|"The guava tree, which gives so much and asks for so little, surely deserves greater attention and cultivation".|
|Betty Molesworth Allen, Malayan Fruits|
The guava is normally cultivated for its fruits. However, guava fruit is very delicate and highly perishable, making its marketing as a fresh fruit very difficult. Present uses of guava are associated with the processing into a wide range of canned products such as fruit slices in syrup, guava jelly, jams, juice and nectar.
The potential for a guava industry in Malaysia is excellent. Present tariff on imported fruits is high and the public has developed the taste for local fruits as substitutes. The guava is by far a more nutritious fruit than most of the imported ones in terms of vitamin A and C content. Although canned guava may lose about 50% of its vitamin C during heat sterilization, the products still contain higher vitamin C than most imported fresh fruits. Dehydrated guava juice powder was used as a source of vitamin C to fortify rations of Allied troops during the Second World War.
A brief description of some of the promising varieties is given in Table 1.
|Variety||Fruit size||Appearance||Flesh colour||Seed||Taste||Products|
|GU 3||large||Oblate, grooved||white||abundant||non-acidic||fresh fruit, juice|
|GU 4||medium||elongate, smooth||white||abundant||non-acidic||fresh fruit, juice|
|GU 5||large||smooth, round||red||abundant||acidic||juice|
|Bentong seedless||medium||irregular||white||absent||non-acidic||fresh fruit, canned slices|
Soil and Climate
Guava can be grown in a wide range of soils, but does best in deep fertile and well-drained loams. It can tolerate a wide range of pH from 4.5 - 8.2. Waterlogging, however, adversely affects the growth. Although guava can tolerate drought conditions much better than other tropical fruits, an annually even distribution of 100 - 200 cm of rainfall is preferred for good growth. The tropical climate of Malaysia is considered excellent for guava cultivation.
Forested areas should be cleared of all shrubs and trees and the ground ploughed in. In areas where the earth is extremely firm, deep cultivation using tractor tines is recommended to break up the subsoil. Drains have to be constructed where the water table is high.
The recommended planting distance is 15' x 15'. This gives about 193 trees/acre. The field should be limed and the planting distance measured out before digging the holes. The holes should be at least 1.0 cu. ft. in size depending on the firmness of the soil. In planting very large acreages, tractor-operated augers should be used for digging the holes.
Guava is a cross-pollinated crop and as such, propagation by seeds will not breed true. Vegetative propagation for this crop is relatively easy and is a common practice in ensuring true-to-type progenies. Three techniques are normally used for guavas, namely, cuttings, air layering or marcotting and budgrafting.
This method is simple in technique but variable in success. The shoots are partially pruned of leaves and cut to lengths of six to eight inches. The cuttings are inserted (proximal ends) into sand beds. The soil medium should be kept constantly moist. Rooting should occur after 12 weeks.
Air layering or marcotting
A young shoot of about 1.0 cm in diameter is selected and a ring of the bark tissue (3.0 - 4.0 cm wide) is removed at the base of the shoot. Hormone dust is applied to the wound for induction of root formation. A handful of moist top soil is then placed around the wound and a polythene sheet and strings are used to secure the ball of soil around it. Rooting occurs within three to five weeks in successful marcots. The shoot can then be cut and the plastic sheet removed before planting. In Malaysia, marcotting for guava has been limited in success and is not commonly used.
This method is most commonly used under local conditions. The advantage of this is that a higher percentage of success can be obtained and more plants can be produced from limited parental materials. However, there is a need to prepare the rootstocks for budding. Guava seeds can be easily germinated in 8" x 12" perforated black polybags for this purpose. Three seeds are sown into each bag to ensure that at least one plant will survive. The plants are ready for budding when the stem at the base is as thick as a pencil.
A 1.0 cm x 3.0 cm incision is first made on the bark of the rootstock and the flap gently peeled away. A similar size bud patch from the scion is then inserted into the cut. The scion patch is firmly secured with transparent budgrafting tapes.
The tapes are removed three weeks after grafting. In another three weeks, the grafts are inspected and where the bud patch survives, the rootstocks are cut back or 'dehorned' to about 4.0 - 5.0 cm away from the bud patch. This is to stimulate the bud to 'break'. The plants can be field transplanted two or three months later. Lateral shoots originating from the rootstocks should be removed in the meanwhile.
The fertilizer schedule for guavas suitable for local conditions is indicated in Table 2 (after Kementerian Pertanian dan Pembangunan Luar Bandar). The compound fertilizer recommended is a 28:9:9 composition of N:P:K. In addition, guavas have been known to respond well to farmyard manure and composts, and an application of 50 lb. per acre prior to planting is recommended.
Fertilizer application should preferably be made every four months to coincide with the stages of heavy nutrient demand. There are normally three peak harvests over one year and it is recommended that the timing of the application be scheduled at one month prior to the new flush of flowering. The dosage of fertilizer per annum must be equally split into three parts for each application.
|Plant age||lb/tree/annum||N/tree/annum (lb.)||P,K/tree/annum (lb.)|
Training and Pruning
It is an important practice to train the trees into establishing a desirable bush-shaped canopy on a single erect stem to control the height and spread of the tree for convenience of harvesting and also to increase the size and quality of the fruits. Pruning is done from time to time on water shoots and suckers arising from the base of the rootstocks, as they are not of the desired material.
Guava is best trained in an open-centre system. The main erect trunk of the young plant is cut back to about 50 cm above the ground at a point just below a bud. Three or four shoots (laterals) are permitted to grow from the main stem just below the cut end and they will form the basis of future branches. These laterals are allowed to develop to about 25 - 30 cm long and then pruned, inducing production of the secondary branches which will carry most of the fruits. Guavas trained on the open-centre system in India have significant increase in yield and fruit quality as compared to unpruned trees.
Budgrafted trees often begin to bear about six months after transplanting in the field. The trees at this stage should not be allowed to be overly heavy in bearing, as this will have adverse effects on their vegetative development in the later years. Pruning of fruitlets and flower buds is recommended for reduction of the crop in the first year of bearing. In the second and subsequent years of cropping however, fruit thinning is not necessary. Under favourable conditions, the yield increases until the trees reach full bearing at eight years and from then on, production continues for fifteen years or more.
Yield taken on two-year old trees in Serdang of three varieties of guava indicated that there are three main peaks in the annual cropping pattern. Although generally regarded as a non-seasonal crop, the yield in between the peaks are low and often negligible. Preliminary observations showed that flushes of flowers appear at the decline of each peak of bearing, the fruits of which contribute to the following season's harvest.
The most promising varieties are GU 4 and GU 5. Two-year old trees of these varieties produce fruits close to 10 tons/ha/year. GU 3 yields only about half as much. In addition, the seasonality of fruit production for GU 5 has a wider spread than the other varieties. indicating that fruits of the GU 5 are more often available. This is an important criterion in considering cultivars for processing to ensure continuity of supply of fruits to the factory.
DISEASES AND PESTS
This disease on young guava fruits is especially common on trees which are poorly managed and are weed infested. Round, brown and raised corky scabs caused by Pestalotia sp. are found on the surface of the fruit, giving it a mottled, unattractive appearance. In less severe cases, the fungi does not cause very extensive damage to the fruit and it may still be consumed after removal of the skin. In serious infestations, however, the young fruits remain underdeveloped and may eventually abort.
Keeping weeds under control is an effective means of reducing the incidence of this disease.
The symptoms of the disease appear mainly on the leaves as reddish-brown, round, powdery colonies. This occurs most frequently in damp, poorly-ventilated areas where weed management is poor. The causal agent is the Cephaleuros algae and may not be the cause of alarm if the infestation is slight. However, in more severe cases, premature leaf fall will occur, resulting in a marked decrease in yield.
Regular pruning of the dense foliage and effective weed control will provide ventilation that checks the incidence of the disease. Coprantol with Arbolineum (white oil) mixed in the proportion of 1:80 sprayed at 0.2% bi-weekly until infestation disappears is recommended.
Oriental fruit fly
The fruit fly is the most important pest that results in insurmountable damage on guava fruits. The species that is commonly found in Serdang is Dacus dorsalis Hend. Another damaging fruit fly, Anastrepha striata, which is widespread in Surinam and some parts of the United States has not been recorded in Malaysia.
The damage is caused by the adult female flies, which deposit the eggs in the maturing fruits. The point of deposition is noticeably marked by the small dark depressions on the surface of the fruits. Development of the larvae when the fruit ripens causes extensive damage and soft rot of the fruit.
To control the infestation, in part at least, fruits should be picked green, when they are still very firm. It is not probable that the fruits are infested at this stage, but even if so, immediate processing will destroy the eggs before the larvae can develop. Over-ripe fruits should not be littered in the orchards as these act as food base for the larvae development of the flies. Sanitation of the orchard at all times is important in reducing the population of the pest. Fenthion (Lebacid) at 0.1% sprayed four weeks before fruit ripening gives very good control.
The larvae of this Lepidopteran feed on young shoots and leaves and form a webbing at the terminus of the shoot before maturing into the adult. The infestation is observed to be seasonal and can be extensive if uncontrolled.
Rogor 40 at 0.1% concentration is very effective in the control. A bi-weekly spray until infestation disappears is recommended.
Mealy bugs are whitish, fluffy insects that cause damage to young supply shoots and leaves by sucking the sap, resulting in the dieback of the tender shoots. The damage is not normally alarming. Control however, can be effected with the use of Malathion or Arbolineum at 0.1% spray.
Helopeltis s. damage
The symptoms of damage are angular necrotic patches on leaves and shoots caused by the secretion of insect toxins in the feeding punctures. Control measure using Rogor 40 is very effective.
The symptom is a dry rot appearing as a band around the lower half of the fruit, often accompanied by splitting of the skin. Pestalotia has been isolated from the infected area, but this was believed to be a secondary infestation. There appears to be some varieties, particularly an Indonesian cultivar with pyriform fruits, which are very susceptible to this disorder. The cause of this phenomenon is not clearly understood at present, but is currently under investigation. The contemporary belief is that it is caused by water stress.
Allen. B.M. (1967) Malayan Fruits. Donald Moore. Singapore. 245 pp.
Chan, Y.K. and T.S. Tee (1976). The cultivation of guava (Psidium guajava L.) Malaysia. Mardi Report No. 45. 23 pp.
Kementerian Pertanian dan Prembangunan Luar Bandar (1975). Report of the Committee on Fruits and Vegetables. Vol. 1. 246 pp.
Mallik, P.C. and D.L. Singh (1960). Deficiency symptoms of nitrogen. phosphorus and potassium in guava. Indian Agric. 4: 44-9
Singh, R.G. and S.N. Dafe (1971). Micronutrient deficiency in Mango (M. indica L.) and guava (P. guajava L.) Allahabad Fmr. 45 : 479-83.
Tingwa, P.O. and S. Abbadi (1968). The vegetative propagation of tropical guava (P. guajava L.) in the Sudan. Sudan Agric. J., 3: 12-20.
Van Brussel. E.W. and G. Van Vreden (1969). Studies on the biology, damage caused and control of the guava fruit fly, Anastrepha striata in Surinam. Surinam Landb. 16: 110-22.
DATE: February 1984
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