Growing Food: A Guide to Food Production

Spacing:

Type Distance (m) Trees/ha

• large varieties

large varieties

• small varieties


• 
  


• 
  

6

10

9

12

4.5 × 6

10

12

34.5

280

100

120

70

280–500

100

70

500 –1000

GROWTH CONDITIONS

Day length: day-neutral.
Growth period: the trees normally produce their first fruit in 3–6 years.
Temperature: growth is much reduced below about 13°C and virtually stops below
10 °C. Maximum tolerated is about 40°C. In order of their hardiness (tolerance to
cold), with the least hardy species (Citron) first: citron, lime, lemon, grapefruit,
sweet orange, sour orange, mandarin, kumquat, trifoliate orange.
Rainfall: 900 mm/a. minimum without irrigation, which is often used, especially for
young trees. Not suited to the humid tropics—high humidity increases damage by
pests and diseases. Mandarins are the species most adapted to high rainfall and
humidity.

trees, to form an open canopy. Suckers and dead wood should be removed.
Wind: citrus species do not tolerate high winds, so windbreaks should be provided
if necessary.

1800 m.
Pests: damage can be caused by: scale insects, aphids, mealy bugs, mites, thrips,
fruit flies, moth borers and the false coddling moth. It has been shown that
indiscriminate insecticide use can create more problems than it solves, discussed in
1J, page 78.
Diseases: Foot-Rot (Root-Rot) (Phytophthora spp.)—worse in high humidity and
in poorly drained soils. Sour orange and mandarin rootstocks show some resistance.
Gummosis, the exuding of gum, is also caused by Phytophthora.Tristeza Virus
(“Quick Decline”) is the most serious and widespread of the virus diseases. Can be
partially controlled with the careful use of insecticides in nurseries, Sweet Orange,
Rough Lemon and some Mandarin rootstocks, and burning of diseased or suspected
branches or entire trees. Citrus Scab is caused by the fungus Elsinoe fawceti,
controlled with copper fungicides (sprayed before and after flowering) and resistant
types. Worse in cool conditions. Sweet Orange and lime are very resistant; sour
orange, lemon and some grapefruit species are very susceptible. Melanose is
widespread. Brown, raised pustules on young twigs, leaves and fruits, especially on
mature trees of all Citrus species. Controlled with copper sprays, remove all
dead/diseased wood.

Orange – small varieties

Mandarins – marcotts

Pomelos – large varieties

Limes – grafted –

Pruning: as a minimum, this should be done in the nursery and on 2 3 year-old –

Altitude: mainly from 0 600 m. On the equator, they do not grow well above about –

GROWING FOOD – THE FOOD PRODUCTION HANDBOOK 255

• Grapefruit – small varieties & grafted