Avocado plants raised from seeds start bearing five to six years after planting. Grafted varieties will produce a few fruit two years after establishment. Mature trees can produce two to three or more bushels of avocados with good management, depending upon variety. Mexican- race seedlings and varieties typically mature during the summer; “Lula” and most other hybrids mature in September or October.
Indicators of Maturity
As the fruit approaches maturity, the percentage of fat in the pulp increases to reach the standard level characteristic of each cultivar. Parallely, the percentage of dry matter of the fruit comes to a constant level. Both can be used as indicators of maturity. Other indicators are the skin color and age: Mature fruits of purple varieties change their color from purple to maroon, whereas fruits of green varieties become greenish-yellow. Fruits are ready for harvest when the seed coat colors within the fruit changes from yellowish white to dark brown. In the case of loose-
seeded varieties, an indication of fruit maturity is the production of a hollow sound when the fruit is tapped manually. Some pickers shake the fruits to see whether the seeds are no longer clinging, looking for signs of maturity.
Avocado fruits do not ripen on the tree; the fruits remain hard as long as they stay on the trees. Mature fruits ripen six to ten days after harvesting. Some cultivars – especially Guatemalan x Mexican hybrids – can be stored on the tree and harvested according to marketing schedules. However, on-tree storing can lead to biennial bearing and crop failure in the following year.
Harvest
Fruits are harvested when they are still immature in order to prolong their shelf-life during long distance transportation, often under simple packaging and handling techniques. The harvesting is achieved manually by a picker climbing the tree and taking a basket or jute bag or by using a ladder. Fruits that cannot be reached by hand are harvested with the use of a long bamboo or alu- minum pole fitted at one end with a wire hook and an
Table 12:
Some Guava Diseases and Organic Management Disease Important to Know Indirect Control Direct Control
Phytophthora • Causes root rot and tree decline; • Use resistant rootstocks such as Morton • Good pruning practice;
cinnamomi • Yellowing of leaves, sparse foliage, wilting Grandee, Thomas, Barr-Duke, Duke-9; • Cu applications on wounds (Bouille bordelaise (Root rot) of leaves and dieback of shoots; • Adequate drainage or avoiding planting 2% and cover with wax);
• This soil borne disease is commonly found in waterlogged areas;
in acid soils with poor drainage; • Build up heavy mulch with bagasse, grass, straw etc.;
• No plowing underneath the tree canopy; • Careful irrigation (avoid flood irrigation);
Colletotrichum • Small brown to black spots on the fruit; spots • Adequate drainage; • Spraying with Bordeaux mixture; gloeosporioides can enlarge and cause the fruit to crack • Rarely causes significant losses on other
(Glomerella cingulata across the spot; thick-skinned fruits;
var. minor) • Another strain of the same fungus causes
(Anthracnose) leaf spot;
• Fuerte cultivar is most susceptible;
Cercospora spot, • Rarely encountered in semiarid regions, • All preventive measures; • Spraying with Bordeaux mixture; powdery mildew, but are serious problems in the humid tropics;
net attached to catch the fruits. The fruits are then placed in bins, pallets, boxes or bamboo baskets lined with banana leaves for transport to the market. Avocado fruits on the same tree do not mature at the same time, so selective harvesting is usually practiced. This requires going over the tree several times until all the fruits are harvested.
Avocados give a commercial yield of 7.5 – 15 ha/ha. The yield ranges from about 100 to 500 fruits per tree (40-200 kg per tree), depending on cultivar and age of trees.
Post-Harvest Handling
Fruits need to be picked carefully. They should be harvested at the correct stage of maturity, when they are still hard and have a minimum oil content of 12 %. Hard, mature fruits are harvested and allowed to ripen during transport and distribution. Up to 14 days transport time is con- sidered satisfactory, though unripe avocados can be stored for up to four weeks if the temperature is kept between 5.5 and 8°C.
In the packing houses, fruits are cleaned with roller brushes. Cleaned fruit pass through graders, where all diseased, injured and defective fruit are removed and fruit are separated into size lots for packing. General size class standards may not be valuable for organic avocado; this has to be checked with the client. Packing cartons and labeling must comply with organic standards and regulations.
Storage temperature for delaying ripening varies with the cultivar:
< West Indian race: 12.5 °C
< Guatemalan race: 8°C
< Mexican race: 4°C.
A relative humidity of 80-90% is recommended.
Fruit can be ripened at 25°C or by exposure to ethylene at 15-17°C for 24 hours and then transported to the market. Both methods are allowed for organic marketing.
2.5.
Coconut
Coco palms (Cocos nucifera L.) originate from Melanesia. South east Asia is still an important cultivation region. The coconut is a monocotyledon plant, and can therefore only proliferate via seeds. It can produce an inflorescence on each leaf axil, and can then have either male or female blos- soms. These are formed on the side, so that generally, the coco palm is cross-fertilized by a variety of bee species, other insects and the wind. Coco palms live to an average age of 60 years.
Every part of the coco palm can be used. The juice from the inflorescence, which can contain up to 15% sugar, goes to make palm-wine. Half-ripened nuts (6-7 months old) are often harvested to be eaten fresh. The coco juice is drunk, and milk squeezed out of the meat (endosperm). Fully ripened nuts (after 11-12 months) provide the so-called copra, which is made from the firm meat of the nut. Copra is high in oil and protein content (65% oil, 25% protein). Coconut oil is produced from drying and pressing the copra. Grated coconut is made from fresh copra. The hard coconut shells are used to fire kilns used to dry the copra, and to make charcoal. When they have been finely grated, coconut shells are used as fillers for objects made of plastic, such as buttons, containers and other objects. Coconut fibers are used in the upholstery industry, to make ropes, as mulching material or as a substitute for peat. The leaves and wood are used as building material and to make household objects (e.g. brooms) and tools.
2.5.1.
Ecological Requirements
The saying “the coco palm loves to stand with its feet in the water and its head in the sky”, offers a very characteristic description of the site requirements of coco palms. A continuous supply of adequate water which can be provid- ed by regular rainfall of about 2000 mm per annum, or from ground water (at a depth of 1-3 m). It cannot tolerate water-logging, though.
These conditions are generally found in tropical and subtropical coastal regions with little rainfall. Coco palms can also grow on deep, water-logging free, alluvial soil, away from the coast – yet a low chlorine content in the soil could have negative effects. These conditions should be well-heeded when choosing a site.
2.5.2.
Soil and Weed Management
Soil
Growth is stimulated by a sufficient supply of chlorine in the soil. The coco can withstand up to1% salt in the soil.
Coco palms can also grow on deep, water-logging free, alluvial soil, away from the coast – yet a low chlorine content in the soil could have negative effects.
Temperature
The coco palm grows best at average temperatures of around 26-27°C. Because of its temperature requirements it cannot grow above 750 m, even near to the equator.
Weed management
The tilling of weeds should be carried out according to which mixed crop system or agro forestry system is used. Measures need then to be taken when the following occurs:
< Legumes used for ground-coverage, such as e.g. Pueraria
phaseoloides, Glycine wightii, Arachi Pintoi, Desmodium ovalifolium, Mimosa invisa, Calopogonium muconoides
or Centrosema pubescens: these plants rapidly develop a dense layer of foliage, and can be mulched. The thick layer of mulching material, along with the shade provided by the crop itself (especially by pueraria), is an effective way of controlling weed growth by suppressing it. When planting Pueraria phaseoloides and Glycine wightii, care should be taken during the rainy months that the young plants are not overgrown by weeds. For this reason, a monthly check and trim is necessary.
< If forage is being produced, regular grazing (rotational grazing) should be interrupted by a hay pasture. Hay can be used for the dry season; and the crop as well as the weed growth (among others caused by animal movement) can be better controlled. In agroforestry systems, animal husbandry should never be practiced within the plantation.
< On young coco palm plantations, it may become nec- essary to remove climbers and epiphytes from the palms.