APPLES (MALUS DOMESTICA)
Apples are hardy deciduous temperate fruit trees in the rose family Rosaceae that originated in Western Asia. The apple tree is small (3-12 metres height) with a broad, often densely twiggy crown. The leaves are alternately arranged ovals with an acute tip and rough margin. The flowers are white with a pink shade that gradually fades. They have a high potential in highland areas where temperatures are low enough to break their dormancy.
There are more than 7,500 apple cultivars varying in yield and size of the tree. Most apple varieties produce fruit buds on short, stubby shoots called ‘spurs’ which develop on 2-3 year-old wood. However, a few are tip bearers, or partial tip bearers, producing all or most of their fruit buds at the very tips of the branches. Different cultivars may be distinguished by the fruit’s flesh colour, juiciness, firmness/crispness, and flesh texture. Other fruit characteristics include taste (acidic, aromatic, sweet, etc.) and skin colour (red, yellow, striped, blushing, and russeting).
|Apple cultivars grown in Kenya|
|Gloster 69||The tree is vigorous, upright spreading producing spurs freely. The fruits are pale greenish yellow, flushed almost oval with a dull deep red color. Flesh is creamy white, fine-textured, juicy, and sweet with briskly pleasant flavour. Excellent for dessert.|
|Mutsu (syn. Crispin)||Vigorous tree with dwarfing rootstock suitable for home gardening. The fruit has yellow-green, shiny, waxy and clear skin with a copper blush and pronounced lenticels. The fruits are large, with oblong and irregular shape. Flesh is very crisp, juicy and coarse-grained with a sprightly flavour. Excellent both for dessert and cooking. The fruit is free from russeting (appearance of corky, roughened, brownish or grayish areas) and will not shrivel in storage.|
|Winter Banana||The tree grows vigorously and alternately bears heavily and lightly. The fruit is pale yellow blushed pink. The skin is waxy, shiny, smooth and greasy with a distinct suture line. The fruit size is medium to large and mainly round to conical in shape. The yellowish-white flesh is crisp and juicy with a distinctive aroma.|
|Golden Delicious||The tree is moderately vigorous, low and spreading with wide-angled crotches. The fruit is initially greenish-yellow and turns golden-yellow but occasionally tinged red. The fruits are large with a round-conical to oblong shape. The flesh is cream, slightly green-tinged, crisp, fine-textured juicy, sweet and a little acidic with pleasant aromatic flavour. The skin is dry and bruises easily. Its excellent multipurpose apple with very good storage qualities.|
|Jonagold||The tree is Moderately vigorous, fairly wide-spreading producing spurs freely. The fruit is bright yellow with some green shades and round to conical shape. The flesh is creamy white, firm, sub-acid, and juicy with a good rich flavour. It is excellent for dessert and processing. Fruits can be stored for up to 5 months.|
|Rome Beauty||The tree is upright spreading and round-headed. The fruit is greenish-yellow and up to one half flushed dull red. Good for eating raw and for all-purpose cooking.|
|Granny Smith||The tree grows upright, is vigorous and bears early and heavily. It requires a long growing season to mature and is an excellent pollen source for other varieties. The fruit is waxy, smooth-skinned and bright green, sometimes flushed purplish-brown. The flesh is white, hard, crisp and juicy. The fruit will store for 4-5 weeks without refrigeration.|
|White Winter Pearmain||The tree grows tall and upright, the bark is dark-red on new areas of growth. The fruit has pale yellow skin with a brownish-red shade. The skin is waxy and tough while the flesh is yellowish-white, crispy, juicy and tender with a sub-acid flavor.|
|Gravenstein||The tree is very vigorous with an upright spreading habit. The medium to large roundish fruits tend to be a bit lopsided, striped with a red over a greenish-yellow skin. The flesh is creamy yellow, very juicy, crisp, fine-textured, distinctively aromatic and slightly acidic.|
|Ana||The trees are vigorous, upright, and of medium height. Fruit size is medium to large with round-conical or conical shape. The flesh has a good mild flavour that is sweet to semi-acidic with crisp to soft texture. The storage ability is poor|
Apples grow well in the altitude range of 1500-2800m asl. Since cultivars with low chilling requirements are available, and dormancy break can be induced artificially, elevations of approximately 1500–2200m are the most suitable.
Apples grow well in areas with 800-1100 mm of annual rainfall. Heavier rainfall causes higher disease incidence especially fungal. In areas of low rainfall, irrigation can be used. There should be sufficient soil moisture at bud break, flowering, fruit set and fruit development to ensure adequate fruit yields and quality.
Deep, fertile, properly aerated and well drained soils are ideal. The optimum pH range is 5.5-6.5.
Optimum night and day temperatures of about 6-80C would enable complete bud breaking. Apple trees require at least 500 hours of cold temperature to induce flowering.
An open site that is not too exposed to strong winds is recommended. The site should be sunny and frost-free. A slightly sloping ground is ideal. All trees and bushes should be cleared from the site.
Dig planting holes of 60 x 60 x 60 cm size at a spacing of 2 – 3 m between trees and 3-4m between the rows. The tree spacing should be wide enough to allow sufficient penetration of sunlight to lower parts of the tree.
To produce true-to-type apple cultivars, vegetative propagation techniques by either grafting or budding are used. The rootstock determines the vigour and eventual size of the tree.
Where space is limited, dwarfing rootstocks may be used. Trees on such stocks will produce fruit within 3-4 years.
For a semi-dwarfing rootstock is used, a first crop is produced after 4-5 years. Trees on this stock are ideal for planting in a lawn or rough grassy area on average soils.
Vigorous rootstocks take 6-7 years before any fruits are produced. The stocks should be used if there is plenty of space and the soil very poor, since these will make extremely large trees which will be difficult to pick and prune without ladders.
All apple cultivars will set a better crop if cross pollinated by at least one other different variety since the cultivars are not sufficiently self pollinating. Growing a good mix of varieties is recommended and varieties which have the same or adjacent pollination groups (flowering periods) should be chosen. If an apple tree consistently flowers without setting fruits, there is need to plant more varieties. Crab apples make good pollinators for apple trees provided they flower at roughly the same time. Alternatively, a ‘family’ tree can be established (single stemmed tree with at least two or three compatible varieties grafted onto it) where all the varieties on the tree will pollinate each other. Honeybees are the most important carriers of pollen and bee keeping is recommended.
The nutrient requirement is high after dormancy when flowers, shoots, leaves and fruit are developing. An annual application of CAN at 150g per tree in the first year after planting is recommended and is increased by 125g per tree in subsequent years to a maximum of 1.5 kg/tree/year. Also, 150g of Double Super Phosphate (DSP) can be applied in the second year after planting and increased each year by 150g up to a maximum of 2.5kg DSP per tree.
Depending on the age of a tree, an area of approximately 60–180 cm radius from the trunk should be kept weed-free. Chemical weed control is recommended. Mulch can also be used to smother weeds while conserving moisture but the mulch should not be in contact with the tree trunk.
Apple fruit trees will grow and fruit better if pruned regularly. The main aims of pruning are to encourage the tree to bear more fruit and to remove unwanted growth. ‘Training’ goes a step further to control the shape and size of the tree. Be careful when pruning tip-bearing varieties not to cut off all the shoot tips. Distinguish also fruiting from new wood when pruning as the fruit buds along the former are rounder and fatter than vegetative buds but if unsure, leave pruning until then
In the tropics, there is a tendency of apple trees to produce upright, strong and sparsely foliated un-branched shoots with limited productivity. Once fruiting starts, the primary consideration should be to strike a balance between vegetative growth and fruit production by controlling tree height and spread, exposure to light and renewal of fruiting wood. The most common pruning procedure is to create the ‘open centre tree’, or the ‘pyramid shape’ tree.
|Apple scab (venturiaina equalis)||This fungus attacks leaves and fruit. Lesions develop on both leaf surfaces, causing distortion. Scabby dark spots are clearly seen on infested fruit; immature fruit growth is distorted and the surface may crack||Use of suitable fungicides e.g. Antracol, milthane super|
|Powdery mildew (Potosphaeral eutrica)||In highly susceptible cultivars like Rome Beauty or Jonathan, infection starts as white felty patches especially at the leaf margin, later extending over the entire shoot. In serious infection, all parts of the blossom may be covered with the fungus and very often fail to set fruit.||Use of suitable fungicides Nimrod 25EC, Ridomil Gold MZ 68WG, Topsin M|
|Armillaria root rot.(Armillaria mellea)||A fungal disease that attacks the roots and can result in the death of the tree. A white layer of fungal growth can be seen under the bark of roots and trunk, and the foliage of infected trees turns yellow and then brown.It is especially problematic in recently cleared land that contains residual tree roots that are a source of innoculum.||Avoid planting in recently cleared land with residual tree roots|
Apple scab Powderly mildew on leaves Adult codling moth
Apples ripen satisfactorily on the tree and should be picked when they have reached optimum colour and size. Depending on cultivar, this will occur 5–7 months after flowering. Cultivars vary in their yield and the ultimate size of the tree, even when grown on the same rootstock. Mature trees typically bear 40–200kg of apples each year, though production can be reduced in years when conditions are un-favourable.
All apples for the fresh market should be handpicked. Avoid bruising and stalk punctures, which damage the appearance of the fruit and also provide entry points for fungi that cause fruit rots.
Post harvest management
Apples can usually be stored for 3–6 months at a constant temperature of –1° to 4° C and 85–95% relative humidity. However this differs between cultivars.
Apples are mainly sold in the local market especially in the urban centers.
There are two main types of apples – dessert varieties which are eaten fresh and culinary or ‘cooking’ apples which are generally large in size and very bitter if eaten raw and need to be cooked before eating (usually with the addition of sugar). A few varieties are dual-purpose – they can be used either for cooking, or eaten raw after a period of storage to allow the apples to sweeten. There are also varieties grown specifically for cider-making.