Enhancing the quality with regulating fruit crops in spring
Fertilisation through cross-pollination
In order to enhance the quality and quantity of fruit, cross-pollination by pollinating insects is highly recommended. No other cultivation measures, whether pruning, fertilisation or crop protection, can be successful if there is no fruit set after flowering.
Apples are, for the most part, self-sterile - that is to say the pollen from each individual varietal cannot be used for fertilisation and pollen from another varietal is therefore required. Given the comparatively large array of varietals in the limited land area of South Tyrol, this does not pose a problem.
At this time of year there is no other flying insect anywhere in the world with such a profuse population as the honeybee. This abundance is fundamental for effective cross-pollination. The honeybee also displays a marked loyalty to flowers, or floral constancy, which means that a bee colony will frequent one particular type of flower until the supply is finished. This constancy is measured at 85% amongst honeybees; in comparison, the bumblebee takes second place at just 40%.
The honeybee’s coat is of the ideal length for pollen to adhere to it well such that it is not lost in flight, and the bee itself is also stable enough to press the pollen into the stigma of a flower. Mobility on the part of the beekeeper is also a great advantage to the honeybee, as many colonies can be brought to a specific orchard as and when the need arises.
In fruit cultivation different varieties of pollen are required for effective fertilisation, but this is not the only factor to take into account; the pollen must also be capable of germinating the egg cell. Fruit crops release germinable pollen within a temperature range of 10 to 19 °C. Likewise in this sphere of activity, honeybees boast another singular attribute which proves to be of immense assistance: Only pollen which is capable of germination is of nutritional value to a bee colony.
Yield regulation through targeted thinning of fruit
The aim of thinning excess flowers or fruit is, on one hand, to improve the quality of the apples and, on the other, to prevent or halt alternate bearing, Thinning trees while they are in blossom has the greatest effect on alternate bearing. With optimal fruiting, it is possible to keep the proportion of under or oversized fruit to a minimum. An over or under-abundance of apples can compromise the quality of the fruit. If there are too many they remain small in size, are less brightly coloured and less flavoursome, while if there are too few, the apples grow too large and do not usually keep for long.
Chemical fruit thinning
When carried out in a timely manner, chemical thinning has a positive influence on bud differentiation and eases the task of the manual thinning, so essential to top-quality production. It is particularly important to note that vigorous trees are more sensitive to thinning agents. Younger plants should also be thinned more carefully up until at least their fourth year. Generally speaking, the most effective thinning agents are those which require most water. Additives such as wetting agents increase water uptake and, thus, the effectiveness of thinning agents.
In addition to the variety of sprays which can be used, string thinning offers another efficient thinning option. String thinners remove some of the blossom with rotating plastic threads. The best time to carry out this task is the stage between green and red budding until the blossom falls; any later could cause severe damage to leaves and branches.
In organic fruit cultivation, hand thinning is the safest and most important measure one can take in order to produce top-quality table fruit. Given that bud differentiation is usually complete by the end of June, measures to interrupt alternate bearing must be carried out around blossoming time. The blossom can be removed with shears or a besom. During vegetation, it is possible to set the optimal number of fruit per tree through targeted hand thinning selected according to the varietal and the system, thus optimising the colour and size of the fruit.