Flower and fruit abortion in avocado and other fruit trees has become a serious issue for farmers in Kenya, leading to massive losses. It is a phenomenon influenced by a combination of environmental, physiological, and biological factors.
 |
| How to Prevent Flower and Fruit Abortion in Avocado and Other Fruits |
Below, I will explore the causes of and possible solutions of fruit and flower
abortion in avocado trees and extend the explanation to
other fruit trees where applicable:
1. Environmental Stress
Extreme Temperature
Avocado
trees are sensitive to both high and low temperatures. Excessive heat (above 35°C)
during flowering can cause damage to the pollen grains produced by flowers.
When this happens, pollination fails, hence the flowers abort. Frost or periods
of extreme cold can also damage the delicate flower blooms or young fruit,
causing them to fall off. Other fruit trees like apples or citrus may abort
fruit under similar temperature stress.
Water Deficiency or Excess
Lack
of water reduces fruit trees’ ability to support flowers and young fruit,
leading to abortion. On the other hand, too much water (waterlogging) depletes
oxygen in the root zone, impairing nutrient uptake and causing fruit drop. This
applies broadly to all fruit trees, not only avocado.
Wind
We
give very little attention to strong winds, yet they can physically damage
flowers or completely dry them out, reducing pollination success. This is a
notable issue for avocados, which have fragile flowers. If you must plant your
avocados on land that experiences strong winds, you should consider planting
wind breakers – other fast-growing trees such as Moringa Oleifera.
2. Nutritional Imbalances
Deficiencies
Lack
of key nutrients like nitrogen, potassium, zinc, or boron can disrupt flower
development or fruit set. Boron, in particular, is critical for pollen tube
growth and fruit retention in avocados and many fruit trees. Boron deficiency
has been identified as one of the major causes of flower abortion in avocados.
To prevent this, ensure that you top-dress your plants with a balanced NPK fertilizer
that has boron.
Over-Fertilization
A
common mistake that farmers make is the application of CAN or NPK fertilizers
that are rich in nitrogen during the flowering stage of their fruit trees. Excess
nitrogen promotes vegetative growth at the expense of fruit development,
leading to abortion as the tree prioritizes leaves over reproductive
structures.
3. Poor Pollination
Avocados
have a unique flowering behavior called "synchronous dichogamy." Each
tree has both male and female flowers which open at different times. If
pollinators (like bees) are absent during one of the flower opening phases, fertilization
fails, and flowers abort.
Cold,
rainy, or windy weather during bloom can reduce bee activity, affecting the
pollination process, hence the fruit setting.
To
overcome this problem, ensure that you plant different varieties of avocados
(or the other fruit you are farming) on the same piece of land. For example,
avocado farmers plant both Hass and Fuerte varieties to take advantage of
cross-pollination.
4. Pests and Diseases
Pests
like thrips, mites, fruit flies, and the infamous false codling moth are a
major cause of fruit and flower abortion in avocado and other fruits. These
pests damage flowers or young fruit, prompting them to fall off. In avocados,
thrips scarring is a common culprit.
Fungal
infections such as anthracnose and botrytis, or bacterial diseases can kill
flowers or fruit directly, or weaken the tree, leading to abortion.
An
early arrest of these pests and diseases through proper chemical or organic
control methods is the only way to overcome this problem.
5. Natural Thinning
In
any flowering season, fruit trees always produce more flowers than they can
sustain to maturity. This leads to a natural shedding process where weaker
flowers or young fruits drop to allow the tree to focus its energies on the
more potent flowers or fruits. This behavior is prevalent in avocados, even
though it is common in apples, pears, and citrus too.
If
photosynthesis is limited (e.g., due to shading or defoliation), the tree may naturally
abort fruits to prioritize survival.
While
this is a natural process, it is influenced by factors that we can control to
some extent: for example, we should ensure that our trees have sufficient
foliage (branches and leaves) before the onset of the flowering season. Proper
pruning should also be done to remove damaged or diseased branches to keep the
tree from concentrating on rejuvenating such parts, and directing the energy to
sustaining as many fruits as possible.
6. Variety related Factors
Hass
and Fuerte avocado varieties are very sensitive to stress. They also have poor
pollen viability compared to other varieties. This also happens with other
types of fruits; for example, certain apple varieties drop fruits more readily
under suboptimal conditions.
To
control fruit and flower abortion due to variety-related factors, ensure that
you select the varieties that best suit the environmental conditions of your
farm.
Important Notes
Avocados
(and many other fruit types) experience a phenomenon called biennial bearing or alternate bearing –
where the trees have a heavy crop yield one year and a typically low yield the next.
The high yield year is called the “on-year” and the following low yield year is
called the “off year.”
A
lot of flower and fruit abortion happens during the off year. Controlling this
phenomenon involves several strategies as explained in this article: How To Prevent Yield Fall in Fruit Farming: Stopping Alternate Bearing.
Summary: Fruit and Flower Abortion Mitigation Strategies
- Ensure consistent irrigation and drainage.
- Monitor and correct nutrient levels (e.g., foliar boron sprays).
- Protect pollinators by timing pesticide use and planting pollinator-friendly cover crops.
- Use windbreaks or shading to reduce environmental stress.
- Thin excessive fruit manually to reduce competition if natural drop is insufficient.