Citrus, which originated in Southeast Asia, is characterized by fragrant flowers and edible juicy fruit. Today, the most important commercial varieties include oranges, grapefruit, lemons, tangerines and to a lesser extent, tangelos and temples. Oranges account for the greatest value in terms of production, followed by grapefruit, lemons and tangerines.
(Source: Agricultural Marketing Resource Center, Date accessed 27 March 2014)
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Citrus can be propagated by seed budding, grafting and marcotting. Commercially, seed budding, which is universally applicable to all citrus species, is the preferred method. Although grafting and marcotting produce satisfactory materials these methods are recommended only for small-scale propagation. Shield budding unites a desired scion variety with a suitable rootstock. Success depends on the skill of the propagation and the conditions of the scion and the rootstock.
- Must be compatible with the scion variety allowing good growth, long life, good yield and good fruit qualities;
- Seeds must be readily available, preferably high poly-embryonic to get uniform seedlings and with high percentage and germination;
- Must be adaptable to a wide range of soil depth, texture, structure, pH, salinity, moisture, and nutrient supply; and
- Must be resistant to soil-borne diseases, such as Phytophthora grimmosis.
Budwood should be taken from parent trees which:
- Hold a record satisfactory production over a period of a t least 5 years;
- Are free from systematic diseases; and
- Have true-type fruit characters.
Budwood should be plucked from green, vigorous, second-flush growth. Its leaves should be clipped and the budwood is collected. It should be immediately labeled, indicating the name of the variety, source of budwood, and date of collection. Only freshly cut budwood should be used. If it needs storage, it should be kept by wrapping it in moist sphagnum moss or similar materials, put in polyethylene bag and kept in a cool place. This will last for 10 days.
By means of shallow cultivation, the nursery is always kept free. Weekly, seedlings are sprayed with the appropriate insecticides to control pests and leaf cutting insects. Every 2 weeks, copper fungicide is mixed with the insecticide to control diseases. Once a month, at time of weeding, one (1) level tbsp 5 g urea is applied around each seedling.
From a budded plant, tape is removed 2 - 3 weeks after budding. If the bud looks fresh and green, the lower half of the tape is left intact until the bud begins to grow. When the budding reaches about 10 cm, lopping can be done to hasten growth. Only one vigorous scion should be allowed.
Cultural practices such as weeding, cultivation, watering and fertilization should be continued to promote the development of the plant. To avoid infestation, spraying of appropriate insecticide should be done every 2 weeks.
Planting can be done anytime of the year if irrigation is available. Balled or bare-rooted budlings are planted in holes big enough and always enriched with a handful of complete fertilizer, high in phosphorous. Topsoil is used to fill the holes and this is pressed down firmly to avoid large air spaces. Newly planted budlings should be watered immediately.
Planting of citrus follows a certain arrangement in which trees are set out in the orchard. Systems used include square, rectangular, triangular, and quincunx. Rectangular and square systems are to be used where intercropping is to be done.
In rectangular and square systems, the rows of trees are set at right angles to each other. In a triangular system, trees are set at the corners of equilateral triangle. In the quincunx system, four trees are set in a square and a tree is planted in the center.
Care for the Bearing Groves
Care for the bearing groves is observed through the following:
Irrigation. This is important to avoid water stress.
Trees are watered until the rainy season begins. Irrigation can be through furrow, hose, or sprinkle.
Fertilization. Plants need 2 - 3 fertilizer applications each year.
- First, when the rainy season begins;
- Second, during the middle of the rainy season; and
- Third, when the rainy season is about to end. Fertilizer can be applied or sprayed.
Fertilizer can be applied directly or sprayed.
Pruning means removing diseased anddead twigs, branches, and leaves which are unproductive and are less exposed to sunlight. Best time for pruning is during the dry season or after harvest.
A certain spray program should be strictly observed. Two or three types of chemicals against a particular pest should be alternated to avoid developing resistance of the chemicals.
Propping and Setting of the Windbreaks.
Ipil-ipil windbreaks on the windward sides of the orchard can be set up to prevent the crop from touching the ground and the branches heavily laden with fruits.
Pest and Diseases
- Many important pests limit citrus growth. A systematic virus-like disease called leaf molting with its insect nectar was responsible for the decline of more than half a million citrus trees.
- Efficient pest management simply requires an understanding of the nature and cause of diseases, conditions that favor the spread of the diseases and the most effective control measures.
- Knowledge of the most common and destructive insect pests therefore becomes vital. To prevent unnecessary injury to plants when using pesticides, make sure that instructions and recommendations in pesticide packages and containers are followed.
Periodically, sampling has to be done to check whether fruits are ready for harvesting. Generally, citrus trees start bearing fruits 3 - 5 years from planting and can be harvested 5 - 6 months from flowering depending on the species and the environment. Unlike other fruits, citrus does not ripen further after it has been harvested, so it is important that it is picked at the right stage of maturity.
Maturity indices include color, juice content, level of soluble solid (sugar), treatable acidity, and solids to acid ratio.
Best time to harvest citrus is from 8 a.m. to 3 p.m., when the dew has dried up and fruits have lost their turgor. Fruits, which are frigid, are easily bruised resulting in brown patches on the rind, which indicate direct injury to the oil cells in the rind. This lowers fruit quality.
The proper way to harvest citrus is by pulling or clipping from the stem. "Twist, jerk and pull", experts say, is the general rule. Use of hand gloves reduces to great extent injuries on the peel of citrus.
Canvas bags of suitable sizes with hooks at the bottom are best for transporting fruits to large, padded, field containers.
Source: Department of Agriculture, Date accessed 27 March 2014