The scientific cultivation of Avocado (Butter Fruit) in Karnataka
Name: Butter fruit (Avocado)
Scientific Name: Persea americana
Variety: Florida Gold
Introduction and Background:
Salient features:
Florida Gold: Florida Gold avocados are known for their bright green, smooth, and glossy skin that stays green even when ripe. They are generally larger than Hass avocados, and come in various shapes such as oval or pear-shaped. The flesh is light yellow-green with a large central seed and a firm texture due to its higher water content. Florida Gold has a mild, subtly sweet flavor that is less rich and buttery than the Hass variety. Because of its lower oil and fat content, it is often marketed as a “lite” or “SlimCado” option, making it a healthier, lower-calorie alternative
Temperature:
Avocadoes do very well under cool tropical conditions with a temperature range from 12° to 35°C. Under sub-tropical conditions, extremes of temperature below 5°C and above 40°C are not favorable.
Similarly, occurrence of frost during winter is harmful to plants.
Light:
Avocadoes are sun loving plants and thus perform excellently under bright sunlight conditions. This is one on the main reasons why avacodes are normally grown as pure crops, and not as intercrops. The shade of any degree proportionately reduces the growth and productivity of plants.
Humidity:
Avocadoes are well adopted to moderate high humidity conditions (50-85% R.H.). Lower humidity desiccates the leaves and leads to sun scorching, and consequent leaf fall. Hot and dry desiccating conditions are detrimental to the growth and productivity of avocadoes.
Rainfall :
Avocadoes grow satisfactorily in moderate to heavy rainfall areas (500 mm to 3500 mm); provided the other factors such as altitude, temperature, drainage etc. are properly fulfilled.
Altitude:
In tropical areas, altitude matters a lot to avocadoes. They perform very well from 800 to 1200 m. from MSL. The sub-tropical types if grown under tropical zones, an altitude of 1000 to 1250 m. favours the growth and productivity, as well as the quality of fruits.
Tropical types can also adapt fairly well to little lower altitudes, say between 600 and 900 mts. Altitudes lower than 500 m. drastically reduce the growth and productivity of avocadoes.
Soil:
For proper growth and productivity, avocado requires the following conditions.
- Deep sandy-loam to loamy soils.
- Clayey soils are not good
- Well drained soils are best; water logging is detrimental.
- Best pH range: 6 to 7.00. Alkalinity of any degree harms the plants.
- The ideal E.C. of soil is below 0.25 and any thing above 0.5 is harmful.
Cultivation:
Spacing: For block planting, the spacings such as 20’x20′, 25′ x 20′ are recommended. For border or bund planting, the plants may be planted at 20′ or 18′ or even 15′ apart looking at the specific situations. High density plantation in avocado is not advisable as trees grow fast and dense, the mutual shading not only makes trees lanky but also brings down the performance of plants.
Land Preparation:
Retain the gentle slope if existed. Terracing can be done in higher slopy conditions. But, too much excavation of top soil leading to exposure of hard subsoil strata should be strictly avoided. In slopy areas contour binding can be employed, but precaution should be taken for safe disposal of rain water, avoiding water stagnation at any given area in the orchard.
Pit digging and filling :-
For planting, pits need to be dug. The adequate dimension is 2′ x 2′ x 2′ in soft, deep and fine textured light soils and 3′ x 3′ x 3′ in relatively harder soils.
Pits need to be dug and filled up atleast a month before planting of grafts. The pits should be filled up with top soil, green leaves, compost or Farm Yard Manure (FYM), mixed with 100 gm hydrated lime and 100 gm of multi-micro-nutrients mixture containing Fe, Zn, Cu, Mg, Mn, B and Mo. The pits should be filled upto the brim level and watered. The mixture in the pit sinks subsequently and again the soil level in the pit should be brought to the brim.
Planting of Grafts:-
- Deep planting in the pit is to be strictly avoided. The Thumb Rule is that “the roots should be in soil and the stem should be in the air”. Deep planting surely leads to collor rot immediately.
- Soon after planting 10-15 gm of Phorate granules to be applied at the base of the plant to ward off termites and root grubs.
- Staking should be done to ensure the straight posture of the plant.
- Watering should be done regularly. The sprouts arising from the root stock need to be removed as and when they are noticed.
- Earthing up (raising of soil at the base of the plant) should be strictly avoided as it leads to bark infection at the collor region of the plant.
Water requirement and drip-irrigation:
Drip irrigation is the most convenient method of irrigation to avocodo orchards, especially at the early stage of the orchard development. The drippers/microtubes from which the water drips, should be placed at least a foot away from the base of the plant. It is very important to see that water doesnot stagnate at the base of the plant at any stage of growth and development of the plant.
The water requirement and watering intervals are as follows:
- 5 litres on alternate days after planting upto 2 months.
- 8 litres on alternate days from 3rd to 6th months.
- 10 litres once in 4-5 days from 6th to 12 months.
- 20 litres once in 4-5 days from 12 months onward upto the end of 2nd year.
- 50 litres once in 4-5 dys in a bearing tree (especially during fruit set and fruit growth)
As the tree grows bigger and bigger, the drippers/microtubes should be placed away from the trunk and in the bearing grown up tree, the drippers should be atleast a meter away from the trunk.
Mulching: Mulching either with plastic sheet or with organic debris is beneficial where water is in short supply and also during the drier months. If organic mulch is employed, periodical checking for termites and ensuring their control is to be taken care of.
Training and Canopy Management:
Training and canopy management are the crucial steps in the scientific cultivation of avocadoes.
- Upto one year no side branches should be cut. The plant has a strong apical dominance and allow it to grow as much as it pushes upward.
- In the beginning of the 2nd year, remove the side branches upto 3 ft. height and make the trunk single stemmed.
- After this allow only 4 branches to take over (one central leader and 3 side branches).
- Allow the central leader branch to grow to 8-10 ft. height and after this nip off the terminal branch. This helps to make an umbrella type of tree canopy.
- The ultimate height of the tree shall not be more than 12 ft. This type of canopy helps in allowing sufficient sunlight to all the interior parts and effecting good aeration. With this, it is possible to have high productivity, ease in farm operations, and convenience in harvesting of produce.Avoid over-crowding of branches through thinning/pruning of branches as and when needed subsequently, after the harvest of the fruits.
Inter-cultivation: Light ploughing / harrowing of the land in the interspace is a must in maintaining weed free conditions and orchard hygiene. This also helps for proper infiltration of rain water and ensuring adequate aeration in the soil. Deep ploughing should be strictly avoided as it adversely affects the feeding roots of avocado plant, which are concentrated in one foot depth in the top soil.
Ensure that water does not stagnate in any part of the orchard at any time. Earthing up to the trunk should be totally avoided as it leads to immediate infection to the trunk which is detrimental to the tree.
Inter-cropping: Inter cropping in the avocado orchard at 20′ x 20′ spacing is not normallly desirable in the interest of proper aeration, penetration of sunlight, avoiding build up of serious pest diseases and in achieving high degree of productivity and quality of fruits.
In case if wider spacing is given to avocadoes, the small statured non-competing inter crops such as Amla, Lime, etc. may be thought of. Those crops which attract fruit flies such as guava, annonaceous fruits (sitapal, cherimoyer, etc.) should not be entertained.
Application of Nutrients:
Manuring and fertilizer application is very important in avocado cultivation in achieving higher productivity and quality of fruits.
Application of adequate quantities of organic matter in the form of Farm Yard Manure/Compost is a must, every year. Growing of green-manure crops in the interspaces also helps to build up humus in the soil, apart from checking the weed growth during rainy reason.
Apart from organic matter, providing inorganic macro and micro-nutrients is must and the details of which are as follows:
Quantity in grams/tree
| Age of the tree | N | P205 | K2O | Multi-micro nutrient mixture | Calcium (Hydrated Lime) |
| 1st year | 50 | 20 | 30 | 50 | 100 |
| 2-3 year | 75 | 25 | 60 | 100 | 200 |
| 4-6 year | 100 | 30 | 300 | 150 | 1500 |
| 7-10 year | 200 | 150 | 500 | 200 | 2000 |
| 10 and above | 500 | 275 | 1250 | 250 | 2500 |
N, P and K fertilizers may also be given through drip, using the water soluble types, in several split doses. Foliar application of micro-nutrients is more desirable (3-5 g./litre of water). Calcium (lime) application may be made not necessarily every year; but be made once in 2-3 years at the quantity recommended for respective age group.
Pest-Management in Avocadoes:
(A) Insect Pests:-
Thrips, mites, mealy bugs, scales, fruit flies and stem-borers are the common insect pests. Their control/management is as follows:
1) Thrips: These affect the tender leaves, inflorescence, flowers and even the young set fruit lets. These appear at all times of the year and more during spring and summer.
Scratching by the thrips causes damage to the tender leaves as brown scars, leaf expansion gets hindered. The affected flowers drop off. The attack on young fruit leads to permanent scar on the fruit.
To control thrips, the following sprays may be taken up.
Acephate: 1.5 g/litre of water.
or
Acephate + Imidachloprid (Company mixture): 1.0 g/litre
or
Imidachloprid: 0.5 to 1.0 ml/litre
(2) Mites:
Red spider mites occasionally cause considerable damage to the young and old leaves alike. Occur mostly during summer months. They colonize on the lower surface, and the affected leaf surface turns brown and wither off.
To control mites, take up the following spray.
Dicofol: 2 ml/litre of water
or
Wettable Sulphur : 3 g/litre
or
Monocrotophos : 1.5 ml/litre
(3) Mealy bugs and Scale insects:-
These occur if the plant becomes dense and grown under shaded areas. They affect mostly the older leaves and stem. Very rarely affect the fruits too. These are sucking insects and cause damage to leaves/stem. They secrete sugary excreta and on which sooty mould disease develops, which obstructs the photosynthesis process.
To control these insects, spray the following.
- Imidachloprid – 1 ml/litre of water, alternated with Acephate 1.5 gm/litre. or Quinolphos – 2 ml/per litre of water
- Organically, these can be controlled to some extent by spraying Neem oil 5 ml/litre mixed with Fish oil Rosin Soap.
Adequate and regular pruning and ensuring proper aeration and penetration of sunlight into the inner areas of the canopy also reduces the incidence of mealy bugs and scale insects.
(4) Fruit Flies:
These are is becoming a serious pest in Karnataka and other states in South India, and more severly in heavy rainfall areas (Western Ghat Districts)
Mature avocadoes become the easy targets for the female fruit flies, which lay eggs inside the pulp. The maggots start feeding on the pulp and the affected fruit rots and drops off. The same fruit fly infects various other fruits such as mango, guava, annonaceous fruits, mandarins, banana, papaya, sapota and ascore of other fruits.
- Hanging Pheramone Traps – using Methyl Eugenol as a lure attracts male flies which get trapped and killed and thereby the population of female flies also comes down. About 10 traps per acre are recommended.
- Smearing of Bait Solution to the tree trunk: The bait solution containing Jaggery 100 gm and Deltamethrin 5 ml mixed in one litre of water to be smeared to the main trunk of the tree in the form of a band, to which the fruit flies of both the sexes attract and get killed. This measure brings their population under check.
- Take up spraying of Deltramethrin 2 ml/litre of water at the time of fruit maturity. This helps in killing both male and female flies.
- Orchard hygiene: Keep the orchard clean and weed-free and bury the infested fallen fruits deep into the soil in a pit. This goes a long way in reducing the population of fruit flies.
(B) Diseases:
Phytophthora root not/collor rot:
This is a serious problem, especially in heavy rainfall areas, or where there is defective drainage in the orchard.
The pathogen enters through the roots and the collor region (bark) and the infected plant becomes dull, leaves turn yellow and drop off, and twings show die-back symptoms. Bark scales off. Then the whole plant dies.
The essential steps in managing this disease are as follows:
- Avoid water logging areas for planting
- Deep planting, leading to burial of the stem, should be avoided
- Drainage should be improved if temporary water logging takes place
- Drippears should be placed at least a metre away from the main trunk
- Do not irrigate frequently
- Earthing up to the base of the trunk should be strictly avoided
- Do not dump manures and fertilizers at the base of the trunk
- When the plant/tree starts showing the dieback symptoms, drench the base of the tree with 1% Bordeaux mixture or 0.3% Copper oxychloride solution
- Spray the infected plant with Metalaxyl + Mancozeb (Company Mixture) combination at 2 gm/litre of water, at monthly intervals, until the plant recovers.
- Apply stem-protection paste to the trunk of the tree upto 3 ft. height to avoid any possible infection.
- (Stem protection paste is prepared by mixing 50 gms Copper oxychloride, 10 ml Chlorpyripros, 5 ml Hexaconazole and 100 gm/ml water based distemper, dissolved in one litre of water).
Anthracnose Leaf/fruit spots:
It’s a common problem in heavy rainfall areas and during the wet season of the year. The disease can affect young leaves, panicles, young fruits, developing fruits, mature fruits and can also become a post-harvest problem.
The disease appears as circular spots on leaves which join together and become patches and later the defoliation takes place. On inflorescence, back spots develop and the raches dry up. On fruits black circular spots develop, widen, sink inside and crack irregularly. During ripening the pulp adjacent to these cracks rots.
Hence, anthracnose should be viewed very seriously and control measures be initiated.
Management/Control measures include:
- Maintain the orchard hygiene
- Over crowding of the trees in the orchard should be avoided. Pruning should be regularly practiced
- Avoid taking intercrops/mixed crops
- As a prophylactic measure take up the spraying of Copper oxychloride: 3 gm/litre of water or Bordeaux Mixture 1% at the beginning of the rainy reason. Then spray: Propiconazole (1 ml/litre) after a month from the 1st spray.
Scab Disease:-
It’s a fungal disease and is a threat to avocado in heavy rainfall areas.
leaves as well as young fruits. Brown scabby areas are noticed on leaves and fruits. The infected leaves and young fruits drop off.
Harvesting of Fruits:
The most common and the best method of harvesting is by hand. The fruits at the non-reachable heights to the hand may be harvested by using self supported ladders or using fruit harvesters (like in mango). Beating of fruits with stick and making them to fall on ground is a wrong method of harvesting and therefore, it should be avoided.
Harvested fruits should be immediately kept in the plastic crates, and during transportation too the fruits should be in the crates.
Yield of Fruits:
The yield of fruits may vary depending upon the canopy area, age of the plant and the degree of maintenance of the trees. A best maintained 5 year grafted tree may yield about 200 fruits and the yield steadily increases year by year. A 10 year tree of the similar maintenance may yield as much as 800-1000 fruits per year.
The weight of the fruit varies according to the clone. The fruits of varying weights such as 200 gm, 300 gm and 500g.