You’ve worked hard all season—pruning, irrigating, feeding, and protecting your apple orchard. The fruits are almost ready, showing size and color. Then suddenly, you notice a carpet of apples on the ground.
This is pre-harvest fruit drop—one of the most frustrating challenges for growers. Studies show it can cut yields by 10–30%, directly reducing your income just days before harvest.
The good news: with the right understanding and timely action, you can keep your apples on the tree until harvest.
Why Do Apples Drop Before Harvest?
As apples begin to ripen they produce large amounts of ethylene, the ripening hormone. Ethylene stimulates softening of fruits and the formation of an abscission layer in the stem. Ethylene enhances the production of enzymes that break down the cell walls and the complex sugars that hold cell walls together in the abscission zone of the stem. As these glue-like substances break down, they leave the fruit connected only by the vascular strands, which are easily broken.
Main Triggers of Fruit Drop
- Cultivar Genetics: Varieties like McIntosh, Golden delicious, Red delicious , and Honeycrisp are prone to drop, while Fuji and Gala hold better.
- Water availability: Lack of sufficient irrigation during dry seasons leads to greater fruit drop as the tree struggles to meet water and nutrient demands.
- Temperature Effect: Research shows warmer days dramatically shorten the time from ethylene rise to drop. The relationship between temperature and the speed of fruit drop is significant, as warmer temperatures dramatically shorten the time between the start of the ripening process (ethylene rise) and the actual fruit drop (abscission).
| Mean Daily Temp (°C) | Days from Ethylene Rise to Drop |
| 4°C | 25 Days |
| 10°C | 13 Days |
| 16°C | 7 Days |
| 21°C | 4 Days |
- Nutrient Imbalance: Poor soil conditions, such as low magnesium (Mg), high potassium (K), and excessive boron (B), can worsen fruit drop. Also, the variations in soil type can play a part. For instance, sandy areas will ripen early and drop ahead of heavier soil types.
- Heavy Crop Load: Overloaded trees thin themselves by dropping fruit.
- Pest & Disease Pressure: Pests (e.g., aphids, mites, etc) and diseases (e.g., Apple Scab) weaken the tree by damaging leaves, fruit, and vascular tissues, reducing photosynthesis and nutrient flow, which leads to premature fruit drop.
- Summer Pruning: Excessive pruning in summer, which lowers the leaf-to-fruit ratio below 20:1, can increase pre-harvest drop
- Weather: Windy weather close to harvest also impacts fruit drop
- Soil moisture: Both excessively wet and dry soil conditions stress apple trees, hindering nutrient uptake and increasing fruit drop. Dry soil leads to water stress, which reduces nutrient absorption and can trigger fruit drop as the tree conserves resources for its own survival. Wet, poorly drained soil can restrict root development, leading to poor anchorage and reduced nutrient uptake, while also increasing disease risk, which indirectly affects overall tree health and fruit retention.
How Can You Control Pre-Harvest Drop?
1. Strengthen Your Orchard Management
- Follow Integrated Pest Management (IPM) to minimize pest and disease damage.
- Thin fruits in June to reduce competition and encourage the plant to put more energy into producing fewer number of larger fruits, high quality apple fruits
- Water management and balanced fertilizer program
- Soil testing to confirm nutrient deficiency or toxicity
Grower Tip: Monitor orchards closely 2–3 weeks before harvest. This is the most critical window when drop usually begins.
2. Use Plant Growth Regulators (PGRs) Wisely
Fruit dropping can be counteracted by using different types of plant growth regulators (PGRs) which have different modes of action, such as inhibiting ethylene production or its perception, or directly delaying the formation of the fruit abscission zone
Here’s a quick comparison:
| Active Ingredient | Common Products | What It Blocks | Best Timing | Pros | Cons |
|---|---|---|---|---|---|
| NAA (Auxin-based) | Planofix, Starfix | Stem loosening | Just before drop begins | Fast action (2 days), cost-effective, great rescue option | Lasts only 5–7 days, can advance ripening in warm weather |
| AVG (Ethylene inhibitor) | ReTain® | Ethylene production | 2–4 weeks before harvest | Delays drop 10–14 days, slows ripening, keeps firmness | Expensive, not a rescue, can delay color |
| 1-MCP (Ethylene blocker) | Harvista™ | Ethylene action | Just before harvest (within 3 days) | Strong rescue, delays drop 10–14 days, no effect on color/ripening | Requires precise timing, costly |
A Closer Look at NAA (Naphthaleneacetic acid)
NAA (Naphthalene Acetic Acid) is a synthetic plant hormone (auxin) used to prevent fruit drop before harvest, especially in apples. It works by stopping the enzymes that weaken the area where the fruit attaches to the stem, keeping the fruit from falling off. However, NAA doesn’t slow down fruit maturity—it can actually speed it up, especially when temperatures are above 85°F. This means that it does not decrease the production or perception of ethylene, but instead it’s mode of action is based on inhibiting the enzymes which work to weaken the cellular composition around the stem, which would normally break the cells apart from one another causing the fruit to drop. . NAA has notable effects on increasing the overall ripening process, resulting in increased red skin coloration, flesh softening, and starch disappearance, while, at the same time, allowing the apple to stay on the tree, decreasing fruit drop. NAA is considered more as a “rescue PGR”, as it is used in order to stop the drop of mature apples due to unforeseen circumstances. It takes about 3 days to start working, and its effect lasts for 7–10 days. Applying it too early or too late can reduce its effectiveness. The PHI of NAA is 2 days.
The optimal rate of NAA is 10 ppm i.e, 100ml / 450 Litres of water. With an excessive use of water / kanal prevalent in the region, the dosage can be reduced upto 100ml / 800 litres of water as well.
Final Word
Pre-harvest fruit drop is a natural process, but it doesn’t have to cost you your crop. By combining good orchard management with timely use of PGRs, you can hold your apples until harvest, protect quality, and secure your returns.
At Orchardly®, we’re committed to helping growers stay ahead of challenges like fruit drop with timely advisories, weather insights, and best practices. Together, let’s make sure your apples reach the market in top shape—where they belong.