Spider mite
Tetranychidae
337 host plants
Last updated
Spider mites feed on plant leaves and needles, creating tiny white or yellow stippled spots that give foliage a mottled appearance. Heavy infestations progress to bronze or bleached foliage with entire leaves dropping; webbing may be visible on leaf undersides. Leaves feel gritty to the touch when colonies are present.
Monitor leaf undersides in dry periods when populations surge. Strong water spray dislodges mites; repeat every few days. Horticultural oil or soap with undersurface coverage suppresses populations. Avoid high-nitrogen fertilizers favoring mites. Conserve predatory insects.
Quick Reference
Order
Acari
Type
mite
Host Plants
337
Peak Activity
April-June: Spring buildup (slow in cool, moist PNW spring). July-August: Pea...
Damage Severity
growth-reducing
Monitoring & Action
How to Monitor
Spring (Apr-June): Begin checking leaf undersides on known hosts (roses, fruit trees, spruce) in May. Look for stippled leaves and fine webbing. Summer (July-Aug): Scout weekly. Look for pale dots on leaf surface (stippling), delicate webbing underside. Hand lens reveals tiny mites. Stress indicator: if stippling appears, plant already under drought stress - irrigation is key. Predatory mites (larger, slower-moving) are an indicator of natural biocontrol activity, working.
When to Act
Stippling alone does NOT trigger treatment threshold. Mites are indicators of plant stress, commonly drought stress. If predatory mites visible (larger, slower-moving) and plant vigor good, no treatment needed. Threshold for intervention: webbing visible AND predators absent AND plant showing visible decline (bronzing, defoliation progressing) AND drought stress confirmed. Young/evergreen plants more sensitive than mature deciduous. Threshold is lower for conifers (cannot recover from defoliation) than for deciduous trees.
What Damage Looks Like
Feeding causes stippling (tiny pale dots) on leaf upper surfaces as individual cells are emptied. As populations build, stippling coalesces into bronzing or silvering of entire leaves. Fine silk webbing becomes visible on leaf undersides and between leaves. Heavily infested plants show premature leaf drop, reduced vigor, and stunted growth. On conifers, damage appears as yellowing or bronzing of needles that progresses from inner to outer canopy. On fruit trees, mite feeding reduces photosynthesis, weakens the tree, and can reduce fruit size and quality. Spider mite damage is almost always associated with drought stress or disruption of natural enemies by broad-spectrum insecticide use.
Cultural Controls
- Overhead watering during July-August (risk window): Water foliage once weekly when temperatures exceed 80°F. Create humid microclimate where mites cannot reproduce efficiently. Do in early morning to minimize fungal disease risk, but mite suppression benefit outweighs minor disease risk during heat spike. This is prevention strategy and often sufficient.
- Targeted underscore watering during active infestation: Spray undersides of leaves with moderate pressure (not full force) every 3-4 days during July-August. Dislodges mites and disrupts webbing. Buys time for predatory mites to catch up.
Host Plants (337)
Acer crataegifolium Hawthorn, Maple Adenium obesum Desert Rose, Desert Azalea, Mock Azalea Agathis australis Kauri Tāne Mahuta, Kauri Pine Alcea rosea Hollyhock Araucaria araucana Monkey Puzzle Tree, Chilean Pine Araucaria bidwillii Bunya Pine Araucaria cunninghamii Hoop Pine, Moreton Bay Pine Araucaria heterophylla Norfolk Island Pine Arbutus unedo Strawberry Tree, Killarney Strawberry Tree, Madroño Asimina triloba Common Pawpaw Custard Apple Athrotaxis laxifolia Tasmanian Pencil Pine, Summit Cedar Berberis aquifolium Oregon Grape, Oregon Grape Holly, Tall Oregon Grape Berberis pinnata California Barberry, California Holly Grape Betula lenta Sweet Birch, Cherry Birch, Black Birch Cephalotaxus harringtonia Japanese Plum Yew, Cow's Tail Pine Ceratonia siliqua Carob St. John's Bread Locust, Bean Cornus capitata Evergreen Dogwood, Bentham's Cornel, Himalayan Strawberry Tree Cotoneaster apiculatus Cranberry Cotoneaster Cotoneaster bullatus Hollyberry Cotoneaster Cotoneaster congestus Pyrenees Cotoneaster Cotoneaster dammeri Bearberry Cotoneaster Cotoneaster divaricatus Spreading Cotoneaster Cotoneaster franchetii Franchet Cotoneaster Cotoneaster horizontalis Rockspray Cotoneaster Cotoneaster intergerrimus European Cotoneaster Cotoneaster lacteus Parney Cotoneaster Cotoneaster lucidus Hedge Cotoneaster Cotoneaster microphyllus Littleleaf Cotoneaster Cotoneaster multiflorus Many-flowered Cotoneaster Cotoneaster salicifolius Willowleaf Cotoneaster Cotoneaster simonsii Simons Cotoneaster Cotoneaster suecicus Cotoneaster suecicus Crataegus ambigua Russian Hawthorn Crataegus autumn Crataegus autumn Crataegus columbiana Columbia Hawthorn Crataegus crus Crataegus crus Crataegus douglasii Black Hawthorn Crataegus germanica Medlar Crataegus laevigata English Hawthorn Crataegus lavallei Lavalle Hawthorn, Carrierei Hawthorn Crataegus monogyna Singleseed Hawthorn, Common Hawthorn, English Hawthorn Crataegus phaenopyrum Washington Hawthorn Crataegus punctata Dotted Hawthorn, Flat-topped Hawthorn Crataegus viridis Green Hawthorn,Southern Hawthorn Daphne cneorum Garland Daphne, Rock Daphne, Rose Daphne Dermatophyllum secundiflorum Mescal Bean Texas Mountain Laurel, Frijolito Eucalyptus cinerea Silver Dollar Eucalyptus, Silver Dollar Gum Argyle Apple Euonymus americanus American Euonymus, Hearts-a-Burstin', Strawberry Bush Fragaria chiloensis Beach Strawberry Sand Strawberry, Chilean Strawberry Glyptostrobus pensilis Chinese Swamp Cypress, Water Pine Water Fir Shui song Hedera canariensis Canary Island Ivy, Canarian Ivy, Algerian Ivy Hedera helix English Ivy Hibiscus syriacus Rose, of Sharon Shrub, Althea Ilex aquifolium English Holly Ilex attenuata Ilex attenuata Ilex cornuta Chinese Holly, Horned Holly Ilex crenata Japanese Holly Ilex glabra Inkberry Inkberry Holly, Gallberry, Evergreen Winterberry Ilex latifolia Lusterleaf Holly Ilex meserveae Meserve Hybrid Holly Ilex paraguariensis Yerba Matá, Maté, Paraguay Tea Ilex verticillata Winterberrry Winterberry Holly, Michigan Holly, Christmas Berry Black Alder Juniperus californica California Juniper, California White Cedar, Desert White Cedar Juniperus cedrus Canary Island Juniper Juniperus chinensis Chinese Juniper Juniperus communis Common Juniper Juniperus conferta Juniperus conferta Juniperus deppeana Alligator Juniper, Checkered-bark Juniper Juniperus formosana Formosan Juniper Juniperus grey Juniperus grey Juniperus horizontalis Creeping Juniper Juniperus monosperma Oneseed Juniper Juniperus occidentalis Western Juniper Juniperus osteosperma Utah Juniper Juniperus pingii Ping Juniper Juniperus procumbens Japanese Garden Juniper, Bonin Island Juniper, Ibuki Juniper Juniperus rigida Temple Juniper, Needle Juniper Juniperus rigida subsp. conferta Shore Juniper Juniperus sabina Savin Juniper Juniperus scopulorum Rocky Mountain Juniper Juniperus squamata Singleseed Juniper, Flaky Juniper, gao shan bai Juniperus virginiana Eastern Redcedar Pencil Cedar Kerria japonica Japanese Kerria Japanese Rose Laburnum watereri Goldenchain Tree, Hybrid Goldenchain Tree Magnolia acuminata Cucumber Magnolia, Cucumbertree Magnolia, Mountain Magnolia Malus 'Indian Magic' Indian Magic Crabapple Malus 'Prairifire' Prairifire Crabapple Malus 'Snowdrift' Snowdrift Crabapple Malus atrosanguinea Carmine Crabapple Malus brandywine Brandywine Crabapple Malus floribunda Japanese Flowering Crabapple Malus fusca Pacific Crabapple Malus hupehensis Tea Crabapple Malus pumila Apple Malus robusta Cherry, Crabapple Malus sargentii Sargent Crabapple, Pigmy Crabapple Malus transitoria Transitoria Crabapple Menziesia ciliicalyx var. multiflora Mock Azalea, Menziesia Menziesia ferruginea Rusty Menziesia, Fool's Huckleberry, False Azalea Microbiota decussata Russian Arborvitae, Siberian Cypress Microcachrys tetragona Creeping Pine, Creeping Strawberry Pine Pinus albicaulis Whitebark Pine, Scrub Pine, White Pine Pinus aristata Bristlecone Pine, Rocky Mountain Bristlecone Interior Bristlecone Pinus attenuata Knobcone Pine Pinus banksiana Jack Pine, Scrub Pine, Banksian Pine, Hudson Bay Pine Pinus bungeana Lacebark Pine, Whitebark Pine, Baipi Song Pinus canariensis Canary Island Pine Pinus cembra Swiss Stone Pine Pinus contorta Lodgepole Pine Pinus contorta var. contorta Shore Pine Pinus contorta var. latifolia Rocky Mountain Lodgepole Pine Pinus coulteri Coulter Pine, Bigcone Pine Pinus densiflora Japanese Red Pine Pinus edulis Pinyon Pine, Piñón Pine, Two-needle Pinyon Colorado Pinyon Pinus elliottii Slash Pine, Swamp Pine Pinus flexilis Limber Pine, Rocky Mountain White Pine Pinus halepensis Aleppo Pine, Jerusalem Pine Pinus heldreichii Bosnian Pine, Snakeskin Pine Pinus jeffreyi Jeffrey Pine, Western Yellow Pine, Bull Pine Pinus kwangtungensis Kwangtung Pine, Guangdong Pine Pinus lambertiana Sugar Pine Pinus leucodermis Bosnian Pine Pinus monophylla Singleleaf Pinon Pine, One-leaved Pine Pinus monticola Western White Pine Pinus mugo Mugo Pine Pinus mugo var. pumilio Mugo pine, Dwarf Mugo pine Pinus nigra Austrian Pine Pinus parviflora Japanese White Pine Pinus parvifola Pinus parvifola Pinus pinaster Maritime Pine, Cluster Pine, Turpentine Pine Pinus pinea Italian Stone Pine, Umbrella Pine Pinus ponderosa Ponderosa Pine, Western Yellow Pine Pinus pumila Japanese Stone Pine, Dwarf Siberian Pine Pinus radiata Monterey Pine Pinus resinosa Red Pine Pinus sabiniana Gray Pine, Foothill Pine Pinus strobiformis Southwestern White Pine, Mexican White Pine, Chihuahua White Pine Pinus strobus Eastern White Pine Pinus sylvestris Scots Pine, Scotch Pine Pinus thunbergii Japanese Black Pine Pinus virginiana Virginia Pine, Scrub Pine, Jersey Pine Pinus wallichiana Himalayan Pine, Bhutan Pine Pinus yunnanensis Yunnan Pine Platycladus orientalis Chinese Arborvitae, Oriental Arborvitae Prunus americana Wild Plum American (Red) Plum August Plum, Goose Plum Prunus armeniaca Apricot Prunus avium Sweet Cherry Prunus besseyi Sand Cherry, Western Sand Cherry Prunus blireiana Blireiana Plum Prunus caroliniana Carolina Cherrylaurel American Cherrylaurel Prunus cascade Prunus cascade Prunus cerasifera Cherry, Plum Prunus cistena Purpleleaf Sandcherry Redleaf Sandcherry Cistena Sandcherry Cistena Plum Prunus dream Prunus dream Prunus emarginata Bitter Cherry, Wild Cherry, Quinine Cherry Prunus first Prunus first Prunus fruticosa Steppe Cherry, European Dwarf Ground Cherry, Mongolian Cherry Prunus glandulosa Dwarf Flowering Almond Prunus ilicifolia Hollyleaf Cherry, Holly-leaved Cherry Prunus laurocerasus Cherry Laurel Prunus lusitanica Portugal Laurel Prunus maackii Amur Chokecherry Amur Cherry, Manchurian Cherry Prunus mume Japanese Flowering Apricot Prunus newport Newport Flowering Plum Prunus okame Okame Flowering Cherry Prunus padus European Birdcherry Common Birdcherry Prunus prostrata Rock Cherry, Mountain Cherry Prunus sargentii Sargent Cherry, Sargent's Cherry Prunus serotina Black Cherry, Rum Cherry Prunus serrula Birchbark Cherry, Paperbark Cherry, Tibetan Cherry Prunus serrulata Japanese Flowering Cherry Prunus snow Prunus snow Prunus subcordata Klamath Plum, Sierra Plum, Pacific Plum Prunus subhirtella Higan Cherry Prunus subhirtella var. autumnalis Autumn Flowering Higan Cherry Prunus tai Prunus tai Prunus virginiana Prunus virginiana Prunus virginiana var. demissa Western Chokecherry Prunus virginiana var. virginiana Common Chokecherry, Eastern Chokecherry Prunus yedoensis Yoshino Cherry, Somei-yoshino Cherry, Tokyo Cherry Pyrus communis Common Pear Pyrus fauriei Pyrus fauriei Pyrus salicifolia Pyrus salicifolia Rhaphiolepis indica Indian Hawthorn Rhaphiolepis umbellata Yeddo Rhaphiolepis Yeddo Hawthorn Rhododendron 'Alice' Alice Rhododendron Rhododendron 'Anah Kruschke' Anah Kruschke Rhododendron Rhododendron 'Anna Rose Whitney' Anna Rose Whitney Rhododendron Rhododendron 'Argosy' Argosy Rhododendron Rhododendron 'Bruce Briggs' Bruce Briggs Rhododendron Rhododendron 'Capistrano' Capistrano Rhododendron Rhododendron 'Carmen' Carmen Rhododendron Rhododendron 'Cheer' Cheer Rhododendron Rhododendron 'Cilpinense' Cilpinense Rhododendron Rhododendron 'Crest' Crest Rhododendron Rhododendron 'Cunningham's White' Cunningham's White Rhododendron Rhododendron 'Cynthia' Cynthia Rhododendron Rhododendron 'Dora Amateis' Dora Amateis Rhododendron Rhododendron 'Dreamland' Dreamland Rhododendron Rhododendron 'Elizabeth' Elizabeth Rhododendron Rhododendron 'Fantastica' Fantastica Rhododendron Rhododendron 'Gibraltar' Gibraltar Azalea Rhododendron 'Girard's Fuchsia' Girard's Fuchsia Azalea Rhododendron 'Glacier' Glacier Azalea Rhododendron 'Goldflimmer' Goldflimmer Rhododendron Rhododendron 'Gomer Waterer' Gomer Waterer Rhododendron Rhododendron 'Hallelujah' Hallelujah Rhododendron Rhododendron 'Hino-Crimson' Hino-Crimson Azalea Rhododendron 'Horizon Monarch' Horizon Monarch Rhododendron Rhododendron 'Hotei' Hotei Rhododendron Rhododendron 'Jock' Jock Rhododendron Rhododendron 'Klondyke' Klondyke Azalea Rhododendron 'Lee's Dark Purple' Lee's Dark Purple Rhododendron Rhododendron 'Lord Roberts' Lord Roberts Rhododendron Rhododendron 'Mandarin Lights' Mandarin Lights Azalea Rhododendron 'Moonstone' Moonstone Rhododendron Rhododendron 'Mother's Day' Mother's Day Azalea Rhododendron 'Nancy Evans' Nancy Evans Rhododendron Rhododendron 'Nova Zembla' Nova Zembla Rhododendron Rhododendron 'P.J.M.' P.J.M. Rhododendron Rhododendron 'Peekaboo' Peekaboo Rhododendron Rhododendron 'Percy Wiseman' Percy Wiseman Rhododendron Rhododendron 'Pohjola's Daughter' Pohjola's Daughter Rhododendron Rhododendron 'Purple Gem' Purple Gem Rhododendron Rhododendron 'Ramapo' Ramapo Rhododendron Rhododendron 'Rosamundi' Rosamundi Rhododendron Rhododendron 'Roseum Elegans' Roseum Elegans Rhododendron Rhododendron 'Sappho' Sappho Rhododendron Rhododendron 'Solidarity' Solidarity Rhododendron Rhododendron 'Stewartstonian' Stewartstonian Azalea Rhododendron 'Taurus' Taurus Rhododendron Rhododendron 'The Honourable Jean Marie de Montague' Jean Marie Rhododendron Rhododendron 'Trilby' Trilby Rhododendron Rhododendron 'Unique' Unique Rhododendron Rhododendron 'Vulcan' Vulcan Rhododendron Rhododendron 'Winsome' Winsome Rhododendron Rhododendron 'Yaku Prince' Yaku Prince Rhododendron Rhododendron 'Yaku Princess' Yaku Princess Rhododendron Rhododendron alabamense Alabama Azalea Rhododendron arboreum subsp. cinnamomeum Cinnamon Rhododendron Rhododendron augustinii Augustine Rhododendron Rhododendron auriculatum No common name (R. auriculatum) Rhododendron bibiani Bibiani Rhododendron Rhododendron bureavii Bureau Rhododendron Rhododendron campylocarpum subsp. coloxanthum Coloxanthum Rhododendron Rhododendron catawbiense Catawba Rhododendron Rhododendron cinnabarinum Cinnabar Rhododendron Rhododendron concinnum Concinnum Rhododendron Rhododendron daphnoides Daphnoides Rhododendron Rhododendron dauricum Dauricum Rhododendron Rhododendron davidsonianum Davidsonianum Rhododendron Rhododendron falconeri subsp. falconeri Falconer Rhododendron Rhododendron formosum var. formosum Formosum Rhododendron Rhododendron forrestii subsp. forrestii Forrest Rhododendron Rhododendron fortunei subsp. discolor Fortune Discolor, Discolor Rhododendron Rhododendron groenlandicum Labrador-tea, Labrador Tea Rhododendron haematodes subsp. haematodes Haematodes Rhododendron Rhododendron hanceanum Hanceanum Rhododendron Rhododendron hippophaeoides var. hippophaeoides Hippophaeoides Rhododendron Rhododendron hodgsonii Hodgson Rhododendron Rhododendron irroratum Irroratum Rhododendron Rhododendron johnstoneanum Rhododendron, johnstoneanum Rhododendron keiskei Keiskei Rhododendron, Keisuki Rhododendron Rhododendron kiusianum Kiusianum Azalea, Kyushu Azalea Rhododendron lacteum Lacteum Rhododendron Rhododendron luteiflorum Luteiflorum Rhododendron Rhododendron lutescens Lutescens Rhododendron Rhododendron luteum Pontic or Pontica Azalea Rhododendron macabeanum Macabeanum Rhododendron Rhododendron macrophyllum Pacific Rhododendron Rhododendron mucronulatum Rhododendron, mucronulatum Rhododendron myrtifolium Myrtifolium Rhododendron Rhododendron niveum Niveum Rhododendron Rhododendron occidentale Western Azalea Rhododendron orbiculare subsp. orbiculare Obiculare Rhododendron Rhododendron oreotrephes Oreotrephes Rhododendron Rhododendron pachytrichum Pachytrichum Rhododendron Rhododendron ponticum Rhododendron, ponticum Rhododendron prinophyllum Roseshell Azalea, Pinkshell Azalea Rhododendron prunifolium Plumleaf Azalea Rhododendron quinquefolium Quinquefolium Azalea Rhododendron racemosum Racemosum Rhododendron Rhododendron roxieanum var. oreonasters No common name Rhododendron rubiginosum Rubiginosum Rhododendron Rhododendron schlippenbachii Royal Azalea Rhododendron serpyllifolium Wild Thyme, Azalea Rhododendron serpyllifolium var. albifolrum White Wild Thyme, Azalea Rhododendron sinofalconeri Sinofalconer Rhododendron Rhododendron sinogrande Sinogrande Rhododendron Rhododendron smirnowii Smirnow Rhododendron Rhododendron stenopetalum Rhododendron, stenopetalum Rhododendron thomsonii subsp. thomsonii Thomson Rhododendron Rhododendron wardii Ward Rhododendron Rhododendron wiltonii Wilton Rhododendron Rhododendron yakushimanum Yak Rhododendron Rosa acicularis Wild Prickly Rose Rosa gymnocarpa Little Wood Rose, Wood Rose, Baldhip Rose Rosa multiflora Multiflora Rose Rosa nutkana Nootka Rose Rosa pisocarpa Clustered Rose, Swap Rose Rosa rubiginosa Sweetbriar Rose, Eglantine Rose Rosa rugosa Rugosa Rose, Beach Tomato, Sea Tomato Rosa woodsii Woods' Rose Rubus calycinoides Crinkle-leaf Creeper Creeping Raspberry Yü-shan raspberry Rubus leucodermis Blackcap, Western Raspberry Rubus odoratus Flowering Raspberry Purple-flowering Raspberry Rubus tricolor Creeping Bramble Korean Raspberry Sciadopitys verticillata Japanese Umbrella Pine, Umbrella Pine Skimmia japonica Japanese Skimmia Skimmia reevesiana Reeves Skimmia Sophora secundiflora Mescal Bean Texas Mountain Laurel, Frijolito Spiraea betulifolia Birch-leaf Spirea, Shiny-leaf Spirea, White Spirea Spiraea densiflora Rose, Meadowsweet, Mountain Spirea, Subalpine Spirea Spiraea double Spiraea, double Spiraea douglasii Rose, Spirea Spiraea fritschiana Korean Spirea Spiraea japonica Japanese Spirea Spiraea japonica var. alpina Daphne, Spirea Spiraea miyabei Miyabe Spirea Spiraea nipponica Nippon Spirea Spiraea prunifolia Spiraea, prunifolia Spiraea splendens Mountain Spirea, Rose Meadowsweet, Subalpine Spirea Spiraea thunbergii Thunberg Spirea Spiraea vanhouttei Van Houtte Spirea, Bridal Wreath Spirea Thuja occidentalis Eastern Arborvitae, American Arborvitae Eastern White-cedar Thuja orientalis Chinese Arborvitae, Oriental Arborvitae Thuja plicata Western Redcedar Thujopsis dolabrata Elkhorn Cedar, Deerhorn Cedar, Hiba Arborvitae, False Arborvitae Tilia americana American Linden, American Basswood Tilia cordata Littleleaf Linden Tilia euchlora Crimean Linden Tilia europaea European Linden, Common Linden Common Lime European Basswood Tilia mongolica Mongolian Linden, Mongolian Basswood Tilia tomentosa Silver Linden, Silver Basswood Viburnum dilatatum Linden, Viburnum, Linden, Arrowwood Waldsteinia fragarioides Barren Strawberry Wollemia nobilis Wollemi Pine
Sources & References
Primary: PNW Insect Management Handbook
- WSU HortSense — multiple spider mite fact sheets
- UC Davis IPM Spider Mites
- Cornell Cooperative Extension: Spider Mites and Their Control
Data Maturity Structured Multiple sources. Expert review underway.