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Chinese chestnut production in the United States: Practice, problems, and possible solutions

Authors:

Abstract

There are fewer than 162 ha of commercial Chinese chestnut orchards in the United States, with approximately half of these in the Southeast. Large numbers of Chinese chestnut seedlings are planted annually in the United States for home and game food production; however, knowledge about chestnut propagation, fertilization, pests, harvest, storage and marketing is not adequate. There is little commercial marketing of U.S.-grown Chinese chestnuts through roadside markets and local farmers’ markets as the supply is low and unpredictable. However, we yearly import 4.5 mill kg of European chestnuts to satisfy the U.S. market. Successful chestnut orchards will require vegetatively propagated selections, intensive management, mechanical harvesting, and control of insect and disease pests.
5&
Chinese Chestnut Production in the
United States: Practice, Problems, and
Possible Solutions^
Jerry A. Payne,^ Richard A. Jaynes,=^ and Stanley J. Kays"'
T/iere are fewer than 162 ha of commercial Chinese chestnut orchards in the
United States, with approximately half of these in the Southeast. Large numbers
of Chinese chestnut seedlings are planted annually in the United States for home
and game food production: however, knowledge about chestnut propagation,
fertilization, pests, harvest, storage and marketing is not adequate. There is little
commercial marketing of U.S.-grown Chinese chestnuts through roadside mar
kets and local farmers' markets as the supply is low and unpredictable. However,
we yearly import 4.5 mill kg of European chestnuts to satisfy the U.S. market.
Successful chestnut orchards will require vegetatively propagated selections, in
tensive management, mechanical harvesting, and control of insect and disease
pests.
The Chinese chestnut, Castanea mollissima Blume, has been utilized as a food
and timber crop since ancient times in northern China, the presumed center of
origin of the species (Vavilov, 1951). Shih Ching, a collection of poems composed
over a period of 500 yr between 1000 and 500 B.C., lists Chinese chestnut as an
economic crop of that period (Keng, 1974). It was first introduced into the United
States in 1853 (Rehder, 1940) and again in 1901 by G. D. Brill (Galloway, 1926).
In 1904, chestnut blight was discovered in New York on American chestnut,
Castanea dentata (Marsh.) Borkh., and interest was stimulated for introducing
Chinese chestnuts and other Castanea species that might be blight resistant. In
1912, W. Van Fleet of the U.S. Bureau of Plant Industry established a 900-tree
test orchard of Asiatic chestnuts at Glendale, Maryland. Most of this earlier
chestnut research and exploration was oriented toward finding a winter-hardy,
timber-type tree with characteristics of the American chestnut and then hybrid
izing the introduced Castanea species with the American for superior blight re
sistance (Jaynes, 1972; McKay and Berry, 1960). The use of Chinese chestnut as
a food crop was an outgrowth of these projects, and seed was distributed to
landowners for establishment in regions formerly occupied by our native Amer
ican chestnut. In 1927, R. D. Beattie searched the Orient for outstanding Chinese
chestnut (Beattie, 1931). The first cultivar selections of Chinese chestnut for food
were made in 1930 (Reed, 1946). These early selections were chosen entirely from
desirable nuts sent by cooperators who had received trees from the USDA; bear
ing habits and other characteristics of the original parent trees were unknown.
' Received for publication 14 June 1982; accepted 20 August 1982.
2 Research Entomologist, USDA, Southeastern Fruit and Tree Nut Research Laboratory, P.O. Box
87, Byron, GA 31008.
' Horticulturist, Connecticut Agricultural Experiment Station, P.O. Box 1106, New Haven, CT
06504.
* Physiologist, Department of Horticulture, University of Georgia, Athens, GA 30602.
Economic Botany, 37(2), 1983, pp. 187-200
© 1983, by the New York Botanical Garden, Bronx, NY 10458
188 ECONOMIC BOTANY (VOL. 37
Small plantings have been established throughout the eastern United States since
the 1930s; however, present commercial acreage is less than 162 ha (Chase, 1976).
O T H E R S P E C I E S O F C H E S T N U T F O R
ORCHARD PRODUCTION
The Japanese chestnut, C. crenata Sieb. & Zucc., is an important orchard tree
in Japan, and, like the Chinese chestnut, is resistant to the chestnut blight fungus.
It has been widely tested since the early introductions of Luther Burbank and
others in the late 1800s, but is less commonly grown than the Chinese chestnut
because the nuts are not as sweet, the pellicle is often folded into the kernel and
difficult to peel, and the trees are generally less well adapted and shorter lived
(Jaynes, 1979).
The European chestnut, C. sativa Mill., is susceptible to the chestnut blight
fungus, but planted trees survive outside the natural range of the American chest
nut in the Midwest and western United States where they usually escape infec
tion. However, such trees are at risk to introduction of the chestnut blight fungus.
There are about 20 ha of producing orchards of European chestnut in central
California just east of San Francisco. The original trees were introduced over 100
yr ago by the settlers of Italian descent. The market for the nuts has been excellent
in recent years with retail prices as high as $6.60 per kg ($3.00/lb) in shell for
jumbo nuts (as few as 12 nuts per lb). Average yields are 2,220 kg/ha (2,000 lb/
acre); however, seedling trees are being top-worked and new orchards planted to
selected, high-yielding cultivars with large nuts. Yields of 3,360-4,480 kg/ha (3,000-
4,000 lb/acre) are anticipated from orchards of grafted trees (Jaynes, unpub
lished).
C U L T I V A R S A N D G E R M P L A S M
N um e r ou s s el e c ti on s o f C h in e se c h e st n ut h a v e b ee n n am e d b ut f e w h av e r e
ceived wide publicity and even fewer have been widely propagated. Best known
selections include 'Eaton,' a likely Chinese hybrid from Connecticut, and the
USDA releases 'Crane,' 'Nanking,' and 'Orrin' (Jaynes, 1979, 1980b). Replicated
cultivar trials should be established in different geographic locations to evaluate
objectively these and other selections.
Major efforts are underway to preserve germplasm of many commercially im
portant fruit and nuts. A repository for chestnut, along with walnut and hickory,
will be established at Carbondale, Illinois, if adequate funds are appropriated
(Anonymous, 1981). In the meantime, no one has responsibility for maintaining
species and cultivars of chestnut (Jaynes, 1974). Much of the USDA material was
lost when their funding of chestnut research ceased in the 1960s, and materials
at other research centers are at risk of being lost.
ORCHARD ESTABLISHMENT
Chinese chestnut is suited to nut production in a wide range of climatic and
soil conditions. It is as cold hardy as the peach, and can withstand -29°C when
fully dormant (Clapper and Gravatt, 1946; Crane, 1960; Jones et al., 1980). Chinese
chestnut trees grow well on many different types of soils if they are well drained.
However, as much attention should be given to selecting a site for Chinese chest-
1983] P A Y N E E T A L . : C H I N E S E C H E S T N U T 189
nut trees as to the soil in which they are planted (McKay and Crane, 1953). Since
Chinese chestnut trees start growth activity in early spring following warm win
ters and are subject to cold injury, they should not be planted in frost pockets
(Crane, 1960).
Most growers plant seedlings because they cost less than grafted trees. Several
growers who have planted orchards of improved cultivars state that grafted trees
are superior to seedlings in nut production (Weaver, 1960; Wilson, 1967). Seedling
trees are highly variable with respect to tree and nut characteristics and some
trees are unproductive. Nuts produced by different seedling trees vary greatly in
size, color, shape, amount of shell pubescence, and time and uniformity of ma
turity or harvest. So far as is known, all cultivars of chestnuts are self-sterile
(Jaynes, 1972, 1975), thus 2 or more cultivars or seedlings must be planted to
gether to ensure cross-pollination. Chestnut appears to be predominantly wind-
pollinated, although many species of insects visit the flowers and may effect cross-
pollination (Clapper, 1954; Jaynes, 1975).
To establish an orchard of uniform trees requires careful attention to vegetation
control. Newly transplanted or young Chinese chestnut trees cannot successfully
compete with briars and brambles of various kinds or with sassafras, sweet gum
sprouts or seedlings, trumpet vines, other weeds or grass. The trees must be
cultivated, at least while they are young, or a combination of mowing and her
bicides can be used to control weeds and grass.
Chestnuts can be productive. Records from one Georgia grower with 8 ha of
seedling Chinese chestnuts on a 7.6 x 7.6-m planting show that yields of 3,000
kg/ha (2,700 lb/acre) can be expected (Fig. 1). Yields of 4,400 kg/ha (2 tons/acre)
have been achieved from an experimental planting of 70 seedling trees per hectare
(10 yr old) at Byron, Georgia. With retail prices of in-shell nuts at about $4.40
per kg ($2.00/lb) the potential for high gross income per hectare is evident.
INSECT PESTS
Weevils are a major threat to production because they attack the developing
nuts. Weevil-damaged nuts are likely to harbor a wide variety of mycoflora and
are more likely to spoil than undamaged nuts (Wells and Payne, 1975). Unless
controlled they can render the crop unfit for use. Two chestnut weevils, the large
chestnut weevil, Curculio caryatrypes (Boheman), and the small chestnut weevil,
curculio sayi (Gyllenhal), are uniformly distributed in the eastern United States
wherever chestnuts are grown (Gibson, 1969). A nut curculio, Conotrachelus
carinifer Casey, is rather widespread in the southeastern United States on some
oak species, but only recently has been of concern to chestnut growers in Georgia
(Payne et al., 1972a). Several methods have been proposed for control including
use of poultry (Reed, 1946), hand collection, hot water, and burning (Anonymous,
1958; Beattie, 1931; Payne, 1982; Payne and Wells, 1978); however, insecticides
are the primary method of control. Since the weevils (depending upon species)
spend 1, 2, sometimes 3 yr in the soil in the larval, pupal, and adult stages, the
soil can be treated with insecticides before the adults emerge (Payne et al., 1972b,
1975b). Adult weevils emerge from the soil during April-August but do not ovi
posit in chestnuts until August and September. Thus, treatment with foliar pes
ticides can be effective if applied before the adults oviposit in the developing nuts
(Payne et al., 1975b).
YEAR
1955 1959 1963 1967 1971 1975 1979
YEAR
Fig. 1-2. Fig. 1. Yield data from an 8-ha seedling Chinese chestnut orchard, 1965-1978, Cordele,
GA. Trees were 15 yr old in 1965. Fig. 2. Yearly U.S. imports of chestnuts, primarily Caslanea
sativa, from 1955-1981.
1983] P A Y N E E T A L . : C H I N E S E C H E S T N U T 191
An Oriental chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu, a recently
discovered pest in the southeastern United States, threatens the chestnut industry
in this country (Payne et al., 1975a, 1976). This cynipid wasp attacks the vege
tative buds and disrupts the shoot growth through formation of galls. Growers
with a few chestnut trees may reduce infestation by gathering and destroying the
infested shoots (Payne and Johnson, 1979); however, commercial growers can
not resort to this strategy because of cost. There are presently no chemical or
biological control programs for chestnut gall wasp and growers with this pest can
expect yield reductions of 50-75% (Payne, unpublished).
DISEASES (PRE- AND POSTHARVEST)
Chestnuts are a perishable commodity easily spoiled by fungi and insects. Ma
ture nuts typically are allowed to drop from trees and may lie on the orchard
floor for several days or weeks before gathering. Decay may begin while the nuts
are on the tree (Fowler and Berry, 1958; Gravatt and Fowler, 1940) or while they
are on the ground (Gossard and Kushman, 1954). Undamaged nuts contain at
dehiscence an array of weakly parasitic organisms that may cause serious nut
deterioration under unfavorable storage conditions (McCarter et al., 1980). Com
mercially, chestnuts may be held in refrigerated storage for several months before
marketing. However, losses due to fungi frequently occur, particularly at the
consumer level (Woodroof, 1963). In experimental storage studies (Hammar, 1949)
spoilage ranged from 5-10% after 1 mo to 15-60% after 7 mo at 2°C. Wright (1960)
reported that 62% of the kernels examined shortly after harvest contained visible
fungal infections. The most common fungi isolated from decayed tissues were
Phoma castaneae Pk. and Pestalotia spp. Of minor importance were species of
Phomopsis, Penicillium, Alternaria, Fusarium, Rhizopus, and others. Research
ers in Italy and France have found that the most common genera of decay fungi
isolated from European chestnut kernels in storage were Penicillium, Fusarium,
Phoma, Aspergillus (A. niger van Tieghem), and Rhizopus (Bidan et al., 1958;
Lanza, 1950; Riccardo, 1963).
Moldy nuts or nuts from which weevils have emerged are generally culled
during packing operations by flotation in water (Wilson, 1967). Because nuts
containing weevils cannot be separated by flotation, the weevils emerge while the
chestnuts are in storage or transit, and the damaged nuts then enter the market
channels. Although such nuts generally are discarded by the consumer, some
might be incorporated into processed chestnut products or food combinations.
The potential for consumption of spoiled chestnuts is increased by the absence
of visible mold on many kernels with incipient fungal infections. Penicillium spp.
were the fungi most frequently (40.7%) isolated from weevil-damaged chestnuts
(Wells and Payne, 1975). Next, in order of frequency of occurrence, were Rhi
zopus, Alternaria, and Aspergillus, each comprising about 17% of the total my-
coflora isolated. A high percentage of Penicillium and Aspergillus isolates from
weevil-damaged Chinese chestnuts were capable of producing mycotoxins (Wells
and Payne, 1975; Wells et al., 1975). No mycotoxins have been found on market
chestnuts, but the potential exists for toxin production should fungal development
occu r on k er nel tissu es .
The chestnut blight fungus, Endothia parasitica (Murr.) Anderson, that was
responsible for destroying the American chestnut, normally is not a serious path-
192 FXONOMIC BOTANY (VOL. 37
Fig. 3. Crown of Chinese chestnut with burs, photographed in mid-August. Fort Valley, GA.
ogen on Chinese chestnut (Graves, 1950). However, cankers induced by this
organism on Chinese chestnut are not uncommon (Headland et a!., 1976), and
seedlings vary in their resistance. Healthy trees generally resist the blight better
than trees under stress. Trees stressed by early frosts, severe winds, and cold
winters are more likely to develop disfiguring cankers that girdle and kill weak
stems and branches (Berry, 1951: Jones et al., 1980).
The European chestnut is highly susceptible to chestnut blight, but remission
of the disease in Italy has occurred naturally in recent years (Anagnostakis, 1982;
Elliston, 1981). This natural or biological control is associated with diseased strains
of the chestnut blight fungus that contain virus-like particles. These strains, des
ignated hypovirulent, have been detected on American chestnut trees in the United
States in recent years (Jaynes and Elliston, 1982). Current research efforts are
directed at using these hypovirulent strains to develop practical control measures.
They could prove to be valuable to orchardists growing blight susceptible trees,
such as C. saliva, infected with virulent strains of the chestnut blight.
The systemic fungicide methyl-2-benzimidazole-carbamate (MBC) has shown
promise in controlling infections of the chestnut blight fungus on American chest
nuts (Jaynes and VanAlfen, 1977). However, there are problems in its practical
application: annual injections may be necessary, foliage injury often results, and
the pathogen may develop resistance as a result of continued use of the material.
FRUIT MATURATION AND BUR DEHISCENCE
Chinese chestnut fruit is a large brown nut approximately 2.5 cm in diameter
and marked at the base with a light brown oval scar. Typically, 3 nuts are con
tained within a prickly 4-quadrant involucre or bur (Fig. 3-5). Cross-pollination
is essential for fertilization, and if insufficient, fewer than 3 nuts may develop.
Fertilization is not required for involucre development and unpollinated trees
often appear to have a normal crop set when in fact no filled nuts are present.
1 9 8 3 ) P A Y N E E T A L . : C H I N E S E C H E S T N U T 1 9 3
Fig. 4. Branch of Chinese chestnut with burs photographed in mid-August, Fort Valley, GA.
Dehiscence of the bur is preceded by an endogenous increase in production of
the plant hormone ethylene and in respiration of the involucre (Kays and Payne,
1982). Premature dehiscence can be accomplished with exogenous application of
growth regulators that release ethylene (e.g., 2-chloroethylphosphonic acid). Eth
ylene produced by the bur appears to function as a natural regulatory system
which triggers and/or facilitates opening of the bur. Burs containing rudimentary,
194 ECONOMIC BOTANY [VOL. 37
A
y-f
Fig. 5. Characteristic shoot, leaves, fruit, and nuts of Chinese chestnut {Castanea moUissima
Blume) (Jaynes 101, NHES).
undeveloped fruits resulting from pollination failure, go through the same dehis
cence process. As the bur begins to open, the seed coat of the nut begins to
change from a cream color to a light brown and finally dark brown. The brown
coloration starts at the tip of the nuts and progresses toward the base.
Nuts which are harvested prematurely through the use of mechanized har
vesting and bur removal, before normal color development, do not store well
(McCarter et al., 1980). However, prematurely harvested nuts may store satis
factorily if first allowed to mature within the harvested bur (Jaynes, 1969).
HARVESTING AND STORAGE
Chestnuts should be harvested daily when they begin to ripen and drop to the
ground (Reed, 1946). Traditionally, chestnuts have been hand gathered from the
ground after they have fallen naturally. This task is time consuming and the supply
of labor for such work is decreasing yearly. At the time of initial nut drop, most
Chinese chestnut seeds do not have the uniform maturity necessary for once
over mechanical harvesting. However, Peterson and Monroe (1977) showed that
when 4-9% of the nuts have dropped naturally a shake-catch harvesting system
can effectively remove and handle nuts in burs. Peterson and Monroe also de
veloped a mechanical means of removing burs.
1983] P A Y N E E T A L . : C H I N E S E C H E S T N U T 195
Ta b le 1 . C o m po si ti o n o f c h es tn ut k e r n el s ( f r es h w e i g h t b a s i s ) .
Species
C. mollissi-
Constituents C. dentata' C. sativa' C. so/ivflC?)'' C. spp. unk'^ C. spp. unk'' C. dentata' "Ealon"'"''
Water 33.4 52.2 53.2 43.4 53.2 47.0 57.6 54.6
Protein 10.2 3.1 5.3 6.4 2.8 9.1 4.4 4.3
Fat 10.2 1.6 2.0 6.0 1.5 8.4 0.9 1.6
Carbohydrate 42.3 40.6 36.7 41.2 40.4 32.4 34.6 37.3
Fiber 1.9 1.4 1.4 1.5 1.1 1.8 1.4 1.0
Ash 1.9 1.1 0.8 1.4 1.0 1.1 1.1 1.1
" Robb as cited by Winto n and Wi nton, 1 932.
'• Colby ibid.
" Jaffa. 1908.
" Woot-Tsuen e t a l.. 19 52.
' Analyses. 1982. Analytical Chemistry Dept.. CT. Agric. Exp. Station, New Haven.
' "Eaton " is a C . m ollissima hyb rid.
Chestnuts are starchy and very different from nuts that contain large amounts
of oil. Chestnuts are high in carbohydrates (32-42%, fresh weight basis) and
relatively low in protein (3-10%) and fat (1-10%). The relative amounts reported
vary greatly, especially for protein and fat (Table 1). Castaneci dentata appears
to have more fat and protein than either C. scitiva or C. mollissima. The apparent
genetic variability for these nutrients could make it feasible to select or even
breed cultivars for high or low fat and protein content. Firm conclusions require
more analyses to provide information on variability of nutrient content within a
cultivar and within and among species.
Fresh nuts, unless properly handled, dry out rather quickly and become hard;
a condition in which they cannot be roasted or boiled satisfactorily without re
generation by soaking. Within a week, especially in the South, the nuts on the
ground or those in opened burs on the trees become dry or they can mold and
spoil. Under proper conditions chestnuts can be stored from the time of harvest
to late April with little spoilage. They can be stored for 4-6 mo at 0°C (Lutz,
1967), and up to 12 mo if the moisture content of the chestnuts is maintained near
40%. This can be achieved by keeping the relative humidity in the storage facility
at 65-70% (Woodroof, 1963). Only chestnuts free of mold or decay should be
stored. An effective postharvest treatment such as a 45-min hot water dip (52®C)
for the control of in-shell insect and fungal contaminations (Wells and Payne,
1980), combined with optimal storage conditions, should preserve the fresh mar
ket quality of chestnuts during prolonged storage.
Jaynes (1969) demonstrated that nuts stored for up to V/2 yr would germinate.
However, the hypocotyl of nuts stored for 5 or more mo often emerges 2-8 cm
and then rests until placed in warm-moist conditions. Such germinated nuts would
be undesirable for marketing. It is essential to prevent the formation of conden
sation on stored nuts to prevent decay. Varieties vary in their keeping ability
(Crane and McKay, 1946), and storage quality of a single genotype may also vary
from year to year. The problem of chestnut storage will be improved by intro
ducing cultivars selected for nuts that store well.
Complete and rapid germination of nuts generally required a pretreatment of
moist-cold storage (0-4°C) of 3-4 mo. Germination is usually complete after 4 wk
at 21-24°C. Occasionally, fresh chestnuts, whether sown in soil for germination
196 ECONOMIC BOTANY [VOL. 37
Qc
LU 30
O
^ 2 0
-10 -9 -7 -6 -5 2
T R E AT M E NT T E MP ER ATU R E 2 4 h rs ( C)
Fig. 6. Germination of chestnut seeds after exposure to sub-freezing temperatures for 24 h.
or held for consumption, are subjected to irreversible cold damage. Imported
nuts are known to have been damaged when subjected to low temperatures on
dockside after unloading. The critical temperature for Chinese and American
chestnuts appears to be approximately -6 to -9°C (16-2rF) (Fig. 6) (Jaynes, un
published). The species, moisture content, and time in storage likely has a mod
ifying effect on the critical temperature.
V E G E T A T I V E P R O P A G A T I O N
Modem, successful fruit and nut orchards are founded on selected cultivars
and this likely will prove true with chestnuts. Chestnut cuttings can be rooted
(Shreve, 1972), but the techniques described are not yet feasible for large scale
production. Commercially acceptable aseptic tissue culture methods have not
been developed (Vieitez and Vieitez, 1980). Stooling, a layerage technique, has
been practiced in Europe, but it is more labor intensive than grafting which has
been successful in this country. Numerous grafting techniques have been de
scribed, including nut grafting and chip budding hypocotyls of germinating seed
(Jaynes, 1979, 1980a). One of the oldest and most successful grafting techniques
is to whip-graft 1- and 2-yr-old seedlings. Larger trees are topworked by bark
grafting. Incompatibility is occasionally encountered with Chinese chestnut grafts,
hence the recommendation to propagate a cultivar on seedlings from open-pol
linated nuts of the same cultivar (Jaynes, 1979). Grafting, and especially top-
working, has proven most successful in the milder climates (Georgia and Cali
fornia versus New England) and where the chestnut blight is rare or absent.
1983] PA Y NE E T A L. : C HI NE SE C HE ST N UT 197
H O M E A N D W I L D L I F E P L A N T I N G S
The largest use of Chinese chestnut seedlings is for home and wildlife plantings.
In addition to man, many kinds of wildlife including deer, raccoons, squirrels,
turkeys, and grouse feed on Chinese chestnut. When the American chestnut was
a major component of the Eastern forest, chestnuts were a staple in the fall diet
of many of these mammals and birds, and even farm animals. Unlike most other
introduced nut trees and native mast trees, such as oak, chestnut generally pro
duces a crop every year, even when given little cultural care. Accurate figures
on numbers of trees planted are not available. At least 180,000 seedlings were
distributed by state-owned nurseries in 1977, a 100% increase over 1966 (Chris-
tisen, 1979). Private nurseries probably sell many more chestnut trees than the
state nurseries. Availability of vegetatively propagated cultivars selected for home
or wildlife plantings would likely stimulate demand for chestnut trees by land
owners.
OUTLOOK
There are several problems in the United States that have limited the com
mercial production of Chinese chestnut (Chase, 1956; Hardy, 1949; MacDaniels,
1954; McKay and Crane, 1953; Payne, 1979; Wilson, 1967). These include insects,
diseases, a lack of concentration of plantings of standard cultivars, and no or
ganization for handling and vigorously advertising the nut. Shipments to the mar
kets have been sporadic with no effort to maintain a steady supply or meet the
demand of any one market; hence the prices have fluctuated widely and have
been generally uncertain. Attractive prices obviously cannot be expected from
any product that has no U.S. standard grades and is generally unknown to the
public. While there is a limited but loyal public buying Chinese chestnuts, there
are those who have tried the nuts for the first time and found them hard, chalky,
moldy, wormy, or mealy, probably because of inadequate insect control, han
dling, and storage. This has discouraged further purchases. This situation could
be overcome by growing selected cultivars, proper advertising, and further de
velopment of the mechanized harvesting and postharvest treatments that cur
rently exist for pecans and walnuts. In spite of all these problems, there is still a
strong demand for chestnuts and chestnut products, because we import over 4.5
mill kg of European chestnuts per year (Fig. 2). Our climate and soils are satis
factory for growing chestnuts, but the combined problems of diseases, insects,
harvesting, and marketing make chestnut culture a risky commercial venture at
t h is t im e .
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... In a few years after its arrival in Italy, D. kuriphilus became a key chestnut pest in many Mediterranean mountain areas. Heavy attacks reduced the fruit yield to less than a half (Payne et al., 1983), together with tree vigour and wood production (Kato and Hijii, 1997). Everywhere, it rapidly recruited many native parasitoid species, from those attacking native gall wasps of oak and forest trees Guerrieri et al., 2010;Panzavolta et al., 2013;Quacchia et al., 2013;Ferracini et al., 2018). ...
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Dryocosmus kuriphilus Yasumatsu (Hymenoptera Cynipidae) was first recorded in Sardinia (Italy) in 2007. Two years later, a biological control program started with the introduction of its non-native parasitoid, Torymus sinensis Kamijo (Hymenoptera Torymidae). Over a nine-year period (2009-2017), data on the relative abundance of D. kuriphilus, its native parasitoids and T. sinensis were collected. Native parasitoids reacted quickly to the large availability of hosts. However, a dramatic change in the abundance of each native species was recorded from year to year. In the first few years, the native parasitoid community and pest abundance did not fluctuate much. The turning point was 2014, when, at the same time, the native parasitoid populations increased and the T. sinensis populations also began to increase. In the following year, both the D. kuriphilus and native parasitoid populations decreased considerably, whereas the T. sinensis populations reached over 50% parasitism. The univoltine D. kuriphilus acted as an asynchronous resource for native bivoltine parasitoids. An asynchronous host-parasitoid interaction produces wide fluctuations in their populations. In this case, D. kuriphilus strongly altered the local community, which was subjected to a chaotic change in composition and species abundance. When T. sinensis became established, it monopolized the pest, making this resource unavailable to native parasitoids that returned to attack almost exclusively the native oak cynipids. In fact, the successful control of D. kuriphilus by the introduction of T. sinensis rebalanced the situation that had been altered by the arrival of the invasive pest.
... Dryocosmus kuriphilus (Hymenoptera: Cynipidae), also known as the Asian Chestnut Gall Wasp (ACGW), is a small gall-inducing wasp that is specialized on attacking chestnut trees (Castanea spp., Fig 1). It is considered as the most important pest on chestnut trees in the world (Brussino et al 2002, Moriya et al 1990 as it can decrease the chestnut yields by 60 to 80 % (EFSA, 2010, Payne et al 1983. ...
Thesis
Biological control (or biocontrol) is the use of living organisms to suppress the population density or impact of a specific pest organism, making it less abundant or less damaging than it would otherwise be. The biological control agent may directly or indirectly interact with more than just the target pest and vice versa. Therefore, monitoring its populations, in conjunction toother ecological factors, may allow to confirm or discard ecology theories or unveil brand new interactions with both abiotic and biotic facets of the recipient ecosystem. Moreover, the methodological aspects of the post release monitoring phase and those of ecological experimentations sometimes do share similarities. In this work I explore how both disciplines are reconciled and how the resulting data from biocontrol could be optimized for its use in ecology.I use data from biological control programs to address questions related to invasion dynamics, community ecology and landscape ecology.In chapter 1, I detail the case studies: (i) the introduction of the parasitoid Torymus sinensis (Hymenoptera: Torymidae) against the Asian chestnut gall wasp Dryocosmus kuriphilus (Hymenoptera: Cynipidae) ; (ii) the introduction of the ectoparasitoid Mastrus ridens (Hymenoptera: Ichneumonidae) against the codling moth Cydia pomonella (Lepidoptera: Tortricidae) ; (iii) a nation-wide survey of Trichogramma species in France in order to characterize the ecological ranges of each species; (iv) the description of egg parasitoid species associated with Iphiclides podalirius (Lepidoptera: Papilionidae) at a fine temporal scale.Chapter 2 is focused on understanding the dispersal of T. sinensis at the scale of several chestnut producing areas. In this chapter, I use monitoring data from release sites to fit a growth model for populations of T. sinensis in order to infer the time since colonization in naturally colonized sites. In chapter 3 I investigate the impacts of the successful control of D. kuriphilus by T.sinensis on the structure of native parasitoid community that recently became associated with the pest. Chapter 4 is focused on cases where scientific valorization ranges from a complete failure (primo-introduction of M. ridens), the diffusion of naturalist knowledge (survey of I. podalirius and related oophagous parasitoids) and/or the identification of some patterns using specific statistics (national survey of Trichogramma species).Finally, by compiling knowledge from the extensive literature on biological control and field experience I then discuss on the potentials and limits of biological control programs for experimental ecology. I conclude that although biological control gives an ecological context to experimentation by allowing to manipulate a wide variety of factors, the context and the organisms at play may not be compatible with any ecological issue. For example, the obvious parallel between classical biological control and invasion biology makes the former extremely useful to study ecological processes that drive the success of invasions. This in turn could yield knowledge that may have implication in other disciplines such as the preservation of endangered species. However, factors like the low detectability of a biological control agent at low densities (coupled with varying sensibility of monitoring methods) may render the study of early stages dynamics and interactions too much of a daunting endeavor.
... (EPPO, 2005;Radócz et al., 2016). On the other hand, the chestnut gall wasp, as a harmful pest, causes great damage to chestnuts worldwide (Payne et al., 1983;Moriya et al., 1989;Murakami et al., 1995;Brussino et al., 2002;Vollmeier et al., 2018). Thus, it was declared as a quarantine pest in 2003 by the European and Mediterranean Plant Protection Organization. ...
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The chestnut gall wasp (Dryocosmus kuriphilus Yasumatsu, 1951) is currently the most dangerous pest for the Anatolian chestnut (Castanea sativa Mill.). C. sativa is one of the most important wood species due to its economic role for the country’s economy. The chestnut gall wasp causes economic damage owing to crop loss in chestnut production, and severe invasions may cause in the death of chestnut trees. In this study, we reported the infestation of the D. kuriphilus from a new distribution area (the Eastern Black Sea Region of Turkey). Distribution of the introduced species has just been detected in a very narrow vicinity of a single valley and the presence of the species is thought to be very new. Moreover, the reason of the infestation is thought to be the plantation of chestnut seedlings which had been imported from abroad. We discussed the possible effects of the pests on chestnut trees and if precautions are not taken against to this species it was predicted that the pest would spread across the entire Black Sea region and Caucasia within 10-15 years. Data on the biology, host plant and the distribution of the chestnut gall wasp in Turkey, are also reported.
... Dini et al. (2012) detected the accumulation of ROS at the site attacked by the gall wasp Dryocosmus kuriphilus. Payne et al. (1983) observed that early necrosis of the tissues adjacent to the larval chamber led to the death of D. kuriphilus. The PRO may have the ability to scavenge reactive oxygen species (Verbruggen & Hermans, 2008). ...
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... Some of the most injurious pests are listed in Table 5.3. On a global scale, the chestnut gall wasp, Dryocosmus kuriphilus is surely the one insect that causes the most damage to chestnut production; when introduced from China to Japan in the 1940s, it caused drastic reductions in the harvest of C. crenata (Saito 2009), and soon after its discovery in the state of Georgia, USA, commercial production based on C. mollissima was almost completely wiped out (Payne et al. 1983). Its accidental introduction to Italy was quickly followed by a similar, catastrophic drop in yield -some areas in Cuneo Province lost the entire crop within a few years of infestation (Brussino et al. 2002;Sartor et al. 2015). ...
Chapter
The chestnuts and chinquapins are a group of about seven species of trees and shrubs in the genus Castanea. They are of considerable importance ecologically in all the areas of their natural occurrence, and the chestnuts especially are of great economic value for their lumber and for their nut crop wherever they are cultivated. Two catastrophic diseases, chestnut blight caused by the ascomycete fungus Cryphonectria parasitica (Murr.) Barr and Phytophthora root rot (ink disease) caused primarily by the soil-borne oomycetes Phytophthora cinnamomi Rands and P. cambivora (Petri) Buisman, have severely impacted chestnut in Europe and North America. Therefore, much of the breeding work continues to focus on breeding for resistance to these two diseases. The most serious insect pest of Castanea is the Asian chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu. Variation in host tolerance to D. kuriphilus has led to development of new gall-resistant chestnut cultivars. Interspecific hybridization offers great opportunity to combine the most favorable traits found in the ample genetic diversity of the genus through introgression into locally-adapted populations. Chestnut breeders in eastern Asia have made great strides towards improvement of chestnut fruit quality and crop yields, and researchers in all chestnut growing regions have made gains in disease resistance by using molecular markers and other genomic tools to assist selection. Biotechnologies that include transmissible hypovirulence as a biocontrol for chestnut blight, tissue culture and other micropropagation techniques, and genetic engineering and transformation technologies are complementary to classical plant breeding programs.
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Chinese chestnut is an important nut tree around the world. Although the types of Chinese chestnut resources are abundant, resource utilization and protection of chestnut accessions are still very limited. Here, we fingerprinted and determined the genetic relationships and core collections of Chinese chestnuts using 18 fluorescently labeled SSR markers generated from 146 chestnut accessions. Our analyses showed that these markers from the tested accessions are highly polymorphic, with an average allele number (Na) and polymorphic information content (PIC) of 8.100 and 0.622 per locus, respectively. Using these strongly distinguishing markers, we successfully constructed unique fingerprints for 146 chestnut accessions and selected seven of the SSR markers as core markers to rapidly distinguish different accessions. Our exploration of the genetic relationships among the five cultivar groups indicated that Chinese chestnut accessions are divided into three regional type groups: group I (North China (NC) and Northwest China (NWC) cultivar groups), group II (middle and lower reaches of the Yangtze River (MLY) cultivar group) and group III (Southeast China (SEC) and Southwest China (SWC) cultivar groups). Finally, we selected 45 core collection members which represent the most genetic diversity of Chinese chestnut accessions. This study provides valuable information for identifying chestnut accessions and understanding the phylogenetic relationships among cultivar groups, which can serve as the basis for efficient breeding in the future.
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Ülkemizde ilk kez 2014 yılında Yalova’da tespit edilen Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) geçen süre zarfında kestane alanlarında yayılmaya devam etmiştir. Kestanenin en önemli zararlısı konumuna gelen Gal arısı ile mücadele çalışmaları devam etmekle birlikte zamanla diğer illerimizden de zararlının görüldüğüne dair tespitler bulunmaktadır. En son olarak ise Zonguldak ve Bartın illerinde yapılan arazi surveylerinde zararlının galleri tespit edilmiştir. Bu illerimizde şu an için sınırlı yayılışı bilinen zararlı ile bir an önce mücadele çalışmalarına başlanmalıdır .
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Yield and quality of chestnut (Castanea mollissima) are affected by nitrogen availability; however, there are few reports on foliar and root absorption of different chemical forms of N in chestnut. To analyze the absorption characteristics of exogenous nitrogen fertilizer labeled by 15N in chestnut, nitrate and ammonium nitrogen uptake and allocation were determined in one-year-old seedlings that received soil- and foliar 15NH4NO3 and NH415NO3. We found that 29% of the nitrate and 25% of the ammonium absorbed by the leaves were translocated to the roots, while 62.01% of the nitrate and 63.27% of the ammonium absorbed by the roots were translocated to the shoots. The seedlings absorbed more nitrate nitrogen than ammonium nitrogen and their foliar N uptake was faster than their root uptake. Most of the N absorbed by the seedlings was fixed in the shoots in both foliar and soil uptake. The proportion of N fixed was greater in seedlings subjected to foliar fertilization than in those treated with soil fertilizer. Foliar fertilizer application can meet the N nutritional needs of fast-growing shoots more effectively than soil fertilizer application. However, soil fertilization was a better long-term N source than foliar fertilization. Thus, ensuring an adequate supply of nitrate N fertilizer in the soil accompanied by a commensurate increase in foliar fertilizer application can effectively meet the nutrient requirements associated with the rapid growth of chestnut seedling shoots.