Flower Abortion in Olive Trees: Causes, Impacts, and Practical Advice
What Is Flower Abortion?
Flower abortion refers to the abnormal dropping or premature abortion of flowers and ovaries in olive trees. This phenomenon can significantly reduce yields, particularly after years of heavy production, due to the alternate-bearing phenomenon.
The Impact of Weather Conditions
1. Humidity, Fog, and Rain During Anthesis
Rainfall, excessive humidity, and fog during the flowering period (anthesis) can seriously interfere with fertilization. In particular, they damage the stigmatic papillae, which are essential for pollen grain germination. Fog is particularly harmful at this stage.
2. Drought and Hot Winds (Sirocco)
Contrary to common belief, during flowering, dry and hot air generally favors very good fertilization in olive trees.
Nitrogen Nutrition and the Role of Mycorrhizae
- Nitrogen deficiency: A lack of nitrogen in the shoots leads to an immediate halt in fruit development.
- Mycorrhizal competition: In nitrate-poor soils, mycorrhizal fungi absorb the available nitrogen for their own growth instead of transferring it to the tree, worsening the deficiency.
- Targeted fertilization: An adequate application of nitrogen fertilizers stimulates root development and ensures the tree's independence from the fungus, significantly improving fruiting.
Other Factors Causing Flower Abortion
Malformations and Pollination
Some olive trees, commonly known as dekkar or male olive trees, have malformed ovaries and produce virtually no fruit.
Pests and Diseases
Attacks by the olive psyllid (recognizable by its cottony secretions), the olive moth, and the development of sooty mold weaken flower clusters and cause flowers to drop.
Prolonged Spring Drought
Long periods without spring rainfall, particularly in May and June, weaken the tree and lead to massive dropping of young olives.
Practical Olive-Growing Tips
- Optimize nitrogen fertilization in spring: Apply suitable nitrogen fertilizers to support the growth of flowering shoots and help prevent young fruit abortion.
- Monitor the weather during flowering: Pay close attention to your orchard during periods of fog or high humidity, as these conditions can impair pollen quality.
- Control pests early (Psyllid and Olive Moth): Inspect your trees regularly from early spring to control psyllids and olive moths before they damage the flower clusters.
- Ensure an adequate water supply in May and June: During prolonged drought, provide supplemental irrigation during fruit set to prevent premature dropping of young fruits.
