The demand for apples remains high the world over. Here are some basic guidelines to produce this popular fruit.
The main wild apple species, whose genetic composition contributes to modern apple cultivars, originated in Central Asia. Marco Polo’s journeys to the East and the establishment of the silk routes led to these wild species being introduced to Europe and, later, to the rest of the world.
In South Africa, commercial apple production occurs primarily in the Western Cape, but there are smaller plantings in the North West, Eastern Cape, Northern Cape and Free State provinces.
Apple trees grow well in temperate zones with cold winters (high chilling) and hot, dry summers. They shouldn’t be planted in areas prone to late frost.
As for most fruit trees, the number of cold units for a specific region will determine the suitability of a cultivar. For apples, cold units are high (900 to 1 200 or more). Insufficient cold units will result in delayed foliation, leading to poor growth and inadequate production.
Trees planted in such conditions will be difficult to manage in a commercial venture.
With climate change in mind, the South African Agricultural Research Council (ARC) is actively involved in breeding new varieties for areas that get less chilling in winter.
Many of the old cultivars formerly grown in South Africa – such as Ben Davis, Gravenstein and Rome Beauty – have been forgotten.
Years of breeding have led to the creation of new cultivars having skin ranging in colour from yellow and green to bright red and pink, including variations such as the blushed types.
Today’s fresh apple cultivars have a crisp texture, good sugar to acid balance and strong apple flavour. Most of these cultivars have no, or little, stem-end rust; they have a typical apple shape and offer high yields, good disease resistance and long-storage potential (up to a year in a controlled atmosphere).
Most cultivars need a cross pollinator, which flowers at the same time as the main scion cultivars, to ensure fruit set and good production. Bees are the main pollination agent and are introduced into orchards during flowering.
Today, all cultivars are budded onto clonal rootstock to ensure good yields. Rootstocks determine the overall size of the tree, production efficiency and resistance to soil-borne diseases. It’s essential to get expert advice when selecting a rootstock.
SOIL AND FERTILISER
- Apples prefer fertile, well-drained, well-prepared soils with a potential root depth of at least 600 mm.
- Avoid sandy, acidic soils.
- Soils that show signs of periodic or permanent damp should be drained or avoided.
- The fertilising programme should be based on the results of soil and leaf analysis, as well as the age of trees.
- Factors such as soil type, the removal of soil nutrients by the crop and expected production should also be taken into account.
- Leaf samples should be taken every January to establish the plant’s nutrient requirements, while soil samples should be taken at 3-year intervals after planting.
- Fertilisers are expensive and some nutrients, such as nitrogen, leaches from soils, especially if they’re sandy.
- Seek expert advice to ensure fertiliser is applied correctly, at the correct dosages.
- The table below provides a guide for the application of fertilisers from year 1 to 4.
- In general, phosphorus and lime are administered during soil preparation.
PRUNING AND THINNING
It’s essential to have a well-formulated plan, based on knowledge of the underlying principles of pruning and the general bearing habitat of a cultivar before pruning.
During its first 3 years after planting, a young tree should be pruned according to the set tree architecture, to:
- Remove branches that prevent sunlight reaching the inner parts of the tree.
- Shape the young tree into a preferred growth pattern.
- Remove dead and diseased branches.
- Thin out early flower buds to simplify the harvesting of fruit.
The best time to prune is during dormancy (from mid-July to the end of August). Remember, though, that summer pruning (after and before harvesting) to remove water shoots is an effective way to improve the penetration of sunlight to the centre of trees.
Doing so will improve fruit colour and production in general, especially for lower branches and inside the tree canopy.
Prune on a sunny day to prevent fungal infections from entering the tree through pruning wounds. Large pruning cuts should be sealed. Disinfect pruning secateurs after each tree pruned, to prevent the spreading of diseases between trees.
Apples can be thinned chemically. Thinning by hand takes place after fruit has dropped as a result of the chemical spray. Chemical thinning is complicated and cultivar restricted, so get expert advice before using this method to thin trees.
PESTS AND DISEASES
- The most important cause of damage and fruit loss in apples are codling and false codling moths.
- Apple scab and mildew are problems on leaves. Climatic conditions are a very important factor in the development of these diseases.
- There could also be other problems, such as mites (red spider and two-spotted mite), mealybugs, banded fruit weevils, fruit flies, cutworms, aphids, thrips and woolly apple aphids.
- Get expert advice for identifying pests and diseases.
Use the correct chemical formulation to control them, and follow the directions to ensure the right dosage and application method are used.
Climatic conditions; soil type; the availability of water; the age and size of trees; and the type of irrigation used, all determine how much, and how often a farmer should irrigate.
- Sandy soils need a little water, applied at short intervals, while clayey soils need more water, at longer intervals.
- Post-harvest irrigation is important as the next season’s fruit buds are formed during this period.
- The trees may be dormant during winter, but they still need water.
- Trees in summer rainfall areas should be irrigated at least once a month.
- As a very general indication, young trees need 300 mm to 400 mm of water per year, and this increases to 500 mm to 700 mm per year for mature, fully-bearing trees.
PICKING AND PACKING
- The maturity of apples is commonly determined by using the standard iodine test.
- This indicates how much starch has been converted to sugar.
- It’s essential to sample fruit on trees correctly. Fruit on the outside will be riper than that closer to the centre of the tree.
- As apples bruise very easily, fruit should be picked and transported with care.
- At the pack house, the fruit is stored in cool rooms at -0.5°C before packing.
Most apples can be stored for 2 to 4 months in an ordinary cool room, whereas it can be stored for up to a year – depending on the cultivar and maturity at harvest – in a controlled-atmosphere cool room.
- This article was written by Taaibos Human and first appeared in Farming SA.