Spider mites are not insects. They are insect relatives, more closely related to the spiders. However, many species can be significant pests of ornamental plants and shade trees. Species of spider mite discussed 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), spruce spider mite (Oligonychus ununguis) and the twospotted spider mite (Tetranychus urticae).
It is currently thought that clover mites (Bryobia praetiosa) are a species complex: some may feed on grasses while others feed on woody ornamental plants and can have very different life cycles. Each can have a different scientific name than what is listed here. A specific subset of these mites may also be found inside homes but they do not feed on people, but rather enter the home to overwinter. The home environment is not suitable for them and they eventually perish, usually within a few days. Clover mites can become active as adults as soon as temperatures are above freezing. This species of mite becomes less active at temperatures above 70°F and enters a summertime aestivation or type of dormancy. In general, many generations can occur per year, however this can vary between the different "species" within this species complex. Adult mites are flattened dorsally, 0.75 mm. long, and their first pair of legs can be longer than the other three. The front set are used to probe and search the environment. Eggs and newly hatched larvae are bright red but after they feed their color changes to a green/greenish black body with an orange tint and orange legs. When crushed, they leave behind an orange-red stain. Clover mites reproduce through parthenogenesis, or unfertilized eggs laid by females, and as such all adults are female.
The European red mite (Panonychus ulmi) is a species of spider mite. It is not an insect, but an insect relative worthy of mention in this guide. It is found throughout much of the Northeast and primarily on plants in the Rosaceae family, but may be found on fruit and shade trees and shrubs worldwide. It is a European species that was introduced into the United States in the early 1900's. It can have as many as seven generations per year (as observed in New York orchards); however points south report 8-10 generations per year. Eggs of this species are different in appearance/location on the host plant depending upon the time of year. In the summer, eggs are laid on the leaves of the host plant and are translucent yellow and spherical. Overwintering eggs are bright red and possess a white stalk that is visible with magnification. Overwintering eggs are laid in the cracks and crevices of host plant bark. Eggs are approximately 1/200th of an inch. Overwintering eggs may be present in the tens of thousands on apple trees. Egg hatch is reported in late April in New York, or just prior to bloom in other parts of its introduced range. Mites will migrate to the leaves to feed. Each female is said to lay a single egg per day. Egg laying continues through the subsequent generations and mites pass through egg, immature (6 legs and then 8 legs), and adult (8 legs) stages. All are described as brick red in color. European red mite numbers increase as the season progresses, and may become unacceptably high if favorable hot, dry summer conditions are experienced.
Honeylocust spider mite (Platytetranychus multidigituli) adults sometimes overwinter in huge clusters on host plant bark. These overwintering adults are less than 1 mm in length and bright orange in color. They may be found in bud scars or cracks in the bark. The eggs of these spider mites are laid in the spring (early to mid-June in New England) and hatch just following budbreak. Each female may lay up to 70 tiny, white eggs along leaf veins and the crotches of leaf veins. Newly hatched immatures have 6 legs and are transparent until feeding occurs, at which time they develop a green color. An individual honeylocust spider mite can develop from egg to adult in as quickly as 4 days in the summer, and 11 days in cooler weather (Johnson and Lyon, 1991). Development may be influenced by weather conditions, humidity, and food availability and quality. Adult forms in the summer range in color from pale yellow to green. The life stages of the honeylocust spider mite include: egg, 6-legged larva, 8-legged protonymph (1st form), 8-legged deutonymph (2nd form), and 8-legged adult (Witte, 2013). Several generations occur per year. Populations may quickly develop, causing severe host plant injury by midsummer, and then collapse. Following population collapse, new growth of honeylocust may remain green. In light infestations, when viable host plant foliage remains available, honeylocust spider mites may continue to reproduce through the fall until the adult females move to the bark to overwinter. Dispersal is reported to occur on wind currents during periods of overcrowding.
The oak spider mite (sometimes called the oak red mite; Oligonychus bicolor) is not an insect, but an insect relative more closely related to the spiders. This species of spider mite is native to New England, but found as far south as North Carolina and west to Kansas. Oak spider mites are dark reddish brown in color, similar to the southern red mite (O. ilicis). Oak spider mites lay their red, barrel-shaped eggs on the surface of leaves in the summer, and in the fall around the axils or crevices of the twigs. Eggs are the overwintering life stage for the oak spider mite. While a precise life cycle for the oak spider mite may not be fully understood, in general spider mites go through similar life stages. In days to weeks, the eggs hatch and the larva emerges. Spider mite larvae are round bodied with only 3 pairs of legs. Larvae feed, molt, and form the first nymphal stage which will possess 4 pairs of legs. At least two nymphal stages typically occur (two molts) after which the adult is formed. Adult females tend to be larger than the males, with rounded abdomens compared to the pointed abdomens of the males.
The southern red mite (Oligonychus ilicis) is considered by some to be the most significant and widespread spider mite pest of broad-leaved evergreens, primarily plants in the Ericaceae and Aquifoliaceae families. While it was first described in North America, it may be native to parts of Asia. The southern red mite is known at least from the United States, Brazil, Italy, Japan, Korea, the Netherlands, and Paraguay. It is considered widespread on broad-leaved evergreens in the eastern United States. The mite overwinters as red eggs on host plant leaf undersides. If the mites are not managed, by the summertime eggs become very abundant. Summertime eggs are a darker red than those found in the winter. Multiple generations can occur per year; however the southern red mite may be most abundant during periods of cooler weather. Therefore, population densities can be the most abundant in the spring and fall. Prolonged periods of high humidity also favor the southern red mite. During the height of the heat of summer, most of the population is in aestivation (a summer time dormancy) in the egg stage (Johnson and Lyon, 1991). Adult males and females are similar in size, with females being slightly bigger (approximately the size of a period). Both require magnification to see, such as a hand lens. Southern red mites are reddish brown and darker in color than most other common spider mites, with translucent coloration on the body nearest the head.
The spruce spider mite (Oligonychus ununguis) has the potential to be one of the most destructive conifer feeding spider mites in the United States and Canada. Adult female spruce spider mites will lay their brown, overwintering eggs beneath host plant bud scales, in the axils of needles, or beneath webbing on host plant branches or stems. Eggs are rounded, flattened from the top down, and have a thread (stipe) sticking up from their center. Larvae hatch from the eggs and develop into nymphs. Each process can happen in a matter of days; 3 days for larvae to develop and 6 days for nymphs to develop. The initial larva only has 3 pairs of legs. After it molts for the first time, 4 pairs of legs are present. Adult spruce spider mites are tiny, approximately 1/2 mm in length. They vary in color from dark green to brown. Adults legs are a salmon pink color. Each year, it is possible for 3-4 generations to occur; in some areas, 7-10 generations per year are reported. A single generation may be produced every 2-3 weeks. When the hot summer months arrive, the spruce spider mite enters a summer dormancy period until cool temperatures return in the fall. Spruce spider mites may be primarily dispersed via the wind.
The twospotted spider mite (Tetranychus urticae) 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.
See individual mite species for information regarding specific host plants. Leaves of plants become bronzed or silver in color when fed upon by the clover mite (Bryobia praetiosa). European red mites (Panonychus ulmi) feed on the leaves of their host plants, removing plant fluid from individual plant cells. When infestations are large, leaves become "bronzed" or discolored, typically by mid-July. In orchards, fewer fruit, dropped fruit, or lower fruit quality are reported. In some cases, fewer buds for the next season's crop have been reported in apple. The time of year, duration of feeding, site conditions, and abiotic conditions can influence the severity of the impact of this pest. In managed landscapes, European red mite activity is primarily an aesthetic issue.
Light infestations of honeylocust spider mite (Platytetranychus multidigituli) cause light, yellow stippling on leaves which may be barely noticeable. Heavy infestations cause distortion of newly emerging foliage and by July, all of the foliage on a severely infested tree may turn brown. Damage is similar to that of honeylocust plantbug. Stippling of infested foliage and canopy bronzing, stunted growth, and premature leaf drop may all occur on heavily infested trees. If damage occurs early enough in the season, the tree may refoliate. Honeylocust spider mite populations may be more severe on dry sites or when drought conditions occur.
The upper surface of the leaves of oaks, especially red oaks, are fed upon by the oak spider mite (Oligonychus bicolor). The oak spider mite causes a bronzing or bleaching of the upper leaf surface, which may be very apparent by June. However, the damage caused by this insect relative is often not noticed until it peaks, usually by late July or early August. Feeding damage may be most concentrated around the leaf midrib. The severe bronzing is most visible on the lower branches of larger trees. Damaged leaves may appear a dull, yellow color, but once the leaf dries out it becomes tan in color. Damage may increase with an increase in temperatures, as well as an increasing amount of impervious surface around the base of the tree (Steven Frank, NC State Extension, 2018).
The southern red mite (Oligonychus ilicis) feeds on the undersides of host plant leaves. This feeding causes bronzed or stippled foliage. On occasion, it is possible for leaves to become distorted if they are fed upon while young and still expanding. It is primarily a pest of azaleas and camellias. Some sources report that populations of southern red mite may disappear when new spring growth develops.
The spruce spider mite (Oligonychus ununguis) may leave behind tiny strands of webbing on the needles of its host plants. As a result of spruce spider mite feeding, damaged needles on spruce hosts often turn reddish brown. Initial feeding may turn the upper surface of the host plant needle a stippled yellow color. This cool season mite is of most significance on ornamental landscape conifers, but may also occur in natural forests. Larvae, nymphs, and adults all feed on the host plant needle. Spruce spider mites often prefer to feed on older rather than new needles. Feeding often occurs in the lower branches, toward the inside of the tree. Damage occurs primarily in the spring and fall. If feeding is heavy, host plant needles may drop prematurely. This pest can reproduce quickly, in large numbers, and may suddenly cause very noticeable injury. Less active in hot, dry weather (typically midsummer). Certain climatic conditions favor spruce spider mites. Their populations have been found to respond favorably to 79°F temperatures and relative humidity between 50-60%; however, simulated rainfall on Fraser fir seedlings significantly limits spruce spider mite populations (Boyne and Hain, 1983).
Twospotted spider mites (Tetranychus urticae) 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.
Look for clover mites (Bryobia praetiosa) with magnification on plants that have been previously symptomatic early in the season, such as mid-late May or around 192 GDD's. Scouting for European red mites (Panonychus ulmi) can occur weekly from just after apple petal fall until approximately August, or until populations are below 10 mites per leaf after August 1. Samples can be taken from at least 4 leaves per tree, at different sides and heights or exterior vs. interior of the tree. View these leaves with at least a 10X hand lens and look for mites on the undersides of leaves. Certain thresholds exist for management in fruit orchards, depending upon the time of year the samples are taken. Finding 1 mite per leaf may result in 40% of leaves being impacted. Finding 3 mites per leaf may result in 75% of the leaves being impacted. Scout for overwintering orange adult honeylocust spider mites (Platytetranychus multidigituli) on host plant twigs near bud scars or in bark cracks and crevices. 10X hand lens may be needed for magnification. Monitor leaves in the early spring and throughout the growing season for increasing stippling or discoloration. Monitor susceptible hosts for the oak spider mite (Oligonychus bicolor) in May and June, and look for the beginning of spider mite activity that may become more severe as seasonal temperatures rise. Scout the lower branches of larger host trees first, as they may be the first to be impacted, particularly those growing in hotter locations (ex. near impervious surfaces such as paved areas). Magnification is required to view spruce spider mite (Oligonychus ununguis) eggs. Tapping host plant branches over white paper may be a useful tool when scouting for spider mite presence. (View with a hand lens.) Do this as soon as any sign of off-green color appears on the foliage. Check 3-4 locations on the plant using this technique. If 10 or more spruce spider mites are found at each location on the plant, chemical applications may be necessary on high-value hosts.
Large populations of clover mites (Bryobia praetiosa) can be reduced by providing supplemental watering to areas where clover mites develop, such as dry areas at the base of sun exposed walls and around evergreens. Planting flowerbeds with plants that are not attractive to clover mites might be helpful, including but not limited to: geranium, chrysanthemum, zinnia, marigold, salvia, rose, petunia or shrubs such as barberry, juniper and yew (Gomez and Mizell, 2021). Tolerate European red mite (Panonychus ulmi) activity whenever possible in ornamental landscapes, as many effective predators and natural enemies typically reduce their populations. Choosing reduced risk pesticides when managing European red mite or other pests on these hosts will help preserve natural enemy populations which are very important in managed landscapes.
Dry conditions or drought favors most or nearly all spider mites, including the honeylocust spider mite (Platytetranychus multidigituli). They feed more under dry conditions, and the lower humidity allows them to evaporate excess water through excretion. Do not plant honeylocust at dry sites if spider mites are a concern. Most spider mite natural enemies require more humid conditions and are stressed by periods of drought. Plants stressed by drought can also change chemically in ways that make them more nutritious to spider mites, thus favoring their populations. Adequate watering of plants during dry conditions can help to limit the impact of drought stress on spider mite outbreaks. Hose plants periodically with a forceful jet of water, which may also physically remove and kill mites, as well as remove dust collecting on foliage that may interfere with the efficacy of mite predators (Cranshaw and Sclar, 2014).
The clover mite (Bryobia praetiosa) has important predators. Take this into consideration if selecting chemical management options on plants in the landscape. A mite predator, lady beetles, and lacewings are all noted to be significant natural enemies of the European red mite (Panonychus ulmi). Orius insidiosus, Stethorus punctum, Amblyseius fallacis, Agistemis fleschneri, and Zetzellia mali are all predators of the European red mite that have been reported in the US. Many are negatively impacted by chemical management of the European red mite, so limit chemical applications to reduced risk options only to preserve natural enemy populations that are very important in regulating the populations of this introduced spider mite.
Additional natural enemies of the honeylocust spider mite (Platytetranychus multidigituli) include lacewing larvae, minute pirate bugs, spiders, predatory thrips, predatory midges, and certain species of lady beetles. An additional predator of honeylocust spider mites includes Zetzellia mali, a predatory mite in the Family Stigmaeidae; however, phytoseiid mites are thought to offer greater management of honeylocust spider mite populations. If chemical management is deemed necessary, select reduced risk options in order to preserve natural enemies and predatory mites to help reduce populations of the honeylocust spider mite.
Populations of southern red mite (Oligonychus ilicis) can be impacted by natural predators. Of those, some information is known about their predatory mite (Phytoseiidae) natural enemies. Laboratory studies of Iphiseiodes zuluagai, Euseius citrifolius, and Amblyseius herbicolus have been conducted and revealed that the adult female life stage of each of those species are the most effective at eating the southern red mite, prefering to feed on their larvae. However, the nymph, adult male, and larval life stages of each of the predatory mites will also feed on southern red mite (Franco et al., 2007). Much of this research, however, has been done in the context of coffee plants. In Brazil, the southern red mite is known as the coffee red spider mite.
Natural enemies of spider mites (Tetranychidae) can include pathogens, viruses, and predators. Phytoseiid mites, spiders, and insects (including some beetles, lacewings, true bugs, flies, and thrips) are also natural enemies of certain spider mites. Specifics regarding the spruce spider mite (Oligonychus ununguis) are not fully understood. However, Typhlodromus spp. may help reduce spruce spider mite populations (Marshall, 1986). A study looking at augmentative biological control of spruce spider mite on juniper using Neoseiulus fallacis and Galendromus occidentalis suggested that releases of predators may not be effective if spruce spider mite populations are currently high. During the trial, the cost of using the predatory mites was 2.5-7 times greater than chemical management options (horticultural oil or hexythiazox) conducted during the study (Shrewsbury and Hardin, 2003). The authors suggest that further research is needed to determine the efficacy and timing of early season predatory mite releases to provide optimal suppression of spruce spider mite.
Natural predators often keep the twospotted spider mite (Tetranychus urticae) 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)
See each individual page for each species of spider mite for species-specific chemical management options.
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.
