WW-06659     1995  

Disease Management Recommendations for Trees and Shrubs

Copyright ©  2012  Regents of the University of Minnesota. All rights reserved.

Table of Contents

Foward
Table of Common and Trade Names
Host Plants

Ash, Green	Boston Ivy	Caragana	Catalpa
Cherry/Chokecherry	Cotoneaster	Cottonwood	Crabapple, Ornamental
Currant, Alpine	Dogwood	Elm American	Elm Siberian
Fir Douglas	Hackberry	Hawthorn	Honeylocust
Honeysuckle	Horsechestnut/Ohio buck-eye	Juniper	Lilac
Maple	Mock Orange	Mountain Ash	Oak
Pine	Plum, Ornamental	Poplar	Rhododendron
Rose	Russian Olive	Serviceberry/Juneberry	Spruce
Sumac	Viburnium	Walnut	Willow

Suggested References

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Foward

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Diagnosis of plant problems can be a difficult and at times impossible task. The goal is a correct diagnosis so that management procedures can be implemented successfully. This guide is designed to provide a description of disease symptoms for disease identification as well as some brief information on disease management. References listed will provide more detailed diagnostic and management information.

Proper plant placement and management in the landscape are very important in establishing and maintaining plant health. In some situations pesticides may be a necessary component of disease management; in other cases they may not be or they are not available. Pesticides are used as an aid to restore plant health, but are seldom a long-term solution for plants on poor sites or with severe mechanical damage.

While pesticide recommendations in this guide are current at the time of publication, the availability and recommended use of specific pesticides may change. The label on the pesticide being used is the final authority on how it is to be legally used. Pesticides on the following pages are listed by the common names of their active ingredients. These names are found on the label under the heading Active Ingredients, often listed in fine print.

Representative trade names may be included along with generic names. This information is supplied with the understanding that no discrimination is intended and no endorsement is implied.

Table of Common and Trade Names

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(Chemicals in italics are generally available in the homeowner market)

Common Name	Trade or Company Name (Noninclusive)
Anilazine	Dyrene
Banrot	Banrot
Benomyl	Benlate, Benomyl, Bonomyl, Tersan 1991
Calcium polysulfide	Lime sulfur, Orthorix
Captan	Captan, Orthocide
Chloroneb	Terraneb SP, Tersan SP
Chlorothalonil	Bravo 720, Daconil 2787, Funginil, Ole, Ortho MultiPurpose Fungicide
Coppers:
Basic copper sulfate	Basic copper sulfate
Copper sulfate	Bordeaux mixture
Copper hydroxide	Champ, Champion, Kocide
Copper oleate	Liquid Copper Fungicide
Dichloran (DCNA)	Botran
Dinocap	Karathane
Dodemorph acetate	Milban
Dodine	Dodine, Cyprex, Syllit
Etridiazole	Ethazol, Ethazole, Etridiazole, Koban, Truban
Fenarimol	Rubigan
Ferbam	Ferbam, Carbamate WDG
Iprodione	Chipco 26019, Epic 30, Rovral
Mancozeb	Dithane M45, Fore, Mancozeb, Manzate 200, Protect T/O
Maneb	Dithane M22, Maneb, Manzate D, Tersan LSR
Metalaxyl	Ridomil, Subdue
Metam-sodium	Vapam
Metiram	Polyram
Myclobutanil	Nova, Rally, Systhane
PCNB	Terraclor
Propiconazole	Alamo, Banner
Streptomycin	Agri-Mycin 17, Agri-Strep
Sulfur:
Lime sulfur (calcium polysulfide)	Lime-sulfur, Orthorix
Wettable sulfur	Kolospray, Microsulfur, Sulfur, Wettable Sulfur
Thiabendazole	Arbotect
Thiophanate-methyl	Bromosan, Clearyâs 3336 Duosan, Fungo, Topsin M
Thiram	Arasan, Thiram
Triadimefon	Bayleton
Triforine	Funginex, Triforine
Vinclozolin	Ornalin, Ronilan
Ziram	Ziram
Zyban	Zyban

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HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Ash, Green Fraxinus pennsylvanica Return to Table of Contents	Anthracnose, Apiognomonia errabunda	F	Initially, tiny purple/brown spots on young leaves. Spots enlarge, coalesce and form brown blotches. Leaf distortion common. Young shoots may be killed back. Defoliation may be severe.	Remove fallen leaves and dead twigs and branches, especially on young trees. CHEMICAL: Chlorothalonil, mancozeb, thiophanate-methyl or zyban beginning at budbreak.
	Ash yellows, caused by a phytoplasma (mycoplasma-like organism)	P	Severe reduction in growth, chlorotic leaves in tufts at end of branches along with dieback. Witchesâ brooms may form on the trunk.	Maintain tree vigor to prolong life. Remove as they become hazard trees. CHEMICAL: None. REFERENCE: Ash Yellows in Minnesota, MI-5898-C.
	Heart rot, Perennoporia fraxinophila	F	Crumbly, soft decay in trunks and larger limbs. Groups of bract-shaped, grayish-white perennial conks appear along the infected branches and trunk.	Remove dead and dying branches. Avoid mechanical injury. CHEMICAL: None.
	Sulfur shelf heart rot, Laetiporus sulfureus	F	Brown cubical rot of roots, butt and trunk with sunken elongate cankers on the surface. Bright yellow to orange, fleshy fungal reproductive structures appear in summer and fall.	Proper pruning: avoid mechanical injury. CHEMICAL: None.
	Verticillium wilt, Verticillium dahliae	F	Acute or chronic symptoms may appear anytime during the growing season. Chronic: small, chlorotic leaves, leaf scorch, slow growth, abnormally heavy seed crop, shoot dieback. Acute: leaf curling or scorching, abnormal red or yellow color, partial defoliation, wilting, and branch dieback, plant death. Symptoms often on only one part of the tree or shrub.	This wilt is soilborne; replace with resistant tree species. Keep infected trees well watered and fertilize with a fertilizer high in potassium. Remove dead branches. CHEMICAL: None. REFERENCE: Verticillium Wilt of Trees and Shrubs AG-FO-1164
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Boston Ivy Parthenocissus tricuspidata Return to Table of Contents	Leaf spot, Guignardia bidwellii	F	Numerous red/brown lesions with light centers and dark margins. Black pin-point dots (pycnidia) appear in center of mature lesions. Defoliation may occur if severe.	Hand pick and destroy infected leaves where possible. Destroy or compost all leaves in the fall. CHEMICAL: Seldom necessary.
Caragana Caragana Return to Table of Contents	Leaf spot	F	Circular lesions with dark margins. Defoliation during wet seasons.	Water infrequently and only at base. CHEMICAL: Not usually necessary. Wettable sulfur.
Catalpa Catalpa spp. Return to Table of Contents	Verticillium wilt Verticillium dahlia	F	See Ash
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Cherry/Chokecherry and other Prunus spp. grown as landscape plants Prunus spp. Return to Table of Contents	Bacterial spot and canker, Pseudomonas syringae pv. syringae	B	Angular or circular, red/brown lesions which drop out giving the leaf a tattered appearance. Occasionally cankers form on twigs and branches.	Seldom serious in landscape settings. Prune cankered wood during dormant period. Cleap up leaves and other debris in fall. CHEMICAL: Copper.
	Black knot, Apiosporina morbosa	F	Infection occurs in spring with olive-green, elongate swellings on branches visible the next spring. Galls turn woody and black later that second summer.	Remove infected branches 3-4ä below galls before budbreak. Remove nearby wild chokecherries. CHEMICAL: Apply lime sulfur as a dormant application following pruning or thiophanate-methyl when dormant, at pink bud, full bloom and 3 weeks later.
	Brown rot, Monilinia fructicola	F	Sudden browning and death of flowers. Cankers on small branches. Most noticeable is the browning and dropping of fruit, often with a gray/brown spore mass on the surface. Infected fruits shrivel (form mummies) and persist on the tree through winter.	Remove and destroy all mummified fruit. CHEMICAL: Benomyl, captan, chlorothalonil, ferbam, iprodione, myclobutanil (cherry only), propiconazole, thiophanate-methyl, vinclozolin, wettable sulfur. Begin as flower buds first open and continue as per label directions.
	Canker, Valsa leucostoma, Leucostoma sp.	F	First symptoms appear on young branches with brown drooping leaves. Elliptical cankers develop at the base of these branches and produce fruiting bodies that exude hairlike yellow tendrils in the spring. Cankers may become perennial.	Promote tree vigor and prevent mechanical damage. Remove and destroy infected branches. Only plant on good sites for Prunus spp. CHEMICAL: None.
	Leaf spot, Blumeriella jaapii (formerly Coccomyces hiemalis)	F	Dark purple spots initially on young leaves. Spots become red/brown and fall out of leaf or entire leaf may yellow and drop.	Remove and destroy infected plant material. Avoid wetting foliage. CHEMICAL: Captan, chlorothanonil, dodine, fenarimol, iprodione, myclobutanil (cherry only), propiconazole, sulfur, or thiophanate-methyl. Begin at petal fall.
	Plum pockets and leaf curl, Taphrina communis	F	Swollen, discolored, and distorted branches. Fruits enlarge greatly and are bladderlike or spongy and pale yellow/green in color.	Remove diseased fruit and twigs. CHEMICAL: Bordeaux mixture or lime sulfur during dormancy.
	Western X disease, caused by a spiroplasma	B	This organism is transmitted by leafhoppers. Early in the growing season light green to yellow foliage indicates the initial stages. New growth may be thicker. Leaves receiving full sunlight turn reddish brown. Proliferation of leaves or stems at the ends of new growth is common. Infected plants die after 3 years.	Rogue out infected plants. CHEMICAL: None.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Cotoneaster Cotoneaster spp. Return to Table of Contents	Fireblight, Erwinia amylovora	B	Symptoms similar to crabapple; blackening and dieback of succulent tissues. Shepherdâs crooking. Dead leaves remain on branch. Cankering common.	Remove infected parts with sterilized tools when plants are dry. Make proper pruning cuts 8-10ä below infected tissue. Limit fertilizer use, esp. nitrogen. CHEMICAL: Fixed coppers (can be phytotoxic).
Cottonwoodö see poplar Return to Table of Contents
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Crabapple, Ornamental (See Home Fruit Spray Guide for information on edible fruits) Malus spp. Return to Table of Contents	Black rot canker, Botryosphaeria obtusa	F	Cankers develop on limbs esp. at wounds, enlarge during the growing season, and may grow for one or more seasons. Dead bark remains attached for 1 year or more then slowly falls apart.	Plant only fully hardy trees and prevent stress, esp. from drought. Remove dead and cankered branches. CHEMICAL: None.
	Cedar-apple rust, Gymnosporangium sp.	F	Yellow/orange spots on leaves, petioles, fruits. Tiny white tubes or cups form on under surface of other plant parts. Spores produced in these tubes infect the alternate host, juniper species.	Where feasible, remove alternate host (junipers) within 1 mile or remove brown galls from nearby junipers. Use resistant varieties. CHEMICAL: Chlorothalonil, fenarimol, mancozeb, maneb, myclobutanil, propiconazole, or triadimefon beginning when orange masses are present on juniper.
	Fireblight, Erwinia amylovora	B	Succulent tissue and flowers turn dark brown to black. Yellow/tan droplets of bacterial ooze may be present. Can spread into woody tissues causing cankers and branch dieback. Common following warm rainy weather.	Plant resistant varieties. Avoid excessive use of nitrogen. Remove and destroy all diseased branches in early spring (before March 15) or late fall. CHEMICAL: Copper.
	Frog-eye leaf spot, Botryosphaeria obtusa	F	Leaves have circular spots with indefinite purple margins becoming brown spots with abrupt margins. Some may enlarge giving the lesion a ãfrog-eyeä appearance. Severe infection may cause yellowing and defoliation. (See black rot canker above.)	Rake up infected leaves. Remove black rot cankers. Grow fully hardy tree species and manage to minimize stress. CHEMICAL: Seldom necessary.
	Powdery mildew, Podosphaera leucotricha	F	White powdery patches on leaves, esp. underside. Twigs, blossoms, and fruits may also become infected. Terminal growth stunted. Infected fruits exhibit light brown russeting.	Remove and destroy infected shoots as they appear early in the season. Prune to allow for good air circulation. Not common. CHEMICAL: Fungicides are seldom necessary. Triforine, wettable sulfur (can russet fruit), fenarimol, myclobutanil, propiconazole or triadimefon.
	Scab, Venturia inaequalis	F	Initially watersoaked lesions, esp. along the veins which turn olive-brown to black and may appear fibrous. Foliage yellows and drops. Fruits develop scabby lesions which may appear corky.	Use varieties with resistance. Apply nitrogen (urea) to fallen leaves in the fall to enchance decomposition or remove fallen leaves to reduce disease pressure. Prune for good air movement. CHEMICAL: Captan, triforine, lime sulfur (fruit injury on some varieties), dodine, maneb, benomyl (do not use alone), thiophanate-methyl (do not use alone),wettable sulfur (may cause russeting), myclobutanil, propiconazole, fenarimol plus captan, ferbam, mancozeb, chlorothalonil, zyban and propiconazole.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Currant, Alpine and other landscape currants Ribes alpinum Return to Table of Contents	Powdery mildew, Sphaerotheca mors-uvae	F	Gray/white powdery or dusty-like fungal growth on leaves and succulent stem. Leaf distortion.	Increase sun penetration and air movement by pruning. Rake and destroy infected leaves in the fall. Water only at base of plant. CHEMICAL: Delayed dormant (green tip stage) of lime sulfur. Wettable sulfur during growing season. Thiophanate-methyl or zyban.
Dogwood Cornus spp. Return to Table of Contents	Leaf spot, Septoria sp.	F	Initially appears as small angular, rusty brown spots which turn tan or gray. Severe infections cause defoliation.	Promote plant health. Remove infected plant material. Avoid overheard watering. Provide good air circulation. CHEMICAL: Bordeaux, chlorothalonil, thiophanate-methyl, or zyban.
Elm, American Ulmus americana Return to Table of Contents	Cankers, Botryodiplodia sp. and others	F	Slightly sunken reddish brown to black cankers form on twigs and small branches. Leaves turn bright yellow and remain attached to the branches for several weeks.	Provide good growing conditions. Avoid mechanical damage. Remove dead limbs. CHEMICAL: None.
	Dutch elm disease, Ophiostoma ulmi	F	First noticed as wilting of branches in the crown. Leaves turn yellow or brown and tend to remain attached to the tree for an extended period. (Yellow leaves may drop prematurely.) Inner bark exhibits dark brown streaking. Lab testing needed to confirm infection. REFERENCE: Dutch Elm Disease, PP-324 (ND)	Remove diseased trees and debark wood stored as firewood. Do not prune between April 15 and September 1 in the southern half of Minnesota. Where applicable, use a vibratory plow to disrupt root grafts and prevent disease spread. CHEMICAL: Root flare injection of Arbotect 20-S to prevent infection of specimen trees. Consult a professional arborist.
	Elm black leaf spot, also called elm anthracnose, Stegophora ulmea	F	Yellow spots form on the upper surface of leaves followed by slightly raised black fruiting bodies.	Promote plant health. Remove infected leaves in the fall. CHEMICAL: Not warranted in home landscapes. NURSERY: Bordeaux or mancozeb.
	Oyster canker, Pleurotus ostreatus	F	White rot fungus which enters through wounds or dead branches causing wood to become brittle and crumbly. White shelf mushrooms are produced after extensive rot has occurred.	Uncommon in urban elms. Avoid improper pruning or unnecessary wounding. Promote tree health. CHEMICAL: None.
	Wetwood or slime flux, Enterobacter cloacae and other bacteria	B	Bacteria ooze from openings on trunks and large limbs in a light brown, slimy matrix known as slime flux. This toxic material is responsible for the long bleached or dark brown streaks on trunks. If severe, leaves may exhibit marginal scorch.	Keep trees healthy. CHEMICAL: None.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Elm, Siberian Ulmus pumila Return to Table of Contents	Cankers, Botryodiploida and other species	F	See ELM, AMERICAN
Fir, Douglas Pseudotsuga menziesii Return to Table of Contents	Swiss needlecast, Phaeocryptopus gaeumannii	F	Inner needles turn yellow, brown and drop. Tiny black fruiting bodies develop on undersides of needles.	Improve air circulation with adequate spacing and weed control. Mulch and water when dry. CHEMICAL: Bordeaux or chlorothalonil end of May; repeat in 4-6 weeks.
Hackberry Celtis occidentalis Return to Table of Contents	Witchesâ broom, fungus (Sphaerotheca phytoptophilia) - mite (Eriophyes celtis) association	F	Clusters of spindly shoots on branches throughout crown.	Aesthetic problem. Brooms can be removed. CHEMICAL: Dormant season sulfur spray may be helpful.
Hawthorn Crataegus monogyna Return to Table of Contents	Rust, Gymnosporangium globosum and others	F	Yellow/orange lesions form on leaf surface in early summer followed by tiny white tubes beneath. Infected fruits also have tiny white tubes. Twigs occasionally infected.	Remove small brown to tan galls on the alternate host, red cedar (juniper), or the entire plant before spring. Remove visible infections on hawthorn before sporulation. Cockspur hawthorn, Crataegus crusgalli, is resistant. CHEMICAL: Chlorothalonil, mancozeb, triadifmefon, or zyban AS PER LABEL DIRECTIONS.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Honeylocust Gleditsia triacanthos Return to Table of Contents	Nectria canker, Nectria cinnabarina and Fusarium sp.	F	Cankers develop as sunken areas originating from a wound or dead branch stub. Advanced cankers are visible as dark brown discolored bark with cracks at the margins. Yellow/orange, salmon/pink, or reddish fruiting bodies form on the cankered areas.	Provide proper cultural care. Avoid stress and mechanical damage. Prune during extended dry periods, make proper pruning cuts. Remove and destroy infected branches during dry weather. CHEMICAL: None.
Honeysuckle Lonicera spp. Return to Table of Contents	Blight, Insolibasidium deformans	F	Tan to brown lesions or blotches form on part or the entire leaf. Lesions may be surrounded by a yellow halo. A thin, white layer of spores is visible on the lower leaf surface. Leaves may be distorted and drop early.	Remove and destroy infected plant material. Prune hedging to provide good air circulation. CHEMICAL: Fungicides may be necessary in nurseries with a history of blight; mancozeb.
Horsechestnut/ Ohio buck-eye Aesculus spp. Return to Table of Contents	Leaf blight, Guignardia aesculi	F	Watersoaked spots on leaves develop into brown spots or blotches surrounded by a yellow halo. Tiny black fruiting bodies may be present in the dead areas. Leaves are shed prematurely.	If possible, reduce canopy density. Rake up and destroy infected leaves. CHEMICAL: Not usually necessary in home landscapes. Chlorothalonil or mancozeb beginning at budbreak.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Juniper Juniperus spp. Return to Table of Contents	Cedar-apple type rusts, Gymnosporangium species	F	Greenish brown galls appear one summer after initial infection. Galls enlarge and turn brown by fall. Small depressions scattered over the surface exude long orange gelatinous tendrils following spring rains.	Remove galls and alternate hosts. Plant resistant species and cultivars. CHEMICAL: None recommended. Nurseries may use Bordeaux, mancozeb, triadimefon, or zyban on susceptible cultivars to prevent branch dieback on young plants.
	Twig blight, Phomopsis juniperovora	F	New branch tips turn brown then gray. Fungus moves from leaves into twigs causing branch death. Most severe in wet years.	Remove and destroy infected twigs and branches. Avoid wounds. Prune during dry periods. Avoid evening irrigation. Keep foliage dry. Do not overfertilize. Grow resistant species and cultivars. CHEMICAL: Mancozeb, thiophanate-methyl, or zyban. Apply when new growth begins.
Lilac Syringa spp. Return to Table of Contents	Bacterial blight, Pseudomonas syringae pv. syringae	B	Affects new growth. Lesions turn black and spread rapidly during wet periods. Tissue distal to the lesion shrivels and droops. White varieties are most susceptible.	Remove infected plant parts using sterilized pruning tools. Space and prune plants to achieve good air circulation. Avoid overhead irrigation. Avoid wounds and plant stress. Do not overfertilize, especially with nitrogen. CHEMICAL: Bordeaux (4-4-100), copper sulfate.
	Powdery mildew, Microsphaera syringae	F	Gray/white powdery fungal growth on the upper surface of leaves as well as shoots and buds. If severe, stunting and deformed growth occur. This fungus also attacks ash and privet.	Space plants and prune to allow for good air circulation. Do not plant in shade. Avoid overfertilization. Water, but at the base and infrequently. CHEMICAL: Seldom necessary. Sulfur, thiophanate-methyl, triadimefon, triforine, or zyban.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Maple Acer spp. Return to Table of Contents	Anthracnose, Discula species and others	F	Tan/brown/black spots and blotches develop on leaves during wet periods. Spring infections result in leaf distortion. Necrosis may follow the veins.	Rake up and destroy or compost fallen leaves. Promote tree vigor. Not seriously damaging to healthy established trees. CHEMICAL: Preventative fungicides should be applied beginning at bud break when deemed necessary. Bordeaux, chlorothalonil, fixed coppers, mancozeb, thiophanate-methyl or zyban.
	Leaf spot, Phyllosticta minima	F	Well-defined lesion on the leaf surface with a light-colored center and dark margin at maturity. Tiny black dots (fruiting bodies of the fungus) are often visible.	Rake up and destroy fallen leaves. Avoid wetting the tree foliage during irrigation. Promote tree vigor. Seldom damaging to healthy, established trees. CHEMICAL: Treat preventatively with Bordeaux 8-8-100, fixed coppers or mancozeb.
	Target-shaped canker, Nectria galligena, Eutypella parasitica	F	Perennial cankers develop around wounds on immature trees, usually within 10 feet of the ground. The trunk is swollen around the canker, which often has a ãtarget-likeä appearance.	Plant on good sites in proper zone. Prevent damage to trunk and limbs. Promote tree vigor. Remove branches with cankers. May become a hazard tree and should be evaluated as such. CHEMICAL: None.
	Tar spot, Rhytisma acerinum	F	Roughly circular, raised black spots on the leaf surface which resemble spots of tar. Seldom a problem.	Maintain tree vigor. Infected leaves can be raked up and destroyed or composted. CHEMICAL: None necessary.
	Wilt, Verticillium dahliae	F	Slow growth, dwarfed foliage and/or wilting. Leaves with scorched margins. Defoliation. Often occurs on only one part of the tree. Green to black vascular discoloration may be present in the sapwood of larger branches and the trunk. REFERENCE: Verticillium Wilt of Trees and Shrubs, AG-FO-1164 (MN), Deciduous Tree Diseases, PP-697 (ND).	Fertilize to promote growth; keep nitrogen to a minimum. Prevent moisture stress. Remove dead limbs. Do not plant susceptible tree species where Verticillium is present in the soil. CHEMICAL: None. NURSERY: Preplant fumigation.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Mock Orange Philadelphus spp. Return to Table of Contents	Bacterial blight, Pseudomonas syringae pv. syringae	B	Small watersoaked spots that turn dark brown to black. A slight chlorotic halo may be present. Lesions may be angular. Leaves may become distorted and shoots may die back. Common in cool wet seasons.	Remove and destroy infected leaves and shoots. Avoid overhead watering. Protect nursery stock from rain and frost. Space plants for good air circulation. CHEMICAL: Fixed coppers.
Mountain Ash Sorbus spp. Return to Table of Contents	Black rot, Botryosphaeria obtusa	F	See Crabapple
	Cankers, several fungi	F	Discolored, dead areas on the limbs and trunk which may increase over time.	Keep trees well watered and avoid injuries. Remove cankered areas properly during dry weather. CHEMICAL: None.
	Fireblight, Erwinia amylovora	B	Succulent shoots suddenly turn dark brown to black, ie, as if scorched by fire. Bacteria may move into the trunk causing cankers and killing limbs and the trunk.	See Fireblight under Crabapple
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Oak Quercus spp. Return to Table of Contents	Anthracnose, Apiognomonia quercinia	F	Starts as small brown leaf spots in the inner and lower portion of the canopy during spring rains. Spots develop into large brown to tan blotches often along the large veins. Foliage may shrivel or appear deformed. Defoliation may occur. New foliage often develops following severe infections. Fungus also infects twigs causing small cankers and twig dieback. Most prevalent on white and bur oak. Contrast symptoms with those of oak wilt below.	Rake and destroy fallen leaves. Keep irrigation water out of the tree canopy. Prune out dead and diseased branches. Keep trees vigorous. CHEMICAL: Preventative fungicides should be applied beginning at bud break. Thiophanate-methyl (Warning: tank mix or alternate this with sprays of different fungicides), Bordeaux, chlorothalonil or mancozeb.
	Armillaria root rot, Armillaria spp.	F	Check declining trees for white felt-like masses of fungus at the base of the trunk between the bark and the wood. Black shoestring-like strands of the fungus, called rhizomorphs, are also present there and in the soil. Honey-colored mushrooms of the fungus may form at the base of the tree in the fall.	Keep trees healthy. Deep water if dry; avoid wetting trunk/root area. Surface watering during warm months softens the main roots in the crown area which favors progress of the fungus. Replant with resistant species such as Scots pine, catalpa, mock orange and sumac. CHEMICAL: None.
	Oak heart rot, Laetiporus sulfureus	F	Fungus invades the roots, trunk and butt of tree through wounds causing a brown cubical rot. First evidence may be the production of a fleshy, yellow shelf fungus on the trunk. However, presence of the fungus suggests considerable rot within and possibility of a hazard tree should be investigated.	Keep trees healthy and avoid wounds. Prune properly. CHEMICAL: None.
	Oak leaf blister, Taphrina caerulescens	F	New growth develops yellow green flecks which develop into a puckered or raised area on the leaf surface. Area is hollow or empty beneath. The blister may have a reddish cast.	Mostly a curiosity in wet years. No control usually needed. CHEMICAL: Spray once in spring before bud swell with chlorothalonil or mancozeb.
	Oak wilt, Ceratocystis fagacearum	F	Wilting and scorching of leaf margins in the upper crown of the tree. May occur first on one limb. Leaves completely brown and remain attached. Oaks in the red oak group may completely wilt and die in two weeks following the first symptoms. Infection in white oaks is slow to progress. REFERENCE: Oak Wilt, MI-3174(MN).	DO NOT prune oak trees between April 15 and July 1. If damage occurs during that period, immediately cover exposed areas with a tree wound dressing. Do not transport or store oak from recently wilted trees. Use a vibratory plow to sever root grafts before removing infected trees. Consult a professional arborist.
	Smooth patch, Aleurodiscus sp.	F	The outer rough bark of white and bur oak trees sloughs off exposing the lighter-colored smooth inner bark.	The fungus does not attack living plant parts. No control is necessary.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Pine Pinus spp. Return to Table of Contents	Brown spot, Mycosphaerella dearnessi	F	Most pine, esp. Scots and ponderosa. Spots that enlarge to bands and encircle the needle develop in late July and August. Diseased needles often have dead tips. Killed needles drop late in the fall.	Nurseries should use seedlings from resistant trees; allow for adequate spacing and avoid shearing and other operations when foliage is wet. CHEMICAL: Mancozeb.
	Dothistroma needle blight (also called red band), Mycosphaerella pini	F	Two-and three-needled pines are affected but most common on Austrian pine. Chlorotic spots appear on infected needles in fall and winter. Spots spread, turn red/brown and girdle needles causing the distal end to die. Black fruiting bodies break through lesion surface in spring. Defoliation can be severe.	Remove the lowest whorl of branches on young trees. Clean out debris and weeds in and around trees. Space plants for good air circulation. Avoid planting in low-lying areas with poor drainage. Growers should shear trees during dry weather. CHEMICAL: Bordeaux (8-8-100). Can be toxic to new needles.
	Needlecast, Lophodermium seditiosum	F	Two-and three-needled pines, esp. Austrian red and Scots pine. Current season foliage develops yellow spots which turn brown with yellow margins in late fall and spring. Black, elliptical fruit bodies mature in or just beneath the epidermis in late summer. Needles brown and drop. Twigs die back. Spores are released during late summer/early fall rains with most infection occurring in August and September.	Improve air circulation with thinning and pruning: cool moist environments favor infection. CHEMICAL: Nurseries should apply mancozeb plus a spreader sticker or chlorothalonil. Make 3-4 applications starting July 1.
	Pine needle rust, Coleosporium sp.	F	Two-and three-needle pines develop light-colored blisters which burst open to release yellow/orange spores in early summer. These spores infect the alternate hosts aster and goldenrod and NOT pine.	Damage is seldom detrimental. Remove or mow goldenrod and aster plants in the immediate vicinity. CHEMICAL: None recommended.
	Pine-oak gall rust or eastern gall rust, Cronartium quercuum	F	Two-and three-needled pines are susceptible. The alternate host is red oak. Globose swellings up to 10 inches in diameter form on pine branches. Yellow/orange powdery-appearing spores form on the gall surface in early summer.	Remove galls on pine branches preferably before spring. CHEMICAL: None recommended. However, if the situation warrants, mancozeb may be applied when yellow pustules form on pine galls.
	Pine-pine gall rust or western gall rust, Endocronartium (Peridermium) harknessii	F	Two-needled pines, especially mugho, ponderosa, red and Austrian pine. There is no alternate host. Rough, globose galls appear on branches and trunk. Yellow/ orange powdery spores form on the gall surface in early summer.	Remove galls on infected trees. Remove all trees with galls for a distance of 300 yards around nurseries and cull infected seedlings. CHEMICAL: Mancozeb when yellow spores are present on galls.
	Shoot (Diplodia) blight, Sphaeropsis sapinea	F	New shoots are invaded and killed in the spring, usually before needle expansion is complete. Needles turn brown; resin soaking is common. Dieback may progress into main stem. Fruiting bodies form at the base of infected needles, on twigs and on second year cones. Austrian pine is extremely susceptible after reaching cone-bearing age.	Keep landscape trees well watered and stress free. Thin forest stands. Avoid shearing during wet weather or high humidity. Plant less susceptible pine species. CHEMICAL: Benomyl, thiophanate-methyl. Begin when new growth starts. Use a spreader sticker. Also Bordeaux.
	White pine blister rust, Cronartium ribicola	F	Five-needled pines are susceptible (eg. eastern white pine, limber pine). Elongate cankers with abundant pitch flow develop on trunks and branches causing branch dieback or ãflagging.ä White blisters containing yellow/orange spores break through the cankered areas in the spring. Spores produced on pine infect the alternate host, Ribes species.	Minimize use of white pine on sites with high blister, rust hazard ratings. Avoid planting currants and gooseberries in the vicinity of white pine. Remove the lower branches on large trees. Scout trees annually for ãflaggingä suggestive of early infection and remove infected branches. CHEMICAL: Triadimefon.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Plum, ornamental Prunus spp. See Cherry Return to Table of Contents
Poplar Populus spp. Return to Table of Contents	Cankers, Valsa sordida (Cytospora chrysosperma), Phompsis sp., Hypoxylon sp., Mycosphaerella populorum, Cryptodiaporthe populea	F	Fungi infect young twigs or wounds creating cankers on branches and trunks. Fruiting bodies commonly form on the face of cankers. Widespread and common on poplar, cottonwood, aspen and willow. Especially serious on Lombardy and silver leaf poplars.	Maintain plant vigor. Remove cankered branches during dry weather. Avoid wounds. Avoid planting in areas with poor air circulation. Trees prone to many cankers should be replaced with another tree species. CHEMICAL: None.
	Leaf rust, Melampsora medusae and other species	F	Yellow to orange pustules break through the surface on both leaf surfaces in mid to late summer. Angular yellow lesions may occur on the opposite leaf surface. Lesions turn black in autumn. Some defoliation may occur. Alternate hosts include hemlock, Douglas-fir, larch, and pine depending on rust species.	Choose a poplar clone with resistance. Keep susceptible conifers 500 yards away from poplar stock. CHEMICAL: Seldom necessary in landscape settings. Triadimefon or triforine.
	Marssonina leaf spot, Marssonina populi	F	Small brown leaf spots with yellow margins. Infection may advance into stem tissue. May be severe during wet seasons resulting in defoliation.	Collect and destroy leaves. Plant in areas with good air circulation. CHEMICAL: Fungicides seldom warranted in landscape plantings. NURSERY: Chlorothalonil at bud break and every 7-10 days if necessary.
	Shoot blight, Venturia tremulae on Populus sp. and hybrids; V. populina on black cottonwood and balsam poplar	F	Brown to black leaf spots rapidly expand on succulent tissue to cause shoot blight. Affected tissues dry out and become brittle.	Remove and destroy infected shoots. Increase air circulation. Rake and remove leaves in the fall. CHEMICAL: Seldom necessary in landscape settings.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Rhododendron Rhododendron spp. Return to Table of Contents	Phytophthora root rot, Phytophthora sp.	F	Damage begins in fibrous roots and spreads to crown. Evidence of damage spreads to cambium several inches above ground. Above ground foliage turns off-color, wilts, and dies. Fungi remain in the soil indefinitely once established and have a wide host range including azalea, mugho pine, yew, and heather. PJM clones are susceptible.	Plant disease-free plants in areas with good drainage. Quarantine new plants for at least a year before setting in production area. Use disease-free cuttings. Do not place containers on poly sheets; place on a minimum 4-inch depth gravel bed. Use low salinity, clean irrigation water. Pot in composted hardwood bark or conifer bark. Sanitation. CHEMICAL: Nursery: Fumigation of media, pots and beds. Soil drench with banrot, etridiazole or metalaxyl.
	Powdery mildew, Microsphaera sp.	F	White powdery fungal growth on leaves, may appear patchy. Infected foliage becomes chlorotic and may drop prematurely.	Plant in areas with good air circulation and avoid overcrowding. Prune to improve air movement in planting and overstory. CHEMICAL: Triadimefon or triforine.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Rose Rosa spp. Return to Table of Contents	Black spot, Diplocarpon rosae	F	Purple to black leaf spots with a fibrous or fringed appearance. Foliage yellows and drops. Leaves are most susceptible while expanding. Severe under wet conditions with susceptible cultivars. Infections on canes are not common.	Rake and destroy fallen leaves especially at end of season. Avoid dense plantings. Prune canes back to two buds when cane infections are present. Plant resistant cultivars. AVOID overhead watering. CHEMICAL: Dormant sprays include lime sulfur and tribasic copper sulfate. Growing season sprays include chlorothalonil, ferbam fixed coppers, mancozeb, thiophanate-methyl, triforine, wettable sulfur, ziram, or zyban.
	Brand and common canker, Coniothyrium wernsdorffiae, and C. fuckelii	F	Discolored areas develop and enlarge on canes; centers turn light brown with darker margins. Cankers may girdle stem.	Avoid cane injuries. Prune canes with a sharp tool immediately above a node. Remove and destroy infected canes well below the visible canker. Keep plants healthy. CHEMICAL: Not necessary, however a dormant application of lime-sulfur may be helpful.
	Crown gall, Agrobacterium tumefaciens	B	Soft spongy or woody galls with an irregular surface and shape develop on the roots and/or crown. Size varies from less than an inch to several inches. Canes may be girdled and killed. Bacteria are soil-borne.	Plant only disease-free nursery stock. Inspect closely before planting. Do not plant where the crown gall organism is present in soil. Avoid planting/cultivation injuries. Destroy infected plants. CHEMICAL: Nursery only: Galltrol as a preventative.
	Downy mildew, Peronospora sparsa	F	Leaves develop purple/red to dark brown spots and turn yellow often with ãgreen-islandä spots. Some defoliation. Gray/white mass of spores on underside of leaves when humid.	Reduce humidity. Rake and destroy leaves, old flowers and stems. CHEMICAL: Commercial; metalaxyl tank mixed with a protectant such as mancozeb; fixed copper.
	Powdery mildew, Sphaerotheca pannosa	F	White/gray, powdery fungal growth on leaves, flowers, and succulent/green plant parts. Distorted growth and flowers. Tip dieback. (Overwinters in infected buds and leaves and on twigs and branches.)	Water only at the base and infrequently to keep humidity low. Do not crowd plants. Locate planting and prune area plants to provide good air circulation. Rake and destroy fallen leaves. Plant cultivars with resistance. CHEMICAL: Dormant spray of lime sulfur. Growing season: Fenarimol, thiophanate-methyl, triadimefon, triforine, wettable sulfur, ziram, or zyban.
	Rose rust, Phragmidium species	F	Orange postules develop on leaves and succulent stems then turn black in late summer. Favored by cool humid weather. (Overwinters on diseased leaves and infected stems.)	Remove and destroy all leaves and infected stems during the dormant season. CHEMICAL: Dormant spray of Bordeaux (8-8-100), lime sulfur or tribasic copper sulfate. Growing season: Ferbam or triforine. (Propiconazole for field-grown roses only.)
	Rose rust, Phragmidium species	V	Intricate chlorotic patterns, rings, and markings develop on the foliage. Symptoms are most evident in spring and fall.	Purchase virus-free plants. CHEMICAL: None.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Russian Olive Elaeagnus angustifolia Return to Table of Contents	Cankers, Phomopsis sp., Tubercularia ulmea and others	F	Discolored areas develop on young stems and enlarge to form cankers. Distinct margins may be present. Cankers may also form on older branches and trunks. Older plants are more susceptible. Very common problem.	Avoid wounds. Remove and destroy cankered branches several inches below canker during dry weather. Cankers and wounds are good sites for decay to start, which may result in hazard trees. CHEMICAL: None.
	Verticillium wilt Verticillium dahliae	F	See Maple
Serviceberry/Juneberry Amelanchier spp. Return to Table of Contents	Rust, Gymnosporangium sp.	F	Slightly raised yellow lesions develop on leaves, succulent twigs, and fruits. Lesions expand, turn orange/red, and develop white tubes beneath. Juniper (red cedar) is the alternate host.	Remove small brown galls on nearby junipers in late winter. If possible, avoid planting juniper near serviceberry. CHEMICAL: Mancozeb; begin when orange tendrils form on nearby juniper galls.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Spruce Picea spp. Return to Table of Contents	Cytospora canker, Leucostoma kunzei	F	Branch dieback in the lower crown with copious amounts of oozing sap. Cankers spread from infection site on branch toward trunk. Needles turn purple or brown then drop. This disease attacks stressed spruce, esp. mature Colorado blue spruce.	Plant on good sites. Avoid wounds and crowding. Maintain plant health. Remove and destroy infected branches in late winter. CHEMICAL: None.
	Lirula needle blight, Lirula sp.	F	Inner needles turn a light tan and remain on the tree. Black, slightly raised, elongate fruiting bodies develop on the lower surface of infected needles.	Plant on good sites. Avoid wounds and crowding. CHEMICAL: Make a single application of chlorothalonil by July 1.
	Rhizosphaera needle cast, Rhizosphaera kalkhoffii	F	Infection occurs on new needles which discolor and shed the next spring and summer. Needles discolor first yellow then purple or brown. Tiny black fruiting bodies replace the white stomata on individual green or discolored needles and can easily be seen with a hand lens. Trees are predisposed by stress, especially drought.	Avoid stress, especially from drought. Increase air circulation by removing lower branches and mowing grass or weeds. Avoid overhead watering. CHEMICAL: Two spring applications of chlorothalonil will protect new needles from infection.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Sumac Rhus spp. Return to Table of Contents	Powdery mildew, Phyllactinia guttata	F	White/gray powdery fungal growth on leaf surfaces and succulent tissue. Growth may be distorted.	Improve light conditions and air circulation. Water only at the base. Prune to open dense plantings. CHEMICAL: Thiophanate-methyl.
	Shoot blight, Botryosphaeria dothidea	F	Small discolored areas on stems enlarge to form cankers which may girdle stems resulting in shoot wilting dieback and death.	Remove and destroy cankered shoots. Avoid plant stress. CHEMICAL: None.
	Verticillium wilt Verticillium dahliae	F	See Maple
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Viburnum Viburnum spp. Return to Table of Contents	Bacterial blight, Pseudomonas syringae pv. viburni	B	Watersoaked irregularly shaped foliar lesions turn brown. Lesion margins may develop bacterial exudate. If severe, foliage may be deformed and shoots may be killed. Symptoms similar to downy mildew.	Remove and destroy infected leaves and plant debris. Space or prune to allow for good air circulation. Water only at the base. CHEMICAL: Fixed coppers.
	Downy mildew, Plasmopara viburni	F	Angular lesions form on the leaf surface. Beneath the lesion a white fungal growth occurs under wet conditions. Severe infection results in defoliation. Compare with bacterial blight.	Avoid overhead irrigation. Increase light penetration and air circulation. Remove and destroy fallen leaves. CHEMICAL: Mancozeb plus spreader sticker or zyban.
	Powdery mildew, Microsphaera sparsa	F	White powdery growth on both sides of leaves.	Space and prune to increase air circulation. CHEMICAL: Chlorothalonil, thiophanate-methyl or triadimefon. Do not use sulfur.
HOST PLANT	DISEASE	*	SYMPTOMS	MANAGEMENT
Walnut Juglans spp. Return to Table of Contents	Anthracnose, Gnomonia leptostyla (Marssoniella juglandis)	F	Small roughly circular reddish to grayish brown spots with yellow halos on leaves. Leaflets drop. Stem lesions are oval to irregular, sunken, and gray/brown with dark margins. Depressed circular to irregular lesions on husks. Early infection results in nut drop.	Rake and destroy fallen leaves and nuts. If possible, remove infected twigs and branches. CHEMICAL: For ornamentals: mancozeb, propiconazole (non-bearing) or thiophanate-methyl. For edible crop trees use Dodine.
Willow Salix spp. Return to Table of Contents	Cytospora canker, Valsa sordida (Cytospora chrysosoperma)	F	Small areas of sunken brown tissue develop on branches. If they enlarge, they may girdle stems resulting in branch dieback.	Remove and destroy cankered branches during dry weather. Maintain plant vigor. CHEMICAL: None.
	Willow scab/Twig blight, Venturia saliciperda and Glomerella miyabeana	F	Black/brown spots develop on midribs of leaves which scorch, wither, and drop. Small brown/black cankers develop on twigs and branches resulting in girdling. (This fungus survives on old dead leaves on the ground and also on infected twigs.)	Rake and destroy fallen leaves and twigs prior to spring growth. Prune out diseased branches. Weeping willow (Salix babylonica) and laurel willow (Salix pentandra) have some resistance. CHEMICAL: Bordeaux (8-8-100) in the fall after leaves have dropped. Two to three spring applications of Bordeaux (6-6-100) beginning when leaves are first visible. Repeat at 10-14 day intervals.

F=Fungi

B=Bacteria

V=Virus

P=Phytoplasma (MLOs)

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Suggested References

Back to Table of Contents

Ash, C. A., Draper, M. A., Lamey, H. A., and Gallenberg, D. J. 1994. Diseases of Trees and Shrubs: A Color Diagnostic Guide. Minnesota Extension Service. St. Paul, MN.

Benyus, J. 1983. Christmas Tree Pest Manual. USDA Forest Service. Madison, WI.

Derr, J., and Appleton, B. L. 1988. Herbicide Injury to Trees and Shrubs: A Pictorial Guide to Symptom Diagnosis. Blue Crab Press. Virginia Beach, VA.

1986. Guidelines for the Control of Plant Diseases and Nematodes. USDA Agriculture Handbook No. 656. US Government Printing Office. Washington, DC.

Harris, R. W. 1983. Arboriculture: Integrated Management of Landscape Trees, Shrubs, and Vines. 2nd ed. International Society of Arboriculture. Savoy, IL.

Horst, R. K. ed. 1979. Westcott's Plant Disease Handbook. 4th ed. Van Nostrand Reinhold Co. NY.

Horst, R. K. 1983. Compendium of Rose Diseases. American Phytopathological Society. St. Paul, MN.

Jones, A. L., and Aldwinckle, H. S. eds. 1990. Compendium of Apple and Pear Diseases. American Phytopathological Society. St. Paul, MN.

Matheny, N. P., and Clark, J. R. 1994. A Photographic Guide to the Evaluation of Hazard Trees in Urban Areas. 2nd ed. International Society of Arboriculture. Savoy, IL.

Moorman, G. Scouting and Controlling Woody Ornamental Diseases in Landscapes and Nurseries. Publications Distribution Center, Penn State University. University Park, PA.

Ostry, M. E., Wilson, L. F., McNabb, H. S, Jr., and Moore, L. M. 1989. A Guide to Insect, Disease, and Animal Pests of Poplars. USDA Forest Service. Ft. Collins, CO.

Pirone, P. P. 1978. Diseases and Pests of Ornamental Plants. 5th ed. John Wiley and Sons. NY.

Riffle, J. W., and Peterson, G. W. 1986. Diseases of Trees in the Great Plains. USDA Forest Service. Fort Collins, CO.

Sinclair, W. A., Lyon, H. H., and Johnson, W. T. 1987. Diseases of Trees and Shrubs. Cornell University Press. Ithaca, NY.

Solomon, J. D., et al. 1993. Ash Pests: A Guide to Major Insects, Diseases, Air Pollution Injury and Chemical Injury. USDA Forest Service. New Orleans, LA.

Stipes, R. J., and Campana, R. J. eds. 1981. Compendium of Elm Diseases. American Phytopathological Society. St. Paul, MN.

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