Phytophthora Root Rot
Phytophthora spp. (P
397 host plants · Oomycete (water mold, not fungus)
Last updated
Data Coverage 3 of 6 dimensions
Phytophthora root rot often presents as a wilting, declining plant with yellowing or reddish foliage that doesn't respond to watering. When you excavate roots, you'll find them brown or black and rotted, beginning with the fine root tips. Larger roots develop distinct lesions with clean edges between the decayed tissue (dark and sunken) and healthy tissue (light colored, firm). Severely affected plants become wobbly and pull easily from the ground, and cankers may form at the base of the stem as the pathogen moves upward. Container nurseries are especially vulnerable in wet winters, as sustained moisture creates ideal conditions for this water-loving pathogen.
Phytophthora species are water-molds thriving in saturated or poorly drained soil. High moisture alone doesn't cause disease, but it greatly favors the production of swimming spores that attack fine roots. Management revolves around water management. Ensure excellent drainage in all planting beds and containers, elevating containers on gravel pads at least 4 inches deep; never place containers directly on plastic sheets, which prevent drainage and spread contaminated water between plants. Quarantine new plants for at least one year before integrating them into production areas. Select resistant cultivars when available. The pathogen can survive years in soil and plant debris, so crop rotation is essential: don't plant susceptible crops in previously infested fields for extended periods, or use new, pathogen-free soil if replanting is necessary.
Quick Reference
Agent Type
oomycete (water mold, not fungus)
Causal Agent
Phytophthora spp. (P
Host Plants
397
Spread
Zoospore dispersal in water; contaminated soil, media, pots, tools; infected ...
Favorable Conditions
High soil moisture (waterlogging, excess irrigation). Poorly drained media an...
Management
Vulnerability Window
Throughout the growing season, especially in wet periods and after propagation when plants are young.
What Triggers Infection
High soil moisture (waterlogging, excess irrigation). Poorly drained media and soils. Saturated conditions favor zoospore production.
Cultural Controls
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- Quarantine new plants for at least 1 year before introducing to production areas.
- Inspect and destroy any plants showing disease symptoms.
- Select resistant cultivars and species where available.
- Use pathogen-free propagation material.
- Ensure good drainage in field beds, field production, and container systems.
Host Plants (397)
Abies alba European Silver Fir, Common Silver Fir Abies amabilis Pacific Silver Fir Abies balsamea Balsam Fir Abies concolor White Fir, Colorado Fir Abies delavayi Delavay's Fir Abies grandis Grand Fir Abies koreana Korean Fir Abies lasiocarpa Subalpine Fir Rocky Mountain Fir, Alpine Fir Abies magnifica California Red Fir, Red Fir, Slivertip Fir Abies nordmanniana Nordmann Fir, Caucasian Fir Abies numidica Algerian Fir Abies pindrow West Himalayan Fir, Pindrow Fir Abies pinsapo Spanish Fir, Spanish Pin Fir Abies pinsapo subsp. marocana Moroccan Fir Abies procera Noble Fir Acer buergerianum Trident Maple, Three-toothed Maple Acer campestre Hedge Maple, Field Maple, Common Maple Acer capillipes Red Stripebark Maple, Red Snakebark Maple, Hakkoda Maple Acer carpinifolium Hornbeam Maple Acer circinatum Vine, Maple Acer coriaceifolium Leatherleaf Maple Acer crataegifolium Hawthorn, Maple Acer davidii David Maple, Père David's Maple Acer freemanii Freeman Maple, Hybrid Red Maple Acer ginnala Acer ginnala Acer glabrum Rocky Mountain Maple, Rock Maple, Douglas Maple, Dwarf Maple Acer glabrum var. douglasii Douglas Maple, Dwarf Maple, Rocky Mountain Maple Acer grandidentatum Bigtooth Maple, Western Mountain Sugar Maple, Rocky Mountain Sugar Maple Acer griseum Paperbark Maple Acer henryi Henry's Maple Acer japonicum Fullmoon Maple Acer macrophyllum Bigleaf Maple Acer maximowiczianum Nikko Maple Acer miyabei Miyabe Maple Acer monspessulanum Montpellier Maple Acer negundo Boxelder Manitoba Maple, Ash-leaved Maple Acer nipponicum Nippon Maple Acer oblongum Evergreen Maple, Smooth Leaf Maple Acer oliverianum Oliver Maple Acer opalus subsp. obtusatum Bosnian Maple Acer palmatum Japanese Maple Acer palmatum var. dissectum Dissected Japanese Maple Acer pensylvanicum Striped Maple, Moosewood Maple Acer pentaphyllum Acer pentaphyllum (no common name) Acer pictum Painted Maple Acer platanoides Norway Maple Acer pseudoplatanus Planetree Maple, Sycamore, Maple Acer rubrum Red Maple Acer rufinerve Redvein Maple, Honshu Maple Acer saccharinum Silver Maple Acer saccharum Sugar Maple Acer sempervirens Cretan Maple Acer shirasawanum Shirasawa Maple Acer spicatum Mountain Maple, Moose Maple Acer tataricum Tatarian Maple, Tartarian Maple Acer tataricum subsp. ginnala Amur Maple Acer tegmentosum Manchurian Stripebark Maple, Manchustriped Maple Acer triflorum Three Flowered Maple Acer truncatum Purpleblow Maple, Shantung Maple Acer velutinum Velvet Maple Agathis australis Kauri Tāne Mahuta, Kauri Pine Alnus alnobetula Circumpolar alder group Alnus alnobetula subsp. crispa American Green Alder, Mountain Alder, Green Alder Alnus alnobetula subsp. sinuata Sitka Alder, Wavy Leaf Alder Alnus cordata Italian Alder Alnus glutinosa Common Alder, European Alder, Black Alder Alnus incana subsp. rugosa Speckled Alder Alnus incana subsp. tenuifolia Thinleaf Alder, Mountain Alder Alnus japonica Japanese Alder Alnus rhombifolia White Alder Alnus rubra Red Alder Alnus rubra f. pinnatisecta Cutleaf Red Alder Alnus sinuata Sitka Alder Araucaria araucana Monkey Puzzle Tree, Chilean Pine Araucaria bidwillii Bunya Pine Araucaria cunninghamii Hoop Pine, Moreton Bay Pine Araucaria heterophylla Norfolk Island Pine Athrotaxis laxifolia Tasmanian Pencil Pine, Summit Cedar Buxus bodinieri Bodinier's Boxwood Buxus microphylla Buxus microphylla Buxus microphylla var. koreana Korean Littleleaf Boxwood Buxus sempervirens Common Boxwood, Common Box European Box Cephalotaxus harringtonia Japanese Plum Yew, Cow's Tail Pine 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 Glyptostrobus pensilis Chinese Swamp Cypress, Water Pine Water Fir Shui song Grevillea aquifolium Holly, Grevillea 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 Juglans ailantifolia Japanese Walnut, Heartnut Juglans californica California Walnut, Southern California Walnut Juglans cinerea Butternut Juglans microcarpa Texas Walnut, Little Walnut Juglans nigra Black Walnut Juglans regia English Walnut, Persian Walnut 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 Microcachrys tetragona Creeping Pine, Creeping Strawberry Pine Paxistima myrsinites Oregon Boxwood, Mountain Lover Picea abies Norway Spruce Picea abies var. pendula Weeping Norway Spruce, Pendulous Norway Spruce Picea asperata Dragon Spruce Picea breweriana Brewer Spruce, Brewer's Weeping Spruce Picea engelmannii Engelmann Spruce Picea gemmata Szechwan Spruce Picea glauca White Spruce, Canadian Spruce, Skunk Spruce Picea koyamae Koyama's Spruce, Yatsugatake-tohi [Japanese] Picea mariana Black Spruce, Bog Spruce, Swamp Spruce Picea omorika Serbian Spruce Picea orientalis Caucasian Spruce, Oriental Spruce Picea pungens Colorado Spruce Picea pungens var. glauca Colorado Blue Spruce Picea rubens Red Spruce Picea sitchensis Sitka Spruce Picea wilsonii Wilson's Spruce 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 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 Apricotc Japanese Flowering Apricot Japanese Flowering Plum 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 Rhamnus alnifolia Alder Buckthorn, Glossy Buckthorn, Breaking Buckthorn Rhododendron 'Purple Gem' Purple Gem Rhododendron Rhododendron airy Rhododendron, airy Rhododendron alabamense Alabama Azalea Rhododendron alice Alice Rhododendron Rhododendron anah Rhododendron, anah Rhododendron anna Rhododendron, anna Rhododendron april Rhododendron, april Rhododendron arboreum subsp. cinnamomeum Cinnamon Rhododendron Rhododendron argosy Argosy Rhododendron Rhododendron augustinii Augustine Rhododendron Rhododendron auriculatum No common name (R. auriculatum) Rhododendron beauty Rhododendron, beauty Rhododendron bibiani Bibiani Rhododendron Rhododendron blue Rhododendron, blue Rhododendron boule Rhododendron, boule Rhododendron bow Rhododendron, bow Rhododendron bric Rhododendron, bric Rhododendron bureavii Bureau Rhododendron Rhododendron campylocarpum subsp. coloxanthum Coloxanthum Rhododendron Rhododendron catawbiense Catawba Rhododendron Rhododendron cheer Cheer Rhododendron Rhododendron chevalier Rhododendron, chevalier Rhododendron christmas Rhododendron, christmas Rhododendron cinnabarinum Cinnabar Rhododendron Rhododendron concinnum Concinnum Rhododendron Rhododendron cotton Rhododendron, cotton Rhododendron crater Rhododendron, crater Rhododendron crest Crest Rhododendron Rhododendron cunninghams Rhododendron, cunninghams Rhododendron cynthia Cynthia Rhododendron Rhododendron daphnoides Daphnoides Rhododendron Rhododendron dauricum Dauricum Rhododendron Rhododendron davidsonianum Davidsonianum Rhododendron Rhododendron day Rhododendron, day Rhododendron deciduous Rhododendron, deciduous Rhododendron defines Rhododendron, defines Rhododendron delaware Rhododendron, delaware Rhododendron dora Rhododendron, dora Rhododendron dreamland Dreamland Rhrododendron Rhododendron el Rhododendron, el Rhododendron elisabeth Rhododendron, elisabeth Rhododendron elizabeth Elizabeth Rhododendron Rhododendron falconeri subsp. falconeri Falconer Rhododendron Rhododendron fantastic Fantastic Rhododendron Rhododendron formosum var. formosum Formosum Rhododendron Rhododendron forrestii subsp. forrestii Forrest Rhododendron Rhododendron fortunei subsp. discolor Fortune Discolor, Discolor Rhododendron Rhododendron frilly Rhododendron, frilly Rhododendron gartendirektor Rhododendron, gartendirektor Rhododendron girards Rhododendron, girards Rhododendron goldflimmer Goldflimmer Rhododendron Rhododendron grace Rhododendron, grace Rhododendron groenlandicum Labrador-tea, Labrador Tea Rhododendron haematodes subsp. haematodes Haematodes Rhododendron Rhododendron hallelujha Hallelujah Rhododendron Rhododendron hanceanum Hanceanum Rhododendron Rhododendron hardijzer Rhododendron, hardijzer Rhododendron harry Rhododendron, harry Rhododendron hino Rhododendron, hino Rhododendron hinode Rhododendron, hinode Rhododendron hippophaeoides var. hippophaeoides Hippophaeoides Rhododendron Rhododendron hodgsonii Hodgson Rhododendron Rhododendron honourable Rhododendron, honourable Rhododendron horizon Rhododendron, horizon Rhododendron hotei Hotei Rhododendron Rhododendron irroratum Irroratum Rhododendron Rhododendron jock Jock Rhododendron Rhododendron johnstoneanum Rhododendron, johnstoneanum Rhododendron kaempferi Torch Azalea Rhododendron keiskei Keiskei Rhododendron, Keisuki Rhododendron Rhododendron ken Rhododendron, ken Rhododendron kiusianum Kiusianum Azalea, Kyushu Azalea Rhododendron lacteum Lacteum Rhododendron Rhododendron lees Rhododendron, lees Rhododendron lems Rhododendron, lems Rhododendron lights Rhododendron, lights Rhododendron loderi Rhododendron, loderi Rhododendron luteiflorum Luteiflorum Rhododendron Rhododendron lutescens Lutescens Rhododendron Rhododendron luteum Pontic or Pontica Azalea Rhododendron macabeanum Macabeanum Rhododendron Rhododendron macrophyllum Pacific Rhododendron Rhododendron moonstone Moonstone Rhododendron Rhododendron mrs Rhododendron, mrs Rhododendron mucronulatum Rhododendron, mucronulatum Rhododendron myrtifolium Myrtifolium Rhododendron Rhododendron niveum Niveum Rhododendron Rhododendron northern Rhododendron, northern Rhododendron occidentale Western Azalea Rhododendron orbiculare subsp. orbiculare Obiculare Rhododendron Rhododendron orchid Rhododendron, orchid Rhododendron oreotrephes Oreotrephes Rhododendron Rhododendron oudijks Rhododendron, oudijks Rhododendron pachytrichum Pachytrichum Rhododendron Rhododendron peekaboo Peekaboo Rhododendron Rhododendron pink Rhododendron, pink Rhododendron pioneer Rhododendron, pioneer Rhododendron pjm P.J.M. Rhododendron Rhododendron point Rhododendron, point Rhododendron ponticum Rhododendron, ponticum Rhododendron president Rhododendron, president Rhododendron prinophyllum Roseshell Azalea, Pinkshell Azalea Rhododendron prunifolium Plumleaf Azalea Rhododendron quinquefolium Quinquefolium Azalea Rhododendron racemosum Racemosum Rhododendron Rhododendron ramapo Ramapo Rhododendron Rhododendron rosamundi Rosamundi Rhododendron Rhododendron roseum Rhododendron, roseum Rhododendron rosy Rhododendron, rosy Rhododendron roxieanum var. oreonasters No common name Rhododendron rubiginosum Rubiginosum Rhododendron Rhododendron sappho Sappho Rhododendron Rhododendron scarlet Rhododendron, scarlet 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 snow Rhododendron, snow Rhododendron stenopetalum Rhododendron, stenopetalum Rhododendron taurus Taurus Rhododendron Rhododendron temple Rhododendron, temple Rhododendron thomsonii subsp. thomsonii Thomson Rhododendron Rhododendron tri Rhododendron, tri Rhododendron trilby Trilby Rhododendron Rhododendron unique Unique Rhododendron Rhododendron vulcan Vulcan Rhododendron Rhododendron wardii Ward Rhododendron Rhododendron white Rhododendron, white Rhododendron wiltonii Wilton Rhododendron Rhododendron winsome Winsome 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 allegheniensis Allegheny Blackberry Rubus armeniacus Himalayan Blackberry Armenian Blackberry Rubus calycinoides Crinkle-leaf Creeper Creeping Raspberry Yü-shan raspberry Rubus dicolor Himalayan Blackberry Armenian Blackberry Rubus hayata Rubus hayata Rubus idaeus red raspberry Rubus laciniatus Evergreen Blackberry Cutleaf Blackberry Rubus leucodermis Blackcap, Western Raspberry Rubus lineatus Silky-leaved Berry Rubus odoratus Flowering Raspberry Purple-flowering Raspberry Rubus parviflorus Thimbleberry Western Thimbleberry Rubus rolfei Creeping Raspberry, Crinkle-leaf Creeper Rubus spectabilis Salmonberry Rubus tricolor Creeping Bramble Korean Raspberry Rubus ursinus Trailing Blackberry Western Blackberry California Blackberry Dewberry Sciadopitys verticillata Japanese Umbrella Pine, Umbrella Pine Solanum aviculare Kangaroo Apple Taxus canadensis Canadian Yew, American Yew, Ground Hemlock Tsuga canadensis Canadian Hemlock, Eastern Hemlock Tsuga canadensis var. pendula Weeping Hemlock Tsuga diversifolia Northern Japanese Hemlock Tsuga heterophylla Western Hemlock Tsuga mertensiana Mountain Hemlock Wollemia nobilis Wollemi Pine