Production of Apples

An apple is a hardy deciduous temperate fruit tree which has potential to grow In high altitude areas in Kenya where the temperatures are low enough to break dormancy. The domestic demand for apples is high although the main  supply is from South Africa due to the limited local supply and lack of specialized facility to store the fruit over a long period of time. However some varieties can keep for long if  they are handled properly during picking, transportation and storage. At the moment, apple production is confined to a  few scattered farmers in the highlands of Kiambu , Kitale and Nandi

ECOLOGICAL REQUIREMENTS

Temperatures

Apples require a day temperatures of above 18°C and night temperatures of above 13°C to break dormancy. However, optimum night and day temperatures of about 6-8°C will enable complete bud breaking. Areas which do not experience low temperatures, chemicals have to be used to supplement the inadequate chilling e.g. winter tar oil (Tropical mortegg) and Thio Urea (NH3)₂

Soil

Apples are best grown in deep, well drained sandy to sandy loam soils. The PH for sandy soils should be 5.5 while for heavy clay soils should be 6.5. It is recommended to carry out a soil test to establish deficiencies in nutrients particularly Phosphorus which affects root development.

Rainfall

1000-1800mm of rainfall per year is adequate. However, very high rainfall is associated with incidences of fungal diseases. In areas of low rainfall, irrigation can be done.

Altitude

Apples grown in altitudes of 1800-2800m above sea level. Such areas include Trans Nzoia District particularly Endebbes, Kipipiri  and Kinangop in Nyandarua District, Timboroa in Uasin Gishu District, Molo and Naivasha in Nakuru District. It is grown in Kiambu, Murang’a, Taita Taveta and Meru.

ESTABLISHMENT

Several varieties have been tried in Kenya and have shown a fair amount of success. Popular cultivars such as Jonathan and Gala are extremely susceptible to fire blight and thus are difficult to grow because they require diligent spraying. However, planting of disease resistant varieties is recommended like Enterprise, Liberty, Goldrush, Jonafree, Pristine, and William Pride which are resistant to Apple scab and fireblight.

Rootstocks

Rootstocks are necessary for apple growing because they provide uniformity of production in the orchard and dwarfing characteristic of the tree when desired. Apple trees on dwarfing rootstocks are recommended to facilitate training, pruning, spraying and harvesting. Trees on dwarfing rootstocks also start producing fruit the second season after planting and generally have a life span of about 20 years and can still be 15 feet tall. Apple trees on semi dwarf rootstocks such as M.7A are large trees of up to 25 feet tall at maturity and generally begin to produce fruits four years after planting and continue ti bear for 25 years. The propagation by use of seed is mainly done for breeding purposes.

Clonal rootstocks

The common method used in propagating rootstocks is by stooling the suckers. Stumps of the desired variety are earthed up an the resulting shoots are removed and rooted in the nursery. They can also be multiplied by layering or from root cutting. Clonal rootstocks from virus tested are used  to produce trees. Common varieties are M4,M9, M11, MM13, M26,MM104, MM106 and MM107. M9 is a dwarfing rootstock although it is susceptible to fire blight while M13 is semi dwarf. Their characteristics in yield vary with MM106 giving the highest yield.

Land preparation

Clear the land of all the trees and bushes. In the case of a forest, first ring bark all the trees to eliminate the possibility of infecting the apple trees with Armillaria melea. Plough to a depth 30cm and remove all the perennial weeds.

Spacing

Apple trees are spaced according to rootstocks, varieties and altitude. 3m×2m or 3m×3m for small varieties, 4m×4m or 4m×5m for medium and large trees.

Planting

Apple seedlings that are dormant are planted during the rainy season. Dig holes 60cm×60cm and separate the top soil from the sub soil. Mix 250g of Triple Super Phosphate (TSP) or 1 debe of manure per tree with the topsoil at planting. The subsoil should be used to fill the hole. Prune broken roots and shorten long roots to 12 to18 inches (Figure 1). Place the tree in the hole and arrange the roots so they aren’t overlapping. About an hour before planting, soak tree roots to hydrate them.

To avoid air pockets, tamp the soil with as the hole is filled then apply 5 or 10 liters of water to the tree.

Add additional soil if needed to maintain the soil at the same level as that surrounding the hole. The graft union of the tree should remain 2 inches above the soil level. At planting, a pollinator variety should be included in the orchard for adequate pollination.

MANAGEMENT                       

Mulching

Mulching maintains moisture around the seedling and also checks weeds growth.

Intercropping

This is essential to utilize the space in the orchard. Crops that can be intercropped with apples are leafy vegetables, beans and peas. This should be done during the first three years of orchard establishment.

Staking

A stake should be placed beside an apple tree ton provide support. A 2×2- inch stake is generally sufficient. For trees on dwarfing rootstocks, the stake should be 10 feet tall and will remain in the ground for the life of the tree. Small trees can be easily overloaded with apples and will lean or break because of their weaker root system. Stakes for trees on semi-dwarfed rootstocks should be 6 to 8 feet tall. Stakes in these trees are needed only I the first five years after planting to support the main trunk. After this time, the root system and the framework of the tree are generally strong enough to support the tree with fruit on it. After selecting a stake, drive it 2 feet into the soil. Secure the tree to the stake by a heavy number 9 wire and a section of an old garden hose or some other material (Figure 2)to prevent scraping off the bark when the tree moves in the wind.

Fertilizing trees

One month after planting, apply about a 250g of Urea fertilizer per tree in a circular band around the edge of the original planting hole. The year after planting, apply about 500g fertilizers per tree in a circular band on the tree canopy at the onset of rains in splits of two. In subsequent years, fertilizer needs will probably increase; the amount of fertilizer to apply can be gauged by the terminal growth made the preceding year. Young trees (one to six years old) should be 30 to 46cm of new growth each year and 30n to 15 cm of growth thereafter. Growth above or below these figures would indicate too much or too little fertilizer. After inspecting the amount of terminal growth, the amount of fertilizer can be adjusted from the amount applied the previous year. In a year when the blossoms are injured by frost and the crop is lost, do not apply any fertilizer because it will promote too much vegetative growth.

Pruning

Pruning is done during the first four years of growth in order to establish structure and form.

1st Year (formative pruning): after planting, prune back the central shoot to 1m from the ground to allow branching below the point of cutting. 3-4 strong shoots are selected from the new shoots. These should be distributed along and around the central leads. The lowest branch should be 70cm from the ground level.

2nd Year:  during the following dormant season, about⅓ to ⅟₂ the length of the scaffold branches is cut back to stimulate secondary or lateral branching. 3-4 laterals are recommended per scaffold branch.

3rd Year; the scaffolds are tipped off to induce more laterals

4th Year (maintenance pruning): cut back the scaffold branches and laterals. Laterals growing too close to the main laterals and scaffolds branches are cut. Those growing upright should be removed together with those criss-crossing as well as the dead and the weak ones. Paint all the cut surfaces to prevent infection.

Training

Apples produce fruit mostly on the lateral branches that are horizontal to the ground. Therefore apple branches should be well spread out by bending them to the horizontal position, to encourage fruit growth, more productivity, light penetration, aeration and disease development.

Wind breaks

They are planted before or during establishment at the orchard to protect the young seedlings from strong winds. The recommended species are Grevillea robusta and Eucalyptus spp.

Dormancy breaking

Dormancy period starts in the month of July and August. Complete natural bud breaking is only possible at attitudes above 3000m; therefore dormancy breaking methods are used for altitudes lower than that. Dinitro aerosol (2.4%) and 6% tar oil (Tropical mortegg) are commonly used for breaking dormancy during the first week of September. Due to their toxicity, timely sprays should be done to avoid injury to flowers and leaves. The chemicals are effective at high temperatures. Manual dormancy breaking is done by hand defoliation 4 weeks after harvest and before it goes into dormancy, reduction of irrigation water and pruning of branches and roots.

Fruit pruning

Where necessary, fruit thinning should be done to leave 2-3 evenly spaced fruits per spur. Excessive fruit set may lower the quality of the fruit while flower and fruit drop may prevent excessive fruit set.

Yields

Mature trees individually can yield up to 20Kg/year when they have attained an age of 7 years. Production can continue for 20 years after which yields start declining.

Fruit handling

Maturity of the fruits is determined prior to harvesting by change in fruit colour to a yellow colour and when the fruits are easily removed from the tree. After picking, fruits should be placed on a cushioned crate or cartons.

DISEASES

INSECT PEST