The avocado, scientifically known as Persea americana, originates from the Americas; however, it thrives in Kenya as well. This fruit holds significant nutritional value due to its substantial protein and oil content, and it is gaining prominence as an export crop.
Avocados are remarkably low in sodium while being packed with potassium, dietary fiber, and vitamins B6, C, D, and E. They are consumed as a fresh fruit and incorporated into various dishes such as salads, soups, and even ice cream. Additionally, avocados are utilized to produce avocado oil, perfume, and avocado paste.
The avocado tree can have an upright growth habit, typically reaching a height of 9 meters, although occasionally it can grow up to 18 meters or even taller. The trunk of the tree measures between 30 to 60 centimeters in diameter, and in some very old trees, it can be even larger. Alternatively, the tree can have a shorter and spreading form, with branches that start close to the ground.
The leaves of the avocado tree are arranged alternately and have a dark-green and glossy appearance on the upper surface, while the underside is whitish. They exhibit a range of shapes, including lanceolate, elliptic, oval, ovate, or obovate, and their length varies from 7 to 40 centimeters.
The tree produces small, pale-green, or yellow-green flowers abundantly in racemes near the tips of the branches. These flowers do not have petals but consist of two sets of three perianth lobes. They are typically covered in fine hairs and are accompanied by nine stamens with two basal orange nectar glands.
The fruit of the avocado tree has a pear-shaped form, often with a slight narrowing at the neck. It can be oval or nearly round and ranges in length from 7 to 20 centimeters, with a width of approximately 15 centimeters.
The avocado’s skin exhibits a range of colors, including yellow-green, deep green, very dark green, reddish-purple, or an almost black shade. Sometimes, the skin may also have tiny yellow dots or speckles. It can have various textures, such as smooth or pebbled, glossy or dull, thin or leathery, and can be up to 6mm thick. The skin can be pliable or granular, and in some cases, it may be brittle.
In certain avocados, just beneath the skin, there is a thin layer of soft, bright-green flesh. However, generally, the flesh of the fruit is pale to rich yellow throughout. It has a buttery texture and can either have a bland taste or a nut-like flavor.
The avocado fruit contains a single seed, which can be oblate, round, conical, or ovoid in shape. The seed measures 5-6.5 cm in length and is hard and heavy. It has an ivory color and is covered by two brown, thin, papery seed coats that often adhere to the flesh cavity. However, the seed can be easily removed.
Some avocados may be seedless due to factors such as lack of pollination or other reasons.
In Eastern Kenya, avocados thrive in specific regions such as Kangundo, Mua Hills, Kathiani (Iveti hills), parts of Mbooni in Machakos County, as well as the high-potential areas of Embu and Meru counties.
The avocado varieties include the following:
- Fuerte: This variety produces thin-skinned, green-pebbled fruit with a very good flavor. It exhibits various shapes and is often preferred for export. The fruit has a pear-like shape.
- Hass: Hass avocados are known for their medium-sized, rounded fruits with rough skin that turns black when ripe.
- Nabal: Nabal avocados have green fruit with a good flavor.
- Puebla: Puebla avocados bear round fruits that range from deep purple to maroon in color. This variety is typically used as a rootstock.
In addition to these varieties, there are several others, including Reed, Simmonds, Booth 7&8, Pinkerton, Bacon, Lula, and Taylor.
In Kenya, the main avocado variety cultivated is ‘Fuerte,’ while ‘Haas‘ is rapidly gaining popularity, particularly among small-scale growers. These two varieties are primarily cultivated for the purpose of exporting to international markets. On the other hand, varieties such as ‘Reed,’ ‘Booth 8,’ ‘Puebla,’ and others are not typically exported.
Avocado thrives at different elevations, with various varieties adapted to specific altitude ranges. For instance, certain types such as ‘Simmonds’ and ‘Booth 7&8’ are well-suited to lowland regions, thriving between 90 and 800 meters above sea level. On the other hand, ‘Hass’ and ‘Nabal’ varieties are better suited to higher altitudes, flourishing between 800 and 2100 meters asl. Lastly, ‘Fuerte’ and ‘Puebla’ varieties are most suitable for elevations ranging from 1500 to 2100 meters asl.
Avocado can thrive in a variety of soil types as long as certain conditions are met. It requires deep soil with good water retention capacity and proper drainage for successful growth. However, waterlogged or saline soils are not suitable for avocado cultivation due to the plant’s sensitivity to excessive moisture and high salinity. The ideal pH range for avocado growth is between 5.5 and 6.5.
Avocado cultivation thrives within a temperature range of 16 to 24 degrees Celsius, providing optimal conditions for growth. However, it’s important to note that temperatures exceeding 33 degrees Celsius can be detrimental to both the fruit and the avocado trees, potentially causing damage.
Furthermore, exposure to high temperatures and direct sunlight can lead to sunburn damage on the exposed fruits, necessitating careful monitoring and protection.
Avocado trees are particularly susceptible to frost, especially those varieties adapted to humid tropic climates. The tolerance of these trees to low temperatures varies depending on various factors, including the tree’s age, vigor, growth stage, and overall health.
Rainfall & Humidity
Avocados have remarkable adaptability to varying levels of rainfall, but for optimal production, a well-distributed annual rainfall of up to 1600 mm is ideal. Avocado trees thrive in climatic conditions characterized by alternating dry and rainy seasons. In areas where rainfall is insufficient, irrigation becomes indispensable.
Excessive rainfall during the flowering stage leads to flower abortion, resulting in a considerable decrease in production. Furthermore, avocados face challenges from fungal diseases that are particularly troublesome in excessively wet weather.
Flowering in avocado trees, particularly in tropical climates unaffected by significant temperature drops, is often stimulated by a brief dry spell lasting up to two months.
During the flowering phase, avocado trees thrive in environments with high relative humidity, ideally around 70-80 percent. However, as the fruit begins to swell, moderate humidity levels are preferred. Excessive humidity creates a favorable environment for pests and diseases such as scales, scab, and anthracnose, among others, to proliferate.
The primary method of propagation for avocados is grafting.
Grafting is typically performed when the seedlings reach a thickness comparable to that of a pencil. Among the various grafting techniques, the wedge grafting method has proven to be the most successful.
The grafting process should be carried out at a stage when the rootstock is soft, while the scion (the plant piece to be grafted) should be in a dormant state. Additionally, it is essential for the scion to be of a size that matches the stock.
To ensure successful grafting, it is crucial to thoroughly wrap the grafting point, both to prevent water from entering the union and to avoid excessive drying out.
Land preparation can be simplified and made more effective by utilizing CLAMPDOWN 480SL 200ml/20l, a non-selective herbicide that effectively eliminates all types of weeds.
To prepare the planting holes, make them approximately 60cm x 60cm x 60cm in size. For pure stands of avocado trees, the recommended general spacing is 9m x 9m.
Fill the holes with a mixture of topsoil, manure, and DAP (Di-Ammonium Phosphate). To enhance nutrient absorption by the young plants and stimulate growth, it is advisable to incorporate manure and DAP with HUMIPOWER. The recommended ratio is 1 ton of manure and 50kg of fertilizer mixed with 1kg of Humipower.
Unless the soil is already adequately moist, water the holes before planting.
When planting the grafts, ensure they are placed in the holes at the same depth as they were in the nursery. The bud union should be approximately 300mm above the ground.
Immediately after planting, water the seedlings, particularly if it is not during the rainy season.
Provide shade for the young plants, and if they are planted in a windy area, it is also necessary to have a windbreak to protect them from leaning to one side and to prevent leaf shedding and bruising.
The spacing required depends on the characteristics of the cultivar and the type of soil. In sandy soil, a distance of 25 x 25 ft. might be suitable, whereas in nutrient-rich, deep soil, the tree can achieve its maximum growth and may require a spacing of 30-35 ft.
If trees are planted in such proximity that they eventually come into contact with each other, the branches will experience dieback.
The main trunk branches are cleared of any suckers and dead branches.
Pruning is done to maintain the tree’s height at 5-8 meters and to make it easier for picking.
However, it is important to limit pruning as much as possible due to the tree’s high vulnerability to sunburn.
It is important to maintain a clean area around the tree by regularly removing weeds and fallen fruits.
Weeds can hinder the tree’s growth by competing for essential resources such as nutrients and water, and they can also attract pests and diseases.
To effectively control all types of weeds in the garden, CLAMPDOWN 480SL 200ml/20l is a recommended non-selective herbicide.
PESTS & DISEASE MANAGEMENT
Avocados are susceptible to attacks from various species of fruit flies. Some of these flies lay their eggs under the skin of just ripening fruit, while others target both young and mature fruit. When the fruit is about the size of a golf ball, a sting lesion appears as a small puncture mark surrounded by a white substance. As the fruit continues to develop, the lesion dries up and transforms into a distinct star-shaped crack on the skin surface.
To address this issue, it is recommended to spray either PENTAGON 50EC at a ratio of 10ml per 20 liters of water, or LEXUS 247SC at a ratio of 8ml per 20 liters of water, or PRESENTO 200SP at a ratio of 5g per 20 liters of water.
False coddling moth
Upon hatching from the egg, the young caterpillar burrows into the fruit, resulting in a visible discoloration at the entry point. While inside, they consume the pulp, leading to early ripening and eventual fruit drop.
To address this issue, it is advised to spray either KINGCODE ELITE 50EC at a rate of 10ml per 20 liters of water, or LEGACY 50EC at a rate of 15ml per 20 liters of water, or SINOPHATE 750SP at a rate of 20g per 20 liters of water.
These insects are characterized by their small and slender bodies, along with two pairs of wings adorned with fringes. They sustain themselves by extracting plant sap through sucking.
Their feeding habits result in harm to both leaves and fruit. The affected areas typically exhibit a whitish or silvery appearance and are often covered in dark-colored droppings.
Fruits that have been attacked show signs of a leathery brown skin, with the most frequent feeding occurring on young fruits.
To combat this issue, it is recommended to spray either ALONZE 50EC at a ratio of 5ml per 20 liters of water, or PROFILE 440EC at a ratio of 30ml per 20 liters of water, or DEFENDER 25EC at a ratio of 40ml per 20 liters of water.
These insects are small in size and are typically brown or greenish in color. They are commonly found attached to avocado leaves, where they extract sap through sucking.
The soft scales, in particular, release significant amounts of honeydew, which can result in the growth of sooty mold on leaves, branches, and fruit. The honeydew also acts as an attractant for ants. On the other hand, armored scales can form a hard encrustation on young twigs, leaves, and fruit, and they do not produce honeydew.
The damage caused by these scales can be severe, especially for young trees, leading to the potential death of small twigs. Although the presence of scales on the fruit’s skin does not cause internal harm, it may lead to the rejection of the fruit, especially when intended for export.
To address this issue, it is recommended to spray either LOYALTY 700WDG at a rate of 5g per 20 liters of water, or EMERALD 200SL at a rate of 10ml per 20 liters of water, or LEXUS 247SC at a rate of 8ml per 20 liters of water.
For cleaning the sooty mold, JAMBO CLEAN should be used at a concentration of 100ml per 20 liters of water.
Spider mite infestation results in the formation of circular necrotic spots that are covered in dense webbing. As the population of mites grows, their feeding leads to leaf distortion and, eventually, leaf drop.
The impact on young trees’ growth is severe, and it can significantly reduce yields.
To combat this issue, it is recommended to spray either ALONZE 50EC at a concentration of 5ml per 20 liters of water or BAZOOKA 18EC at a concentration of 10ml per 20 liters of water.
The coconut bug, both adults and nymphs, have a tendency to feed on both young and mature avocado fruits. Their feeding activity results in the formation of necrotic depressions resembling bruising. Over time, a hard lump develops, which can be easily removed when the fruit is peeled.
Helopeltis bugs exhibit a preference for feeding on young plant tissue. They pierce shoots, stems, leaves, peduncles, petioles, and fruits. Their feeding causes the appearance of brown necrotic patches. Leaves that have been attacked display angular lesions, which often lead to holes as a result of subsequent biting insect activity. Feeding on young shoots can cause dieback, while on fruits, it manifests as a dark water-soaked mark surrounding the feeding puncture, eventually turning into a lesion with a light brown center and a black edge. The affected fruit may release sap that forms a whitish deposit as it dries.
When stink bugs are disturbed, they release a distinct and unpleasant odor. Typically, they feed on the growing fruit. Their feeding punctures lead to localized necrosis, causing spotting and deformation of the fruit.
To address this issue, it is recommended to spray either LOYALTY 700WDG at a rate of 5g per 20 liters of water, or EMERALD 200SL at a rate of 10ml per 20 liters of water, or LEXUS 247SC at a rate of 8ml per 20 liters of water.
Swarming leaf beetles
Large groups of this insect have the potential to inflict significant harm on the fresh, growing shoots. Affected terminal growth appears scorched, and the growth of young trees can be significantly stunted. On occasion, developing fruits may also fall victim to their attacks.
To address this issue, it is recommended to apply a spray of either KINGCODE ELITE 50EC at a ratio of 10ml per 20 liters of water, or SINOPHATE 750SP at a ratio of 20g per 20 liters of water, or LEXUS 247SC at a ratio of 8ml per 20 liters of water.
Avocado root rot (Phytophthora cinnamomi)
Trees, regardless of their size and age, can be susceptible to this disease. Infected trees exhibit small, pale, or yellowish-green leaves that often wilt and prematurely fall, resulting in a sparsely populated appearance.
In the advanced stages of the disease, branches experience die-back, and the fruit remains undersized, leading to a significant reduction in crop yield. Feeder roots become blackened, decayed, and eventually perish. Ultimately, the infected tree succumbs prematurely.
To address this issue, it is recommended to apply a soil drench treatment using either GEARLOCK TURBO 250WP at a rate of 50g per 20 liters of water, or PYRAMID 700WP at a rate of 100g per 20 liters of water, or CHANCETYL ELITE 800WDG at a rate of 100g per 20 liters of water.
Anthracnose (Colletotrichum gloeosporioides)
When the fruit reaches its maturity stage, a significant post-harvest issue arises. Infection occurs during the early stages of fruit development, and the fungal infection remains inactive until the fruit ripens. The disease manifests as depressed spots on the fruit, and these spots can develop into a deep-seated rot, penetrating the flesh. During wet weather, the spots may be covered by a slimy, salmon-pink mass of fungal spores.
If the storage conditions are warm and humid, the disease can progress rapidly.
To address this problem, it is recommended to spray either RANSOM 600WP at a rate of 15g per 20 liters of water, or DUCASSE 250EC at a rate of 20ml per 20 liters of water, or EXEMPO CURVE 250SC at a rate of 15ml per 20 liters of water.
Scab (Sphaceloma perseae)
The fungus easily attacks young and tender tissues such as leaves, twigs, and fruits.
Visible lesions take the form of small dark spots that are slightly raised and oval to elongated in shape. As the disease progresses, these spots merge together, resulting in a rough, corky texture on the surface of the fruits. While this affects the appearance of the fruit, the internal quality remains unaffected.
Fruits are susceptible to the disease only during their early stages of development, up until they reach approximately half of their full size.
To address this issue, it is recommended to spray either DUCASSE 250EC at a rate of 20ml per 20 liters of water, or RANSOM 600WP at a rate of 15g per 20 liters of water, or ABSOLUTE 375SC at a rate of 10ml per 20 liters of water.
Cercospora leaf & fruit spot (Pseudocercospora purpurea)
This disease primarily affects the quality of fruits, and the extent of infection can vary from one season to another, resulting in substantial losses.
When infected, lesions initially appear as small, light-yellow spots on both fruits and leaves. As the infection progresses, these spots turn reddish-brown and eventually become hardened and cracked.
On leaves, the affected tissue becomes thin and brittle, often leading to its detachment, resulting in ragged holes.
To address this issue, it is recommended to spray either EXEMPO CURVE 250SC at a rate of 15ml per 20 liters of water, or RANSOM 600WP at a rate of 5g per 20 liters of water, or DUCASSE 250EC at a rate of 20ml per 20 liters of water.
Bacterial soft rot (Erwinia carotovora)
When fruits are infected, they exhibit an external darkened metallic sheen. Internally, the flesh appears grey to black, becoming soft and emitting a foul, putrid odor.
To combat this issue, it is recommended to use copper-based fungicides such as GREENCOP 500WP at a rate of 50g per 20 liters of water, TRINITY GOLD 425WP at a rate of 50g per 20 liters of water, or COLONIZER 440WP at a rate of 50g per 20 liters of water.
Stem end rot (Dothiorella dominicana, Phomopsis spp., Botryodiplodia theobromae & Lasiodiplodia theobromae)
The onset of the disease is marked by a dark brown to black rot originating from the stem end, forming a dark brown ring. The rot gradually progresses towards the opposite end of the fruit. Within the affected fruit, the water-conducting tissues display dark streaking, a characteristic that sets stem end rot apart from anthracnose.
To address this issue, it is recommended to spray RANSOM 600WP at a rate of 15g per 20 liters of water, EXEMPO CURVE 250SC at a rate of 15ml per 20 liters of water, or ABSOLUTE 375SC at a rate of 10ml per 20 liters of water.
To ensure optimal growth and high fruit yields, it is crucial to provide the plants with essential nutrients.
This can be achieved through the application of both basal and foliar fertilizers.
Basal fertilizers, such as DAP, CAN, NPK, UREA, and others, are absorbed by the plants through their roots. Depending on the organic matter content of the soil, farmyard manure may also be added to enhance fertility.
On the other hand, foliar fertilizers are absorbed by the plants through their foliage. These fertilizers supply both macro and micro nutrient elements. Examples include OPTIMIZER, DIMIPHITE, ZINC GOLD, LAVENDER, GOLDCHANCE SERIES, VITABOR GOLD, and others.
Applying these fertilizers helps prevent nutritional deficiencies and ensures that the plants receive the necessary nutrients for healthy growth and abundant fruit production.
When conducting foliar sprays, it is recommended to include INTEGRA at a rate of 3ml per 20 liters of water. INTEGRA acts as a sticker, spreader, wetter, and penetrant, enhancing the effectiveness of the respective product, be it an insecticide, fungicide, foliar fertilizer, or herbicide.
To prevent the development of resistance in pests, especially with fungicides and insecticides, it is advisable to alternate the use of different chemicals throughout the crop’s growing season. This practice helps in reducing the risk of pests becoming resistant to a single chemical if it were consistently used.
The timely application of products, such as fertilizers, insecticides, fungicides, and herbicides, is of utmost importance. It ensures that these substances are applied at the appropriate stages of plant growth or when pests or diseases are most susceptible, maximizing their effectiveness.
For basal fertilizers and manure, it is recommended to mix them with HUMIPOWER. This addition enriches the soil by introducing organic matter, enhances nutrient uptake by plants, stimulates beneficial microbial activities, and promotes electrochemical balance, among other benefits.
Maturity, Harvesting & Postharvest Handling
The harvesting time for avocados typically occurs between 5 to 10 months after flowering, although this timeline can vary based on the avocado variety and the ecological conditions of the region.
Determining the optimal harvesting time can be challenging, especially for varieties that do not change color as they mature. However, for dark-colored varieties, it is generally an indication of maturity when they transition from green to a dark color. Green-colored varieties, on the other hand, may exhibit a smoother texture, corky spots, and a yellow tint on the skin and stem.
To harvest avocados, clippers are used for fruits within reach, while a long-handled picking pole with a sharp “V” on the metal rim is employed for higher fruits. The stem is cut, and a sturdy cloth bag is used to catch the fruit as it falls.
It’s important to note that avocados do not ripen while still attached to the tree. Leaving them on the tree for too long increases the risk of wind-induced damage, resulting in bruised or broken fruits.
Immature avocados do not ripen properly and instead become rubbery, shriveled, and discolored. When picked at the right time, fully grown and firm avocados typically ripen within 4 to 5 weeks at room temperature.
A ripe avocado can be identified by gently squeezing it, and if it yields to light pressure, it is ready to be consumed. Ripe avocados can be stored in the refrigerator for two to three days.
Avocados are highly susceptible to bruising and scratching, requiring careful handling. For shipment, they are packed and protected in single or double-layer boxes or cartons to ensure their safety.
When exported, avocados are transported in refrigerated conditions on surface vessels, which helps maintain their quality during transit. However, it’s important to note that avocados are susceptible to chilling injury, which manifests as dark-brown or gray discoloration in the mesocarp when stored in refrigeration. The degree of susceptibility to chilling injury varies depending on the avocado variety, the stage of harvesting, and the duration of storage. Most commercial varieties can be safely stored at temperatures between 4-13ºC for at least two weeks.
After removing avocados from storage, the optimal temperature for ripening is 15ºC. This temperature promotes consistent and desirable ripening of the fruits.