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Stebbins, R.L. 1990. Requirements for a United States chestnut industry. p. 324-327. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber Press, Portland, OR.

Requirements for a United States Chestnut Industry

Robert L. Stebbins

  1. INTRODUCTION
  2. THE CHESTNUT INDUSTRY
    1. U.S. Markets
    2. Cultivars
    3. Pests and Diseases
    4. Range of Production
    5. Propagation
    6. Orchard Establishment and Productivity
    7. Harvest Mechanization
    8. Storage
  3. PROCESSING
  4. PROSPECTS
  5. REFERENCES

INTRODUCTION

At present there is no U.S. chestnut (Castanea spp.) industry. Certain conditions must be met for the industry to develop to even modest levels of production. First, trees of high quality cultivars with resistance to chestnut blight must be made available in quantity It will be necessary to develop or improve mechanical harvesting, shelling, and peeling. Since many Americans alive today have never seen a chestnut, a marketing effort to familiarize them with this "exotic" nut and its uses will be needed. Established markets for exported nuts exist in Japan and other countries where consumers are familiar with it. Since removal of the "skin" (pellicle) from the kernel is too time-consuming for most homemakers, already-peeled kernels should be marketed.

THE CHESTNUT INDUSTRY

U.S. Markets

Before the chestnut blight incited by Cryphonectria parasitica Murr. (formerly Endothia parasitica [Murr.]), was introduced from China on Chinese chestnut trees (C. mollissima Bl.). America had a chestnut industry based on wild stands of Castanea dentata Borkh. That industry vanished a half century ago as the disease decimated the American chestnut.

The USDA Foreign Agricultural Service reported 4,293 metric tons of chestnuts imported in fiscal 1986-87, and 3,441 tons in 1987-88 (J. Young, pers. correspondence), valued at 6.5-6.7 million dollars. The primary exporter of chestnuts to the U.S. was Italy with about 84% of the volume, followed by China, Spain, Korea and eight other countries. In addition, an unknown quantity of dried chestnuts were imported. Wholesale prices have been $2.10 per pound ($4.62 per kg) for the larger sizes. Nuts are sterilized in Italy, brought here in sea containers, and fumigated using methyl bromide in port as required by USDA Animal and Plant Health Inspection Service (APHIS). Fresh nuts are refrigerated.

The most traditional use of chestnuts is roasted whole, with the shell and peel. Roasted chestnuts are sold in fall and winter on street corners in most Eastern cities. In Japan, Chinese chestnuts from Korea are marketed in that fashion. Peeling is done by the customer as the nuts are eaten.

The chestnut market in the northeastern U.S. is not entirely an ethnic one, but it is centered around the Thanksgiving and Christmas holidays. Recent immigrants of Italian, Portuguese, Chinese, Korean, and Japanese origin, form the most receptive markets for in-shell chestnuts which could be produced in U.S. orchards. In the west, Oriental food stores are a natural first opportunity. Because of the problems in storage, fresh chestnuts are available only seasonally. New Zealand is preparing a chestnut industry for export primarily to Japan (New 1988). U.S. marketers could come into that same market six months later. The volumes of processed chestnuts which could be marketed probably are greater than those which could be sold fresh. Marketing will probably not pose a problem until U.S. production reaches a hundred tons or more. If orchards average two tons of nuts per acre, this level of production could be reached quickly once suitable nursery stocks are available. Market research will be required both for the domestic market and to explore export opportunities.

Cultivars

Nuts from seedling trees will not be satisfactory except in the short run, while supplies of domestically produced chestnuts are very small. Resistance to chestnut blight must be the first criterion for a cultivar. The blight has occurred in Oregon, and was found by OSU Extension Agent Robert Rackham in orchards in California. There are no regions of the U.S. where the blight is not a potential threat. Of those cultivars of European parentage which have been preserved in California, 'Collosal' is not blight resistant but 'Silverleaf', which has not developed the blight in orchards where the blight exists, appears to have some resistance. Chestnut blight was found in Oregon and eradicated (Holdeman 1984). Oregon State University has brought in blight resistant "Dunstan" cultivars 'Revival' and 'Carolina' from Chestnut Hill Nursery in Florida, under quarantine by the Oregon Department of Agriculture. They have been planted at the Lewis Brown Horticultural Research Farm, Corvallis, and kept under close scrutiny for any evidence of the blight. Progress has been made in breeding blight-resistant chestnuts (Burnham et al. 1986, Jaynes 1975).

A second important characteristic of a good chestnut cultivar is the ease with which the "skin" or pellicle can be removed from the kernel. The flavor of the pellicle is so astringent that few people would eat them without first removing it. The French classify chestnuts into "marron" types and other. With marrons, the "skin" (pellicle) is not convoluted into the kernel. If they are true to their reputation, 'Collosal' kernels can be peeled very easily The "Dunstan" hybrids also have this reputation. Japanese chestnuts (C. crenata Sieb. & Zucc.) are hard to peel, as are Chinese chestnuts. Japanese chestnut breeder Dr. Yoshihiko Sato at Yatabe Fruit Research Station, Japan, is currently screening selections which are sweet and peel easily. The Chinese-American hybrids are also difficult to peel.

Although the decline of the European chestnut industry has been blamed on chestnut blight (Caries 1984), lack of mechanization in processing may also be partly responsible. While some Japanese blame Korean competition for the decline in their industry, Japanese housewives' reluctance to peel the nuts may also be a factor. If a chestnut industry is established in the U.S., its growth will eventually depend on some way to mechanically shell and peel the kernel in preparation for market.

While large sized nuts are easy to sell at profitable prices small ones are not. Chinese chestnuts are small to medium in size, 4.5-13 g (Wallace 1986), and 20 g is large for a Chinese chestnut (Miller 1988). American chestnuts, are small, 3-6 g, Japanese chestnuts are large, while European chestnuts are large and variable, some peeling quite easily, others with great difficulty. "Dunstan" hybrids are claimed to be large, weighing 13-20 g (Wallace 1986).

Pests and Diseases

The native American chestnut, has been almost entirely killed by chestnut blight. Breeders have produced new cultivars of blight-resistant chestnuts by hybridizing C. dentata with C. mollissima (Jaynes 1979) and backcrossing. Significant progress in the area of blight control has been made lately (Griffin 1986).

In Japan, chestnuts are highly susceptible to trunk cankers caused by a fungus of the genus Phytophthora. Nurserymen in Australia (Rinaudo 1988) and breeders in Japan (Yoshihiko Sato, Yatabe, pers. commun) find that European chestnut is even more susceptible to this disease than Japanese. With careful water management in dry climates Phytophthora trunk rot can be avoided.

Oregon maintains a quarantine against chestnut materials with the following insect pests: large chestnut weevil, Curculio proboscideous F., small chestnut weevil, Curculio auriger Casey, nut curculio, Conotrachelus spp. and oriental chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu (Oregon Dept. Agric. 1986).

In western Oregon, severe depreciation of chestnut trees by deer has occurred. Groundhogs were a problem in Ohio (Miller 1988), as were periodical cicadas.

Range of Production

With its low chilling requirement, 20-30 days of chilling (Westwood 1978), chestnuts can be grown as far south as Florida. Some cultivars of Chinese and American chestnut are hardy enough for conditions in the northeastern U.S., withstanding -20°C after sufficient acclimation. Chestnut seems to be tolerant of high summer temperatures in the central valleys of California. These characteristics give the nut a very wide potential production range.

Propagation

Japanese nurseries use veneer grafting for propagation of chestnut. An Australian nurseryman uses T budding when the little leaves are just beginning to emerge in spring. With chip budding, a large, 2.3-3 cm bud base is used. Most U.S. nurseries graft onto dormant rootstocks in spring (Lagerstedt 1988). Some grafters have experienced much difficulty due to root pressure flooding out the grafts. Grafted trees have often died a year or more after transplanting, due to graft failure (Berganz 1988). Chestnuts can also be increased through micropropagation (Chevre and Salesses 1985).

Orchard Establishment and Productivity

Chestnut trees begin to produce at an early age, and can produce two tons or more of fresh nuts per hectare (Burnett 1988). Irrigation appears to be necessary for quick establishment in the dry summers of western Oregon. Central leader training appears to be best for strong limb structure.

Harvest Mechanization

The nuts fall to the ground within about a week after they have become ripe in the hulls. Once fallen, they are subject to depredation by birds, squirrels, and mold. Since the nuts fall over a period of several weeks, several harvests are required to get a maximum yield of high quality nuts. More frequent harvest will be required where autumn weather is rainy

Some progress in mechanical harvesting has been made (Miller 1988). John DeMartini, chestnut grower in Linden, California (DeMartini 1983), cited hand harvest as the major cost which requires a high market price if chestnut production is to be attractive to U.S. growers. Many nuts come down in the burs, and will have to be removed mechanically DeMartini uses a converted walnut huller. Chestnuts are softer than walnuts, and could be more easily bruised. Most cultivars will require multiple picks to avoid deterioration on the ground while waiting for the rest of the crop to come down.

Storage

Chestnuts are usually not dried. They are stored fresh. They attain a rock-like hardness if dried to a moisture content below about 15%, and are useful only for grinding into flour. Unless they are held at cold temperatures, they will mold in storage. Dooley et al. (1980) stored European chestnuts in Australia, in air and controlled atmosphere storage (2.5% CO2:2% O2) at 0°C. Quality was monitored with measurements of weight loss, soluble solids, starch content, and fungal deterioration. Chestnuts were successfully stored for 13 weeks in both air and controlled atmosphere storage, but fungal deterioration was lower in the controlled atmosphere. They dipped the chestnuts in a solution of 100 ppm Rovral and 100 ppm benlate with 0.1% Tween 20 as a wetting agent immediately after harvest. All air-stored chestnuts were placed in polystyrene plastic trays and loosely wrapped with plastic bags to retain moisture. During both air storage and controlled atmosphere storage there was a reduction in starch content and an increase in soluble solids. This was detected as a sweetening of the chestnuts during flavor assessments. Fungal infection was 10-15% in the air stored nuts and only 0-5% in CA stored nuts.

Curing, or partial drying of chestnuts before storage, has been recommended to sweeten nuts by converting some of the starches into sugar. Curing is not required before cold storage because starches are slowly converted into sugar during storage. Curing may decrease the quality of chestnuts by allowing fungal invasion and moisture loss after harvest.

PROCESSING

About 70% of the consumption of Japanese chestnuts is used for boiled or steamed nuts (Itoo 1984). The remainder (30%) are for processing into sugar syrup products and "marron glace," a glazed candy. Many confectioneries process the nuts into products such as chestnut candy, mashed sweet potato with chestnut, and cake with chestnut. The most important problem in processing is peeling the pellicle of the chestnut. About 80% of the labor in processing is used in the peeling process, which is mostly done by hand using a knife. This causes the high cost of chestnut confectioneries. Thermal blast peeling is a process which holds promise for chestnuts (Harris and Smith 1988). Chestnut flour is useful for baking (Berganz 1988), and is safe for people who are allergic to wheat products.

U.S. producers could displace imports and expand the U.S. market for in-shell chestnuts, but a much larger tonnage could be marketed if a peeled product were made available (Miller 1988). It is unlikely that many homemakers will want to do that job in their own kitchens.

PROSPECTS

Either partial or complete answers to most problems of chestnut production have been developed. Some progress on mechanical harvesting has been made in California (Robert Rackham, personal communication) and in Ohio (Miller 1988). Thermal blast peeling has been successful on an experimental scale in Alabama (Harris and Smith 1988). Storage techniques have been developed (Dooley et al. 1980). Insect and diseases of chestnuts may be kept out of the Pacific Northwest through use of quarantines (Oregon Dept. Agric. 1980). Propagation of chestnut trees can be accomplished by budding, grafting, or other means (Lagerstedt 1988). By continuing to improve the crop and addressing the processing and marketing problems, domestic production could replace about 4,500 tons of imported nuts, and expand domestic consumption.

REFERENCES

Last update March 11, 1997 by aw