selecting chemical management options.
Trees suffering drought stress should be provided with adequate watering to reduce the impact of spider mite feeding. Do not over fertilize trees infested with spider mites or piercing-sucking insect pests, as this can benefit the pests more than the tree itself. Syringing, or spraying mite infested foliage with a heavy stream of water, may help knock the spider mites off their host and provide management on ornamental/specimen trees or shrubs. If done on a regular basis, syringing can have the same effect as strong rain events which help dislodge the mites and reduce the severity of their feeding. Certain weed species may cause an increase of spider mite populations by providing an overwintering location, and their removal may help reduce twospotted spider mites near individual plants.
Natural predators often keep this pest at low levels. Miticides and insecticides can often be lethal to beneficial predatory mites, so monitor for the presence of predatory mites and other natural enemies before making chemical management decisions. Select reduced risk chemical management options (if necessary) in order to preserve natural enemy populations. Predatory mites (Amblyseius spp., Metaseiulus spp., and Phytoseiulus spp.), lady beetles (Stethorus spp., Stethorus punctum), minute pirate bugs (Orius spp.), thrips (Leptothrips spp.), and lacewing larvae (Chrysopa spp.) are all considered important predators of twospotted spider mites (Fasulo and Denmark, 2009). If monitoring for predatory mites by shaking branches onto white paper, look for orange/red colored mites that are fast moving and have long legs.
Abamectin (NL)
Acephate (NL)
Beauveria bassiana (NL)
Bifenthrin (NL)
Chlorpyrifos (N)
Chromobacterium subtsugae (NL)
Cypermethrin (NL)
Etoxazole (N)
Fenazaquin (NL)
Gamma-cyhalothrin (L)
Hexythiazox (NL)
Horticultural oil (L)
Insecticidal soap (NL)
Lambda-cyhalothrin (L)
Malathion (L)
Metarhizium anisopliae (robertii) (NL)
Neem oil (NL)
Spinosad (NL)
Spiromesifen (L)
Tau-fluvalinate (NL)
Do not apply broad-spectrum insecticides to manage twospotted spider mite on host plants with robust natural enemy populations. For example, pyrethroid insecticides are known to be very detrimental to predatory mites that otherwise help reduce twospotted spider mite populations (Hull and VanStarner, 1983). Twospotted spider mite may develop resistance to certain acaricides after prolonged use. Most miticides are not effective on the egg life stage of the twospotted spider mite.
Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), and neem oil (soil drench).
When used in a nursery setting, chlorpyrifos is for quarantine use only.
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
