Karen Rane, UMD Plant Diagnostic Laboratoryrane@umd.edu

http://dnr.maryland.gov/forests/Pages/MarylandersPlantTrees/Recommended-Tree-List.aspx

White Oak Group Rounded lobes on leaves Acorns mature in one season

and sprout when they fall in autumn

Species include: White oak Bur oak Swamp white oak Chestnut oak

White Oak – Maryland State Tree

Red Oak Group Pointed or bristled lobes on

leaves Acorns mature in 2 seasons and

sprout in spring Species include:

Red oak Black oak Pin oak Shingle oak Willow oak**

Oak Wilt:Native fungusCeratocystis fagacearumNow Bretziella fagacearum

1881/1944 – Wisconsin1942 – se MN & IA1973 – IL, WV, AK, NE, IN1977 – TXNOW Found in 21 states+

Oak WiltRed oak group more susceptible

than white oak group Vascular wilt disease – fungus

infects xylem (water conducting tissue)

Fungus spread by sap beetles (Nitidulids) feeding in crownBeetles attracted to pruning

wounds Also spread through root grafts

between healthy and infected trees

Robert Wright UNL Lincoln

USDA

Oak Wilt SymptomsLate spring to mid-summer, off-color, wilted foliage in upper

crown In red oak group, extensive leaf drop in summerFallen leaves still have green tissue at base or near

midveinRed oak group – trees die rapidly (a few weeks to a few

months)White oak group – no extensive leaf drop, trees die within

a few yearsHard to distinguish from decline

Discoloration (brown streaking) in sapwood in red oak group

Oak Wilt

NY State Urban Forestry Council

J. O’Brien, Bugwood.org

Oak Wilt Symptoms

Red oak group Defoliation within 3-4 weeks of first symptoms!

Oak Wilt in White Oak Group

Trees can live for 4-10 years, symptoms not as distinct as red oak

Oak Wilt Symptoms and Signs

Streaking in sapwood Photos: S. Jensen, Cornell Univ, Bugwood.org.

N. Pataky, Univ. of Ill.

Pressure Pad/Spore MatBark cracks

On Dead Trees

Disease Cycle

http://www.forestpathology.org/graphics/oakwilt.png

Root Grafting- Movement from Tree to Tree

Distribution of Oak Wilt – May 2013

US Forest Service

Oak wilt, 2008, New York

NYS Dept of Envirnmental Conservation

Diagnosing Oak Wilt Branch pieces at least 1” in

diameter, 10” long from branches with recent symptoms

Ship with ice packs – keep branches cool!

Sample trunk base of dead trees

Iowa State Plant Clinic

Texas Plant Disease Diagnostic Lab

Culture of C. fagacearum

G. Ruhl, Purdue

Managing Oak Wilt

Remove infected trees promptly Disrupt root grafts Protect high-value trees with

fungicide injection “Industry Standard” – Alamo

(propiconazole) Prevent spread by nitidulid beetles –

prune oaks in winter- Wound paints – water-based latex

IF Oak Wilt is confirmed…

NYS Oak Wilt Infection Area- AfterNYS Dept of Environmental Conservation

Trench dug to break root grafts.

NYS Dept of Environmental Conservation

Key Oak Wilt SymptomsLeaf discoloration during growing season Half green, half brown

Leaf drop on red oak group during summer!

....But what problems occur on oaks in Maryland??

Oak Anthracnose

Caused by fungus Apiognomoniaquercinia (Discula quercinia)

All oaks affected, white oak very susceptible

Symptoms: irregular leaf spots and blotches Often following along leaf veins Infected leaves can be distorted Mostly on lower branches

Young leaves are most susceptible

Photos: Joseph O’Brien, USDA Forest Service, Bugwood.org

Oak Leaf Blister

Caused by fungus Taphrina caerulescens

Red oaks most susceptible Yellow-green blister-like lesions that

turn brown Spores overwinter on bud scales Spring infection (cool, wet weather) Usually no impact on tree health

Tubakia leaf spot

Caused by the fungus Tubakiadryina

Occurs late summer to fall Usually on red oak group Circular brown leaf spots Little impact on tree health

* A different Tubakia species causes bur oak blight in Midwest

S. Tirpak, Rutgers Univ.

Cankers on Oaks

Caused by fungi (Diplodia/Botryosphaeria, Endothia, Hypoxylon)

Infection of small twigs to large branches/trunk

Most severe on trees under stress Often associated with wounds

Edward L. Barnard, Florida Department of Agriculture and Consumer Services, Bugwood.org

Endothia canker

Cankered region on northern red oak caused by Diplodiacorticola infection Cankered region and necrotic lesion on black oak

caused by Diplodia corticola infection

Twig cankers caused by D. corticola

Photos: Danielle Martin, USDA Forest Service

Diplodia Canker

Hypoxylon Canker Caused by Biscogniauxia

atropunctata var. atropunctata(syn. Hypoxylon atropunctatum).

Opportunistic pathogen – infectsstressed trees

Many oak species, as well as other hardwoods

Bark loss, revealing silver- gray fungal stroma

Stroma turns black over time

Robert L. Anderson, USDA Forest Service, Bugwood.org

Root Rot Diseases Some infect fine roots, some infect larger

woody roots Lower trunk (crown) may also be infected Fungi or fungus-like microorganisms

(water molds) Soil-borne pathogens Damage to root system results in

twig/branch dieback and poor growth Some cause wood rot – creating hazard

trees

Armillaria Root rot

Common wood decay fungus Wide host range Can infect stressed trees as well as

apparently healthy trees Symptoms – dieback, decline Impact on structural integrity of tree Survives in the soil, and on dead fallen

logs or tree stumpsJ. O’Brien, USFS Bugwood.org

Armillaria root rot: Signs Rhizomorphs

Mycelial fan

Honey mushroom

Phytophthora root rot - Oak

Caused by several Phytophthoraspecies (water molds)

Death of fine roots, sometimes death of phloem at crown or bleeding cankers

Does not cause wood decay Soil-borne pathogens, infect many tree

and shrub species Often associated with poorly drained

sites Symptoms: poor growth, dieback

M. Putnam, Oregon State Univ.

Sudden Oak Death

NOT in Maryland oaks (yet!) Caused by Phytophthora ramorum Causes bleeding cankers and death

of west coast oaks and tanoaks Also causes leaf and stem blight on

nursery crops (rhododendron, pieris, camellia, etc)

Has been introduced to MD on nursery stock from West Coast –regulated pathogen!

Bleeding canker on Red oak – NOT Sudden Oak Death

May be caused by other Phytophthora species, or insect borers

Inonotus dryadeus Root Rot

White rot of wood, sometimes no other symptoms

Bacterial Leaf Scorch Caused by the bacterium Xylella

fastidiosa Infects grape (Pierce’s disease), oak,

elm, sycamore, sweet gum Spread by sharpshooter leafhoppers Invades the xylem, blocking water

transport Marginal necrosis of leaves, often with

yellow border Discoloration spreads branch by

branch Symptoms develop in mid-summer

Bacterial Leaf Scorch

Red Oak

Bacterial Leaf Scorch

Sharpshooters

Managing Bacterial Leaf ScorchNo cure for infected treesCultural practices to reduce

moisture stress may help slow symptom developmentReplacement plan!

Tree Decline Loss of vigor/health due to

multiple factors Symptoms include off-color

foliage, smaller than normal annual twig growth, death of small twigs, thinning crown, early fall color

Symptoms develop over several years

Tree Decline – Two TypesRecently Transplanted Trees:Transplant Shock Older, Established Trees

Oak Decline in Maryland Found in older oaks (red oak, chestnut

oak) 50-70 years old Large trees in home yards – wooded

home sites History of root disturbances Environmental stress (drought) Clients often think symptoms happened

“overnight”! Also occurs in forested areas, but

causal factors may be different

http://www.forestryforum.com/board/index.php?topic=91515.0

MD Factors in Oak DeclineEnvironmental Stress (drought)Defoliation from insects or disease (more than one year)Damage to root zone from construction, soil compactionBacterial leaf scorch in landscape trees (possibly forest

trees also)Root diseases (Armillaria, Inonotus, sometimes

Phytophthora)Secondary borers – twolined chestnut borerHypoxylon cankersOak Wilt – possibly….

Avoiding Tree Decline

Match the tree to the site. Make sure site has adequate

space for root growth. Maintain health and vigor of trees

by proper watering and fertilizing. Avoid any changes to site after

trees are in place.

Managing Trees in Decline

Prune out dead branches – in winter in oak wilt areas! Protect the tree from additional site

disturbance. Maintain health and vigor of tree by

watering during dry periods. Very difficult to regain full canopy

once tree is in decline

J. O’Brien, USFS, Bugwood.org

University of Maryland Plant Diagnostic Laboratory

Dept. of EntomologyUniversity of Maryland4112 Plant Sciences Building4291 Fieldhouse DriveCollege Park, MD 20742-4454

301-405-1611rane@umd.eduhttps://extension.umd.edu/plantdiagnosticlab

When Field Observations are not Enough…..