Walnut

Advances in
Production Technology of Walnut
1

Outline
• Introduction & Importance.
• Origin, distribution & systematics.
• Botanical description.
• Ecological requirements.
• Commercial varieties.
• Propagation.
• Planting & layout.
• Tree architecture & pruning.
• Flowering physiology.
• Orchard cultural practices.
• Harvesting & handling of fruit
• Walnut plant protection.
• Future thrusts.
• References.
2

Catkin – Spike that
bears the staminate
flowers and pollen
producing anthers.
4

Introduction
• Walnut is an important nut fruit grown in temperate climate.
• The fruit became known as the Persian walnut possibly because of its extensive use by
Persia (now Iran) for bartering with neighboring countries.
• After its introduction to Greece, trees were taken to Rome where they became known as
Jovis Glans – which translates to Jupiter’s Acorn. This description comes from the
classical Golden age when it was said that while ordinary men lived on Acorns (The acorn,
or oaknut, is the nut of the oaks and their close relatives). Jupiter and his fellow gods
feasted on walnuts. This has since become the Latin name Juglans regia, meaning the
royal nut.
• The term “English” commonly applied to the Persian nut is actually a misnomer; English
people never develop a walnut industry in Great Britain. But this misconception
developed from the use of English trading ships to transport this nut of commerce
around the world.
5

• In fact, word “walnut” originates from ‘wahlnut’, an old English word for
“Welsh-nut”. Welsh was a term used to indicate a person not of Saxon origin.
Hence, the English also considered the nut a foreign nut.
• It is known by different names throughout the world (as akhrot in Hindi, doon
in Kashmiri and Gardgani in Unani).
6
• The Greeks called walnuts Karyon, meaning “Head”,
because the shell resembles a human skull and the
walnut kernel itself looks like a brain.
• Cultivation of walnut started from 1500’s in Europe and
they are now grown worldwide with California being
the largest producer.
Conti…

Botanical name Juglans regia L.
Family Juglandaceae
Center of origin South East Europe (Iraq)
Chromosome number X = 16, 2N = 32
Sex form Monoecious
Inflorescence Catkins
Type of Dichogamy Protoandry and Protogyny
Mode of pollination Cross pollination
Mechanism of pollination Anemophyllous (wind pollinated)
Growth curve Double sigmoid
Type of fruit Nut
Edible portion Lobed cotyledon
Nature of fruit Non-climacteric
King of nuts, Ashrot, English or Persian walnut, Carpathian
7

Composition and uses
• Very rich source of proteins, fats and minerals and is
concentrated source of energy.
• It contains good amount of Vitamin B₆ among all the
other nuts.
• Both immature fruits and green hulls of walnut are
very rich sources of ascorbic acid containing about 2-
2.5% and 0.4-0.8% on fresh basis respectively.
• Walnuts contain important phytochemicals as well as
high amounts of polyunsaturated fats which do offer
potential benefits for both brain health and brain
function.
• It has Omega-3 which plays a part by helping to
reduce oxidative stress in the brain.
Nutritional value per serving of 100 g *
Energy 2,738 kJ
Carbohydrates 13.71
Dietary fiber 6.7
Fat 65.21
Saturated fats 6.13
Monosaturated fats 8.93
Polysaturated fats 47.17
Protein 15.23
Iron 22%
Magnesium 45%
Phosphorus 49%
Calcium 10%
Vitamin K 3%
Vitamin A 20 IU
* Source : Ozkhan et al. 2005
8

Walnut: a potential multipurpose nut crop for
reclaiming deteriorated lands and environment *
• Because of urban development and changing land-usage, most lands have been
deteriorated by human. In addition, natural disasters have exacerbated this problem.
• Vahdati et al. (2018) reported that walnut trees with their strong root system have a
key role in maintaining lands against destructive factors such as erosion and human
activity.
• Furthermore, walnut is a multi-purpose nut crop tree that can be used for wood
production in forests and as an ornamental plant in landscape design.
• It can be cultivated in deteriorated lands not only to prevent soil erosion but also as a
productive and lucrative product. Even if walnut trees yield in deteriorated lands is just
1 t ha-¹, its revenues will be five times higher than many annual crops.
Place of research: University of Tehran, Iran
*Source: https://www.researchgate.net/publication/322637454

Importance and uses
• Almost all the parts of the plant are utilized in one or other way but the fruit and timber have been put to
maximum use.
• Walnut is one of important nut fruit of the India being exported to more than 40 countries of the world
with earnings of more than Rs. 300 crore of foreign exchange annually.
• Immature fruits of walnut can be utilized for preparing various products like pickles, chutneys, marmalades,
press juice and syrups.
• Walnut oil has pleasant aroma and is used for edible purposes, artists oil colours, varnishes and soap
making.
• It’s oil is immensely beneficial for women suffering from menstrual dysfunction.
• The tree yields valuable timber, which is most suitable for carving, making furniture and butts of guns.
• Walnut shell flour is extensively used on large scale a diluents for agricultural insecticides.
• Kernels are widely used in confectionary and bakery industries in the preparations like cake, pastries,
chocolate, candy and ice cream.
• Decoction prepared from inner may be used to heal constipation, slow digestion, as a stimulant for the liver
or even to cure skin diseases. 10

11* Source: https://www.imagenesmi.com/im%C3%A1genes/variety-of-walnut-44.html

Origin,
Distribution and
Systematics
12

Origin and distribution
• The history of walnut is lost in antiquity.
• O. Rourke (1969) records its spread from Asia Minor to other parts of the world.
• While Slate (1969) considers it older than man on the basis of fossil testimony.
• In India, it is mainly grown in Jammu & Kashmir, Himachal Pradesh, Uttrakhand and
Arunachal Pradesh. J & K largest producer contributing more than 85% of the total
production of the country.
State Districts
J & K Anantnag, Pulwana, Budgam, Baramulla, Srinagar, Doda, Poonch, Udhampur, Rajouri and Kathua.
HP Kullu, Mandi, Shimla, Kinnaur, Srimour, Chamba.
UK Nanital, Dehradun, Pauri, Tehri, Chamoali, Almora, Pithoragarh.
13

Area and production in World *
Country Area (ha) Production
(t)
Share in world
production (%)
Productivity
(t/ha)
China 4,00,000.00 16,55,508.00 48.43 4.14
Iran 64,000.00 4,85,000.00 14.19 7.58
USA 99,148.00 4,18,212.00 12.23 4.12
Turkey 93,233.00 1,83,240.00 5.36 1.97
Ukraine 13,900.00 1,12,600.00 3.29 8.10
Mexico 68,009.00 96,476.00 2.82 1.42
France 19,009.00 38,314.00 1.12 2.02
India 30,800.00 36,000.00 1.05 1.17
Romania 1,435.00 35,073.00 1.03 24.44
Chile 16,254.00 35,000.00 1.02 2.20
Afghanistan 2,317.00 13,902.00 0.41 6.00
World 9,65,552.00 34,18,502.2 - 3.54
* Source: World scenario of walnut production during 2011 (FAO, 2013) 14
Highest area
& production
Highest Productivity
Lowest area
& production
Lowest Productivity

Area and productivity in World *
15
* Source: World scenario of walnut productivity during 2011 (FAO, 2013)

16
Area and production in India *
2016-17 2017-18 2018-19 (1st advanced estimate)
Area Production Area Production Area Production
112 287 109 300 108 301
Area in '000 Ha
Production in '000 MT
* Source: Horticultural Statistics, NHB 2018-19

State-wise area & production of walnut *
17
State 2014-15 2015-16 2016-17
Area Production Area Production Area Production
Jammu &
Kashmir
86.10 213.86 69.24 206.43 69.24 206.43
Uttarakhand 19.24 22.22 17.24 19.32 17.24 19.34
Himachal
Pradesh
4.51 1.57 4.47 2.25 4.47 1.86
Arunachal
Pradesh
5.00 0.60 1.11 0.60 1.12 0.60
Total 114.85 238.25 92.06 228.60 92.08 228.23
* Source: Horticultural Statistics, NHB 2017
Area in '000 Ha
Production in '000 MT
Highest area
& production
Lowest area
& production

State wise area & production of walnut *
18
* Source: Horticultural Statistics, NHB 2017

19
States Districts 2014-15 2015-16
Area Production Area Production
Jammu & Kashmir Kupwara 8.67 20.79 8.67 35.82
Kulgam 6.12 34.45 5.77 23.09
Doda 6.42 10.59 6.48 19.78
Pulwana 4.38 7.73 4.81 16.84
Badgam 7.44 18.72 3.99 14.53
Poonch 8.07 11.51 7.01 14.48
Baramula 3.11 14.01 3.11 14.01
Kishtwar 4.59 6.49 4.64 11.84
Uttarakhand Almora 2.81 8.47 2.81 8.74
Dehradun 2.69 3.02 2.69 3.82
Pauri Garhwal 2.00 2.01 1.99 2.03
Himachal Pradesh Sirmaur 1.11 0.65 1.10 0.94
Chamba 1.28 0.52 1.26 0.60
Shimla 0.32 0.03 0.32 0.30
Arunachal Pradesh West Kameng 0.36 0.48 0.39 0.39
Tawang 0.02 0.04 0.02 0.04
District wise
area &
production
of walnut *
* Source: NHB 2017

Export Potential of walnut *
The country has exported 3595.69 MT of Walnuts to the world for the worth of Rs. 127.21
crores/ 19.72 USD Millions during the year 2017-18.
20
The major importing countries of walnut from India are UK, France, Germany, Egypt
and Netherland.
Export Destinations (2017-18)
Agri-export zones of walnut
• State: Jammu & Kashmir.
• District/Area: Baramulla, Anantnag, Pulwama, Budgam,Kupwara, Srinagar, Doda, Poonch,
Udhampur, Rajouri and Kathua.
* Source: http://agriexchange.apeda.gov.in/indexp/Product_description_32headChart.aspx?gcode=0203

Taxonomy
• Walnut belongs to family Juglandaceae.
• The genus Juglans L. (Manning), containing about 21 species of walnut all over
the world. Genus Juglans are native to China, Japan, India, Persia, Mexico,
Central America, The West Indies, The Andean region of South America from
Columbia and Venezuela to Argentina, and the United States.
• Juglans consists of four sections :-
Rhysocaryon (black walnut)
Cardiocaryon (Japanese, Manchurian & Chinese walnuts)
Trachycaryon (Butternut)
Juglans (J. regia)
21

Important species of genus Juglans
Species Scientific name
English or Persian walnut Juglans regia
Southern California black walnut Juglans californica
Northern California black walnut Juglans hindsii
West Indian walnut Juglans jamaicensis
Arizona black walnut Juglans major
Texas black walnut Juglans microcarpa
Eastern black walnut Juglans nigra
Japanese walnut or heartnut Juglans ailantifolia
Chinese walnut Juglans cathayensis
Manchurian walnut Juglans mandschurica
The Butternut Juglans cinerea
22
Conti….

• The Juglans regia is distinguished by the dehiscence of hull, which separates from the
shell at maturity (Manning, 1978). It is the most important being commercially
cultivated in many countries.
• Juglans nigra L. is the most important species of USA which is also known as Eastern
American Black Walnut grown east of the Rocky Mountains for wood. The nuts are of
high flavour but are uneconomical for commercial cultivation because of their hard-
shell and poor hulling characteristics.
• Juglans hindsii Jeps are the Northern American Black walnuts which are native to
North California of USA and today's it is extensively used as rootstock for Juglans regia
but under Indian conditions blackline disease is associated with this stionic
combination. Its nuts are slightly smaller and have smooth shells and kernels less
pronounced flavour.
24

• Juglans californica S. Wats is also known as Southern California Black Walnut
which are native to southern California have spreading type trees or bushes,
they formerly used as a rootstock for English walnut.
• Juglans rupestris Engelm is native to Arizona, New Mexico and Texas.
• Juglans major Heller is found in New Mexico, Arizona, and Colorado.
• Juglans cineria L. is known as butter nut, native to North America (Georgia to
Arkansas and New Brunswick). It is relatively a slow growing tree and bears
highly flavoured nuts which are difficult to hull. Trees are less deeply rooted than
other Juglans species.
25

Cold hardiness
• The black walnut, Juglans nigra is hardy but Persian walnut (Juglans regia) are
not usually hardy.
• In California, they may grow late in the fall and can be killed by moderate freezes
below -9 ͦC.
• Some selections from Manchuria and the Carpathian Mountains in Poland are
hardy to -40 ͦC. Most of these selections begin growth so early in the spring that
shoots are killed by spring frosts.
• The Butternut, Juglans cincera, is hardier than other nut species and can be
grown in northern United States & Canada.
26

Walnut tree
• Walnut is deciduous tree, branches with lamellate pith; trunk smooth or
with scales; furrowed bark; leaves large and aromatic, leaflets opposite.
• Walnut plant exhibit allelopathic effect and do not allow weeds or other
vegetation beneath it.
Walnut shoot cut longitudinally to show chambered pith. Scale in mm
28

Flowering habit
• Flowers are monoecious (having male
and female flowers on the same plant).
• The staminate flowers emerge laterally
on the previous season’s growth and
hang in catkins.
• The pistillate flowers appear in the
form of nutlets at the tip of current
season’s growth.
• Flowers appears before or after leaves.
29

Fruit type of walnut
Involcure
It is fusion of sepals, bracts and bracteoles.
• The outer husk or hull is composed of
involcural tissues. Involcure is fusion
of sepals, barcts and bracteoles. And,
it is not part of the ovary wall
(pericarp).
• The ovary wall (pericarp) dries at the
time of maturity & it is hard,
indehiscent layer surrounding the
seed.
• So, walnuts are referred to as true
nuts or dry drupes or drupaceous
nuts.
30
Growth direction

Edible portion of walnut
• Nuts almost round with pointed tip, are flattened at base & slightly compressed along the sides,
indented with shallow to deep irregular grooves, shell thin to thick, light to dark brown in colour.
• Kernel or seed sweet, loosely or tightly adhered to the deeply contoured inner surface. Seed 2-4 lobed,
remaining within the shell in germination.
• Endocarp encloses seed with deeply lobed cotyledons, which is covered by a thin brown seed coat.
• Edible portion is cotyledons.
Nut or
shell
Fruit
Seed
or
kernel
Walnut
Shell
31

Altitude
• It grows in temperate regions between the altitudes of 900-3500 m above sea
level. However, commercial cultivation beyond 2500 m is not recommended as it
results to erratic bearing & even total crop loss in some year when there is late
spring frost.
33
1500 m &
above
Superior quality nuts, with light colored kernel and a characteristics
thin shell.
Low
elevation
Kernels turn brown because of high temperature at time of
ripening.

Temperature
• It requires cool period in autumn to promote leaf fall and the physiological
process of plant hardening and induction of dormancy.
• The plant can tolerate as low as -11 ͦC during deep dormancy without serious
damage.
• Walnut is not recommended in areas where late spring or early fall frost is
common as freezing temperature kills the growing points of walnut trees and
severely affects production.
• High temperature at 38 ͦC cause sun burning on hulls & shriveling of kernels
resulted sometimes into black nuts.
• The chilling hours requirement varies with the cultivars as 700 & 1500 hours are
needed for Payne & Franquette cultivars, respectively, at or below 7 ͦC.
34

Rainfall
• Requires 760-800 mm rainfall or irrigation equivalent. To obtain high yield, avoid
planting in drought prone zones. Spring rainfall is associated with increased
problems from walnut blight.
35
• The plant can grow and crop much more slowly if exposed to persistent winds. It
is also susceptible to limb breakage. Thus, shelter is needed to promote good
growth during establishments years.
Wind tolerance
• High yielding cultivars will leaf out late in the spring thus escaping frost injury.
Cobly & Himalayas varieties are reported to be hardy & can withstand cold
injury (Sharma, 1988).
Spring frost

Soil
• Slightly acidic soils between pH 5.5-6.5.
• It grows best on deep, friable loamy soil/slit loam or clayey loam supplemented
with lime & rich in humus, where roots can develop to a depth of 3-4 m.
• It can not tolerate wet soils for extended period.
36

Important State wise grown varieties
State Varieties Released by Research Institute
J & K CITH Walnut – 1,2,3,4,5,6,7,8, 9 & 10 CITH, Srinagar, J & K.
Hamdam (2001), Sulaiman (2001) SKUAST-K.
HP Gobind, Roopa, Ratna, Pratap & Sholding -
UK Charata No. 2,4,6,13 & 10 -
38
• Some other varieties: Govind, Roopa, Lake English, Eureka, Placentia (Commercial
cultivar of Himachal Pradesh), Wilson, Menlanaise, Pieral Lara, all are walnut
selections grown in India.
• Interspecific hybrid: Royal (J. hindsii × J.nigra), Paradox (J. hindsii × J. regia) and
vimorin (J. regia × J.nigra).

Variety Characteristic features
CITH Walnut-1 Trees moderately vigorous, terminal/lateral bearing, high yield (60 kg/tree at 15th year),
very high nut weight (27.2 g), extra large, soft shell, light colour, smooth texture,
intermediate seal; very high kernel weight (12.8 g) with kernel recovery 47%; kernels very
light to light in colour, easy removal in halves, plump and well filled.
very high nut weight (21.9 g), very large, soft shell, light colour, smooth texture,
light to light in colour, easy removal in halves, plump and well filled
39

40
CITH Walnut-6 Trees moderately vigorous, terminal bearing, high yield (30 kg/tree at 15th year), very high
nut weight (24.0 g), broad ovate shape, light colour, rough texture, intermediate seal;
medium kernel weight (12.2 g) with kernel recovery 51%; kernels light in colour, easy
removal in halves, plump and well filled.
nut weight (24.7 g), elliptic shape, rough texture, amber colour, strong seal; medium kernel
weight (12.4 g) with kernel recovery 50%; kernels light in colour, easy removal in halves,
plump and well filled.
nut weight (20.4 g), long trapezoid shape, light colour, rough texture, intermediate seal;

CITH Walnut-1 CITH Walnut-2 CITH Walnut-3 CITH Walnut-4 CITH Walnut-5
CITH Walnut-6 CITH Walnut-7 CITH Walnut-8 CITH Walnut-9 CITH Walnut-10
* Source : Verma MK (2014) Walnut production technology IARI, New Delhi 41

42
CITH Walnut-9 Trees moderately vigorous, terminal bearing, high yield (50 kg/tree at 20th year), very
high nut weight (21.2 g), round shape, light colour, rough texture, intermediate seal;
CITH Walnut-10 Trees moderately vigorous, terminal bearing, high yield (30 kg/tree at 20th year), very
high nut weight (20.0 g), long trapezoid shape, light colour, rough texture,
intermediate seal; medium kernel weight (11.2 g) with kernel recovery 56%; kernels
light in colour, easy removal in halves, plump and well filled.
Hamdan Trees semi dwarf, terminal/lateral bearing, high yield, medium nut weight (14 g),
large, strong, good seal and rough texture nuts; medium kernel weight (7.6 g) with
kernel recovery 54%; light in colour. Developed and released by SKUAST (K), Srinagar
in 2001.
Sulaiman Trees vigorous, terminal/lateral bearing, high yield, good nut weight (21 g), round
shape, good strength, attractive appearance; high kernel weight (10.9 g) with kernel
recovery 52%; light to extra light with easy to remove kernel halves. Developed by
SKUAST (K), Srinagar, India.

43
Pusa Khor Oil content 55%, regular & heavy bearing with good quality nuts.
Payne Trees moderately vigorous, upright, lateral bearing, moderate yield, precocious,
medium nut weight (12.8 g), good strength and appearance; medium kernel weight (6.4
g) with kernel recovery 50%; light in colour, good quality, easy to remove kernel halves
and compatible pollinizer used for ‘Tehama’, ‘Chico’and ‘Hartley.
Sunland Trees vigorous, lateral bearing, variable yield, good nut weight (17.9 g), well filled, large,
oval, solid-shell; high kernel weight (9.8 g) with kernel recovery 55%; good quality, large,
plump, oval shape and compatible pollinizer used for ‘Chico’, ‘Tehama’ and ‘Tulare’.
Tehama Trees vigorous, lateral bearing, high yield, medium nut weight (14.1 g), solid shell, weak
seal; medium kernel weight (6.8 g) with kernel recovery 48%; light coloured, poorly
filled and compatible pollinizer used for ‘Serr’.
Howard Trees moderate, lateral bearing, high yield, medium nut weight (14.3 g), large, strong,
good seal and rough texture nuts; medium kernel weight (7.2 g) with kernel recovery
51%; light in colour and compatible pollinizer used for ‘Cicso’ ‘Franquette’ and
‘Fernette’.

44* Source: http://midvalleynut.com/

45
Hartley Trees large, terminal bearing, moderate yield, medium nut weight (14.3 g), attractive
shape; medium kernel weight (6.5 g) with kernel recovery 45%; light in colour, easy to
remove kernel halves and compatible pollinizer used for ‘Cicso’ and ‘Franquette’.
Chandler Trees moderately vigorous, lateral bearing, higher yield, medium nut weight (13.2 g), oval
in shape, shell smooth, light in colour, thin shelled; medium kernel weight (6.5 g) with
kernel recovery 49%; kernels extra light in colour, easy removal in halves, not well filled
and compatible pollinizer used for ‘Cisco’, ‘Franquette’ and ‘Fernette’.
Franquette Trees vigorous, terminal bearing, fair yield, medium nut weight (11 g), mediumthin shell
with good seal; medium kernel weight (5.5 g) with kernel recovery 50%; good quality, light
to extra light in colour and compatible pollinizers used for ‘Chandler’.
Vina Trees of moderate in size, spreading type, tendency to over bear, lateral bearing, high
yield, medium nut weight (12.6 g), good seal, strength good; medium kernel weight (6.2 g)
with kernel recovery 49%; often colour is not adequate and compatible pollinizer used for
‘Chico’, ‘Chandler’, ‘Tehama’ and ‘Howard’.
Serr Trees very vigorous, moderately lateral bearing, variable yield, medium nut weight (14.4
g), thin shelled, good seal, well filled; medium kernel weight (8.1 g) with kernel recovery
56%; light colour, excellent quality.

46
* Source: https://www.researchgate.net/publication/324862109

Comparison of old and new walnut varieties, Davis, California (5- year means) *
Variety Lateral buds producing
Pistillate flowers (%)
Av. Kernel weight
(g)
Harvest period
(early, mid or late)
Payne 80 5.2 E-M
Hartley 5 5.9 M
Franquette 0 5.2 L
Serr 50 7.6 E
Ashley 90 5.3 E-M
Sunland 80 9.9 L
Chico 90 5.0 E
Vina 90 5.6 E-M
Tehama 80 6.7 E-M
Amigo 80 6.0 E-M
Howard 80 6.5 E-M
Pedro 80 6.5 E-M
Chandler 80 6.3 L
Old
varieties
New
varieties
* Source :
After Ramos
1985 47

Lateral bearing trait in Indian walnut (Juglans regia L.) germplasm:
a potential yield contributing trait in early age of the tree *
• Chand et al. (2018) conducted research at ICAR-Central Institute of Temperate
Horticulture (CITH), Srinagar, India during 2015-16 with the objective of trait
specific characterization of walnut accessions with specific emphasis on lateral
bearing trait.
• The most widely grown varieties ‘Sulaiman’ and ‘Hamdan’ were used as local
check. All the accessions were monitored to identify the bearing habit.
• Only one accession CITH-W-121 (IC-0622836) was found with lateral bearing trait,
which had fruit bearing on leafy shoots emerging from terminal, sub terminal as
well as from lateral buds of 1-year-old shoot. It was reported for the first time in
indigenous genetic resources of walnut which is an important trait to improve
productivity.
Place of research: ICAR-CISH, Srinagar

• Lateral leafy shoots emerged all along 1-year old shoot, in which about 50% lateral leafy
shoots bearing 1−3 fruit per panicle. Overall 40−60% lateral leafy shoots in a tree were
bearing fruits in this accession.
• In term of yield, CITH-W-121 (11.07 kg per tree) was found significantly superior to Sulaiman
(5.85 kg per tree) and Hamdan (5.48 kg per tree).
• This accession has desirable traits like well filled, plump and light coloured kernel with
moderately easy removal of kernel halves and is having a good balance between vegetative
growth and fruit bearing.
49Morphology of fruit bearing branch of CITH-W-121;
Conti….

Propagation
50
Seed propagation Vegetative propagation

Seed propagation
51
• The walnuts are stratified till December.
• The seed germination starts in the beginning of the March.
• It shows poor seedling growth in 1st year but it establishes good root system.
• In 2nd year it develops quickly and ready for transplanting by the time the growth
stops in the autumn.

Seed planting in California
52

• Walnuts generally propagated on seedling rootstock raised from open pollinated seeds.
• Commercial rootstocks- J. regia, J. hindsii, J. nigra, J. microcarpa, J. californica & J. sielboldiana.
• In Asia, Juglans regia (English walnut) seedlings are suitable for use as rootstock. It has better
compatibility & resistent to crown rot disease. But, it unsuitable for water logged, saline & nematode
infected soils.
• In California, J. hindsii (the northern California black) is still used because it is tolerant to salts in the soil or
irrigation and because of its resistance to oak root fungus Armillaria mellia. Other rootstocks being used in
USA are J. hindsii, Paradox (J. hindsii x J. Regia) and Royal (J. hindsii x J. nigra).
• Hybrid of open pollinated J. hindsii & J. regia called ‘Paradox’ is more resistant to crown rot and root
lesion nematodes (Browne et al. 1977; McGranahan and Catlin 1987).
• Juglans nigra (Black Walnut) rootstocks produce slightly less vigorous trees. However, it is susceptible to
black line disease, which can rapidly kill a mature tree.
• Rootstocks are bred to grow in different soil types and conditions, and provide the best anchorage, vigor, and
resistance or tolerance to soil borne pests and diseases. However, no individual rootstock is tolerant of all factors that
impact walnut production. The strengths and weaknesses of each rootstock should be considered in the context of a
specific orchard location.
53
Walnut rootstocks

Size, chilling requirements and other characteristics
of seeds of walnut species used as rootstocks *
Species Seed size
(g)
Chilling
requirement
(days)
Optimal Chilling
temperature ( ͦC)
Speed of
germination
(days)
Seed viability
(years)
J. cinerea 0.03-0.09 90-120 5 45 3-5
J. hindsii 0.07-0.18 60-120 - 30 3-5
J. nigra 0.04-0.22 60-120 5 25 3-5
J. (Paradox) hybrid 0.11-0.14 60-80 - 25 3-5
J. regia 0.07 30-60 5 20 1-3
* Source : USDA (1974) and USDA (1961) 54

Vegetative propagation
• Walnut propagated by seed & seedlings have long juvenile period. So, it is
propagated by vegetative means i.e. cleft grafting, patch budding & epicotyl
grafting.
• Vegetative propagation gives lower success rate in walnut than in pome & stone
fruits, because walnut seedlings have hallow internodes & the survival/success
through various means of grafting is very poor (20-25%). The graft union at
initial stage remain fragile & break even through slight jerk.
• Better success was obtained when grafting was done either in a green house
have temperature 28 ͦC & 80-100% RH or the grafts after preparation were
placed in an incubator at 25 ± 1 ͦC with 75 ± 2% RH.
• Epicotyl grafting has also given encouraging success in walnut propagation.
55

Cleft grafting
56
• It gives higher success when graft is incubated at 26 ͦC & 90% RH for 3 weeks before planting in
the nursery.
• Best time for cleft grafting is mid January.

Patch budding
• Most common method with 30-35%
success rate.
• Mid June is the optimum time for
grafting.
• In Kashmir, this method is found
fairly successful.
57

Optimizing early grafting of Persian walnut by evaluating
different rootstocks, covering materials and grafting methods *
• Grafting on epicotyl of young seedlings has been introduced as a simple and rapid
method for walnut propagation. Although this technique improves the grafting
success and propagation efficiency, it is technically more demanding than the
conventional walnut grafting procedures and is yet to be optimized.
• Raufi et al. (2017) investigated the influence of rootstock type (dwarf and standard
genotypes), graft union covering materials (perlite, sawdust, coco-peat and perlite
at 1:1 ratio, and without cover - control) and different epicotyl grafting procedures
(Gandev-Arnaudov and Frutos) on grafting success and performance of the grafted
plants in order to optimize the walnut epicotyl grafting.
58
Place of research: Department of Horticulture, College of Aburaihan, University of Tehran, Pakdasht, Tehran, Iran
* Source : https://www.researchgate.net/publication/323254982

59
Grafting process of young Juglans
regia seedlings by Frutos procedure
A) Cutting the rootstock from
1.5±0.5 cm above the epicotyl.
B) Making a 1.5±0.5 cm cut in the
middle of the rootstock stem.
C) Inserting the prepared scion into
the rootstock
D) Covering the grafting point with a
parafilm stripe.
E) The grafted plant, 30 days after
grafting.
Frutos
Procedure

• Walnut seedlings were grown in a greenhouse. After four weeks, dormant shoots
of walnut ‘Chandler’ were grafted to the epicotyl of young walnut seedlings.
Grafting success and callusing quality were recorded 30 days after grafting.
• Growth parameters of the grafted plants, including number of nodes and length of
internodes, height and diameter of scion, and survival of the grafted plants, were
determined 150 days after grafting.
• Enhanced grafting success and performance of the grafted scions were obtained by
following the Frutos’s procedure.
• Moreover, the highest grafting success (75.1%) and survival of the plants (91.7%)
were obtained by using the dwarf rootstock and application of sawdust as graft
union cover.
• In conclusion, performing walnut epicotyl grafting according to Frutos’s procedure
by using dwarf genotypes as rootstock and covering the graft union with sawdust
was suggested to obtain maximum propagation efficiency (68.7%).
60
Conti….

Exploring combinations of graft cover and
grafting method in commercial walnut cultivars *
• Majd et al. (2018) conducted an experiment to determine the best method of
grafting and the covering of graft union in walnuts (two cultivars of ‘Chandler’
and ‘Franquette’) during 2014 and 2015. Best results was obtained on
‘Franquette’.
• He concluded that covering by moist sawdust was better than the other two
covers & the omega method caused the best quality of callus, the highest
callused grafts (89.1%) and the most successful graft-take (81.6%).
• Meanwhile, V grafting caused the highest survival percentage (65.8%) and
growth of scions (107.9 cm).
Place of research: University of Tehran, Iran.

62
Covering of graft union with
(A) Polyethylene film
(B) Moist mixed covering (cocopeat +
soil + manure in a 1:1:1 ratio)
(C) Moist sawdust
(D) Four weeks after covering with
moist sawdust
Covering
methods
Callus
quality1
Callused grafts
(%)
Graft-take (%) Graft survival2
(%)
Scion growth (cm)
Sawdust 2.51a 98.61a 83.33a 72.21a 206.91a
Mixed Cover 2.04b 86.1b 68.05b 56.94b 199.33b
Polyethylene 1.34c 76.38c 56.94c 50c 194.08c
Effects of different covering materials for banding graft union on callus quality, callused grafts, graft-take
(%), graft survival (%), and scion growth of Persian walnut. Also all values are the means of the two years
data (2014 and 2015).
Values are the means of a callus scoring rating from 1 (low callusing) to 4 (very high callusing).
Graft survival = (S/G) 100, where S = number of surviving plants, and G = number of graft-takes.
Conti…

• Saddle and V grafting were performed by a machine (Carlo A. Manares Co., Italy) &
this machine was to cut rootstocks and scions in two different ways.
• In saddle grafting, V shaped scion was made by machine.
• In V grafting, V shaped incision was made on rootstock by machine.
• Tongue grafting was done with hand using a sharp knife.
• Omega grafting was done using an omega hand-held machine (Zhangjiagang Xingxing
Tools Co., China).
63
Callus quality in different methods of walnut grafting Omega hand-held machine

64
Method of grafting Callus
quality1
Callused
grafts (%)
Graft-take
(%)
Graft survival2
(%)
Scion
growth
(cm)
Omega 2.7 89.1 81.6 49.1 80.0
Saddle 2.2 81.6 71.6 57.5 104.4
V 2.3 84.1 77.5 65.8 107.9
Tongue 2.0 72.5 64.1 49.1 90.4
Effect of different methods of grafting on callus quality, callused grafts, graft-take ( %),
graft survival (%), and scion growth (cm) of Persian walnut Also all values are the
means of the two years data (2014 and 2015).
Values are the means of a callus scoring rating from 1 (low callusing) to 4 (very high callusing).
Graft survival = (S/G) 100, where S = number of surviving plants, and G = number of graft-takes.

Walnut propagation using a hot water installation
and growing the obtained plants in containers *
• Walnut is among the fruit species difficult to be propagated and therefore different
techniques and methods have been developed all over the world to improve the survival
percentage of the new plants.
• Gandev (2017) conducted an experiment in the period 2013-2015 at the Fruit-Growing
Institute. One-year old seedlings of common walnut (Juglans regia L.) were used as
rootstocks, grafted with ‘Izvor 10’ cultivar. The plants were put for callus formation in
the constructed hot water installation.
• Successfully propagated plants were grown in containers for two years. The results
showed that the developed hot water installation leads to obtaining 83.1% of
successfully propagated plants.
• The conclusion was drawn that the constructed hot water installation favoured the
production of a high percentage of successfully propagated plants, which could be
grown in containers for two years.
Place of research: Agricultural Academy, Fruit-Growing Institute, Bulgaria, SE Europe

Top working
• Late spring (end of March to April) is preferred for top working.
• It is done by modified cleft grafting.
• The dormant scion wood should be cut well in advance & stored in refrigerator
after proper packing.
• Bleeding is a problem in top-grafting especially when it is done in early spring.
This can be avoided by heading back the rootstock 2 weeks earlier of actual
operation.
• After grafting, the open wound must be covered by grafting wax. The stem
portion needs white washing to give protection against sunburn.
66

Micro propagation
• Micro propagation have been investigated for the successful large scale
propagation of walnut.
• Rodriguez & Sanchez-Tames (1981) were 1st to report establishment of walnut
cultures in-vitro & to describe the development of roots or shoots from the
cultured walnut embryos.
67

Walnut grafting in California
68

Layout & tree density
• Square or quincunx design.
• Every 8th row, a pollinizer variety is planted perpendicular to the usual direction of
the wind.
70
Type of plant Spacing
Seedling trees 12 × 12 m
Grafted on J. regia 10 × 10 m
Grafted on J. nigra 8 × 8 m

Pit digging & filling
Type of soil Pit size
Clayey or not very fertile soil 1 m deep & 1 m in diamter
Loamy soil 0.3 m deep & 0.3 m in diamter
71
• Fill the pit with mixture of rotten FYM & top soil at the ratio of 1:2.
Planting
• Plant the seeding in late dormant or early spring season.
• Irrigate immediately.

Walnut tree planting in California
72

High density planting in walnut
• No dwarf rootstocks are used at present, but higher densities are being used and
it resulted higher yield per hectare.
• Martin et al. (1962) reported that walnuts at 15.2 × 9.2 m produced as much per
tree in the early years and more per hectare than those at 15.2 × 12.2 m or 15.2 ×
15.2 m (standard spacing).
• Long term net monetary returns were greatest from the most dense planting.
73

Tree Architecture & Pruning
74

Bearing habit & yield
• Self - fertile, but dichogamous.
• Pollen release from male flowers does not coincide with bloom of female flowers.
So, pollinizer is needed.
• Age to start commercial bearing is 6-10 years & trees may bear for about 100 years
or more.
• Grafted and budding plants gives fruiting about 4 to 5 years.
• A grown up tree yield an average of 50-80 Kg/tree and mature tree yield is 80-100
Kg/tree.
• Peaches often inter planted for first 10-15 years.
• The bearing habit also influences tree structure and affects the productivity
(Laurens et al., 2000).
• The lateral bearing is associated with precocity (Serr, 1962; Forde, 1979) and higher
yield (McGranahan and Leslie, 1991; Solar et al., 2001).
• The lateral bud fruitfulness is considered as a most significant yield factor, which can
also be manipulated through breeding (Akca and Ozongun, 2004). 75

A contemporary narration on presence of cluster bearing
trait in Juglans regia L. in Indian Himalayan region *
• The Persian walnut (Juglans regia L.) bear fruit in panicle of 1 to 3 fruits and
occasionally with five fruits per panicle.
• Previous report showed that cluster bearing is a rare trait in J. regia.
• Chand et al. (2018) conducted a selective survey with the objective to identify
cluster bearing walnut genotypes and an intensive survey was done in four village
viz., Dadom Pora, Nowhar, Hanjum, Shum Nag of Budgam district of Jammu &
Kashmir (India) during 2015-16.
76
Place of research: Budgam district of Jammu & Kashmir (India)

• As a result, one cluster bearing genotype of J. regia was identified from Shum Nag
village and named as SN-1.
• This genotype was found with up to 10 fruit per terminal having approximately 40-
50 percent frequency of clusters of 10 fruits.
• However, maximum terminals were observed with 2-10 fruits per cluster. In this
genotype, mean nut weight, kernel weight and kernel recovery were recorded
13.11g, 6.16g and 46.24%, respectively.
77Fruits inside tree canopy of SN-1, Fruit cluster, nut and kernel of SN-1.

Training & pruning
• Walnut is usually trained to a modified central leader with 5 or 6 main laterals
distributed up and down the main stem.
• Carry out pruning operation in early spring season. Further delay causes excess
bleeding.
78
Age of tree Pruning pattern
Young tree (16-17 year old) Cut back 3 years old shoots
Middle aged tree (34-35 year old) Cut back 3 years old shoots
Mature tree (40 year old) Cut back 4-5 years old shoots
• Initiate selective thinning out of limbs in the top and sides of the tree before
overcrowding becomes serious.
• Do not remove more than 25% of the branch structure at any time.

Flowering
• The walnut seedling takes about 8-10 years to come into bearing but grafted begin
fruiting early in about 4 or 5 years.
• Under Shimla conditions, peak flowering period of walnut is mid April which is
prolonged till first week of May in late blooming cultivars.
• Walnut is monoecious plant i.e. staminate and pistillate flowers are born separately on
the same tree.
Kind Flower initiation Flowers borne on Season of anthesis relative to
season of initiation
Male flower Early summer Lateral buds, 1 year shoots Next spring
Female flower Late summer Terminals of current shoots Next spring
80

Pistillate
(female flower)
Staminate
(male flower)
Male & female flower position
81

Male flower
• The staminate flowers emerge laterally and hang in catkins.
• Catkin i.e. pendulum like male organ of the plant, grow
individually from the top of the leafless stems of previous
season.
• The cylinder shaped catkins grows 3 inches long & 3 quarters
of an inch in width. Catkin comprise of a large number of
closely packed & minute flowers of a plain arrangement.
• Each of tiny flowers has a short shoot, a supporting bract,
two tangential bracteoles and a perianth of 6 leaves
surrounding an indefinite number of nearly stamens that are
directly attached to the base without any stem.
Female flower
• The pistillate flowers appear in the form
of nutlets of 4-8 flowers at the top of the
green stems that grow on the same year.
• The flowers have no petals and consist of
large reflexed stigmas attached to the
ovary and a supportive perianth made up
of 4 leaves in two pairs each.
• In addition their bracteoles and twin
disposition of the fruit is suggested by
comparatively large plump stigmas.
82

Pollination problem of walnut
• Walnut is self fertile, but dichogamous plant. Dichogamy : opening of male and female flowers at different
times on monoecious plant. It ensures cross pollination. Both protoandrous (English walnut) and
protogynous varieties (Eg. Meylan, XXX Mayette and Chico) exist in walnut.
• Dichogamy varies with the age of the tree and is more pronounced in young trees. Mature trees not
only have more catkins, but produce them over a longer period and thus better overlap the female bloom.
• Climate influences dichogamy. During warm periods, catkins respond more rapidly than female flowers.
Continuous cold weather in late winter and early spring delays blooming while warm winters tend to
hasten bloom development.
• Normal tree bear 7-8 times more catkins than pistillate flowers. Pollen viability is less than 25% & short
period of stigma receptivity. Pollen is normally released 10-12 days after bud burst; full bloom of female
is usually 15-18 days later although this varies with cultivars.
• Walnut flowers are anemophilous. Effective pollination can be assured by planting early and late cultivars
whose pollen shedding overlaps each other. A solution to dichogamy is to plant a protoandrous variety
with protogynous one so that male bloom of each overlaps the female bloom of the other. 83

Pollen collection & storage
• The problem of dichogamy is aggravated by short periods of both pollen viability & stigma
receptivity (Polito 1985). Pollen is normally released 10-12 days after bud burst; first bloom of
female flowers is usually 15-18 days later although this varies between cultivars.
• Walnuts are self -fertile & cross compatible. So, above problem can be solved by pollen collection
and storage.
• Best catkin for pollen production is the one that has already a few of its anthers dehisce. Each
catkin may produce 2 million pollen grains.
• Crane et al. 1973 concluded that sub-freezing temperatures would kill walnut pollen. Walnut
pollen seems to lose viability in a week or less at room temperature.
• Forde and Griggs (1975) showed that J. regia pollen remains viable for at least 1 year in a freezer
at -19 ͦC.
• Luza and Polito (1987) showed that J. regia pollen ranges from 4.6 to 12.1 % moisture content &
germination declines as pollen moisture falls below 5 %, but if dry pollen is held in water
saturated environment it remains its ability to germinate in vitro.
84

Pollination & early fruit growth
• After stimulation of pollination and
fertilization, the fruit growth begins.
• The non-pollinated pistillate flowers
make some initial growth but ultimately
drop down after about three weeks in
absence of fertilization.
• The pollen comes down from the stigma
through pollen tube and enters ovary.
85
Light cream colour Kernel
Light green colour Shell
Green dark colour Hull

Endocarp growth
(20-26 June)
Testa growth
(3-8 June)
Mesocarp growth
(22-25 May)
Endocarp harden
(5-10 August)
Harvesting time
(mid September- Oct.)
Nut mature
(15-25 September)
• Two rapid periods of walnut
fruit growth are interspersed
by a period of relatively slow
growth.
• During 1st growth period, the
fruit gains size and weight.
• The fruit attains form and
becomes richer in chemical
constituents during the 2nd
growth period.
• In the developing walnut
fruit, glucose, sucrose and
fructose are the predominant
sugars.
• Ethylene application hastens
fruit abscission.
Late season fruit growth
Growthdirection
86

Flower development in walnut: altering the
flowering pattern by gibberellic acid application *
• Hassankhah et al. (2018) studied the patterns of walnut pistillate flowers developing as a result of applying gibberellic
acid (GA₃), the research was conducted as a factorial design with 2 factors (three levels of trunk diameter (10 to 12 cm,
12 to 14 cm and 14 to 16 cm) and four levels of GA3 (0, 50,100 and 200 mg/l)) on ‘Chandler’ commercial cultivar.
87
(A) Floral induction periods in
late May and early June
(B-D) Floral initiation periods
from September
(E and F) Floral differentiation
periods in March to April
Different levels of GA₃ were
sprayed twice on the trees, i.e.
2 and 4 weeks after flowering.
Based on the results, different
development stages included
induction; initiation and
differentiation of the pistillate
flower bud were observed
respectively.
• Pedicel (pd)
• Bract (B)
• Perianth (pr)
• Vascular bundle (VB)
• Leaf primordial (lp)
Anatomy of walnut female flower bud differentiation

• The results of GA₃ application showed that GA₃ treatment can alter the flowering pattern of
walnut. GA₃ application significantly increased the number of male flowers, total flowers, and
male: female flower ratio per branch.
• The number of female flowers increased by increasing the tree trunk diameter. The highest
number of female flowers (62.3) was observed in trees with trunk diameters between 14-16 cm
and application of 100 mg/l of GA₃.
• Linear regression analysis showed a positive and strong relation between truck diameter with
total flower number as well as female flower number.
88
Place of research: University of Tehran, Iran

Manure & fertilizer
Fertilizer/tree 1st yr 2nd yr 3rd yr 4th yr 5th yr 10th yr 20th yr & onwards
Urea (g) 20 30 40 60 85 490 3915
DAP (g) 65 65 65 65 65 130 1085
MOP (g) 30 40 50 65 80 415 2400
• Manure and fertilizers are generally applied based on leaf nutrient analysis report.
• In the absent of plant and soil nutrients analysis information, apply nutrients as
below details.
• Full doze of P and K and half dose of N should be applied two weeks before
expected bloom.
• Rest half dose of N should be applied into two equal splits, which should be
applied three weeks after fruit set and during early July. 90

Intercropping
• Intercrop walnut trees with legume fodders, in areas traditionally under pasture
farming system.
• For other farming systems, use low growing and non-competitive vegetables such
as non-climbing beans and other legumes, tomato, and onion and more
competitive vegetables such as chili and asparagus.
• Intercrop during the first 4-6 years after planting only.
• If sustained intercropping is planned from the establishment of the orchard,
modify the spacing, that is, much wider between rows of mature trees.
91

Irrigation
• Basically walnut trees are grown under rainfed conditions. If rain is not sufficient
and well distributed, irrigation is essential for walnut cultivation.
• Low water supply to the trees results in slow growth, reduced yield and low nut
quality and fruit dope.
• More irrigation is needed at during fruit setting and development stages. But
excessive supply of water cause root and crown disease.
92

Weed control
• The use of chemicals has become prevalent in controlling weeds.
• The herbicides, simazine and diuron have been successfully used in weed control
of young and established walnut orchards.
93

Mulching
• Mulching is essential in walnut orchards when the plants are younger.
• It also important after applying fertilizer to older trees.
• Mulching materials around the plant or trees to help conserve soil moisture,
regulated soil temperature & reduce weed growth etc.
94

Harvesting & Handling of Fruit
95

Maturity indices
• The nuts are covered over with hulls which split
at the time of maturity.
• Hull or husk dehiscence occurs 1-4 weeks after
the nuts are mature.
• When about 80% of the hulls have cracked
exposing the nuts, it is the time for walnut
picking. Nuts should be harvested at PTB stage
i.e. when packing tissue turns brown.
96

Harvesting & Handling in India
• The nuts fall down the ground are collected or they are made to drop on the
ground by shaking the branches with hands or striking them with bamboo
poles.
• The total harvest is done in two or three times at few days interval.
• In Himachal Pradesh, harvesting commences from August and extends up to
last week of September, whereas in Kashmir walnuts are harvested in
September.
• The nuts are collected from the ground, cleaned, washed and dried upto 8%
moisture content by spreading them on the floor.
• Delay in drying causes rapid loss in nut quality and makes it susceptible to mould.
Drying of nuts stabilizes the product weight & prolongs storage life.
97

Grading according to size
The nuts should be graded suitably according to the size, colour and variety.
98* Source: http://acmewalnut.com/buy-california-walnuts/

99
Grading according to colour
* Source: https://www.sciencedirect.com/science/article/pii/S0308814617306015
Price is inversely related to color. Light colored get high price.

General storage
• In-shell nuts are alive, their respiration and metabolic activity is much lower at low
moisture content of the dried nuts.
• Walnuts have a high oil content (60-70%) and thus subject to rancidity during storage.
(Rancidity is complete or incomplete oxidation or hydrolysis of fats and oils when
exposed to air, light or moisture, resulting in unpleasant taste and odour.
• The randicity of unshelled nuts can be detected after 4 months at 21 ͦ C and 2 years at 1 ͦ.
• Storage at 75-80% RH and 3.5-6% moisture content is best. Most nuts when fully dried,
can be stored foe very long periods at -18 ͦC without injury or loss of quality.
• Walnuts are packed for storage in gunny bags and further, lined up with paper on all sides
to avoid shaking and breaking of walnuts.
100

Walnut harvesting & processing in California
101

Walnut leaf blotch or Walnut anthracnose
Causal organisms Type of damage Control
Gnomonia leptstyla,
Marssonina juglandis
It causes the nut to turn black
and then fall, as well as brown
blotches on leaves and fruits.
Burn fallen leaves and use
Bordeaux mixture.
103
* Source: https://balkanecologyproject.blogspot.com/2015/11/the-essential-guide-to-everything-you.html

Walnut blight
104* Source: https://pesticideguy.files.wordpress.com/2013/02/46-walnut-blight.jpg
Causal organisms Type of damage Control
Xanthomonas campestris
pv. judalandis
It causes black spot on leaves, holes and
blotches on fruit, and possibly damage of
shoots. Blight affected male catkins affect
nut growth to the most when it occurs
during cool and wet periods.
Spray metallic
copper @ 4.5
Kg/ha
(Teviotdale et
al. 1985).

Black line formation of walnut
• The name of the disease comes from typical dark line between the stock and grafted tissue.
• This is a classical example of delayed incompatibility, is caused by a virus ( a strain of the
cherry leaf roll virus - CLRV-W). It affects only non-regia rootstocks (when English walnut is
grafted onto rootstock ‘Paradox’.
• The virus spreads through pollen, seed and infected grafts, so it spreads fast.
• Affected plants suffer yellow drooping leaves, stunted growth and early leaf fall. The tree
may suffer dieback and death.
• For its control, only virus free scion wood should be used for grafting and budding.
105
* Source: http://www.padil.gov.au/pests-and-diseases/pest/main/136659#

Foot and root rot
• This is a fungal disease that attacks the stem where it touches the ground and
also attacks on root.
• Small infected are seen on leaves.
• Avoid planting walnut trees in moisture and cool soil.
• Provide proper drainage system.
• Treat soil with formaldehyde, or bavistin before planting.
• Use only resistance rootstock.
106

Powdery mildew
• It is a caused by Phyllactinia roboris.
• Greyish to white powdery spore mass appears on upper and lower surface of
leaves.
• It can be control by spray the trees wetable sulphur (300g/100 litre of water) or
carbendazim fungicide (50g/100 litre of water).
107

Insect-pests
• Pest management is a problem in walnut because of giant trees.
• Planting of grafted trees, using dwarfing rootstock, training and pruning and
choice of lateral bearing cultivars altogether help in reducing tree size for easy
spray and harvesting.
• Sanitary measures involve planting of healthy trees, precautions against the
transfer of disease and insects through tools used in pruning and cultivation
(Johnson 1960).
108

Walnut leaf gall mite
• Scientific name: Aceria arinoea.
• Raised bumps (0.5 inch long) form on the leaves resembling a caterpillar’s body.
• Its difficult to get rid of this pest, but fortunately damage dealt is usually small and
not life threatening pest for the plant
109* Source: https://www.naturespot.org.uk/species/walnut-leaf-gall-mite

Walnut aphid
• Scientific name: Chromaphis jiglandicola.
• Aphid suck sap from the underside of leaves and tender shoots during April-
September.
• Due to severe infection, leaves fall, kernels shrivel & sooty mould develops on
honey dews.
• Spray carbaryl (0.2%) at 7 day interval twice.
110
Walnut aphids feed on lower side of leaf.

Codling moth
• Scientific name: Cydia pomonella.
• It id found in Ladakh region.
• 3 generations of moth damage the fruits.
• Its 1st generation larvae enter the growing fruit through the blossom & cause dropping of
the immature fruits. The 2nd generation of pest enter the nut through the side of the husk.
• Spray Diazinon or carbaryl (0.2%) for its control.
111
* Source: https://pnwhandbooks.org/insect/nut/walnut/walnut-codling-moth
1st generation of moth larva bore into nut

Walnut weevil
• Scientific name: Alicides porrectirostis.
• The female lays eggs on the fruits & on hatching, it feed by boring hole on kernels causing
premature fruits drop.
• The pest can be checked by spraying twice carbaryl (0.2%) at 7 days interval.
• Collect the dropped, infected fruits and burn them.
112
Adult of walnut weevil Eggs of walnut weevil

Husk fly
• Scientific name: Rhagoletis complete.
• This is the most important and serious pest in walnut.
• The fly lays eggs on developing fruits and the maggots destroy them.
• Management: Use the pheromone traps or spray dipterex.
113

Future thrusts
• Walnut cultivation was found to be declining, mainly due to factors such as low
productivity arising from a lack of good quality planting material, poor
pollination, low tree density per unit area, predominant terminal bearing, long
juvenile period, big tree size (30-37 m), poor filling, poor success rate of grafting,
and climatic fluctuations (Rana et al., 2007).
• There is a need to select varieties having desirable traits, such as lateral bearing,
short stature and earliness in bearing, good nut size and better nut kernel ratio.
• Disease and insect pest resistant traits are needed to be incorporated to realize
full potential augmenting the profit of the grower.
114

References
• Westwood M N Temperate Zone Pomology 3rd edition.
• Pradhan S Walnut: Cultivation & Management.
• Dhillon W S (2013) Fruit Production in India. Narendra Publications House, New
Delhi-11006 (India).
• Bal J S (2015) Fruit growing. Kalyani publishers, New Delhi-110002.
• Ali K A and Ahmad S (2019) Insect Pests of Walnut and their Management.
• Joshi P S Temperate Fruit Cultivation in India.
• Dewan M L, Nauttyal M C and Sah V K Nut fruits for The Himalayas.
• Sharma G, Sharma O C and Thakur B S Systematics of Fruit Crops.
• Ramos, D. E. 1985. Walnut Orchard Management, University of California, Davis,
USA.
115

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