Hickory wilt (Ceratocystis smalleyii)

Synonyms: Ceratocystis smalleyi

Common Names: Ceratocystis canker of hickory, hickory canker, bitternut hickory canker

Description:

Hickory wilt (caused by the fungus Ceratocystis smalleyi) is a disease that kills hickory trees, especially bitternut hickory [1][2]. It works together with a native insect, the hickory bark beetle: the beetle attacks weakened trees and its wounds let the fungus in, which then forms many cankers in the bark and clogs the tree's water-carrying tissue, causing the crown to die back quickly [1][2]. MISIN tracks it because it is a recently recognized, poorly understood disease that can kill hickories, and people can move it on hickory wood [1][2].

Identification:

Hickory wilt is a disease, so you identify it by what it does to the tree rather than by something you can pick up. The clearest signs are on the trunk and larger branches: numerous small cankers (dead, sunken or diffuse patches of bark), often with reddish dead inner bark beneath them and reddish-brown staining in the wood under the canker [1][2]. Tiny entry and exit holes made by the hickory bark beetle are commonly found alongside the cankers [2]. As the many cankers and the fungus block water movement, the crown thins and dies back, sometimes over a single season [1].

The disease is easiest to notice in summer, when a hickory's crown suddenly thins, browns, or dies back while nearby trees stay green [1]. On the bark, look year-round for clusters of small cankers paired with the pinhole-sized beetle holes [2]. Because the trees most at risk are already stressed ? for example by drought ? watch stressed bitternut hickories most closely [1].

At-a-glance cues:

1. Many small cankers (sunken or diffuse dead patches) on the trunk and large branches of a hickory [1][2]
2. Reddish inner-bark death and reddish-brown stained wood beneath the cankers [1][2]
3. Pinhole-sized hickory bark beetle entry and exit holes alongside the cankers [2]
4. Rapid crown thinning and dieback, often on stressed bitternut hickory [1]

Habitat:

Hickory wilt lives in hickory trees, so its "habitat" is its host. It mainly affects bitternut hickory (Carya cordiformis), with other hickories affected to varying degrees [1][2]. It is found wherever these hickories grow ? in forests, woodlots, and landscapes [2]. The disease is most damaging on trees that are already stressed, such as those weakened by drought, which are also the trees the hickory bark beetle is most likely to attack [1].

Hickory wilt is a recently recognized disease, reported from bitternut hickory across the north-central and northeastern United States, including Iowa, Indiana, Minnesota, New York, Ohio, and Wisconsin [2]. The origin of the fungus is uncertain ? it was only described and linked to this disease in the 2000s ? so whether it is native or introduced is not firmly settled [1][2].

Reproduction:

Hickory wilt spreads as a partnership between the fungus and the native hickory bark beetle. The beetle bores into hickory trees ? especially stressed ones ? and its tunnels and wounds give the fungus a way into the bark and wood [1][2]. The fungus then grows and produces spores in the bark and beetle tunnels, and beetles moving from tree to tree help carry it along [1][2]. People can also move the disease over longer distances by transporting infested hickory wood, logs, and firewood [2].

There is no "seed-set" timing to target here as with a weed. The practical steps are to keep hickories healthy so they are less attractive to the beetle, avoid moving hickory wood, and watch stressed bitternut hickories for early signs (see Management) [1][2].

Impact and Damage:

Hickory wilt is not a danger to people or pets ? it harms hickory trees [1]. For a homeowner, it can kill a yard or woodlot hickory, often within a season or two once the crown begins to decline, and the dead tree then becomes a removal cost and a potential hazard [1]. There is no known cure once a tree is heavily infected [1].

In forests, the disease contributes to the decline and death of bitternut hickory, particularly where trees are stressed and the hickory bark beetle is active [1][2]. Repeated cankers and the resulting loss of water movement can kill mature trees, reducing hickory in the forest and the hickory nuts that feed wildlife [1]. Because the disease is still poorly understood and was only recently recognized, its full long-term impact on hickory forests is still being studied [1][2].

Similar species:

Hickory bark beetle damage (from the native beetle Scolytus quadrispinosus) is the condition most easily confused with hickory wilt, since the beetle and the fungus often occur together. Beetle attack alone can cause crown dieback and leaves the pinhole-sized entry and exit holes, but the wilt disease adds the many bark cankers and the reddish-brown stained wood beneath them.

General hickory decline from drought or other stresses can also cause crown thinning and branch dieback that resembles hickory wilt. It is distinguished by the absence of the distinct bark cankers and the reddish sapwood staining that the fungus produces.

Monitoring and rapid response:

Signs to watch for:

1. Many small cankers on the trunk and large branches of a hickory, with reddish dead bark and reddish-brown stained wood beneath [1][2]
2. Pinhole-sized hickory bark beetle holes alongside the cankers [2]
3. Rapid crown thinning or dieback on a hickory ? especially a stressed bitternut hickory ? in summer [1]

What you can do:

1. Keep your hickories healthy and less stressed ? water during drought and avoid wounding the bark ? since stressed trees are the ones the beetle and fungus attack first [1].
2. Do not move hickory firewood or logs ? buy and burn firewood locally, since moving infested wood can carry the disease and the beetle to new areas [2].
3. If a hickory is declining with cankers and beetle holes, have it checked, and remove and properly handle severely affected or hazardous trees [1][2].
4. Watch for and report declining bitternut hickories so new occurrences can be confirmed and tracked (below) [1].
5. Land managers and crews should monitor hickory stands ? especially after drought ? and remove declining, beetle-infested hickories to reduce local spread [1][2].

When to call a professional:

1. Large, valued, or hazardous hickories, or a stand of declining hickories ? have a certified arborist or forester assess them, since confirming the disease usually needs lab testing [1][2].
2. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Park J, Juzwik J, et al. (2013). "Multiple Ceratocystis smalleyi Infections Associated with Reduced Stem Water Transport in Bitternut Hickory." Phytopathology 103(6):565?574. semanticscholar.org
2. USDA Forest Service, Research & Development. Ceratocystis smalleyi infections and stem water transport in bitternut hickory (research record). research.fs.usda.gov

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