CITRUS

Introduction and Importance
Swingle (1943) devided the genus citrus into three independent genra: Citrus, Poncirus and Fortunella. All three genra belong to sub-family Aurantiodeae of the family Rutaceae. Citrus cultivars are grown in varying quantities in countries with tropical or sub tropical climate. Citrus stands first in area and production among the worlds tree fruits. In Paksitan also, citrus fruits are the most important fruit crops grown on the ara of 160,000 hectares with production of 1.5 MMT annually. Citrus fruit is grown in all four provinces of Pakistan but Punjab produces over 95% of the crop because of its greater population, favourable growing conditions and adequate water. Citrus is devided into different groups Sweet oranges, Mandarine, Grape fruit, Lemon and Lime which are being grown commercially.

  Area And Production Of Citrus In Pakistan:

Major Citrus Growing Areas in Pakistan: 
Punjab Distt:      Sargodha, Sahiwal, Lahore, Sialkot, Jhang, Minwali, Multan, Gujranwala
NWFP:               Mardan, Peshawer, Swat, Swabi, Noshera, Hazzara
Sind:                 Sukkur, Khairpur, Nawabshah
Baluchistan:      Mekran, Sibi and Kech.

Varieties:
Following are the main commercial varieties:
Sweet Orange    Succri,. Mausami, Washington Navel, Jaffa, Red Blood, Ruby Red and  Valencia Late.
Mandarines        Feutrells Early and Kinnow
Grape Fruit        Mash Seedless, Duncan, Foster and Shamber
Lemon               Eureka, Lisbon Lemon and rough Lemon
Lime                  Kaghzi Lime and Sweet Lime

Propagation:
All the improved varieties are propagated by means of budding on rough lemons or sour orange. Rootstocks are generally grown through seed, T budding/T grafting are the usual method of citrus cultivars propagation. Budding may be done durng spring (Feb-March) and autumn (August-October) when bark slip freely from both scion and stock. Bud should be sselected from mature wood of productive and healthy trees. In sweet lime propagation through cutting is a common method.

Soil And Climate:
Citrus trees can be grown on a wide range of soils, including deep sandy loam, loam and clay loam. However, they do not grow well in very heavy, clayey, sandy, alkaline or water logged soils. Citrus fruits trees are grown in tropical and sub-tropical climate. Temperature is the main factor affecting, time of blooming, maturity, producting and fruit quality of citrus.

Pruning:
At the time of transplanting the top portion should be balanced with the roots by removing some of the leaves, if necessary. Annual pruning is done to remove dried, diseased and those branches overcrowding the top of the tree. For a young citrus tree to have good frame work, no branches should be allowed on the main stem and two to four evenly spaced main limbs should be selected to provide balanced frame work. In Pakistan however, no systematic pruning is followed except for removal of dried, diseased and unwanted twigs.

Water Management:
The preferred method of irrigation is a basin round each tree the size of. There should be channels connecting basins so that irrigation of fruits trees can be independent of the intercropped area between the tree lines which have different water requirements. Growth sensitive periods to water shortage are flowering time (Feb/Mar), fruit setting (Apr/May).

Fertilizers and Manures:

• Apply FYMs at the rate of 40 to 80 kg per tree during the winter season in Dec/Jan before flowering.

• Apply 3-4 kg SSP and 1.5 to 2 kg of Urea 15-20 days (Jan/Feb) febore flowering.

• Supply a further amount of Urea of 1.5 kg per tree after fruit setting (Mar/Apr).

• If necessary 1.5 kg of Potassium Sulphate may be applied at the time of applying FYM.

• Watering is essential after each application of fertilizer.

Pessts and Diseases:
Aphids: These are small brown coloured insects. They suck the sap from the leaves and branchesand cause great damage to trees and reduction of yield. Aphid attack is severe during Feb and April. Use Dizenon 40% or Eldrine 20%, 1 kg in 450 litres of water. Insecticides should not be applied within 6 weeks of marketing the fruit.

Citrus Leaf Minor: This attacks the leaves. the attacked leaves become curled and deformed. If causes great losses in growth and yield.Use Malathion 57 or Matasystox 50% at the rate of 500 grams in 450 litres of water per acre for its control.

Lemon Butterfly: This also attacks fresh leaves. It can be controlled effectively by using Malathion and Metasystox.

Citrus Whitefly: This attacks the fruits and causes great losses in yield and quality. This pest can also be controlled by using Malathion 57%. This should not be applied within 6 weeks of marketing the fruit.
Red Scales: These are sucking types of insects and cause great damage to kinnow and sweet oranges in Punjab. They can survive throughout the year. Use Parathion or Malathion at the rate of 752 grams in 450 litres of water per acre for its effective control.

Foot Rot: This is a fungus which attacks the root of the trees. Its attack is severe in poorly drained soils. The affected tree gradually dries up. Remove the soil from around the affected trees without damaging the roots and improve on farm drainage for its effective control.

Withertip: This disease is caused by nutritional deficiencies. The branchess and fruits of the affected trees start drying and the tree becomes uneconomical to maintain. Apply a balanced dose of Bordeaux Mixture 450 after cutting affected branches from the trees.

Citrus Canker: This is a bacterial disease. It attacks leaes and the fruits. It forms canker like spots on the leaves and stems of the fruit causing great reduction in yield and quality of the fruit. There is no effective treatment for this disease except to cut and remove the affected trees and spray Formaldehyde at the spots from where the diseased trees have been removed.

Harvesting:
Picking of citrus fruits is done almost throughout the year. The fruit should be picked when it is fuly ripe. It will not develop taste or sugar in storage after picking. The best method is to pick the individual fruit by holding it in one hand and cutting the stalk with a knife and collecting it into boxes or baskets to avoid injury to the stem. The average yield expescted from different types of fruits of various species are 500 to 1000 fruit per tree.

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