FARMER'S BOOKSHELF

An information system of tropical crops in Hawaii
Department of Tropical Plant & Soil Sciences
University of Hawaii at Manoa



Guava

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Information from this publication:

Guava (Psidium guajava L.) in Hawaii--History and production. 1983. G.T. Shigeura and R.M. Bullock.


Other Links

Guava. Julia Morton.
Hawaii Guavas. Hawaii Agricultural Statistics Service.
Tropical Guava. California Rare Fruit Growers, Inc.


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Botany

The guava is in the Myrtle family (Myrtaceae), which can be easily identified by flowers with long conspicuous stamens and yellow anthers.

The guava fruit is a berry with a thick pericarp and fleshy seed cavity. The fruits are soft when ripe, making postharvest handling difficult and critical. Poor handling of the ripe fruit can result in great losses in the field and factory where decaying and damaged fruits are discarded before processing. When these ripened fruits are further allowed to be exposed to the hot sun, the guava flesh becomes very soft and mushy. These fruits become difficult to puree in this condition, possibly due to actual chemical breakdown in the tissue.

The flesh color of the fruit is becoming increasing important as the use of coloring dyes in food products is being restricted. Fortunately, in Hawaii, the 'Beaumont', selected from the wild, has the desired pink flesh color. Flesh color of guavas from the wild range anywhere from white to yellow to salmon-orange and pink, all of which blend into an unattractive yellow-orange product. Wild guava fruits need to be blended with the pink to produce nectars with acceptable color.


Photos of guava.


Climatic Requirement

The guava is a hardy shrub that has acclimated itself well to the various conditions at the lower elevations in Hawaii, where it is still considered a noxious weed. It is a serious pest in pastures, especially where no weed control is practiced.


Wind
The guava tolerates and can withstand strong prevailing winds or winds of hurricane velocities. Its root system is a fine mat supporting the tops and requires a tremendous horizontal wind force to uproot the tree. In addition, the guava wood is strong and flexible and pliable, enabling the tree and its branches to bend in a whiplike fashion in a strong wind.

Growth and fruit production can be reduced when the trees are grown in areas with constant prevailing winds of 10-15 miles an hour. In such situations, the trees will grow and develop away from the wind with short, stubby limbs facing the wind. These branches perform as a windbreak, protecting and permitting the leeward branches to develop. When such growth is evident, a low windbreak without much lateral growth can be used along the field edges. A larger orchard extending over 150 meters (500 feet) in length or width will benefit from the use of tall columnar or upright trees on the edges and possibly within the field.


Rainfall
In Hawaii, guava trees are found growing in the 500-cm (200-inch) annual rainfall belt with continuous freestanding water, as well as in desertlike areas found at Kawaihae and Ka'u, where annual rainfall is less than 25 cm (10 inches). In these areas, the trees are not too productive, seemingly only surviving and demonstrating the ability to withstand extreme conditions in water supply.

In areas that tend to be too dry for crops during the summer months, irrigation is advisable. Guava growing on pahoehoe or a'a lava, even in the Hilo area where rainfall can be 300 cm (125 inches) per year, will respond to additional water during brief dry periods. Since water supply throughout the production cycle from flowering to harvesting is critical, irrigation should be included in any commercial planting of guavas.


Temperature
Recorded air temperature at weather stations in most areas in Hawaii is often assumed and used, agronomically, to indicate the radiant energy received from the sun and used by crops. The relationship is not absolute, but is the easiest to obtain and sometimes the only record available where no pyronometric records are kept.

However, due to the constant trade winds and a great body of tempering ocean water surrounding the islands, the relationship between elevation, temperature, and radiant energy is constant and very highly correlated. The higher the elevation, the colder and cloudier it becomes. Assuming the physiological activities within plants are affected by elevation and its accompany temperature and radiant energy, then we can relate tree performance, i.e., growth and yield, to elevation.

In Hawaii, this relationship is easier and more reasonably drawn since air movement over the islands is relatively constant trade winds and is not affected in the varying air movement usually obtained over continental land masses. Consequently, temperature, radiant energy, and elevation will be considered synonymous and interchangeable and will be used as such in this text. Exceptions to this general rule in Hawaii are land with southern exposures where cloud and fog overcast is at a much higher altitude, permitting a longer and more intense light-exposure period below to enable production at a higher elevation.

Field observations and some data now available in Hawaii suggest that minimum temperatures can be critical. Guava trees growing at lower elevations are generally vigorous and large with a heavy set of fruits, while at 650 meters (2000 feet) or higher become very erratic depending on temperature differences due to cloud cover. Along the Hilo coast where cloud cover sets in at 490 meters (1500 feet), along the Kona coast at 650 meters (2000 feet), and along the Ka'u coast at 820 meters 92500 feet)--with it southern exposure--seem to be the upper elevations where guava can set fruits.

In the higher areas with cloud and fog overcast, the trees and leaves are small with interveinal tissues turning red to purplish-red during the winter months. Further preliminary evidence and field data gathered at Hamakua, Hawaii, at 640 meters (1900 feet), where recorded air temperature goes down to 7C (42F) in February, indicate that flowers initiated during this cold period abort before or after anthesis to result in very low production of fruits in the summer months following.

The guava can be economically grown at elevations in Hawaii where pineapple, macadamia, coffee, papaya, mango, and banana are profitably grown. Except for a few areas with a definite southern exposure, most of the areas above 60 meters (1800 feet) in Hawaii are not suitable for growing guavas profitably.


Soil

Soil, per se, as a requirement of growth is not a major consideration in Hawaii. Guava is found growing as a weed on every conceivable soil type from the basic a'a and pahoehoe lavas found in the Puna and Kona areas to land types useful only as conservation, forest reserve, or pastures. However, an improvement in management and cultural practices in marginal areas results in increased growth and production. Its hardy and versatile characteristics make the guava a plant that is difficult to control as a weed and, thus, one of the easiest crops to grow commercially. Hence, commercial operations in guava can be profitable on almost any land with adequate management.


Land Preparation

Land preparation should be minimal in the reuse of abandoned sugarcane or pineapple land, depending on the weed or brush conditions. When the area is overgrown with tall weeds, the field should be plowed under for proper weed disposal. At the same time, if soil calcium or magnesium is low, calcium carbonate, calcium silicate, dolomite, or magnesium oxide can be worked into the soil at plowing.

On land with a slope exceeding 15-20%, shallow contour rainwater drain ditches that will not interfere with field operations should be put in. A cover crop of low grasses, clovers, or some other leguminous ground covers may be used to reduce or eliminate the need for drain ditches and to minimize weed control.

Preparation of pastureland can be handled in a similar same to eliminate old cattle trails and ruts and to permit the safe movement of mechanical equipment. Fertilizer additives for calcium and magnesium nutrition can also be plowed in at this time.

Preparation of a'a lava land should be more carefully handled though clearing costs will be slightly higher. Forested a'a lands have organic materials formed by the years of plant growth interlaced in the top foot or two of lava rocks. The total amount of these materials is usually small, but since this is the only part of this soil type that holds water and has the cation exchange capacity (CEC) to hold on to the nutrients, it should be guarded and properly placed to permit its better utilization. Consequently, in clearing a'a land, the organic fraction should be initially bulldozed into piles or strips, and the remaining terrain should then be brought to a reasonable level by ripping the solid rock base that is usually beneath the a'a.

Finally, the stored "topsoil" material can then be brought back to cover the already leveled terrain to help support the growth of trees. This procedure is much better than clearing land in one operation, and thereby burying the organic matter in the low hollows and beyond the reach of the new tree roots. Area cleared in the latter manner will require topsoil or cindery materials on the surface to permit better tree growth.

Pahoehoe lava land is the least desirable and should be avoided in growing any crop, including guava. Pahoehoe land is sheet lava that meagerly supports vegetation in the large crevices and low spots where fine cindery material may have accumulated. In the Hilo area, where rainfall is high and good friable farmland is not available at a reasonable cost, small growers are forced to use pahoehoe land for guava cultivation. In such situations, the land is usually ripped using a heavy tractor to create trenches or areas of loose rocks of various sizes down the tree rows. The trees are then planted in these ripped strips with the addition of about a cubic foot of cindery material or potting soil.

With proper cultural care, the guava trees will do reasonably well in these ripped areas and produce fruit profitably. However, to support guavas ideally on pahoehoe, the land should be thoroughly ripped throughout the area to a depth of about 2 feet with additional cindery materials to permit adequate lateral extension of the root system. The cost of such preparation will be high, but will pay for itself in time.


Nursery Tree Propagation

Guava tees for eventual field planting can be nursery propagated by grafting, budding, stem cuttings using succulent green stems, or root cuttings.


Grafting or Budding
Seedlings for grafting or budding can be propagated using seeds of guava from the wild or seeds from clonal trees. There is no evidence now to indicate that seed source for the production of rootstocks is important. Fresh seeds should be obtained form clean, ripe fruits, thoroughly washed to eliminate the pulpy materials clinging to the seeds and treated with a fungicide to prevent damping-off before planting in the seedbed. If damping-off is evident as the seedlings emerge, the surface of the media and the seedlings should be treated again with a fungicide.

When the seedlings are 3 to 4 cm (1 1/2 inches) tall, they should be planted in small containers for later nursery row planting, or they may be planted in 4-liter (1-gallon) containers for the propagation of large seedlings for later use in budding or grafting. Whether to use the nursery row or container-grown seedlings in tree propagation is a matter of preference, convenience, and cost. The result should be producing healthy seedlings. Healthy, succulent, and highly vegetative seedlings thus propagated can be grafted or budded when they are about 1 cm (1/2 inch) in diameter, 25 cm (10 inches) above ground level. The guava can be grafted or budded using any accepted method.

The Forkert, a modified patch bud method, has been found ideally suited to guava. A patch size approximately 1 cm (1/2 inch) X 1 1/2 cm (3/4 inch) seems to take better than when a smaller patch or bud is used. The trees from which buds are taken should again be highly vegetative with lush, succulent growth to permit easy separation of buds from the stem. Buds on brown stems with leaf scars hard and grown over are better to use than younger buds with leaf scars still distinct and soft. In Australia, small oval punches about 1 cm on the long diameter are being used on macadamia and guava to remove buds that are fitted into punch-holes similarly created for a perfect match on the stock seedlings.


Green Wood Stem Cuttings
Green wood stem cuttings can be used in cutting propagation. Use a three-node stem cutting with two leafy nodes and a basal node without leaves, or a similar cutting without a basal node. Use an intermittent mist chamber with bottom heat and media temperature maintained at 27C (80F). The cuttings thus prepared should be treated with a root hormone mixture of 2% indolebutyric acid (IBA) suspended in fine dolomitic limestone or insecticidal talc. The concentrations of IBA from 0.25 to 2.00% used in the same series of tests did not affect the rooting percentages. However, the development of the root mass was significantly better with 2% IBA than at the lower concentrations.

The cuttings should be adequately rooted for container transplanting after 6 to 8 weeks in the mist chamber. The transplant containers need to be large enough to nurse the cutting for about 4 to 6 months until the plants are ready for field transplant. A good well-drained potting soil should be used, and water supplied adequately. The trees can be easily damaged and growth delayed when plants at this stage are mishandled.


Root Cuttings
Roots are an excellent source of propagation material from the fields since the surface roots under normal field conditions readily develop shoots when exposed to light or when slightly injured by herbicides or moving ground equipment. Trees propagated in this manner are just as good as trees propagated by any other means, but the method is applicable only if the parent orchard was started from cuttings rather than having been budded or grafted on a seedling rootstock. However, this method of propagation is quite inadequate in a large nursery operation since the material source is low.


Seedling Orchard
Although this method is not a recommended practice, for economic reasons seedlings can be used to establish an orchard. The design of planting then needs to be different since most of the seedlings will not be like the parental type in yield, taste, and fruit flesh color. When the deficiency becomes obvious, these should be eliminated or topworked with either clonal 'Beaumont' or 'Ka Hua Kula' as early as possible.


Dwarf Trees
Dwarfing rootstock trials should be continued using the forma Cujavillus and strawberry guava. Preliminary trials indicate this work should be reinitiated.


Orchard Management

Orchard Design

Clonal orchard. The planting design of any crop should be determined only after considering the tree's growth habit, its response to pruning, harvesting method, and other cultural methods to be used in the care of the orchard. Fortunately, the guava can be pruned and trained to any dimension or pattern the grower wishes.

It can be trained into a large, low-hanging bush to permit hand harvesting or into a small tree with a single trunk to permit mechanical harvesting. A properly pruned and trained tree can be confined to a foliage canopy approaching 4 meters (11 to 12 feet) in radius. This radius can be maintained by judicious pruning in conjunction with crop cycling.

To maximize production, tree limbs must be developed to cover the land area as completely as possible. This can be done in time by pruning and tree training. However, a better way to do this is initially to reduce the "blank" areas between the trees in the orchard by planting them on an equilateral triangle (quincunx) system and at a desired distance between trees rather than on a square design.



Table 1.  Equilateral triangle (quincunx) design data.

            Distance (ft.)  Distance (ft.)    No. of    No. of
               between         between        trees     sq. ft.
Design no.   trees in row        row         per acre   per tree

1                 25            21.7             80       543
2                 24            20.8             87       499
3                 23            19.9             95       458
4                 22            19.1            104       420


The spacing between trees on any given farm is a decision for the individual grower to make after he considers the production potential of his land based on fertility, availability of water, intensity of sunlight, wind exposure, etc. However, Design No. 1, with 25 feet between trees and 21.7 feet between perpendicular rows, optimizes production. If the grower prefers, for conditions of his own, closer spacing and more trees can be used.


Seedling orchard. For economic reasons, an orchard established with seedlings should be planted with an operational area of 24 to 25 feet between rows with trees planted in-row at 8- to 12-foot spacing. The trees should be rouged out or topworked as soon as off-types develop, or as cash flow is available for topworking of undesired trees.


Fertilization

Leaf analysis can be used a guide to guava fertilization. Recommended leaf values are:


Table 2.  Tentative leaf analysis guide to guava fertilization.

            Optimum
Element      value

Nitrogen     1.70%
Phosphorus   0.25%
Potassium    1.50%
Calcium      1.25%
Magnesium    0.25%
Sulfur       0.18%
Zinc         20 ppm
Manganese    60 ppm
Copper        8 ppm
Boron        20 ppm
Iron           --
The guide values are tentative and should be refined with further data. The table gives the elemental values as % or parts per million (ppm) of the oven-dried leaf material.


The index leaf is the four leaf in a whorl of leaves of an actively growing major terminal, counting the first expanding young leaf in the whorl as No. 1. A 10-leaf sample should be taken at random from 10 trees in an area where the information is desired. If plant growth and appearance in the area are uniform, one sample is sufficient. More samples from an area are suggested if differences are visible.

If deficiencies are indicated by symptoms or leaf analysis, corrective measures should be taken immediately. If not, because of the crop cycling procedure, whatever fertilizer program is suggested should be applied after the completion of the current crop for the benefit of the succeeding crop. Recent preliminary data and observations indicate that calcium is related to the firmness of fruits and blossom-end rot of matured fruits. Leaf calcium level to correct this condition appears to be 1.25% or higher.

The lands now used for guava cultivation are either old, marginal areas where sugarcane or pineapple was cultivated, or virgin lava forests that were considered commercially unproductive until recent times. In either case, fertility of these lands should be monitored before planting and if called for, calcium or magnesium should be incorporated in the soil at preparation time.

The most economical calcium sources are calcium carbonate from beach sand, calcium oxide from burnt lime, and calcium hydroxide from hydrated lime. These can be plowed in before planting to supply the need for calcium. For magnesium needs, magnesium oxide or dolomite should be used.

There is no data to indicate that soil pH obtained under Hawaiian conditions (pH 3.5 to 7.0) is a factor in guava fertilization and production. Until experimental data indicate otherwise, pH as a factor need not be considered for the soil types used to grow guava in Hawaii.

When soil analysis records are available, the values given in Table 3 can be used to better approximate the nutritional need that must be met by the soil.



Table 3.  Optimum nutrient levels for Hawaiian soils (parts per million).

Element   Optimum    Conditions

P          40-50         --
           25           low

K          200           --

Ca       2000-4000   humid soil
           2000      semidry soil

Mg       1/5 of Ca       --


An orchard, during the first few months in the field when leaf sampling is not possible, should be adequately fertilized at a 2- or 3-month interval with a complete fertilizer including calcium, magnesium, and the trace elements to establish the basic foundation of structural branches as soon as possible. Leaf sampling should be applied as indicated. At the end of the 2nd year or at the beginning of the 3rd, the trees can then be put into production cycling.


Pruning

Within the first 3 to 4 months after field planting, the guava tree needs to be pruned and trained to allow maximum production of fruit as soon as possible and at the lowest possible cost. Operation costs of herbicide, pruning, and harvesting can be considerably reduced when orchard trees are trained to a single upright stem. The fruit-bearing lateral structural branches emerge from the single stem beginning at a height about 60 cm (2 feet) above ground level rather than at ground level as usually is the case in an untrained tree.

As the trees become older and better able to support the scaffold branches, the main trunk can be extended upwards by cutting off the lower interfering scaffold branches. Training to establish this single stem can be further advanced into the nursery propagation stage by pinching off laterals on the young stem to permit a single upright development. In getting this system of growth to develop properly, it may be necessary to hold the trees upright by staking in the early stages of training, especially on a tree propagated as a cutting.

A single-stem tree is desirable whether harvesting is done by hand or with mechanical tree shakers. In the latter method of harvesting, depending on the machine used, the trunk height may need to be extended to accommodate the equipment. All trees should be trained to make operational movement at the base of each tree comfortable and easy.

Lateral structural branches should be pruned and trained to radiate outwards from the central axis of the tree. Branches that do not fit into such a pattern should be gradually removed. A lateral branch that begins to extend beyond the confines of a symmetrical tree should be cut and eliminated at its junction with another more confined branch. With this manipulation, the remaining side branch becomes the branch terminal to support the tree in fruit production until it, in turn, may be eliminated because of overextension.

On trees that are harvested by hand, vertical branches that extend skyward beyond the reach of the hand harvesters should also be cut at the junction with another more confined branch. The remaining limb, if necessary, should then be bent into a horizontal or at least a nonvertical position.

Guava trees are pruned to increase yield and to reduce the total cost of field operations by eliminating obstacles and branch hazards, allowing easier movement around the trees. Except for tree training to a single trunk and canopy development, pruning thereafter is done only in conjunction with crop cycling. The messy, distracting small twigs within the crown of the tree need not be eliminated since these branches can bear fruit to add to the total tonnage produced. In time, these branches will dry out and save the grower some unnecessary trimming cost.


Crop Cycling

The principle of crop cycling is to harness the natural flowering and fruiting tendencies of the guava and contribute to increased yield and profitability. The concept is based on the guava flowers are borne only on new, succulent, vigorously emerging vegetative growths. These new growth flushes can be either new emergences of lateral bud on older stems within the crow or extensions of already established terminals of various size and vigor.

The seasonal harvest pattern of wild guava in Hawaii is a response to growing conditions naturally occurring here. Being situated in the northern hemisphere, Hawaii's cool winters begin about December 1 and extend to the end of March, and its hot and drier summers extend from June 1 to the end of August. At the same time, except in leeward Kona on the island of Hawaii where the high mountains contribute to a rainfall pattern reversal, rainfall is heavier during the winter months and lighter during the summer months.

There are two short periods during the year when the temperature and available water from rainfall following a period of drought are conducive to the natural triggering of massive vegetative growth with its development of flowers and subsequent fruit-ripening approximately 5 months later. The first of these periods begins about February 1 and the second about August 1. The total rainfall in February is somewhat less than either January or March, contributing to a drier and warmer period in February. When this warmer period is sustained and with timely rainfall, a massive flush of vegetative growth with its flower buds takes place, resulting in a heavy harvestable crop of fruits in about 5 months.

The second period when vegetative growth is again triggered begins about August 1 after the dry summer months. The consequence of these reactions to water and temperature at the critical periods is two distinct guava harvest seasons, the February and March flowers producing fruits to mature in August through December, and the August flowers producing fruits in January through April.

This natural fruiting tendency of guavas growing unkempt in the wild is increased, reduced, delayed, advanced, or shortened depending on the yearly weather change. The resulting dilemma of the factory operating sporadically only a few months of the year is obvious, necessitating part-time employment or a drastic shifting of full-time employees in the total work force. With the advent of commercial cultivation of guava and the attendant care given to the orchards, the delivery of fruits at the factory has now extended over a longer period for a more continuous operation even though it is, as yet, very low in some months. With complete use of the crop cycling technique, operations at the factory should become constant throughout the year.

Production on a large plantation on the island of Kauai is now being completely cycled to permit year-round operation with continued production of fruits in the field contributing to efficiency in the output of purees in the factory to be marketed in an orderly manner. Increased efficiency and cost reduction in factory operation can become an important item in the cash flow ledger. In addition, a systematization of field operations enables the formation of separate field work crews for pruning, herbiciding, fertilizing, and harvesting to increase efficiency, resulting in large cost savings.

The production of guava fruits can be cycled by systematic cultural manipulations, i.e., pruning of trees, fertilization, irrigation, or defoliation. All of these methods singly or in combination are effective in influencing flower bud formation by forcing the trees into vegetative growth. Urea at 2 lb/gal with added surfactant has been found very effective in defoliation.

However, since urea at that rate induces excessive vegetation, the recommended defoliant mixture per 100 gallons (378 liters) of final spray solutions is 2 1/2 pints (1200 ml) ethrel, 50 lb (12 kg) urea, and 1 quart (900 ml) surfactant. Its use on guava has been cleared by the Environmental Protection Agency (EPA) and the State government under the Hawaii Pesticide Law 24C registration, SLN No. H1800012.

The recommended method in crop cycling procedure should be instituted immediately after a crop is harvested or when the next cycled crop is desired. A crop harvest will begin approximately 7 months after cycling treatment. The cycle period is somewhat shortened to 6 1/2 months if the fruit formation and enlargement period straddles the summer months, and lengthened to 7 1/2 months if it straddles the winter months.

The trees should initially be pruned. On a very lush tree, about 25 to 30% of the undesirable limbs can be eliminated. On a less vigorous tree, only about 20% of the undesirable limbs need to be eliminated. After this severe pruning, fertilize at the rate of about 3/4 pound per inch in diameter of tree trunk as indicated by leaf analysis. The amount of fertilizer to apply will vary with leaf analysis information, the area being farmed, the available climatic conditions, and the grower himself. Water, if available, should be applied at this time. Defoliation beyond these treatments further adds to the precision in fruit set. The guidelines offered here should and will change with experience and as the needs differ.

The use of defoliation can sometimes be lessened or reduced. Reduced use of ethrel can be very effective on a hot, dry, or sunny day. However, weather conditions, especially temperature and rainfall on the spraying days, can be very fickle, hour by hour, and considerable caution needs to be taken when dosage manipulations are to be attempted. Then, too, while defoliation is not harmful to a tree, when ethrel is used continually at high concentrations, there may be an accumulation of ethylene within the tree, which may cause overblooming and a resultant poor fruit set.

With this in mind, the rates of ethrel and urea can be reduced. These additional treatments may be used under differing conditions and are given below:


Treatments (100 gallons of spray mixture)

(a) 1 quart (900 ml) ethrel; 24 lb (10.9 kg) urea; 1 quart (900 ml) surfactant.

(b) 1 1/2 quart (600 ml) ethrel; 24 lb (10.9 kg) urea; 1 quart (900 ml) surfactant.


The crop cycling procedure disrupts the normal production tendencies of guavas obtained under natural circumstances. In response to natural climatic conditions, the guava produces a light crop of fruits in the spring months and a heavier one in the fall. The total yield under these conditions is relatively low since it is a simple response to two growth factors-sunlight and water.

To force the tree into increased production by satisfying its other needs--fertilizer, supplemental pruning, and defoliation--is good farming since the cycling procedure extends the production potential of guava beyond its natural tendency. There is no current indication that crop cycling or defoliation is detrimental to the health of the trees nor are there grounds to expect such a consequence. Until data are gathered to support this negative thought, crop cycling should and can be employed in guava production. However, work with growth regulators should be continued.

As in other tree crops, flower bud and fruit abscission in guava is a continuing problem from the time the flower buds emerge to the time fruits are about 1 inch in diameter. Preliminary observation suggests that as many as 90% of the flowers initially set do not form harvestable fruits. Although the exact causes are not known, drought and erratic rainfall appear to be the definite factors in this loss. Considerable research with growth regulators is indicated.


Harvesting

Although harvesting needs to be mechanized as the industry expands, at the current time harvesting is done by hand using pails for temporary storage of fruits. Filled pails are emptied into lug containers, which in turn are loaded onto trucks to be hauled to the factory.

During the height of the season, harvest intervals cannot be more than 2 or 3 days. Otherwise, losses in overripe and insect- or disease-damaged fruits can become very severe. The fruit is soft and requires considerable care in picking and handling. Once picked, the fruit deteriorates rapidly if left standing in the hot sun in the fields. If feasible, fruits should be hauled to the factory twice a day or as soon after picking as possible. When in the field, they should be stored in a cool location under the trees or in a centralized shed protected from the scorching sun.

Storage overnight in tightly stacked boxes on the truckbed is undesirable since the temperature within the stack of boxes can be higher than the surround air temperature. However, when overnight storage is necessary, the boxes should be placed in a well-aerated, covered area.

The best way to maintain quality is to process the fruits soon after harvest and have the fruit puree immediately chilled, frozen, or aseptically packaged. If necessary, the factory should be run 24 hours a day. An alternative procedure that may be used is to have reefer chill vans in the field to receive the fruits as fast as they are picked. This alternative may be economically unsound now, but efficiency approaching these requirements should be strived for to maintain quality.

Mechanical harvesting trials with a tree shaker are very positive, but there are problems that need to be resolved before mechanical harvesting can become a reality. The type of machine, shaking stroke, proper maintenance of harvest fruits, and ripening of green fruits harvested are some problems that need to be solved.


Guava--Recommendations for maintaining postharvest quality. University of California, Davis.


Cultivars

'Beaumont', introduced in 1960, and 'Ka Hua Kula', identified in 1972 and introduced in 1978, are the only processing guavas now recommended and grown commercially. Both of these cultivars have a high puree recovery percentage, are pink in color, have a pleasant aroma, and are delicate in flavor and high in total solids. They are somewhat low in acidity.

These are also very high yielding and can be trained and pruned to whatever shape or system the grower desires. In commercial field trials 'Ka Hua Kula' appears to yield better than 'Beaumont' and seems to be a lower tree with less branch extension than 'Beaumont'.


Weed Control

Guava is hardy, aggressive, and a perennial that has only recently become a cultivated crop. It is capable of growing and fruiting under severe competition from other plants. Consequently, weed control efforts in a guava orchard may be only minimal to begin with since control expenditure can become too high. There are several ways weeds can be controlled, however.


Minimal Control
Eliminate only tall weeds by hand that grow into the crown of the tree or in the space between trees. Eventually, however, such minimal management will result in an unproductive orchard unless further efforts in weed control is expended as cash flow develops.


Surface Mulching
Mulching at the base of trees can be done very inexpensively using black polyethylene sheets, cinder materials, or organic materials such as wood shavings. The latter two materials should be applied thick enough to prevent weed growth yet permit rainwater penetration to the root area. Black polyethylene sheets prevent soils surface evaporation and tend to produce water under the sheets through condensation, supporting tree growth besides affording weed control.


Mowing
Mowing throughout the orchard with an off-set tow mower is a good method to eliminate tall, woody plants or grasses. However, this method can become expensive since the weeds at the base of the trees will consumer a large portion of the applied fertilizer, depending on the application technique and available water. In such situations, the total amount of applied fertilizer needs to be increased.


Herbicide and Mowing
Herbicide around the base of trees with only occasional mowing in the areas between trees is a good method. The herbicide area can be gradually expanded into the mowing area as the trees become larger and older. This method is probably the most economical to use.


Complete Weed Control with Herbicides
The use of chemical weed control may initially appear expensive, but when properly applied, it can become a good economical method to achieve the gradual elimination of weed seeds and vegetative propagules.

Weed Control publications, CTAHR.


Insects and Other Pests

Insects and other pests of guava. KnowledgeMaster, CTAHR.