Alternate bearing refers to the irregular crops pattern that occurs in fruit trees. Essentially, a year with heavy crops is followed by a year with very little to no crop.
Alternate bearing is very often linked to a poor management of the fruit trees. This phenomenon can affect mango,pistachio, apple, pear, plums, apricot, orange , hazelnut, olive etc. Fruit trees that bear small fruit and an earlier harvest like cherry, sour cherry are not affected by alternate bearing.
The main cause of alternate bearing is an abnormal heavy crop on the fruit tree. In favorable conditions, trees can bear up to 5 times more fruit that they can actually carry and this lead to a struggle for food between the branches and the fruits, on one side, and fruits and bud differentiation, on the other. Bud differentiation processes is essential for the next season’s fruiting so without bud differentiation there will be no fruit next year.
Keep in mind that alternate bearing doesn’t mean that after a year with a very high crop means that next year you will have no fruits at all. There can still be fruits but significantly less than normal.
Alternate bearing can take place in individual blocks, in single trees within an orchard, in one side of the tree canopy, or one branch only.
How to control it
- Planting of regular bearing varieties
When choosing what fruit trees you want to plant and what varieties be mindful to select the ones with a regular bearing. For example, if you choose to plant apple trees then you should know that Golden Delicious and Fuji are highly susceptible to alternate bearing and varieties like Gala, Idared, Granny Smith are less susceptible to alternate bearing.
2. Pruning
Pruning reduces alternate bearing by restoring the vegetative vigour where it is declined excessively due to over-cropping.
3. Fruit thinning
You can remove, by hand, smaller fruits before the summer drop to reduce alternate bearing.
4. Proper management of the fruit trees
You should provide adequate nutrients to the fruit trees, irrigation and a proper management of pests and diseases should do the trick.
5. Girdling
Reduces excessive vigor and improves flowering and fruiting.
Garden and Orchard 