Information provided by Phytech’s Head of Agronomy, Ziv Attia, PhD
Why Are Your Avocados Dropping Too Soon? Every avocado grower knows the frustration: perfectly good fruit scattered on the ground before it’s picked. It’s not uncommon, but it’s not good for business. Fruit dropped too soon can represent lost profit and waste. But why does it happen, and more importantly, how can you prevent it?
A Common but Costly Problem
When fruit drops from the tree too early, there are usually clear signs that explain why. Avocados provide a great example. Rather than detaching cleanly at the abscission zone (where the stem naturally separates), the fallen fruit still has part of the stem attached. This isn’t random– it’s a delayed response to plant stress that occurred weeks or even months earlier.
Another key clue? A dark ring around the seed of fallen fruit. This stain is a telltale marker of stress that happened during cell division and early fruit fill, long before the fruit actually dropped. When avocados are picked directly from the tree, there should be no dark stain around the seed.
What’s causing the stress?
Avocado trees are sensitive. Stress at critical growth stages can trigger fruit drop.
Water stress (too much or too little)
Avocados need consistent soil moisture. A study published by Silber et al. in 2019 highlights the importance of consistent irrigation for Hass avocado trees to prevent fruit drop and ensure high yields. The study found that water and nutrients are crucial during flowering and fruit set. Avocado trees need a lot of support and monitoring during these stages.
The researchers also found that trees that always received enough water and were not stressed did not experience alternate bearing. Trees under water stress had significantly lower yields in "off" years. This points to the significance of intentional, precise irrigation.
Interestingly, the same study found that consistent mild water stress is better than short, intense stress in summer. Trees can adapt to ongoing water stress by growing fewer leaves and reducing water loss. However, short-term stress during summer growth can be more damaging. This may lead to increased levels of premature fruit drop later on.
From these findings, it’s clear that too much water can suffocate roots, while too little can lead to dehydration. Water stress during the early stages of fruit growth led to fruitlet drop later on, which in turn reduced avocado yield. Both overwatering and drought stress conditions can trigger fruit drop, as trees prioritize survival over fruit development under stress.
Root health & soil conditions
Avocado root growth slows as the developing fruit demands more energy, making early-season irrigation and nutrient management crucial. A well-hydrated and nourished root system helps the tree absorb water and nutrients when it needs them most. However, because avocado roots are shallow, they are susceptible to irrigation imbalances. Too little water leaves roots dry and unable to function, while too much water reduces oxygen levels, leaches nutrients, and weakens root activity. Careful water management before fruit development ensures strong roots that can support healthy growth throughout the season.
How to Prevent Avocado Fruit Drop
Since fruit drop is often a delayed response to earlier stress, prevention starts with early detection and proactive management.
Improve Irrigation Management
For optimal irrigation management, integrating advanced technologies like Phytech can be a game-changer. Phytech allows growers to detect water stress in real time, enabling them to make proactive decisions and optimize water use. This technology provides continuous monitoring of tree health, water demand, and environmental conditions, helping farmers to adjust irrigation levels accurately.
Our hydraulic data and alerts systems help growers optimize irrigation efficiency, ensuring even water distribution with pressure maps and variability management. The system offers detailed tracking through flow meters, fertigation and tank-level monitoring, valve sensors, and in-field pressure readings, giving full visibility into water usage. Real-time alerts notify growers of critical irrigation issues, such as pressure fluctuations, deviations from irrigation plans, and filter station status, allowing for immediate action to prevent water stress and improve overall tree health.
Track tree stress with dendrometers
The same study by Silber et al. found that dendrometers and the maximum daily shrinkage (MDS) values they collect can accurately identify key growth stages and stress levels in avocado trees. By analyzing trunk diameter variation (TDV) data, the researchers tracked trunk growth rate (TGR) and MDS, providing valuable insights into the tree’s phenological stages. (including shoot, fruit, and root growth cycles).
Dendrometers work by capturing the minute changes in a tree's diameter in microns. These tiny fluctuations occur as a trunk expands with water uptake and contracts during water loss. By measuring these small changes in tree trunk size, dendrometers provide early warnings of water stress before it impacts fruit retention.
These fluctuations represent evapotranspiration, which helps determine how much irrigation is then needed. This is particularly important for avocados, as proper watering during flowering is crucial for fruit set. During this time, the trees have a higher water demand due to the increased transpiration from the flowers.
Watch for patterns and trends
Having data year after year allows you to recognize patterns and understand the history of your trees. While you might not catch every issue in the first season, over time, you’ll be able to spot early signs of stress and make better-informed decisions.
Consistent monitoring helps you learn what works for your orchard, so each year you can fine-tune your approach and respond faster to changing conditions. Without that ongoing data, it’s hard to know exactly what’s happening with your trees, and you could miss crucial insights that affect yield.
Take control of fruit drop before it happens
Fruit drop is bad luck– but it’s also a predictable response to past stress. By understanding the causes and using the right tools, growers can catch issues before they impact yield. Investing in precision irrigation and real-time monitoring is an investment in healthier trees with better fruit retention.
Are you seeing unexplained fruit drop in your orchard? It’s time to start tracking plant stress before it costs you.
Contact a Phytech expert today to learn how the Frost App can work for you.
References
Silber, A., Naor, A., Cohen, H., Bar-Noy, Y., Yechieli, N., Levi, M., Noy, M., Peres, M., Duari, D., Narkis, K. and Assouline, S., 2019. Irrigation of ‘Hass’ avocado: effects of constant vs. temporary water stress. Irrigation Science, 37, pp.451-460.
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