Forest 

Service

Northeastern Area 

State and Private Forestry NA–PR–02–17 July 2017

Oak Wilt in the 

Northeastern 

United States

Oak wilt is a deadly vascular disease caused by a fungus 

(Ceratocystis fagacearum) that affects all native oak 

trees. Oaks are common in the Eastern United States 

and can be found in more mesic sites mixed in with 

other northern hardwoods such as sugar maple (Acer 

saccharum) or in drier sites with pines (Pinus spp.). Red 

oaks (northern red (Quercus rubra), pin (Q. palustris), 

and scarlet (Q. coccinea)) are more susceptible to oak 

wilt than white oaks (white (Q. alba), swamp white (Q. 

bicolor), chestnut (Q. montana), post (Q. stellata), and 

bur (Q. macrocarpa)). Red oaks can die within 6 weeks of 

infection whereas white oaks might take several years 

to die.

Current Range

Oak wilt was first described in Wisconsin in the 

1940s and has since become common as far east as 

Pennsylvania and as far south as Texas. It is an invasive 

disease that is expanding its range. Oak wilt was first 

detected in New York State in 2008 in Glenville. A 

considerable effort was conducted to eradicate the 

disease in Glenville. During 2016, the disease was 

detected in both Long Island in eastern New York and 

Canandaigua in western New York. 

Symptoms

Affected trees start showing symptoms, such as 

browning of leaves from the edge of the leaf margin 

inwards towards the base, in July (figure 1). The pattern 

of symptoms is different between white and red oak 

species. Infected white oaks die slowly, one branch at a 

time. In contrast, red oaks die quickly, shedding leaves 

from the top of the crown downward (figure 2).

Figure 1.—Top: Red oak 

leaves with oak wilt 

symptoms. (Courtesy 

photo by New York 

State Department 

of Environmental 

Conservation)

Middle: Bur oak leaves 

with oak wilt symptoms. 

(U.S. Forest Service photo 

by Danielle Martin)

Figure 2.—Right: Red oak 

on Long Island with oak 

wilt symptoms — leaf 

browning and shedding. 

(Courtesy photo by New 

York State Department 

of Environmental 

Conservation)
Disease Cycle

Oak wilt spreads locally from tree to tree via root grafts. 

It can also be spread over longer distances by sporecarrying beetles that visit wounds of healthy trees. Once 

the oak wilt fungus enters a tree, it spreads through the 

tree’s xylem vessels that carry water from roots to leaves. 

In response to the fungus, the tree plugs the xylem 

vessels, which causes the wilting symptoms. The fungus 

produces fungal mats that grow from the xylem towards 

the bark and create pressure that cracks the bark 

(figure 3). Fungal mats are produced in red oaks the 

following fall or spring after they die. Fungal mats release 

a sweet odor that attracts sap-feeding beetles called 

Nitidulids (Coleoptera: Nitidulidae). Nitidulids that visit 

fungal mats become coated with sticky spores that can 

infect healthy trees.

Management

Oak wilt management hinges on avoiding injury to 

healthy trees, removing infected trees, and breaking 

root connections between infected and healthy trees. 

Infected trees should be removed and debarked, buried, 

or chipped to prevent the fungus from spreading. Root 

graft disruption using either a trencher or vibratory plow 

prevents the fungus from spreading from infected trees 

to healthy trees (figure 4). Avoid wounding or pruning 

oaks in the spring and summer when sap beetles that 

carry fungal spores are active. 

If you observe oak wilt symptoms, please contact your 

local forest health specialist, State Extension Service, and 

State Departments of Agriculture and Forestry. 

For more detailed information, please refer to these 

publications:

O’Brien, Joseph; Mielke, Manfred; Starkey, Dale; Juzwik, 

Jennifer. 2011. How to identify, prevent, and 

control oak wilt. NA–FR–01–11. Reprinted 2017. 

U.S. Department of Agriculture, Forest Service, 

Northeastern Area State and Private Forestry. 40 p. 

https://www.na.fs.fed.us/pubs/howtos/ht_oakwilt/

identify_prevent_and_control_oak_wilt_print.pdf. 

(12 July 2017)

Pokorny, Jill. 1999. How to collect field samples and 

identify the oak wilt fungus in the laboratory. 

NA–FR–01–99. Radnor, PA: U.S. Department of 

Agriculture, Forest Service, Northern Area State and 

Private Forestry. https://www.na.fs.fed.us/spfo/pubs/

howtos/ht_oaklab/info.htm. (12 July 2017)

Figure 3.—Spore mat produced by the oak wilt fungus (Ceratocystis 

fagacearum) in a dead red oak. (Courtesy photo by New York State 

Department of Environmental Conservation)

Figure 4.—A vibratory plow can be used in oak wilt management to 

disrupt root grafts and stop the fungus from spreading from infected 

trees to healthy trees. (U.S. Forest Service photo by Joseph O’Brien)

Prepared by:

Isabel Munck, Forest Pathologist, USDA Forest Service, 

Northeastern Area State and Private Forestry, Durham, 

NH 03824

Northeastern Area

State and Private Forestry

11 Campus Blvd., Suite 200

Newtown Square, PA 19073

Phone: 610–557–4103

https://www.na.fs.fed.us

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