biology of economic agriculture

1. Carambola’ / Star Fruit
Belimbing (Averrhoa carambola L.)

2. Botanical Description
• The star fruit tree is slow-growing, short-trunked
with a much-branched, bushy, broad, rounded
crown and reaches 6 - 9 m in height.
• Its deciduous leaves, spirally arranged, are
alternate, imparipinnate,15 - 20 cm long, with 5
to 11 nearly opposite leaflets, ovate or ovate-oblong,
4 - 9 cm long; soft, medium-green, and
smooth on the upper surface, finely hairy and
whitish on the underside.

3. • Pruning will keep the tree from getting too
large while still allowing it to bear fruit
prolifically.
• A good tropical fruit tree for limited space.

4. • The leaflets are sensitive to light and more or
less inclined to fold together at night or when the
tree is shaken or abruptly shocked.
• Small clusters of red-stalked, lilac, purple-streaked,
downy flowers, about 6 mm wide, are
borne on the twigs in the axils of the leaves.
• The showy, oblong, longitudinally 5- to 6-angled
fruits, 6.5 -15 cm long and up to 9 cm wide, have
thin, waxy, orange-yellow skin and juicy, crisp,
yellow flesh when fully ripe.

5. • The fruit has a more or less pronounced oxalic
acid odor and the flavor ranges from very sour to
mildly sweetish and tastes something like a mix
of apple, pineapple, and kiwi fruit.
• The so-called "sweet" types rarely contain more
than 4% sugar.
• Slices cut in cross-section have the form of a
star.
• There may be up to 12 flat, thin, brown seeds
1/4 to 1/2 in (6-12.5 mm) long or none at all.

6. A. Leafy shoots B. Inflorescence C. Flower D. L/S of Flower
E. Fruit F. C/S of Fruit G.Seed

8. Origin and Distribution
• The star fruit is believed to have originated
in Ceylon and the Moluccas but it has
been cultivated in southeast Asia and
Malaysia for many centuries.
• It is commonly grown in the provinces of
Fukien, Kuangtung and Kuangsi in
southern China, in Taiwan and India.

9. • It is rather popular in the Philippines and
Queensland, Australia, and moderately so
in some of the South Pacific islands,
Guyana, and in Guam and Hawaii.
• There are some specimens of the tree in
special collections in the Caribbean
islands, Central America, tropical South
America, and also in West Tropical Africa
and Zanzibar

10. Varieties
There are 2 distinct classes of star fruit:
• the smaller, very sour type, richly flavored,
with more oxalic acid;
• the larger, so-called "sweet" type, mild-flavored,
rather bland, with less oxalic
acid.

11. Climate
• Classed as tropical and sub-tropical because
mature trees can tolerate freezing temperatures
for short periods and sustain little damage at –3
ºC.
• It can grow up to an elevation of 1,200 m (in
India).
• Requires moisture for best performance; ideally
rainfall should be fairly evenly distributed all year
(In Australia, it is claimed that fruit quality and
flavour are best where annual rainfall is 1800
mm).

12. Soil
• No particular preference for soil type; the
star fruit does well on sand, heavy clay or
limestone, but will grow faster and bear
more heavy fruits in rich loam.
• It is often chlorotic (show burn symptoms)
on limestone soil.
• It needs good drainage; cannot stand
flooding.

13. Propagation
• The star fruit is widely grown from seed
though viability lasts only a few days. Only
plump, fully developed seeds should be
planted. In damp peat moss, they will
germinate in one week in summer, require
14 to 18 days in winter. The seedlings are
transplanted to containers of light sandy
loam and held until time to set out. They
are very tender and need good care.
Seedlings are highly variable.

14. • Air-layering has been practiced and
advocated. However, root formation is
slow and later performance is not wholly
satisfactory.
• Inarching is successful in India,
• shield-budding in the Philippines and the
Forkert method in Java. Trees can be top-worked
by bark-grafting, a popular
technique in Java.

15. • For mass production, side-veneer grafting
of mature, purplish wood, onto carambola
seedlings gives best results:
- the rootstocks should be at least 1 year
old and 1-1.5 cm thick.
- grafted trees will fruit in 10 months from
the time of planting out.
- mature trees can be top-worked by bark-grafting.

16. Cultural Practices
• The tree needs full sun.
• A spacing of 6 m has been advocated but if the
trees are on good soil no less than 9 m should
be considered.
• Trees 2.5 - 3 m high respond well to 0.5 kg
applications of N, P, K, Mg in the ratio of 6:6:6:3
given 3 to 4 times per year.
• If chlorosis occurs, it can be corrected by added
iron, zinc and manganese. Some advisers
recommend minor-element spraying 4 times
during the year if the trees are on limestone
soils.

17. • Moderate irrigation is highly desirable
during dry seasons.
• Heavy rains during blooming season
interfere with pollination and fruit
production.
• Inter-planting of different strains is
usually necessary to provide cross-pollination
and obtain the highest
yields.

18. Harvesting and Yield
• In Malaysia, they are produced all the year
round
• The fruits naturally fall to the ground when fully
ripe.
• For marketing and shipping they should be
hand-picked while pale-green with just a touch
of yellow.
• Trees that received proper attention have
yielded 45 to 115 or even 135 kg of fruit per tree

19. Pests and Diseases
• The carambola is relatively pest-free except for
fruit flies. In Malaya, fruit flies (especially Dacus
dorsalis) are so troublesome on carambolas that
growers have to wrap the fruits on the tree with
paper. Experimental trapping, with methyl
eugenol as an attractant, has reduced fruit
damage by 20%.
• Reniform nematodes may cause tree decline.

20. • Anthracnose caused by Colletotrichum
gloeosporioides may be a problem
• Leaf spot may arise from attack by
Phomopsis sp., Phyllosticta sp. or
Cercospora averrhoae.
- Cercospora leaf spot is sometimes
reported in Malaysia, (but widely
occurring in Ceylon, China and in the
Philippines as well).

21. Plant Facts:
• Common Name: Star Fruit, Carambola
• Botanical Name: Averrhoa carambola
• Family: Oxalidaceae
• Plant Type: Deciduous tree
• Origin: Ceylon and the Moluccas
• Form: Short-trunk with a much-branched,
bushy, broad, rounded
crown

22. • Height: to 12 m
• Rate of Growth: Slow
• Salt Tolerance: Low
• Soil Requirements: Not too particular as
to soil, but will grow faster and bear
more heavily in rich loam. Needs good
drainage; cannot stand flooding.

23. • Water Requirements: Medium drought
tolerance
• Nutritional Requirements: Balanced liquid
fertilizer monthly, side dressings of
composted manure
• Light Requirements: Full sun

24. • Leaves: Deciduous leaves, spirally arranged,
are alternate, imparipinnate, 6 to 10" long,
with 5 to 11 nearly opposite leaflets, ovate or
ovate-oblong, 1 1/2 to 3 1/2" long; soft,
medium-green, and smooth on the upper
surface, finely hairy and whitish on the
underside. The leaflets are sensitive to light
and more or less inclined to fold together at
night or when the tree is shaken or abruptly
shocked.

25. Various forms of terminal leaf

26. Flowers
Small clusters of red-stalked, lilac,
purple-streaked, downy flowers, are
borne on the twigs in the axils of the
leaves.

27. Flowers

28. Fruits
Showy, oblong, longitudinally 5- to 6-
angled fruits, have thin, waxy, orange-yellow
skin and juicy, crisp, yellow
flesh when fully ripe. Slices cut in
cross-section have the form of a star.
Flavour ranges from very sour to mildly
sweetish. May be up to 12 flat, thin,
brown seeds or none at all.

29. Fruits

30. Pests or diseases:
- Fruit flies,
- black beetles,
- stinkbugs,
- nematodes,
- anthracnose,
- leaf spot,

31. Fruit fly

32. Dacus dorsalis attacking fruit

33. Fruit borer (Cryptophlebia encarpa)

34. Symptom on young fruit caused by
Lymantriid larva (Porthesia scintillans)

35. Archips tabescens Walk
a Lepidopteran larva attacking young fruit

36. Adoxophyes privatana Walk
Lepidopteran larva attacking
new shoots & young leaves

37. Indarbela disciplaga Swinch
Frass left behind by stem borer (left)
larva within the stem (right)

38. Fruit wrapped to avoid insect and
disease attack

39. Propagation: Cuttings, air-layering,
or seeds

40. Bud grafting

41. Cantuman baji sisi
(Side veneer grafting)

42. Technique for planting star fruit on
ex-mining land

43. Popular Clones

44. Dome-shaped canopy of B2 clone (L)
Elliptical shaped terminal leaflet of B2 clone (R)

45. Young shoot of B2 reddish brown in colour

46. Flower on terminal branch of B2 clone
(light purple in colour)

47. Dome-shaped canopy of B10 clone (L)
Young leaves of B10 turned upwards (R)

48. Young leaves of B10 reddish in colour (top)
Flower on terminal branch purplish in colour

49. Differences between stamen length and stigma of
two clones B2 and B10

50. Dome-shaped canopy of B17 clone (L)
Leaf base of leaflets raised (R)

52. Various forms of canopy