General: Walnut family (Juglandaceae). Small to medium-sized native trees with stiff upright branches and a wide-spreading crown, the young twigs, stems, and leaflets have hairs sticky-oily to the touch; terminal buds 12-18 mm long; bark brownish-gray, thick, shallowly divided into smooth or scaly plates. Leaves are pinnately compound, the leaflets (7-) 11-17, ovate to lanceolate or oblong-lanceolate, ± symmetric, mostly 5-11cm long, with finely toothed margins, terminal leaflet present, the lower surfaces densely covered with stellate hairs. Flowers are unisexual, female (pistillate) and male (staminate), but on the same tree (the species monoecious), usually not opening simultaneously on any individual tree; male flowers in slender catkins 6-14 cm long, the female flowers in terminal clusters of 6-8 flowers each. Fruit is an oblong-ovoid nut 4-6(-8) cm long, single or in clusters of 2-5, with a hard, thick, deeply furrowed shell enclosed by a thick husk with a sticky-glandular surface. The nuts usually remain on the tree until after leaf fall. The common name refers to the mature nut kernels, which are sweet and oily, like butter.

Wallia cinerea (L.) Alef.:
Canada (North America)
United States (North America)

Juglans cinerea L.:
Canada (North America)
United States (North America)

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Juglans cinerea occurs throughout the central and eastern United States and southeastern Canada (Fernald 1950, Smith 1988, Brown and Kirkman 1990, Gleason and Cronquist 1991, TNC HO 1992).

Butternut is primarily a species of the northeastern and north-central US and southern Canada from southeastern New Brunswick to Ontario and Quebec; in the US in Minnesota to Missouri and eastward through Tennessee into North Carolina and Virginia, with disjunct outlyers in Arkansas, Mississippi, Alabama, South Carolina, and Georgia. It is uncommon throughout most of its range and formally listed as rare in many of the states in which it occurs. For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.

The butternut canker is killing Juglans cinerea across its range. Because the trees do not root-sprout, the range is contracting.

Trees , to 20(-30) m. Bark light gray or gray-brown, shallowly divided into smooth or scaly plates. Twigs with distal edge of leaf scar straight or nearly so, bordered by well-defined, tan-gray, velvety ridge; pith dark brown. Terminal buds conic, flattened, 12-18 mm. Leaves 30-60 cm; petiole 3.5-12 cm. Leaflets (7-)11-17, ovate to lanceolate or oblong-lanceolate, ± symmetric, (2.5-)5-11(-17.5) × 1.5-6.5 cm, margins serrate, apex acuminate; surfaces abaxially with abundant 4-8-rayed fasciculate hairs, scales, and sometimes capitate-glandular hairs, axils of proximal veins with prominent tufts of fasciculate hairs, adaxially with scattered fasciculate hairs or becoming glabrescent; terminal leaflet present, usually large. Staminate catkins 6-14 cm; stamens 7-15 per flower; pollen sacs 0.8-1.2 mm. Fruits 3-5, ellipsoid to ovoid or cylindric, 4-8 cm, smooth, with dense capitate-glandular hairs; nuts ellipsoid to subcylindric or ovoid, 3-6 cm, surface with ca. 8 high, narrow, longitudinal main ridges, with narrow, interrupted, longitudinal ridges or lamellae between main ridges.

There are some pubescence differences which will help to distinguish Butternut from the Black Walnut, even when the distinctive dark pith is not exposed. In J. cinerea, there is often a pad of dense small hairs extending transversely along the upper margin of the old leaf scars; in J. nigra, this pad is absent, although the circular area of bud pubescence is confusing, and some specimens are ambiguous. The underside of the leaflets in J. cinerea is +/- densely covered with mostly stellate hairs, while in J. nigra the pubescence is sparser and mostly of simple hairs. The pubescence of cinerea, including that on the fruit, is more clammy than that of J. nigra. Persons familiar with the species in the field will also know differences in fragrance of the foliage and fruit and in stain from the husks--all difficult to expresss in words (Voss, 1980).

Wallia cinerea (Linnaeus) Alefeld

Comments: Juglans cineara typically grows in rich mesophytic forests, lower slopes, ravines, and various types of bottomland, including banks and terraces of creeks and streams, and floodplain forests (Fernald 1950, Gleason and Cronquist 1991). This species achieves its best growth in well-drained bottomland and floodplain soils.

The following provides additional information on the specific habitats of J. cinerea in several states from different parts of the species' range:

The habitat in Ohio is mesic river terraces and ravines (Cusick 1992).

Michigan habitat includes streambanks, swamp forests, and upland beech-sugar maple, oak-hickory, and mixed hardwood stands (Voss 1985). In southern Michigan sites, associates may include such species as Ulmus americana (American elm), Acer saccharinum (silver maple), Fraxinus quadrangulata (blue ash), Betula alleghaniensis (yellow birch), Tilia americana (basswood), and many woodland and swamp herbs. In some areas, butternut occurs occasionally as a roadside tree.

The habitat in Illinois and Wisconsin is mesic and riparian hardwood forests, where associates of the overstory include Acer saccharum (sugar maple), Carpinus caroliniana (blue beech), Celtis occidentalis (hackberry), Fagus grandifolia (American beech), Prunus serotina (black cherry), Quercus alba (white oak), Quercus macrocarpa (bur oak), Quercus rubra (red oak), Tilia americana (basswood), and Ulmus americana (American elm). The herbaceous associates of this habitat include Claytonia virginiana (spring beauty), Dicentra cucullaria (squirrel corn), Hydrophyllum appendiculatum (appendaged waterleaf), Isopyrum biternatum (false meadow-rue), and Solidago caesia (woodland goldenrod). In wooded floodplain habitats, associate plant species include Celtis occidentalis, Cryptotaenia canadensis (honewort), Elymus virginicus (Virginia rye grass), Fraxinus pennsylvanica (red ash), Galium aparine (cleavers), Geum canadense (geum), Hydrophyllum virginianum (Virginia waterleaf), Laportea canadensis (wood nettle), Ranunculus septentrionalis (swamp buttercup), Toxicodendron radicans (poison ivy), Rudbeckia laciniata (cutleaf coneflower), Ulmus americana, and Viola sororia (woolly blue violet). A characteristic habitat in the Chicago region is springy, wooded, calcareous slopes, where limey water percolates through gravelly soils. Associate plant species in this habitat may include Angelica atropurpurea (angelica), Caltha palustris (marsh marigold), Cardamine bulbosa (spring cress), Fraxinus nigra (black ash), Lilium michiganense (Michigan lily), Mitella diphylla (bishop's cap), Ribes americanum (swamp gooseberry), Smilacina stellata (starry false solomon's seal), Solidago patula (swamp goldenrod), and Symplocarpus foetidus (skunk cabbage) (Swink and Wilhelm 1979).

The habitat in Indiana is mesic forests (Homoya 1992).

The typical habitat in Kentucky is mesic wooded ravines along streams, mesic limestone gorges, mesic deciduous forest, second growth in mixed hemlock forest, and upland mesic woods, occurring with Fraxinus americana (white ash), and several other species (KY HP 1992).

In Tennessee, Juglans cinerea occurs along creek bottoms in mesic forests and on lower slopes (TN ESD 1992).

In Mississippi, this species occurs on calcareous bluffs, along river and stream drainages, in mesophytic forests, and calcareous ravines. Populations are often found on north-facing slopes. Associate plant species include Acer spp. (maple), Carya spp. (hickory), Juglans nigra (black walnut), Liriodendron tulipifera (tuliptree), and Quercus macrocarpa (bur oak) (MS NHP 1992).

Habitat in Delaware consists of northwest-facing slopes of pastures, banks of streams running through meadows, and floodplain woods with partial shade (DE NHP 1992).

In Massachusettes this species a generalist in terms of soil moisture (it's found along a continuum from river bottomlands to mesic forests to talus and dry balds) but it does not seem to be a generalist in terms of bedrock substrate-in MA it avoids acid, nutrient poor substrates and appears to be restricted to areas underlain by basalt, marble, or dolomite (M. Dow Cullina, pers. comm., 2006).

Flowering spring (Apr-Jun). Rich woods of river terraces and valleys, also dry rocky slopes; of conservation concern; 0-1000 m; N.B., Ont., Que.; Ala., Ark., Conn., Del., Ga., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Vt., Va., W.Va., Wis.

Adaptation: Butternut is found most frequently in rich woods of coves and stream benches and terraces, on slopes, in the talus of rock ledges, and on other sites with good drainage; at elevations of 0-1000 (-1500) meters. Young trees may grow in considerable competition, but they are shade-intolerant and mature trees must reach the overstory. Flowering occurs from April-June and fruiting from September-October.

General: Seed production begins at about 20 years and is optimum from 30-60 years. Good crops can be expected every 2-3 years, with light crops during intervening years. Premature seed losses may result from consumption by insects, birds, and rodents, and a lack of butternut trees in the immediate vicinity may limit pollination and fruit formation. Seeds germinate in the spring after seedfall and a cold period at 20°-30° C. for 90-120 days to break dormancy.

Stumps of young butternut trees and saplings are capable of sprouting. The trees are reported to be slow growing and seldom live longer than 75 years.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: > 300

Comments: Thousands of occurrences across a wide range.

Juglans cinerea achieves optimal growth on well-drained soils of bottomlands and floodplains, but rarely occurs in pure stands. According to Rink (1990), this species grows best in riparian sites and well-drained soils, but is seldom found on dry, compact, or infertile soils. Rink also notes that butternut is found at much higher elevations (up to 4900 ft) in the Virginias than black walnut. Butternut is shade-intolerant, growing best in full sunlight. Young trees can tolerate some competition from the side, but will not withstand shade from above. This species needs to be in the canopy in order to survive. Reproduction is successful only in areas where shade does not inhibit its growth, such as stand openings or in fields (Skilling 1993, Ostry et al. 1994).

This species is being seriously impacted, if not devastated, by a canker fungus (Sirococcus clavigignenti-juglandacearum) that is spreading rapidly throughout its range, and few stands remain uninfected. The origin of the disease is unknown, although Fogelson and Campbell (1990) believe it may have been introduced about 40 years ago on the east coast of the United States. According to Anderson (1993), 40- year-old cankers have been observed in North Carolina. Long noted as suffering from a canker dieback (frequently called "butternut decline"), scientists from Wisconsin first identified the disease agent as a new species of Sirococcus in 1967, although tests of trees in North Carolina demonstrated its presence there in 1952. This disease has spread quickly (within 30 years) throughout butternut's range, infecting and killing trees in all locations. In the Great Lakes states, all sites examined by researchers had been infected with canker. The disease vectors are poorly known, but the canker is believed to be transmitted at least in part by raindrops splashing spores from infected trees onto healthy ones, and possibly via insects. If the spores become airborne, they are able to be dispersed over great distances. The spores are produced throughout the growing season and can survive when weather conditions are cool and skies are overcast. (Kuntz et al. 1979, Fogelson and Campbell 1990, Forest Service News 1992, Ostry et al. 1994).

Symptoms of the disease include the appearance of lens-shaped cankers on the trunk, limbs, twigs, and immature nut of the tree. In spring, an inky-black, thin fluid is exuded from the cankers. These cankers usually continue to grow in size and girdle the tree, eventually killing it by destroying the cambium. The girdling of the tree often causes a wilting of the leaves, especially noticeable in the crown (Fogelson and Campbell 1990). Trees with reduced vigor become susceptible to insects and secondary disease agents, particularly Melanconis juglandis (E. and E.) Graves, which causes branch dieback (Skilling 1993).

Butternut is an important source of mast for wildlife, especially in the northern part of its range, where black walnut (Juglans nigra) does not occur. Squirrels and other rodents are some of the consumers of the seeds. (Ostry et al. 1994).

Male and female flowers borne seperately on the same tree. Squirrels, rabbits and white tailed deer eat the nuts. Squirrels disperse them.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 3
Species: 3
Species With Barcodes: 1

Canada

Rounded National Status Rank: N3 - Vulnerable

United States

Rounded National Status Rank: N3 - Vulnerable

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Occurs infrequently in forest stands throughout most of the eastern United States and Canada. The abundance and condition are both in rapid decline due to butternut canker disease, with no known remedy. At the time of this review (2006), even with the canker evident and widespread, there are a large number of occurrences persisting and resistant trees, though rare, are found in many areas of the range. The species is not currently vulnerable to extinction, but there is certainly reason for longer-term concern. The rank should be reevaluated frequently.

Environmental Specificity: Moderate to broad.

Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status, such as, state noxious status and wetland indicator values.

Global Short Term Trend: Decline of 10-50%

Comments: Butternut is experiencing a rapid decline due to the spread of butternut canker. The disease has spread rapidly throughout the species' range, and the downward trend is likely to continue until disease resistant trees are identified, propagated, and successfully reintroduced.

Schlarbaum et al. (1997) reported that 77 percent of butternut trees in the southeastern United States died in a 30 year period. Forest Service survey data indicated overall declines of 23% in the number of butternut trees in 7 midwestern states over various time intervals ranging back to 1990 (USDA NRCS 2004).

Global Long Term Trend: Increase of 10-25% to decline of 30%

Comments: The major threat to Juglans cinerea throughout its entire range is susceptibility to the butternut canker disease caused by the fungus Sirococcus clavigignenti-juglandacearum. The fungus disrupts nutrient flow through cambium areas, which is generally fatal. It may take trees more than 40 years to die, but in many cases, death has rapidly followed infection. Following dieback, this species does not leave live rootsprouts and usually does not leave viable seed. The wood, which is highly prized for cabinet-making and other types of woodworking, is in great demand. "Pre-emptive salvage" cutting, in which any remaining healthy trees are cut in the attempt to get full value for them before they become diseased, is common (at least in the Great Lakes states). The salvage of non-infected trees, however reduces the pool of potentially disease resistant individuals. Woodlot management is also a a form of threat to this species, since it may not involve providing the types of disturbance (e.g., soil disturbance) needed by this shade-intolerant species to successfully reproduce and establish new individuals. Unless management practices are altered to allow for open, disturbed areas, it is unlikely that there will be significant butternut reproduction (Skilling 1993).

In many areas healthy butternut trees have been found growing adjacent to diseased trees and these presumably resistant trees have remained healthy over a 12 year period (Ostr and Woeste 2004).

Butternut canker disease can be identified by the following characteristics or conditions: (1) trees with dying branches or dead tops, and tufts of shoots (epicormic shoots) below the dead portions; (2) discolored bark that in spring exudes an inky-black, thin fluid from cracks in the cankers, and in summer has sooty bark patches that commonly have a white margin; and (3) cankers of various types. In early stages, cankers are sunken and elongate, originating at leaf scars, buds, and in various tree wounds. In latter stages, cankers are visible on older stem and branch portions, many loosely covered with shredded bark and bordered by successive callus layers. Infected trees are also characterized by dark brown to blackish wood portions in elliptical patterns beneath the bark. Dieback occurs through single or coalescing cankers girdling branches, and branch suckers and stem sprouts quickly become infected and die.

An additional threat is hybridization with Juglans ailantifolia (heartnut), a species from Japan which is marketed as a nut tree (McDaniel 1979).

Restoration Potential: The restoration potential of butternut is uncertain, owing to the rapid spread of butternut canker. Since most remaining trees are infected with the fungal disease, or will likely be infected, recovery may be extremely difficult. Many of the infected trees are expected to die within the next 20 years, although Anderson (1993) notes that there are many trees in North Carolina that have survived 40 years with canker. There is presently no known cure for the annual fungus. However, several apparently resistant butternut trees have been located adjacent to infected trees in Virginia and elsewhere. It may be possible to clone these and other apparently disease-resistant butternut trees to produce shoots that could be reintroduced throughout the species' range. The U.S. Forest Service and several state forestry units are working to locate and test trees that may be resistant to infection. (Fogelson and Campbell 1990, Skilling 1993).

Activities that should be undertaken to help restore butternut populations include: (1) conducting inventories for butternut to assess its health and status; (2) increasing the understanding of the butternut canker disease cycle; (3) developing silvicultural methods that will ensure effective regeneration; (4) beginning a seed collection program along with test seeding and transplanting plans; (5) locating disease-resistant trees within the forest; (6) establishing clone banks and seed orchards by using propagation techniques, including tissue culture; (7) testing the possibility of developing resistant trees by using intraspecific tree breeding techniques; and (8) monitoring the effect of current management being employed where butternut is growing and making beneficial refinements as needed. (Ostry et al. 1994).

Preserve Selection and Design Considerations: There are no known preserve designs that would optimize the conservation of this species due to the rapid rate of infection and spread of butternut canker disease.

Management Requirements: There are no effective or practical management techniques known that would completely protect butternut due to the butternut canker. Some sites are being managed by extracting infected individuals to inhibit the spread of the canker, a treatment Skilling (1993) states has no known value. In addition, the practice of extracting healthy trees from infected stands to salvage the economically valuable wood serves to further reduce the potential pool of resistant germplasm. At present, the best management prescription is to locate and monitor butternut stands so that potentially resistant germplasm strains can be identified. Criteria for identifying candidate trees include the following: (1) the tree must be in a stand already infected with canker where the possibility of exposure is high; (2) the tree must be canker-free, or if cankers are present, must have overgrown them; (3) the tree must be at least 10 inches in diameter at breast height (dbh) to ensure that it has been exposed to canker over a number of years; and (4) the tree(s) must be owned by someone who is willing to let researchers collect scion wood (grafting material) as well as nuts from the tree(s) over a number of years (Ostry et al. 1994).

At least three fungicides have been tested on butternut canker (Anderson 1988). One of those fungicides is benomyl, which has provided some effective treatment at low concentrations. However, this treatment is not practical for treating scattered trees within a forest stand.

Because butternut is a shade-intolerant species, its natural propagation can be assisted by managing forests to create disturbance conditions (e.g., canopy gaps, openings, soil disturbance) needed for colonization and establishment of new individuals. As openings grow closed over time, they should be made larger so that established butternut trees can achieve full growth and development (Ostry et al. 1994).

All occurrences of healthy (non-infected and resistant) trees should be tracked; resistant trees, which are of the greatest importance for conservation of the species, should be most actively sought and identified.

Management Programs: Concern over the fate of butternut has led to moratoriums on harvesting. In Minnesota, the Department of Natural Resources issued a moratorium in 1992 on cutting healthy butternut trees on state lands administered by the Division of Forestry (Rose 1992, Skilling et al. 1993). The moratorium did not prohibit the salvage of diseased trees, but encouraged private landowners to abstain from harvesting healthy trees to maintain an optimal pool of potentially resistant germplasm. The U.S. Forest Service has placed a moratorium on cutting healthy butternut trees in National Forests as of March 1993. Within Region 9 of the U.S. Forest Service, butternut has been placed on the sensitive species list; in Region 8 it has been placed on the sensitive species list in Mississippi, with similar designation recommended for several other National Forests.

Management for butternut within the Great Smoky Mountains National Park consists of gathering fruits from wild populations and either storing them for several years or planting them immediately. Germination of seeds is slow and may take several months, but the process can be hastened by treating seed coats with a weak acid to soften them. Seeds are germinated in soil-filled medium pots. Approximately 100 seedlings have be germinated and transplanted into suitable habitat within the same year using this method. Long-term monitoring of tagged butternut trees has also been initiated within the Park, and studies have found that virtually all butternut trees within the Park are infected (Rock 1992).

Monitoring Programs: Annual monitoring for this species in Delaware and the Great Smoky Mountains National Park is conducted in order to update occurrence records and to determine the rate of disease infection (DE NHP 1992, Rock 1992). Contact:

William McAvoy Botanist, Delaware Natural Heritage Program Division of Parks and Recreation Department of Natural Resources and Environmental Control, 89 Kings Highway P.O. Box 1401 Dover, DE 19903 Telephone: (302) 739-5285

Janet Rock Botanist, Great Smoky Mountains National Park Natural Resources Management 107 Park Headquarters Road Gatlinburg, TN 37738 Telephone: (615) 436-1244

Management Research Programs: Research into the identification and propagation of resistant strains of butternut to butternut canker disease is being conducted at the North Central Forest Experiment Station in St. Paul, Minnesota. This research focuses on three approaches: (1) the establishment of grafted clonal lines of butternut from putative resistant trees located in the field; (2) the development of methods to propagate these resistant lines so that resistant plant material will be available; and (3) the development of techniques to produce butternut in vitro by embryo, callus, and nodal explants and to develop an in vitro inoculation system to identify somaclones with resistance to butternut canker; (4) establish field plantings of material from objectives 2 and 3 and determine if field resistance is related to laboratory resistance (Skilling et al. 1990, 1992, 1993). Investigations are also being conducted to obtain samples of the canker fungus from throughout the range to determine if there is genetic or pathogenic variation within the fungus population. This information will assist in evaluating whether different isolates are needed to confirm resistance (Skilling et al. 1993). Detailed results of research conducted in the past three years may be found in progress reports prepared by Skilling et al. (1990, 1992, 1993).

Management Research Needs: As resistant strains of butternut trees to butternut canker disease are successfully propagated, management research will need to focus on reintroduction efforts and the preparation and maintenance of site conditions so that growth and reproduction of butternut will be optimized.

Biological Research Needs: In the years since detection of the butternut canker researchers have clarified several aspects of the disease; the major remaining conservation need is related to using resistant material and other techniques to retain and restore the species (Ostry and Woeste 2004). Resistance has been noted in many trees and may originate from natural phenotypic variants (Ostry and Woeste 2004) or possibly from hybridization with a close Asian relative, Japanese walnut (Juglans ailanthifolia) (Michler et al. 2005). Trees with possible resistance are being propagated and assessed but data are needed on the heritability of resistance and in general further genetic characterization is needed before classical breeding or genetic modification can be used to produce canker-resistant trees (Michler et al. 2005).

Comments:

Anyone observing what they believe to be disease-resistant trees (individual trees that appear to be canker-free within infected stands and are not residential shade trees) should contact Dr. Darroll Skilling, North Central Forest Experiment Station, 1992 Folwell Avenue, St. Paul, MN, 55108, telephone (612) 649-5116.

Needs: Resistant germplasm from throughout the range should be preserved ex situ. Resistant specimens should be protected in situ. Healthy trees throughout range (whether or not resistance is known) should be conserved where possible. But there are no effective or practical management techniques known that would completely protect butternut. Some sites are being managed by extracting infected individuals to inhibit the spread of the canker, a treatment Skilling (1993) states has no known value. In addition, the practice of extracting healthy trees from infected stands to salvage the economically valuable wood serves to further reduce the potential pool of resistant germplasm. At present, the best managemnet prescription is to locate and monitor butternut stands so that potentially resistant germplasm strains can be identified. Criteria for identifying candidate trees include the following: (1) the tree must be in a stand already infected with canker where the possibility of exposure is high; (2) the tree must be canker-free, or if cankers are present, must have overgrown them; (3) the tree must be at least 10 inches in diameter at breast height (dbh) to ensure that it has been exposed to canker over a number of years; and (4) the tree(s) must be owned by someone who is willing to let researchers collect scion wood (grafting material) as well as nuts from the tree(s) over a number of years (Ostry et al. 1994).

Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.” These plant materials are readily available from commercial sources.

Two hybrids show strong growth and extreme hardiness and produce nuts similar to the butternut in clusters of 10-15.

Juglans cinerea X J. regia = Juglans X quadrangulata

Juglans cinerea X J. ailantifolia = Juglans X bixbii

Butternut canker is killing the species over its whole range. The fungal pathogen (Sirococcus clavigignenti-juglandacearum) apparently was introduced from outside of North America. It was first reported from southwestern Wisconsin in 1967 but is believed to have spread from the southeastern US coastal region, where it first appeared about 40-50 years ago. The Forest Service estimated in 1995 that 77% of the butternuts in the Southeast were dead. The fungus infects trees through buds, leaf scars, and possibly insect wounds and other openings in the bark, rapidly killing small branches. Spores produced on branches are spread by rain, resulting in multiple, perennial stem cankers that eventually girdle and kill infected trees – these do not resprout. The cankered portions should be removed and destroyed and the wounds should be covered with fungicidal paint; leaves that might harbor fungus (brown leaf spot) should be destroyed.

A few healthy butternut trees have been found growing among canker-diseased and dying trees and may be resistant. Black walnut apparently is unaffected. A research coalition has been formed to locate surviving trees or populations, characterize sites, identify trees with putative resistance, develop screening methodology for disease resistance, study fungal physiology, and preserve germplasm.

Fire easily top-kills butternut and older trees rarely sprout from the root crown or stump. A single hot fire or repeated cool fires can effectively eliminate the species in mixed hardwood stands

There is commonly a zone of no-growth or inhibited growth around walnut trees, because they produce a naphthoquinone (juglone) that selectively inhibits growth of associated plants. Juglone is concentrated in root tissue and fruit husks, with lesser amounts in the leaves, catkins, buds, and inner bark.

Comments: J. cinerea is a highly valued lumber species because of its beautiful grain and soft texture. The nuts serve as feed for wildlife. The pigment from the husks was used to dye Confederate soldiers' uniforms during the Civil War.

Butternut is called "white walnut" because of its light-colored wood, which has a natural golden luster that becomes satin-like when polished. The wood is only moderately hard and saws and carves easily. It has been used for furniture, cabinetry, instrument cases, interior woodwork, including hand-carved wall panels and trim, and church decoration and altars. It is stocked in specialty lumberyards because little is cut annually.

Butternuts were often planted close to the house on farmsteads for their use as food. Kernels were used in baking and cultivars have been selected for nut size and for ease of cracking and extracting kernels.

They have been popular in New England for making maple-butternut candy. Early settlers used the fruit husks and inner bark to make orange or yellow dye and the root bark provided a laxative.

Stewardship Overview: Butternut is shade-intolerant, achieving its best growth in full sunlight and requires some form of disturbance, such as soil disturbance and the creation of canopy gaps for successful reproduction and establishment (Skilling 1993).

This species is critically threatened by the rapid spread of a canker fungus (Sirococcus clavigignenti-juglandacearum), which is killing trees (including sprouts and seedlings) throughout its range (Ostry et al. 1994). A majority of trees throughout the range may be infected with butternut canker, and recovery will be difficult. Many stands of butternut trees have been seriously impacted, leaving small clusters of very vulnerable individuals. The range of infection has apparently increased dramatically in recent time. For example, 77 percent of the trees have died in North Carolina and Virginia (Anderson 1993). A treatment with no known value (Skilling 1993) is the culling of infected trees to attempt to prevent the spread of the disease to other individuals within a stand or area. Considerable branch dieback is caused by Melanconis juglandis (E. and E.) Graves, a fungus that appears to attack trees of low vigor. Anderson and LaMadeleine (1978) reported that Melanconis oblongum Berk is associated with dieback in branches and twigs, causing deformation but not tree mortality. Although butternut canker is the primary global threat to this species, butternut is also threatened to some extent by plant succession in areas where the pre-settlement disturbance regime no longer exists, preventing the creation of open conditions necessary for the successful reproduction of this shade-intolerant species.

Conservation needs include compiling a more accurate assessment of the problem, such as determining the degree of damage, how widespread the disease is, the distribution of the species and the disease, and also assessing forest health and trends. Research needs include studies of the disease and disease vectors, and the development of improved screening techniques for determining resistant strains of butternut for germplasm preservation and testing. Research is being directed toward the identification and propagation of disease-resistant trees. The North Central Forest Experiment Station of the U.S. Forest Service is coordinating research with several state agencies, universities, and private individuals in a three-part study to: (1) plant grafted clones of butternut in the field from resistant trees; (2) find methods of propagating these clones; and (3) develop the techniques for producing butternut tissue ("somaclones") that can be inoculated in order to determine which germplasm is disease resistant (Forest Service News 1992). One management technique is simply to avoid cutting healthy trees such that potentially resistant individuals can ultimately be identified. It will be important to identify and monitor significant butternut stands to help determine disease invasion and spread. When apparently resistant trees are found, these individuals can be utilized for germplasm testing, propagation, and preservation.