Strawberry
Fragaria
spp.
Input from Dr. R. P. Awasthi, Dr. N. K. Joolka, and Dr. Y. S. Parmar
University of Horticulture and Forestry,
Nauni, Solan; HP; 173230, India.
STRAWBERRY
is an attractive, luscious, tasty and nutritious fruit with a distinct
and pleasant aroma, and delicate flavour. It has a unique
place
among cultivated berry fruits. Rich in vitamin C and iron, it
is
mainly consumed as fresh. Jam and syrup are also prepared from
strawberry. It is cultivated in topical and sub tropical
areas
round the year. In India, it is cultivated on commercial
scale in
Himachal Pradesh, Uttar Pradesh, Maharashtra, West Bengal, Nilgiri
hills, Delhi, Haryana, Punjab and Rajasthan. Owing to wide
climatic and soil adaptation and high returns, it has tremendous
potential in India. Its cultivation can be extended to other
suitable areas having assured irrigation and transport facilities.
Climate
and soil
Strawberry
grows well under temperate climate. Some cultivars are grown
in
subtropical climate also. Daylight period of 12 hr or less
and
moderate temperatures are important for flower-bud formation. Each cultivar may have a different day length and temperature
requirement. Some cultivars are adapted to septentrional
culture
(short days in autumn and hard winter) or to meridional conditions
(long days in autumn and moderate winter). Strawberry Senga
Sengana, Redgaunlet and Gorella are grown under septentrional
conditions, while Tioga is an important cultivar of meridional
region. It can make flower buds under longer day length.
Besides,
there are several day neutral strawberries—Sivla, Fern, Muir,
Heckar, Tristar and Trileute that have made their cultivation
possible in different times of the year. Day-neutral
strawberries
are high yielder. Temperature plays a critical role in the
development of strawberry at a particular place.
The
strawberry can be grown on any type of soil—poor sand to
heavy
clay—provided proper moisture, organic matter and drainage is
present. Strawberry ripens somewhat earlier on sandy soil than
on
clay soil. There is definite cultivar adaptation to
soils. Some
grow better on heavier soils and others on light soils. Water
should not stagnate in the field. Since most of its roots are
found in the top 15 cm soil, keep this layer porous and rich in
humus. Strawberry is not much sensitive to soil
reaction. However, it prefers a slight acidic soil. At
higher pH, there is less root growth. There should be no
underlying lime layer up to 15-20 cm, otherwise it causes burning of
leaves. In drier areas, alkali soils must be avoided, thus,
sandy
loam to loamy soil with pH 5.7-6.5 is ideal for strawberry cultivation.
Varieties
All
the cultivated varieties of strawberry are octaploid. A
number of
cultivars have been introduced and evaluated from
time-to-time. The promising ones are:
Chandler
Fruit
is of exceptionally high dessert quality with outstanding color and
flavour. It is very resistant to physical damages caused by
rain. Plants are tolerant to viruses. Fruits are
large,
flesh and skin firm and flavour excellent. It is suitable for
fresh market and processing. On an average, berry weights
15-18
g. The fruits have good TSS (12%), acidity (0.85%), vitamin C
(55.5mg/100g) and sugar content (6.1%).
Tioga
An
early –maturing cultivar, it is tolerant to
viruses. Fruits
very large, flesh and skin firm, dessert and processing quality good,
TSS 12.2%, acidity 0.98% and sugar 6.2%. Average berry
weights
about 9g.
Torrey
Tolerant
to viruses, it produces numerous runners. Fruits large, flesh
and
skin medium firm, dessert quality excellent, processing quality good,
TSS 12.0%, acidity 0.97% and sugars 6.1%. Average berry
weights
6.9g.
Selva
A
day-neutral cultivar, it has the capacity to produce off-season
fruits. It is different from day-neutral or ever bearing
types. Fruits large, flesh and skin firm, conic to blocky in
shape, dessert quality good. It can be handled and shipped
fairly
well. Skin bright red, attractive, flesh red, internally
somewhat
hollow, light in color at core, average berry weighs 15-18g, TSS 11.1%,
acidity 1.0% and sugar 5.5%.
Belrubi
Fruits
large, conical (necked fruit), skin bright red, flesh attractive red,
somewhat firm, less hollow at core, high quality, sweet, slightly
subacid, average berry weight 15 g, TSS 11.8%, acidity 0.98%, sugars
6%. Plant produces adequate runners.
Fern
It
is a day-neutral, early-ripening and over-bearing cultivar. Fruits
large, medium, conical, solid internally, slightly hollow, skin
red, flesh red, firm, flavour excellent, suitable for fresh market and
processing. It tastes sweet to slightly sub acid. Average
berry weight 20-25g, TSS 11.2%, acidity 0.98% and sugars 6.1%.
Pajaro
It
is very successful under summer system. Plant tolerant to
virus. Fruit has good dessert and processing
quality. Fruit
is quite susceptible to physical damage caused by rain. Fruits
large flesh very firm, skin firm, red color, average berry weighs 7.6g,
TSS 12.2%, acidity 0.97% and sugars 5.5%.
Besides, Premier, Red Coat, Local, Jeolikot, Dilpasand, Bangalore,
Florida 90, Katrain Sweet, Pusa Early Dwarf and Blakemore are also
grown.
Propagation
Strawberry
is commercially propagated by runners. Generally one plant
produces 7-10 runners but under proper management, it can go up to 15
runners/plant. It can also be propagated through crowns (3-5
plants/crown), but division of crowns of older plants is too tedious
and expensive for cultivars producing runner plants
readily. Runner formation can be stimulated with the
application
of IBA (100 ppm) 10 days before flowering, and also with Morphectin
(50ppm).
Propagation by seed is not suitable as the seedlings do
not come true-to type. Due to this, old strawberry buds may
have
many untrue seedlings undesirable for propagation.
Where viruses
and nematodes are present, primarily in commercial plantation, the
growth and production of plants may be reduced by half or
more. It
is desirable to procure virus-free plants for commercial plantations.
In addition, these plants are raised in fumigated soils to control
nematodes. Planting virus and nematode-free stock, and keeping
it
clean provides protection against serious diseases.
For large
scale propagation of virus-free plants, tissue culture is widely
used. Under favourable conditions, one strawberry meristem can
be
multiplied to yield more than one million plants in a
year. Plants
can be regenerated from meristematic callus, anthers and immature
embryos.
Cultivation
Planting
Soil preparation is very important for strawberry cultivation. It
should start during summer when the soil is ploughed with a soil
turning plough so that the insects present in soil may die. It should
be followed by repeated ploughings to make soil friable. Remove weeds
and stubbles. Since most of its roots are confined in top 40 cm soil,
the soil should be made friable. Deep cultivation improves water
absorption by the crop. The weeds can also be controlled by applying
paraquat. Soil should be fumigated before planting to control fungal
diseases, particularly verticillium wilt. Soil fumigation with a
mixture of methyl bromide and chloropicrin helps increase foot system,
reduces N fertilizer requirement and control several weeds.
September-October is ideal of planting runners or crowns in hilly
areas. The planting material should be healthy, disease and
insect-free. Early formed, well-developed runners are ideal for
planting. Fruit buds are established during the fall of the first
season. The September-October planted plants are well-established in
the field and start giving quality fruits in spring season. If the
planting is done too early, plants lack vigour and result in low yield
and quality of fruits. If planted very late, runners develop in March
and crops are light. In Punjab and Haryana, planting during November is
promising.
If planting is done in spring, use only healthy and vigorous plants.
The larger the plants at the end of first season, the larger will be
the succeeding crop.
In temperate humid regions, planting can be done in spring. If the
weather is undesirable, plants can be stored in polythene bags at
31*-32*C until conditions are favourable. Cold storage plants usually
grow as well as freshly dug field plants.
Strawberry can be planted by hand. However, care should be taken to
prevent damage and drying of roots of runners. Runners are uprooted
from nursery, made into bundles and planted in the field. These can
also be kept in cold storage before transplanting. The soil should be
frequently irrigated to reduce water stress in the leaf. Defoliation
suppresses the plant growth, delays fruiting and reduces yield and
quality
Training
There are 4 training systems-matted row, hill and plastic mulch.
Generally matted row system is followed in our country.
Matted row:
This is the simplest and least expensive method. The runners are
usually planted at 90 cm x 45 cm spacing. In Himachal Pradesh, a
spacing of 60 cm x 25 cm for Chandler is optimum. After the initial
growth of the first year, runners are allowed to cover the vacant space
all around the mother plants ultimately covering the whole vacant space
and giving the appearance of a mat. It is generally followed in heavy
soils which are free from weeds. In this system, more number of plants
can be accommodated/unit areas which give a higher yield under suitable
conditions. The overcrowding may cause higher fruit rot. Thus care must
be taken to maintain the optimum number of plants without overcrowding.
Spaced row:
This system is suitable for cultivars that are moderate to weak in
producing runners. The daughter plants are spaced at definite distances
by covering the selected tips of runners with soil which become plants.
This is done till the desired numbers of daughter plants are obtained
for each mother plant. The runners formed later on are removed.
Hill
system:
This system is followed for the cultivars developing a few runners. All
runners are removed from the mother plants. The individual plants
become large and bear more than those in matted row: the plants are
planted 25-30 cm apart in twin rows 20-30 cm apart and 100-110 cm
spacing between twin rows. A small tractor can be used for tillage.
Where cultivation is done manually, the rows can be spaced closer at 60
cm. In some cases triple rows are set.
Plastic film:
Green or black plastic film is used as a mulch for the hill system to
control weeds and conserve moisture, but on hot hays, some scalding of
berries takes place. In this system, berries are kept clean and rot and
mold are reduced. The plants bloom earlier. These are prone to damage
by frost.
Manuring and
fertilization
There are different recommendations for strawberry grown in different
states in India. In Himachal Pradesh, application of 50 tonnes farmyard
manure along with 40 kg each of p205 and k20/ha at the time of
preparation of beds is recommended. The N (80kg) should be applied in 2
split doses; half in September or after the establishment of plants in
September-October, and the remaining half before blooming.
For Uttar Pradesh hills, apply farmyard manure (25-37.5 tonnes), N
(75-100kg), P2O5 (80-120kg), k2O (50-80kg)/ha. The farmyard manure
should be mixed in soil at the time of preparation of planting bed.
Full dose of P2O5 and half of k2O are placed in the planting rows at
15-20 cm depth. Half N should be broadcast in inter-row spaces a month
after planting and the remaining half N and K2O should be side dressed
at the time of flowering. Foliar spraying of N (0.5%), P2O5 (0.2%) and
k2O (0.5%), 4 times between August and February is also advised.
Aftercare
The flower stems should be removed as they appear on plants after
planting. If not removed, flowers create a drain on the plants,
reducing their vitality, number and size of daughter plants. This
practice also helps establish the plants and aids in tolerating heat
and drought. The removal of flower strains from cultivars which produce
small number of daughter plants increases the number of runners and
plant set.
In Hill system, runners should be cut as and when they appear. With
matted row system, surplus plants should be removed from outside the
rows during late summer or autumn. The operation can be performed
normally or with the help of cultivar and other specialized machinery.
Keep the crop weed-free during first season by cultivating, applying
herbicides, or plastic sheet. The soil should be worked towards the
plants. It should be ensured that soil remains around the crown without
covering them. Cultivation should be restricted to only upper 2.54-5.08
cm of the soil. It should be continued till the straw mulch is applied
(where it is used). Weeds should not be allowed to grow. Emergence of
weeds during the fruiting season also affects pollination by honey
bees, thereby reducing yields drastically.
Irrigation
Irrigation
is a must and in humid regions, even short droughts reduce the yield,
damaging the shallow root system. Since strawberry is a shallow-rooted
plant, the plants require more frequent but less amount of water in
each irrigation. Irrigation of newly-planted buds results in increased
runner production and early rooting. Strawberry plants produce optimum
growth when the soil moisture tension is maintained at less than 1.0
atmosphere. Excessive irrigation is, however, detrimental which
encourages growth of leaves and stolens at the expense of fruits and
flowers and also increases the incidence of Botrytis rot.
Irrigation should be applied in furrows between the rows. The alleys
are usually cultivated after 2-3 days of each irrigation. Care should
be taken that water should not wet the leaves and fruits as it may
increase the incidence of fungal infection. To obtain better fruit size
and quality, it should be irrigated judiciously during harvesting.
Nowadays trickle and sprinkler irrigation systems are becoming popular.
In trickle irrigation, 30% water and energy are saved. Less disruption
of picking schedules, better water supply during winter and less
rotting of strawberries and saving in water are added advantages.
Sprinkler irrigation is, however, valuable in areas where there may be
heat stress (>85ºC temperature) and need for frost control using
50
ppm water.
Harvesting
and postmanagement
Strawberries
are generally harvested when half to three-fourths of skin develops
colour. For distant shipment green or white and still hard berries are
harvested. Delaying in picking usually increases the proportion of
overripe and rotten berries. The picking duration differs from
cultivar-to-cultivar. It is 5.5, 3.5 and 32 days for Tioga; 55, 30 and
30 days for Torrey during first, second and third year respectively in
Himachal Pradesh. For Harayana conditions, it is 53 days for Tioga and
43 days for Torrey. Depending upon the weather conditions, picked
should be done every second or third day. Ripening is faster is hot
weather. Do not leave any ripe or rotted berry in the field. Berries
should be picked along with a small steam portion attached. Picking
should be done in the morning. It facilitates better shelf-life. Thus a
yield of 96.53, 47.52, 52.08, 47.83 and 44.24q/ha from strawberry
Tioga, Torrey, Howard 17, Catskill and Blakemore respectively may be
taken. However, with proper fertilizer management an average yield of
175-300q/ha may be taken.
Some plant bioregulators-GA3 (50ppm) sprayed 4 days after flowering,
and maleic hydrazide (0.1-0.3%) sprayed after flowering increase yield
up to 31-41% Morphectin (50ppm) improves the fruit size.
Strawberries
are harvested in small trays or basket. They should be kept in a shady
place to avoid damage due to excessive heat in the open field.
For distant marketing, strawberries should be precooled at 4ºC within
2hr or harvesting and kept at the same temperature. After precooligng,
they are shipped in refrigerated vans.
Strawberries can be stored in cold storage at 32ºC up to 10 days.
Afterwards they lose their fresh bright colour, showing some shriveling
and deterioration in flavour. Strawberry fruit can be frozen for their
processed product or as dessert. The strawberries having high flavour
and a bright red colour. Olympus, Hood and Shuksan are quite
suitable for ice-cream making, whereas those of Midway, Midland,
Cardinal, Hood, Red chief and Beauty are ideal for processing.
Physiological
disorders
Albinism
is a physiological disorder in strawberry due to lack of fruit colour
during ripening. Fruits remain irregularly pink or even totally white
and sometimes swollen. They have acid taste and become less form.
Albino fruits are often damage during harvesting and are susceptible to
Botrytis infection and decay during storage. It is probably caused by
certain climatic conditions and extremes in nutrition.
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