• Gallard Pruning Services John Gallard 0428 761 798 , john@gallardservices.com.au Servicing Hunter Valley and other areas upon request.
  
• Mulching service Peter Birch - Thunderbolt's Olives 0428 669 157 , thunderboltsolives@bigpond.com Mulches wood up to 300mm diameter Servicing NSW areas

• EV Olives Wenbo 203 Everton Road, Markwood VIC 3678 PH: 03 5727 0209, Email: wenbowwu@hotmail.com Service: Contract Bottling & Cask Filling
  
• Fini Olives Jim Hollingworth 237 Orange Springs Road, Regan's Ford, Gin Gin WA 6503 PH: 08 9259 4131, Email: jimh@finiolives.com.au

• Costa - Mount Camel Mechanical Harvesting Contractors servicing around the Mount Camel area with New Generation Sicma B411 Plus call 0488 010 173
• John Daniel - Tarlia Olive Estate Servicing NSW, QLD, SA, TAS, VIC & WA John Daniel resides in Lewiston on the outskirts of Adelaide, SA. Email: jtdaniel@adam.com.au
• Peter Haslett - Haslett Harvesting PO Box 164 Paringa, SA 5340 mail@haslettharvesting.com.au 08 8595 8046  (AH) Servicing SA.
• Puma Olive Harvesting Self propelled tractor mounted shaker.Capable of 1T/hr. Contact: Fran Goryan Ph: 0408 897 869  or 08 8823 3287 Servicing SA only.
  
• Andrew Bucknell Ph: 02 6343 7101  or 0428 232 798 bucknell@westnet.com.au 6 years experience, Sicma F3 harvester Looking to expand into QLD and SA Click here to download information for Andrew Bucknell
  
• Preston Valley Grove Sicma Speedy Harvester Contact Mick Ryan for more info Ph: 0419 907 701 , email:info@prestonvalleygrove.com.au
  
• Barilla Olive Harvesting Lot 286 Stebonheath Rd, Munno Para Downs. S.A. 5015 Shaker Harvesting, grove layout is important, please book early. Servicing South Australia Contact: Steve Barilla Ph: 0411 402 405 , email:bariloil@tpg.com.au
  
• National Olive Harvesters Pty. Ltd. 1 Nelson Road Lameroo S.A. 5302 Over-the-row Style Harvesting,Shaker Harvesting Servicing: ACT,NSW,QLD,SA,TAS,VIC & WA Contact: Ian Mead Ph:0885774062 or 0427879125 E-mail: iwmead@internode.on.net
  
• EV Olives Wenbo Wu 203 Everton Road, Markwood VIC 3678 PH: 03 5727 0209 or 0408 519 955, Email: wenbowwu@hotmail.com Service: Contract harvesting New generation harvester, small or large jobs, bin hire, fruit transport  & processing
  

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At the 5th International Conference on Sustainable Agriculture and Biosystems, researchers in Iran presented findings on why fruit and flower drop occurs in fruit trees and what growers can do to reduce losses. Drawing on their work, we explore the phenomenon of fruit and flower drop, the underlying causes, and practical remedies for orchard managers.    

The Role of Fruit Trees in Agriculture

Fruit trees contribute significantly to agricultural economies across the world. Their production supports farm income, provides employment for skilled horticulturists, and underpins industries ranging from fresh produce to processing and food manufacturing. Cultivation involves a complex mix of practices: careful irrigation management, balanced fertilisation, pruning, pest control, and the application of modern technologies. Beyond economics, fruit trees are valued for their nutritional contributions, supplying sugars, oils, proteins, vitamins, and essential minerals through both fresh consumption and processed goods.

The Phenomenon of Fruit and Flower Drop

Fruit and flower drop is a natural occurrence in many tree species. Its extent varies according to cultivar, climate, soil type, and orchard practices. In some cases, drop is beneficial, helping the tree regulate excessive fruit load through “natural thinning.” But when drop is excessive or occurs at the wrong stage, it becomes detrimental, reducing yields and profitability.

Researchers typically divide drop into three categories:

1. Natural Drop: This type results from competition between a very high number of flowers. Up to 90% of flowers and fruitlets may be shed in some species, but the remaining fruit usually develop adequately. Growers sometimes assist by thinning to ensure the fruit that remain receive sufficient nutrition and reach high quality.
2. Abnormal Drop: This type is more damaging because it affects flowers and fruits at various stages of development, including larger fruit, often reducing yields significantly.
   
3. Extreme Temperature Drop: This occurs during periods of hot, dry weather (often around June in many regions). While widespread, it usually has limited impact on the final crop load.

Causes of Abnormal Drop

Environmental Factors

• Extreme cold or heat events can damage blossoms or young fruit.
• Strong winds, particularly dust-laden storms, may strip flowers and fruit from trees.
  
• Heavy rainfall or hail can injure delicate blossoms.
  
• Excessive direct sunlight can cause sunburn, leading to premature fruit drop.
  

• High-pressure pesticide or nutrient spraying can dislodge flowers.
• Over-application or incorrect doses of sprays may also contribute to flower drop.
  

• Poor pollination and failed fertilisation result in flowers dropping.
• Over-competition for nutrients between flowers and developing fruit increases drop.
  
• Nutrient deficiencies, especially nitrogen and zinc, play a role.
  
• Irregular irrigation - including overwatering that suffocates roots - can trigger drop.
  
• Shallow soils limit root systems, reducing nutrient uptake and increasing drop.
  
• Weak or diseased leaves caused by pests, fungal infections, or poor tree health reduce a tree’s ability to support fruit.
  
• Misuse of plant growth regulators or tank mix errors in spraying can disrupt flowering.
  
• Infections of flowers or fruit by fungi or insects often lead to drop.
  
• Natural ripening and senescence also account for some degree of fruit shedding.
  

The Science Behind Fruit and Flower Drop

The underlying mechanism of drop is closely linked to plant hormones. As fruits grow, the concentration of auxins (growth-promoting hormones) declines, while ethylene levels rise. This shift lowers the fruit detachment force (FDF), weakening the connection between fruit and tree. The abscission zone (the separation layer) becomes increasingly sensitive to ethylene, causing fruit drop. Environmental conditions such as temperature and humidity interact with these hormonal signals to intensify drop.

Remedies to Reduce Fruit and Flower Drop

Growers can apply several strategies to reduce drop and improve fruit set:

• Fertilisation: Apply fertilisers well before flowering to build soil fertility. Nitrogen should be supplied before bloom, not after, to avoid negative effects.
• Micronutrient Sprays: Foliar applications of calcium, zinc, and boron—adjusted for tree age and timing - can enhance pollination and fruit retention.
  
• Pruning: Moderate winter pruning balances vegetative growth with fruit production.
  
• Girdling: In some fruit tree industries (e.g., apples and pears), carefully removing a ring of bark from branches at flowering can improve fruit set.
  
• Irrigation Management: Avoid excessive watering during bloom and fruit set to prevent root suffocation.
  
• Growth Regulators: The use of auxin-based products, such as seaweed extracts (rich in auxins, cytokinins, and gibberellins), can delay fruit drop and extend the flowering period.
  
• Pest and Disease Management: Prompt control of pests and fungal infections prevents cascading effects on fruit drop.
  
• Pollination Support: For self-incompatible varieties, ensure compatible cultivars or introduce pollinators like bees and butterflies.
  
• Windbreaks: Plant hedges or wind barriers to reduce wind damage and limit flower and fruit loss.

Practical Advice

While some degree of fruit and flower drop is unavoidable, excessive losses can usually be mitigated through careful orchard management. Attention to fertilisation, irrigation, pest control, and pollination provides the best defence against unnecessary drop.

Further Reading and References

• Concentrated Seagold Seaweed Extract
• Nitrogen Fertilisers
  
• Boron Application
  
• Calcium Fertilisers
  
• Zinc
  
• Soil Test & Leaf Analysis
  
• Pruning and Grafting tools
  
• Pruning machines 
  
• Gardening tools
  

Olive trees are well adapted to hot and dry Mediterranean climates, but even they can suffer from sunburn (also called sunscald) when exposed to intense sunlight, heat stress, or when bark that was previously shaded becomes suddenly exposed. In mature or neglected/abandoned groves - especially those with heavy pruning or thin canopies - the risk can increase significantly. 

Sunburn damage weakens trees, opens the way for pests and disease, slows growth, and in severe cases may lead to branch dieback or decline. It’s worth recognising early and managing before the damage becomes irreversible.

Sunburn Damage to Olive Tree Trunk -The image above shows classic symptoms: cracked, peeling bark and exposed wood.

Recognising Sunburn Damage in Olives

Here are key symptoms to watch for:

• Bark becomes discolored (straw, pale, or bleached areas) compared to healthy bark.
• Cracking, peeling or flaking bark, sometimes exposing pale wood beneath.
  
• Sunken or collapsed bark patches where the surface is depressed.
  
• In severe cases, sections of bark slough off entirely and expose dead wood.
  
• Cankers or lesions forming in the affected areas.
  
• Reduced leaf vigor, scorching or browning of leaves, especially near the canopy edges.
  
• Fruit drop or shriveling if the tree is already bearing. High heat stress may trigger olive abscission.
  
• Over time, branch dieback or trunk weakness in the sunburned section may appear.
  

One important effect is that sunburned bark is more vulnerable to pest and fungal invasion, such as wood-boring insects or opportunistic pathogens that exploit the compromised protective barrier. 

Because olive trees often live many decades, even older trees can sustain recovery—provided the damage is not too extensive and you intervene early.

Why Sunburn in Your Olive Grove Is a Concern

• Reduced growth and productivity: Damaged bark and cambium reduce the tree’s ability to translocate water and nutrients. The tree may divert energy to healing instead of growth or fruiting.
• Structural weakness: Sunken or damaged trunk areas may become weak points, prone to breakage or cracks later, especially under wind stress. 
  
• Higher susceptibility to pests and pathogens: Exposed or cracked bark invites insects (borers) or fungal pathogens to colonize. 
  
• Delayed recovery: If large patches are affected, the tree may require a long time to compartmentalize the damage, and growth may be permanently affected in that area.
  

Preventative Measures & Remedies

Here’s a set of strategies you can apply now or over seasons to protect your olive trees and help heal existing damage.

1. Maintain or restore shade to the trunk

• When pruning, retain lower branches or scaffold limbs that offer partial shading to the trunk. Don’t prune so aggressively that bark is suddenly exposed. 
• Use ground covers, mulch, or low shrubs around the dripline (but not touching the trunk) so that radiant heat from bare soil is reduced.
• If possible, plant shade species (small trees or shrubs) in-line rows or adjacent to blocks to break sunlight incidence midday or afternoon.

• Whitewashing or painting the trunk with a light, water-based paint (often diluted limewash or similar) helps reflect sunlight and reduce temperature extremes. Many growers use this method on sensitive or newly exposed trunks. 
• Use tree wrap or reflective sleeves on trunks, ideally on the side facing intense sun (often western or northwestern exposure in Australian climates). Wrapping material should allow air movement—avoid tight plastic wraps that trap moisture. 
  
• In olive orchards, kaolin clay sprays (e.g. “Surround” brand or similar) are sometimes used on foliage and trunk to reduce radiant heat absorption and protect against sun and heat stress. Some trials report yield improvements by reducing fruit burn and drop under high-heat conditions.
  

• Ensure the tree is not already under water stress. Provide adequate soil moisture during hot seasons (without overwatering).
• Use mulches (organic materials like prunings, compost, bark chips) to help moderate soil temperature and reduce evaporation, which helps maintain a stable microclimate for roots.
• Avoid practices that leave the soil bare and hot—bare clay can retain and radiate heat back onto trunks.

• Remove loose or dead bark carefully, but don’t over-prune or cut live tissue aggressively. Let the tree compartmentalize the damage naturally.
• For deeper or cankered sections, consult a tree health specialist to assess whether you need to trim back to sound wood or apply wound dressings.
• Monitor the area over seasons; the tree may form callus growth around the margin of the injury and seal it internally if conditions are favorable.
• Avoid additional stress (drought, nutrient deficiency, pests) in damaged trees so energy is available for healing.

• As you rehabilitate your grove, assess tree spacing, row orientation, and tree height to reduce reflective heat loading.
• Avoid creating large expanses of bare, reflective ground under rows. Maintain a cover crop, grass alley, or soil cover to diffuse heat.
• Track which trees show signs of sunburn after pruning or canopy changes. Use careful pruning patterns that don’t suddenly expose shaded bark.

Signs of sunburn in olive trees

Sunburn appears as pale, bleached bark patches on exposed trunk surfaces, cracks or peeling bark, and sometimes sunken or depressed bark areas. In advanced damage, bark may fall off, leaving wood exposed. Leaves near the margins of canopy may show browning or scorching, and fruit may drop prematurely under heat stress.

If you can, have a sample branch punched from just beyond the edge of the sunburn area so an arborist or consultant can evaluate whether live cambial tissue remains. Also, map out which exposures (north, west, etc.) in your grove tend to show sunburn more often—this helps plan protective shading or wrap strategies.

As you re-establish your grove’s health in other areas (soil fertility, drainage, pest and disease management, good pruning), protecting against sunburn becomes part of the maintenance process rather than a standalone issue.

References

• UC IPM (University of California): guidance on whitewashing trunks to prevent sunburn/sunscald on trees. 
• The Olive Centre: overview of sunburn damage in olive trees, risk factors (water deficit, heat), and vulnerability to borers.
• Tessenderlo Kerley technical note: kaolin (Surround) particle film reduces heat load/sunburn and can improve olive yield/quality under high-radiation conditions.
• Peer-reviewed study (Horticulturae/MDPI): mineral clay particles (incl. kaolin) evaluated on olives for effects on yield and oil quality.
• Research summary (IPB/Portugal): field experiments with kaolin 5% on ‘Cobrançosa’ olives under rainfed and deficit irrigation; particle film proposed to reflect heat/irradiance. 
• Australis Plants (AU olive resource): practical tips—white water-based paint (50:50) or trunk wraps on young/renovated olives; risk after hard summer pruning.
• NSW DPI (citrus reworking guide—general orchard practice): after heavy cutting, paint exposed trunks/limbs with diluted white water-based paint to prevent sunburn (principle applicable to olives after renovation pruning). 
• Agriculture Victoria (orchard recovery): recommends whitewash/diluted white paint on trunks/large limbs to minimise sunburn following canopy loss—relevant where olive canopies are thinned or defoliated. 
• Australian Olives (Olives Australia): Peacock spot factsheet (context—sunburned tissue predisposes to disease; useful companion reference for disease pressure in humid regions).

“Olive trees must put out fresh growth each year to produce fruit.”

Training shapes the tree to support efficient harvesting and encourage early production

When trees reach the canopy size best suited to their environment, yields may begin to drop. This often happens because the inner canopy receives limited sunlight, leading to leaf loss and a reduced Leaf-to-Wood Ratio. If a tree grows beyond its ideal size, it creates challenges for mechanical harvesters. Excess height and width, along with thick branches, can strain or damage harvesting equipment, reduce fruit removal efficiency, and slow the harvest. Because olive trees need to produce new shoots annually to maintain fruiting, consistent growth is essential—and pruning becomes an important management practice. Pruning improves fruit size, oil content, light penetration, and the Leaf-to-Wood Ratio. It also stimulates fresh growth and lowers water and fertiliser demand. 

1- TREE TRAINING 

Purpose: Establish early productivity with stronger yields, extend the productive lifespan of the tree, enhance fruit quality, and prepare trees for the harvesting system used in the grove. 

Timing: Training occurs within the first three years of the tree’s development. 

In the first year, pruning is minimal (assuming nursery trees arrive with a good structure). Remove lower or overly vigorous branches that compete with the central leader. The goal is to maintain an upright main trunk with outward-growing horizontal branches. Water shoots should be removed so they do not compete for nutrients and moisture.

During the second and third years, gradually remove lower branches below approximately 600–1000 mm. 

A balance is essential. Removing too much canopy reduces the tree’s photosynthetic area, slowing its progress until new growth resumes.

Light pruning involves removing only small sections of foliage (such as a few short shoots), which keeps the tree stable. This can be done from August through late May. 

Heavy pruning removes larger amounts of foliage, prompting a stronger regrowth response but also increasing frost risk. Heavy cuts should generally be delayed until late September unless conditions are warm enough to begin earlier. 

Tree training may also include tying and skirting as part of shaping and preparation.

2- PRODUCTION 

Young trees contain many non-productive branches because they are still actively growing. Once these branches mature and begin producing fruit, they eventually become exhausted and stop fruiting. At that point, they need to be removed to make room for new productive growth and renewal of the canopy. 

LoIf the bloom is light, pruning should focus mainly on non-productive wood to preserve as much fruiting potential as possible. In years with heavy bloom, pruning can be more assertive without significantly reducing the crop. 

Timing: From bud break through early December.

3- AFTER HARVEST (CLEANING) 

The goal at this stage is to remove large damaged branches left behind after mechanical harvest. This step can be postponed by applying copper after harvest and waiting until spring to remove the affected wood.

Read More: ● Marcelo Berlanda ● Mechanical Pruning ● Mechanical Harvesting