• Irrigation
• Nutrition
• Pruning
• Pest and Disease Control

Irrigation

"A grove without an effective irrigation system is unlikely to deliver consistent yields year after year. Many growers still underestimate the water needs of olive trees, and few actually monitor soil moisture levels. This is why so many groves have never achieved a commercial crop."  Marcelo Berlanda Specialist Olive Consultant

Water stress negatively affects flowering, fruit set, oil accumulation (oil production), fruit size (table olives), fruit quality, and overall tree health. However, many growers lack a proper system to monitor soil moisture or manage irrigation effectively. 

Marcelo recommends:

"Growers should inspect soil moisture weekly during spring and summer, and every two weeks in autumn and winter. Use a shovel to dig at least 400mm under the tree canopy to check moisture. If the soil is hard to dig, it’s too dry – even if the canopy shows no visible signs of stress." 

Advanced soil moisture monitoring tools can also provide reliable data on a digital display or computer dashboard. 

For optimal grove health, growers must consistently check soil moisture and prevent water stress.

Nutrition

As discussed previously, taking leaf samples is essential to assess your trees’ nutritional status. This information guides the creation of a fertiliser program, a critical component for boosting or maintaining yields.

Typically, no fertiliser is needed in winter, unless you’re addressing soil amendments. However, some groves have severe nutrient deficiencies requiring fertiliser even in winter. Where proper irrigation systems aren’t in place, growers must broadcast fertiliser before rain to allow rainfall to incorporate nutrients into the soil profile, an inefficient use of resources but often the only option.

When applying fertiliser in these conditions, target the area beneath the canopy and, if possible, cultivate the soil to improve incorporation and reduce product loss.

Olives need four essential nutrients: Nitrogen, Phosphorus, Potassium, and Calcium. Check product labels carefully. As a general guideline, aim for:

• Nitrogen 15%
• Phosphorus 5% or less
• Potassium 10% or less
  
• Calcium 2% or less
  

Pruning

Avoid pruning during the coldest part of winter and when it’s wet or foggy to reduce the risk of bacterial and fungal disease spread.

The main goals of pruning are to remove dead wood, reduce canopy size, restore tree balance, encourage healthy new growth, and increase fruit set in spring.

Tip: After pruning, apply a copper-based spray to protect wounds from infection by fungi and bacteria.

Pest and Disease Control

Pest & disease management is crucial for sustaining yield and tree health. Winter’s colder temperatures reduce insect activity, offering a prime time to tackle pest issues.

Set up a comprehensive Pest and Disease Monitoring Program. During winter, check marked trees (previously affected by pests or diseases) every two weeks; in spring, check weekly. Look under leaves and on new growth for signs like crawlers, yellow spots, black sooty mold, or anything unusual.

Proactive, weekly management is essential for a successful grove.

If you need further assistance, please contact us.

What is Phytophthora Root Rot?

Phytophthora root rot is a destructive soil-borne disease of olive trees caused by Phytophthora species (water-mould pathogens). At least seven Phytophthora species have been identified attacking olives in Australia . These pathogens infect roots and can extend into the lower trunk, causing root decay and crown cankers that girdle the tree. If left untreated, Phytophthora root rot can kill olive trees, either through a rapid collapse or a slow decline over several seasons . The disease has been observed in many olive-growing regions worldwide, often linked to periods of excessive soil moisture. 

Symptoms: Infected olive trees typically show a loss of vigour and drought-like symptoms even when soil moisture is adequate. Foliage becomes sparse as leaves wilt, turn yellow, and drop prematurely . Shoot dieback starts at the tips of branches and progresses downward. In advanced cases, entire limbs or the whole canopy may wilt suddenly, especially under stress conditions like hot weather, flowering or heavy fruit load . Root and trunk symptoms include soft brown rot of feeder roots and lesion-like cankers at the crown or lower trunk; peeling back bark at the base often reveals reddish-brown discoloration of the wood. Affected trees may respond by shooting new suckers from the lower trunk or roots as the upper canopy dies back . Over time, the trunk can exhibit cracks or distortions due to the underlying canker damage . In some cases, trees can decline gradually over years, whereas in other cases they collapse quickly when the compromised root system can no longer support the canopy (for example, during a heatwave or late summer) . 

Contributing Factors and Disease Spread

Waterlogging and Poor Drainage: Excess soil moisture is the single biggest contributing factor to Phytophthora root rot in olives. Phytophthora thrives in saturated, oxygen-deprived soils. Australian conditions have consistently found Phytophthora outbreaks correlated with waterlogged conditions, claypan soil layers, or generally poor drainage in groves. Even a short period of waterlogging (as little as 24 hours) in warm temperatures can kill fine olive roots and predispose trees to infection. Low-lying orchard areas, heavy clay soils that drain slowly, or sites with a high water table create ideal conditions for the pathogen. It’s important to note that while waterlogging is a common trigger, Phytophthora can sometimes cause problems even in well-drained soils if the pathogen is present and environmental conditions (temperature, soil moisture) become favourable. In high-rainfall climates or during unusually wet seasons, otherwise well-drained olive blocks may still experience Phytophthora issues if drainage cannot keep up with prolonged rainfall. 

Susceptible Rootstocks: Most olive trees in Australia are grown on their own root stock (i.e., not grafted), but in cases where different rootstocks or wild olive (Olea europaea subsp. africana) seedlings are used, susceptibility can vary. Caution is advised when using feral/wild olive trees as rootstocks or nursery stock. These plants can originate from areas where Phytophthora is present in the soil and may introduce the pathogen or be less tolerant to it. There is currently no widely available Phytophthora-resistant olive rootstock, so all varieties should be assumed susceptible. Research by Spooner-Hart et al. noted that the emergence of Phytophthora problems in Australian olives has coincided with the expansion of plantings into non-traditional (non-Mediterranean) climates and heavier soils. This underscores the role of environment and rootzone conditions in disease incidence.

Warm, High-Rainfall Climates: Olives are traditionally adapted to Mediterranean climates (winter rain, dry summers). In parts of Australia with warm temperatures and summer-dominant rainfall (e.g., coastal Queensland and northern New South Wales), the risk of Phytophthora root rot is higher. The pathogen is widespread in soils and waterways in these regions and can easily infect olive roots when wet, warm conditions persist. Growers in such climates must be especially proactive with prevention measures. High humidity and frequent rain not only favor the pathogen but can also mask early drought-stress symptoms - an infected tree might not show obvious distress until a dry period or heat event reveals the extent of root loss.

Disease Spread: Phytophthora produces motile spores (zoospores) that swim in free water, so the pathogen spreads with water movement through soil and runoff. It can be introduced or spread in a grove via infected nursery stock, contaminated soil on equipment, flood irrigation water, or even the boots of workers moving from an infested wet area to a clean area. Once in the soil, Phytophthora can persist for years in root debris or as resilient spores. Thus, any practice that moves soil or water (e.g., tractor(s) and farm equipment, drainage flows) from an infected zone to an uninfected zone can facilitate the dissemination of the disease. Growers should avoid transferring mud and material from known infested blocks and ensure any new trees planted are from disease-free sources (pathogen-free). 

Best Practices for Managing Phytophthora in Olives 

Successful management of Phytophthora root rot in olives relies on an integrated strategy. This includes preventative chemical treatments, supportive nutritional therapies, and cultural practices to improve soil conditions and reduce pathogen spread. The goal is to protect healthy roots from infection, eradicate or suppress the pathogen in soil where possible, and help affected trees recover. Below are the current industry best practice:

Preventative Use of Phosphorous Acid (Phosphonate) Fungicides

Caption.

Phosphorous acid (also known as phosphonate or phosphite) is a key fungicide for mana PhozGuard 620 Phytophthora in many tree crops and is a cornerstone of preventative treatment in olives. Phosphonate does not act like a typical fungicide that directly kills the pathogen on contact,  instead, it works by inhibiting Phytophthora growth and stimulating the tree’s own defense mechanisms. This dual mode of action makes it most effective as a preventative treatment, applied before or at the very early stages of infection, to help the plant resist invasion. Phosphorous acid is available under various trade names (e.g., Phosguard620) with different concentrations of active ingredient. Always confirm that the product is permitted for use on olives and follow the label or permit directions. 

Application timing and rates: On woody perennial crops like olives, foliar sprays of phosphonate are typically applied approximately every 6 weeks during the growing season for ongoing protection. This ensures a consistent level of the fungicide within the plant, as it is systemic and will move into the roots. Label rates depend on product concentration; for example, products with around 600 g/L a.i. are used around 2.5 mL/L, 400 g/L formulations at 5 mL/L, and 200 g/L formulations at 10 mL/L (when applied with an air-blast sprayer to fully cover the foliage). For young or small olive trees, high-volume spraying to runoff ensures good coverage. Crucial timing is just before periods of high risk - e.g., before winter rains or summer wet spells - so that the roots are protected in advance. 

In situations where an olive tree has very little foliage left (severe defoliation from root rot), phosphonate can be applied as a bark spray or trunk injection. Spraying a ~10% phosphorous acid solution directly on the trunk or injecting the solution into the lower trunk can deliver the fungicide to the vascular system when leaves are insufficient. Trunk application is usually done in autumn or spring when the tree is actively translocating, to maximise uptake. Always exercise caution with concentrated trunk sprays to avoid phytotoxicity and adhere to recommended concentrations carefully.

Mode of action and benefits: Once absorbed, phosphonate is translocated downward with the sap flow, reaching the roots and inhibiting Phytophthora in infected tissues. It also primes the tree’s immune response. Treated trees often show not only disease suppression but also improved new root development in some cases. Phosphonate is valued for being relatively inexpensive and having low toxicity to humans and non-target organisms, making it a practical choice for routine preventative use. In warm, high-rainfall regions of Australia where Phytophthora is endemic, applying phosphonate prophylactically to young olive trees can protect them until their root systems establish. Many agronomists recommend an initial phosphonate spray or injection soon after planting in such regions, followed by periodic treatments during the wet season.

It’s important to remember that phosphonate is a suppressive, not an eradicant, treatment. It significantly reduces Phytophthora levels and activity in the tree but does not eliminate the pathogen from the soil. Therefore, repetitive or at least annual reapplications are needed to maintain protection. If treatments are stopped, Phytophthora can rebound if conducive conditions return. Also, phosphonate works best on preventing new infections and halting early disease - severely diseased trees (with the majority of roots already rotted) may not recover with fungicide alone. In those cases, phosphonate can only prevent further spread while other measures support the tree’s regrowth.

Other fungicides: Another chemical option is metalaxyl-M (e.g., Ridomil Gold), a systemic fungicide specifically targeting oomycete pathogens like Phytophthora. Ridomil can be applied as a soil drench or via injection to kill Phytophthora in the root zone. It has shown effectiveness in olives, but similar to phosphonate, it does not sterilise the soil and must be reapplied periodically to keep the pathogen in check. Phosphonate is often preferred for long-term management due to lower cost and resistance risk, but Ridomil drenches can be useful as a curative kick-start in heavily infested soils or to protect newly planted high-value trees. Always rotate or mix chemical modes of action as allowed, to prevent the development of fungicide resistance in the Phytophthora population. 

As an example for conventional application... Calcium nitrate at 10 g/L plus Solubor (boron) at 1.5 g/L, mixed in water, applied as a fine foliar spray every 6 - 8 weeks. Calcium nitrate provides a readily absorbed form of calcium (along with some nitrogen to spur growth), and Solubor is a common soluble borate fertiliser that assists to correct boron deficiency. These can be tank-mixed and sprayed to cover the foliage; ideally, apply in the cooler part of the day (morning or late afternoon) to reduce the risk of leaf burn.  Liquid boron applications like Agrodex Boron are usually recommended.   

Foliar Calcium and Boron to Aid Recovery 

In addition to fungicides, nutritional support plays a critical role in managing Phytophthora root rot - especially for helping infected trees recover. Two nutrients in particular, calcium (Ca) and boron (B), have been observed to assist olive trees suffering from root rot. Calcium and boron are closely associated with the growth of new shoots and root tips; they are essential for cell wall strength (Ca) and cell division/floral development (B). Some olive varieties have relatively high requirements for Ca and B compared to other fruit trees, and deficiencies of these nutrients often manifest as dieback of shoot tips (boron deficiency can cause tip death and poor new leaf growth, while calcium deficiency leads to weak stems and twig dieback).

When roots are compromised by Phytophthora, the tree’s ability to uptake nutrients from the soil is severely impaired. Ailing roots mean even if fertilisers are in the soil, the tree may still suffer from nutrient deficiencies. Foliar feeding can bypass the damaged root system and deliver nutrients directly to the leaves and young shoots. Foliar sprays of calcium and boron have shown positive results in reducing twig dieback and stimulating new growth on moderately affected olive trees. The recommended practice (from field experience in Australia) is to apply calcium and boron together on a regular schedule during the active growing season:

Complete Foliar Nutrient Programs for Impaired Roots

Beyond calcium and boron, a complete foliar nutrient program is advised for olive trees with significantly impaired root systems. Because root rot limits uptake of both macro- and micro-nutrients, foliar applications of a balanced fertiliser can supply the tree with essential nutrients until roots recover. Many agricultural suppliers offer soluble foliar fertiliser blends (NPK plus Trace Elements) that can be sprayed on the canopy. These blends often contain nitrogen, phosphorus, and potassium, as well as micronutrient like zinc, manganese, iron, copper, molybdenum, etc., in plant-available forms. Applying such a foliar feed can green up a chlorotic, declining tree and promote new leaf and root development while bypassing the diseased root system.

A suggested regimen is to spray a complete foliar fertiliser (for example, an NPK 20-20-20 with trace elements, or a product formulated for orchard foliar feeding) on a monthly or bi-monthly schedule during the growing season. This can often be done in conjunction with the calcium nitrate and boron sprays - either by alternating them or, if compatibility is confirmed, combining them in one tank mix. Be cautious when mixing fertilisers with fungicides: phosphonate is generally compatible with many fertilisers, but always jar-test combinations or consult product labels.

Foliar nutrient programs should be tailored to the grove’s specific deficiencies. If leaf analysis or visual symptoms indicate particular nutrient shortages (e.g., yellowing between veins might indicate magnesium or iron deficiency, small, distorted new leaves could indicate zinc deficiency), include or emphasise those nutrients in the foliar mix. Maintaining good overall nutrition will improve the tree’s resilience. Stronger, well-nourished olive trees have a better chance to compartmentalise Phytophthora infections and resume normal growth once conditions improve. Remember that these sprays supplement but do not replace soil fertilisation; once roots recover function, reinstating a normal soil fertiliser program (adjusted for any residual soil fertility and the tree’s regained capacity) is important for long-term production.

Improving Soil Drainage and Grove Management 

Cultural controls that improve the soil environment are fundamental to managing Phytophthora - no chemical or nutrient can fully substitute for a well-drained root zone. Growers should evaluate their grove for any conditions that contribute to waterlogging or poor root health and take corrective action:

• Improve drainage: Ensure that water is not pooling around olive roots for extended periods (see image right PC Australis Plants - water pooling around olive trees). For new plantings, select well-drained sites or use raised beds/mounded rows in heavier soils. Building the planting rows as mounds (for instance, 30 - 40 cm above the aisle) allows water to drain away from root zones more quickly. In existing groves, consider installing drainage solutions such as surface drains, French drains, or deep ripping between rows to break up hardpans. If a hard clay subsoil (clay-pan) is identified, deep rip or auger planting holes through it and backfill with a more friable soil mix before planting, to prevent perched water tables. Also, maintain grassed inter-rows or gentle slopes to channel excess rainwater off the orchard rather than letting it stagnate. After heavy rain, inspect the orchard to identify any spots where water stands and address those with drains or by regrading the soil. 
• Optimise irrigation: Over-irrigation can be just as harmful as poor natural drainage. Adjust your irrigation scheduling and method to prevent waterlogging. Use soil moisture sensors if possible to guide irrigation, and err on the side of “drier” rather than “wetter” when Phytophthora risk is high. For example, instead of one long irrigation set, you might split it into shorter, more frequent sets that allow more oxygen into the root zone between waterings. Microsprinklers or drip emitters should be placed such that they wet the root zone adequately but do not create continuously soggy conditions. Make sure emitters are functioning correctly and not leaking excessively in one spot. If at high risk, avoid irrigating just before evenings or periods of cool, humid weather - it can extend soil wetness duration. Proper irrigation management is part of integrated Phytophthora control, as noted by Queensland’s Department of Agriculture: avoid both over- and under-watering, since stress from drought can also predispose trees to infection or make symptoms worse.
  
• Soil amendments: Increasing soil organic matter can improve structure and drainage in the long term. Using mulch or cover crops in the inter-row can enhance soil porosity and microbial activity (which can sometimes suppress pathogens). Apply organic mulches under the dripline of olive trees to help soil structure, but keep mulch a few inches away from the trunk to avoid creating a perpetually moist collar around the base. In clay soils, the addition of gypsum can help flocculate clay particles and improve permeability. Gypsum (calcium sulfate) applied under the canopy can also provide calcium to the soil profile, which some studies suggest may reduce Phytophthora spore formation or activity (noting that very high soil pH can actually favor the disease, so use gypsum (pH-neutral) rather than lime unless you need to correct acidity). Always test soil pH before adding lime.
  
• Grove hygiene and design: Treat Phytophthora-affected sections of the grove almost as a biohazard area to prevent spread. Do not move soil from infected areas to clean areas - for example, if you dig out a dead tree, dispose of that soil away from the orchard or sterilise it. Clean farm machinery, tools, and footwear after working in a muddy, suspect area. Restrict access to the orchard when the soil is wet (to avoid picking up mud on tires). If using surface water (from dams or creeks) for irrigation, be aware that it could harbor Phytophthora spores from upstream sources - consider water treatment or use of drip irrigation that limits soil splash. In windbreaks or nearby vegetation, note that some ornamental or wild plants can be hosts for Phytophthora; controlling weeds and alternative host plants may reduce inoculum reservoirs. When replanting where an olive tree died of root rot, it’s wise to improve the site drainage and possibly leave the hole fallow or treat the soil (some growers solarise the soil or apply fungicides like metalaxyl pre-plant) before putting a new olive in the same spot
  
• Adjusting grove practices: Other cultural adjustments can reduce stress on at-risk trees. For instance, avoid heavy pruning of diseased trees (they need as much healthy leaf area as possible to regenerate roots) - only remove dead wood and lightly shape to balance the canopy. Do not remove those water shoots or suckers that often appear on the lower trunk of sick trees; as recommended by Australis Plants, allow these shoots to grow (pruning them back only moderately so they don’t become dominant branches) because they help the tree regain foliage and vigor. They can always be pruned off later once the tree fully recovers. Likewise, be cautious with fertilising a tree with a severely compromised root system - small, frequent doses or foliar feeds are safer than a heavy soil fertiliser application, which the damaged roots cannot absorb (and which could burn them or leach away). Finally, monitor Phytophthora-affected trees closely. If a tree is not responding to treatments (fungicide + nutrients) and continues to decline, it may be better to remove it and focus efforts on protecting surrounding trees. A rotting stump or roots can continue to harbor the pathogen, so in some cases, stump removal or fumigation might be warranted in patch areas of severe infection.

Phosphorous Acid vs. Calcium - Boron Treatments: Efficacy and Limitations

Both phosphonate fungicides and calcium-boron foliar feeds are important tools in managing Phytophthora root rot, but they serve different purposes and have distinct advantages and limitations. It’s not an either/or choice - in fact, they are complementary in a comprehensive management program. Below is a comparison to clarify their roles for growers:

• Phosphorous Acid (Phosphonate) Fungicide: This is a direct disease-control agent. Its primary benefit is its proven efficacy in suppressing Phytophthora within the tree. Phosphonate is currently the most effective chemical for slowing root rot in olives; it can arrest the progression of the pathogen and protect new growth when applied properly. Advantages of phosphorous acid include its systemic action (it reaches roots from foliar or trunk application), relatively low cost, and safety profile (no significant residue issues in fruit, and safe to handlers when used as directed). It also has some plant health benefits, like promoting new root initiation. However, phosphonate has limitations: it is preventative and works best if in the plant before heavy infection occurs. It will not revive roots that have already been killed, nor eliminate the pathogen from the soil. Continuous use is needed to maintain protection, and over-reliance on any single fungicide mode of action can risk the pathogen developing reduced sensitivity (though Phytophthora resistance to phosphonate has been reported only in a few cases, it’s still a consideration). Also, for certified organic olive production, synthetic phosphonate use is usually not allowed - organic growers have extremely limited options beyond cultural controls and perhaps some biofungicides (which have lower efficacy). So, phosphonate is a powerful tool, but it addresses the cause of the disease (the pathogen) rather than the tree’s weakened condition.
• Calcium-Boron Foliar Nutrition: This is a supportive treatment aimed at the tree’s health, not at killing the pathogen. The calcium nitrate + boron sprays help the olive tree by supplying critical nutrients to emerging shoots when roots cannot do so. The key advantage of this approach is that it tackles the symptoms (tip dieback, stunted new growth) and helps the tree to produce new foliage and roots despite the disease. By strengthening cell walls (Ca) and improving meristem growth (B), the foliar nutrients can reduce twig dieback and fruit drop, thus maintaining yield potential better than if the tree were left to decline. Calcium and boron applications are relatively inexpensive and can be easily combined with other foliar feeds. Crucially, they can improve a tree’s vigor, which indirectly makes it more resilient and better able to recover once the pathogen is suppressed. The limitation, of course, is that calcium and boron do not target Phytophthora at all. If used alone, they would not stop the root rot from spreading; a tree might look momentarily better as new leaves flush, but the disease could still be advancing in the roots unabated. Therefore, relying solely on nutritional sprays would be insufficient in a moderate to severe Phytophthora outbreak. Another limitation is that foliar uptake of nutrients can be affected by weather (rain can wash sprays off, very hot days can cause foliar burn or poor absorption), so timing and repetition are important. Finally, one must ensure that other nutrient needs are met - Ca and B address a specific issue, but a tree might also need nitrogen or potassium, etc., which is why a complete foliar nutrient program is recommended alongside Ca+B. 
  

It’s also worth comparing phosphonate with the other fungicide option, metalaxyl (Ridomil). Phosphonate and Ridomil both suppress Phytophthora, but in different ways. Ridomil is more of a curative, directly toxic to the pathogen, whereas phosphonate has those immune-boosting properties. Ridomil can knock back an active infection faster, but it has a higher cost and a risk of resistance development in the pathogen population with overuse. In practice, phosphonate is often used for regular protection, and Ridomil (if used at all) might be reserved for spot-treating severe cases or as a pre-plant soil drench in known infested sites. Both chemicals require reapplication; neither provides permanent protection. Always follow an Integrated Disease Management philosophy when using these tools - they are most effective when combined with the cultural and nutritional strategies described above.

Integrated Disease Management (IDM) in Australian Olive Groves

Managing Phytophthora root rot requires an Integrated Disease Management approach, especially in Australia’s warm, high-rainfall olive-growing regions. No single intervention is a silver bullet; instead, growers should implement a suite of preventive and remedial measures that together minimise disease impact. Below is a summary of IDM practices for Phytophthora root rot in olives: 

• Start with healthy, disease-free planting material: Only source olive trees from reputable, Phytophthora-free nurseries. Inspect the root systems of new trees (if possible) - healthy roots should be white and fibrous, not brown or foul-smelling. Avoid planting olives that show any signs of root rot or cankers. This prevents introducing the pathogen to your grove.
• Select and prepare sites wisely: Prioritise well-drained sites for new olive blocks. If you must plant in a heavier soil, invest time in soil preparation (deep ripping, adding gypsum/organic matter) to improve drainage. Form planting mounds or raised beds to keep root zones high and dry. Identify any low spots in the field and address them (through drainage tiling or by simply not planting olives in the very wettest spots). Good site selection and preparation are the most cost-effective long-term defense.
  
• Optimise water management: Design irrigation systems and schedules to meet olive water needs without creating waterlogged conditions. Use drip or micro-sprinklers to localise water and avoid overspray. Regularly check that irrigation is not contributing to puddling. During rainy periods, turn off irrigation entirely. Remember that olives are drought-tolerant compared to many fruit trees; slight under-watering is safer than over-watering in Phytophthora-prone areas. Also, avoid planting cover crops or pasture in the orchard that require frequent irrigation - keep the inter-row groundcover something that can survive on minimal water.
  
• Monitor and act early: Train yourself and staff to recognise early symptoms of Phytophthora (e.g., leaf yellowing, tip dieback, unusual leaf drop or wilting that isn’t explained by heat alone). Mark suspects trees and considers taking soil or root samples for lab testing to confirm the Phytophthora species. Early detection allows for prompt phosphonate treatment and targeted drainage fixes before the problem spreads or the tree is too far gone. If one tree in an area shows symptoms, proactively treat neighboring trees - they may be infected but not yet showing severe symptoms. 
  
• Apply chemical controls as part of a program: Use systemic fungicides like phosphorous acid as preventative sprays during high-risk periods (e.g., before and during the wet season). Follow up with repeat applications as per the label to maintain protection. If a tree is identified with active root rot, consider a curative treatment (such as a high-rate phosphonate injection or a metalaxyl drench around the root zone) to immediately reduce pathogen load, then continue with routine phosphonate. Always check the APVMA permits and registrations to ensure the product and method you choose are allowed in olives, and observe any withholding periods if the grove is in production. Rotate chemical modes of action if possible to prevent resistance - although options are limited (essentially phosphonates and phenylamides like metalaxyl), do not rely on just one product year after year without guidance. 
  
• Nutritional and soil health management: Maintain adequate nutrition in the grove to avoid stressing trees. Ensure soil pH and fertility are in the optimal range for olives (pH ~6.5 - 8, adequate but not excessive nitrogen, and sufficient phosphorus and potassium based on soil tests). Stressed or malnourished trees are more susceptible to infection and less likely to recover. After flooding or waterlogging events, consider applying a broad-spectrum foliar fertiliser to give trees a boost, as waterlogging can leach nutrients and damage roots. Incorporate organic matter through mulching or cover cropping (with species that do not harbor Phytophthora) to improve soil structure and microbial diversity, which can create a more hostile environment for the pathogen. Some growers also introduce biological controls like Trichoderma or mycorrhizal fungi into the soil, aiming to outcompete or antagonise Phytophthora - while scientific results on these are mixed, a healthy soil biota generally benefits root health.
  
• Hygiene and quarantine practices: Treat Phytophthora like you would a contagious disease. Clean pruning tools between trees (a bleach or alcohol dip can kill Phytophthora on tools). After removing dead trees or doing any excavation in an infected area, disinfect equipment and even shoes - soil clinging to a shovel or tractor tire can carry zoospores across the orchard. Avoid moving water from a known infested block to other blocks (for example, don’t pump runoff water from a sick block into your irrigation dam). If possible, keep a footbath or a brush station at the entry to a sensitive grove so that visitors don’t inadvertently bring in mud. Avoid sharing equipment with other farms known to have Phytophthora issues, or insist on thorough cleaning. If you yourself have multiple orchards, visit your Phytophthora-free orchard before visiting the infested one on the same day (not after), to reduce the chance of carrying soil back. These biosecurity measures may sound tedious, but they can save you from turning a localised problem into a farm-wide one. 
  
• Resistant varieties and rootstocks: As of now, there are no olive cultivars immune to Phytophthora, but research is ongoing into relative tolerance. Some anecdotal reports suggest that certain olive varieties handle wet feet slightly better than others - for instance, hardy traditional cultivars vs. some high-oil, fast-growing cultivars - but all will succumb if conditions are bad enough. If establishing a new grove in a high-risk site, consult local olive experts or nursery suppliers about any available rootstock or clone bred for Phytophthora resistance. The olive industry internationally is exploring grafting onto rootstocks of closely related species (like wild olive) for disease resistance, but these are not yet common practice. In the future, planting resistant rootstocks could become part of IDM (as it is in the avocado industry), but for now, Australian growers must focus on the other measures. 
  

Conclusion

Managing Phytophthora root rot in olives is challenging, but with vigilant management, it is possible to minimise losses and even restore affected groves to health. The keys are prevention (through site selection, drainage, and preventative fungicides) and support (through nutrition and careful cultural care for stressed trees). Australian olive growers should view Phytophthora management as an ongoing part of grove management, much like pruning or pest control, especially in regions prone to heavy rainfall. By implementing the integrated strategies outlined above, growers can significantly reduce the impact of Phytophthora root rot, protecting their trees and investment. Remember that every grove is different - monitor your olive trees closely and adapt these recommendations to local conditions, and always reference current guidelines from olive industry research and local agricultural authorities. With a proactive, informed approach, even the threat of “root rot” can be managed, and olive trees can continue to thrive and produce in the Australian landscape.

Sources: 

• Spooner-Hart, R. et al. (2005). Sustainable Pest and Disease Management in Australian Olive Production. RIRDC Publication No. 05/080. 
• Spooner-Hart, R., Tesoriero, L., & Hall, B. (2007). Field Guide to Olive Pests, Diseases and Disorders in Australia. RIRDC (eds.).
  
• Australis Plants Nursery. (2007). Phytophthora Root Rot in Olive Trees - Practical guidelinesPhytophthora Root Rot in Olive Trees
  
• Fruit Tree Lane (Australis Plants). (2023). Managing Phytophthora Root Rot in Olive Trees.
• Bailey, A., Hall, B., & Tesoriero, L. (2017). Symptoms and management of Olive diseases and disorders. The Olive Centre Blog.  
  
• Business Queensland, Dept of Agriculture. (2022). Phytophthora Root Rot – Integrated Management.
  

Marcelo Berlanda’s “Pruning for Production” guide highlighted why olive pruning is vital to sustain yields. This article builds on that foundation, focusing on how to encourage the growth of productive fruiting wood in Australian olive groves.

Why Productive Fruiting Wood Matters 

Olive trees bear fruit on one-year-old shoots – the growth produced in the previous season. Ensuring a steady supply of these young, fruitful shoots each year is critical for consistent yields. Without renewal, canopies fill with aging wood that carries fewer leaves and buds, leading to lower productivity. Pruning is therefore geared toward a few fundamental objectives : 

• Maintain a high leaf-to-wood ratio: An olive canopy should have abundant healthy leaves for each unit of wood. Excessive old wood with sparse foliage is unproductive. Pruning removes overly woody, leafless limbs to optimise the leaf/wood and leaf/fruit balance that drives fruiting. In practice, growers aim to leave enough leaves to support developing fruit (often discussed as an optimal leaves-per-fruit ratio) while eliminating wood that no longer bears productive shoots. 
• Promote new fruiting shoots: By cutting back old branches, the tree’s energy is redirected into new shoot growth. When these new shoots receive enough light and nutrients, they will form next year’s flower buds. Regular renewal pruning prevents the canopy from “running out” of fruitful wood. As olive expert Shimon Lavee noted, a strong flush of vegetative shoots in an “off” year provides the well-developed buds that form the next year’s heavy crop. Conversely, if few new shoots grew (for example, after an exhausting “on” year), the following crop will be light. Pruning helps balance this biennial tendency by stimulating fresh shoots each cycle. 
• Maintain light penetration and airflow: Productive fruiting wood needs sunlight. Olive flower buds are more likely to differentiate (turn from vegetative to reproductive) when exposed to adequate light. A dense, shaded interior will have blind wood with dormant buds that never fruit. Pruning opens the canopy so that sunlight reaches inner shoots, enhancing their fruiting potential. Research shows that flower bud induction is improved by light - “opening the trees for effective light penetration... increases fruiting potential by enhancing flower bud differentiation”. Along with light, better air movement helps keep foliage dry and healthy (as discussed later in pest management). 
• Prevent aging and sustain vigour: As olive wood ages, it can become less fruitful and more prone to dieback. Pruning is a form of controlled rejuvenation - removing limbs showing age or senescence to stimulate new growth (renewal). This keeps the tree in its productive prime longer. A well-pruned tree “does not lose its vitality or prematurely age”. Olive trees are long-lived and capable of sprouting new shoots from old wood, so with skilful renewal pruning, even very old trees can be reinvigorated. 
• Optimise tree structure for management: Pruning also shapes the tree for efficient harvest and orchard operations. By managing height and width, growers improve harvest efficiency (whether by hand or machine) and reduce branch breakage from heavy crops. An open managed structure lets sprays penetrate and workers/equipment access the tree. All these benefits tie back to nurturing productive wood - a compact, sunlit canopy zone where fruitful shoots thrive.  

Physiology of Shoot Growth and Bud Formation

Understanding how and when olive fruiting buds form helps refine pruning practices. Unlike deciduous fruit trees, olives do not have a true winter dormancy – their buds remain in a state of quiescence and will grow when conditions permit. Flower buds initiate relatively late: studies have shown that olive buds begin differentiating into inflorescences about 2 months before bloom (around late winter/early spring in the local climate). This means the buds on this year’s spring flowering shoots were formed in the late summer or autumn of last year, on the previous year’s wood. Crucially, those buds needed sufficient resources and light while they were forming.

Several physiological factors influence fruitful bud development: 

• Last year’s shoot vigour: Shoots that grew the previous spring and summer tend to have more nodes with flower buds. Very short, weak shoots often have fewer buds, but paradoxically, excessively vigorous shoots (“water sprouts”) often remain vegetative. Research in Tunisia (2025) found that thinner, moderately vigorous shoots carried higher inflorescence numbers than very thick shoots. This suggests that extremely strong vegetative growth (often caused by heavy winter pruning or excess fertilisation) can actually reduce floral initiation, whereas controlled, moderate shoot growth produces the best fruiting wood. Growers should aim for new shoots of medium length (e.g. ~20–40 cm, depending on cultivar) with good leaf cover – these are the shoots most likely to bear olives. Very long shoots can be tip-pruned in summer to encourage lateral fruiting spurs, but excessive heading should be avoided as it may induce unwanted branching that doesn’t flower. 
• Light exposure of buds: Olive buds need light to differentiate into flowers. Buds heavily shaded by an overgrown canopy often remain latent or become vegetative. A classic recommendation is to ensure sunlight can filter to all bearing shoots, including those in the lower and inner canopy. Connor et al. (2014) emphasised that all foliage must receive at least ~20–30% of full sunlight for the critical steps of shoot growth, floral initiation, and fruiting to occur. In hedgerow orchards, the lowest parts of the canopy wall are often the limiting factor for light – if those interior shoots get below-threshold light, they won’t set fruit. Pruning strategies like thinning out dense upper branches or narrowing the canopy can increase light to these shaded buds, thereby activating more fruitful sites. As one guide succinctly puts it, “remove any part that shades other younger parts of the tree” to keep the fruiting zone vigorous. 
• Resource allocation and alternate bearing: Olives are prone to alternate (biennial) bearing, partly due to resource competition between one year’s crop and the next year’s buds. A heavy fruit load (“on” year) not only uses up carbohydrates but also produces hormones (gibberellins from seeds) that can inhibit floral bud initiation for the following year. This is why a tree laden with fruit often grows fewer new shoots and may bloom poorly the next season. Pruning can mitigate this by adjusting the crop and stimulating vegetative growth at the right time. Strategic pruning in an “on” year (e.g. immediately after harvest) helps divert some resources to new shoot development, balancing the tree. In an “off” year, lighter pruning or none may be needed so as not to remove too much of the vigorous growth that will form next year’s inflorescences. The goal is to even out the boom-bust cycle: moderate pruning annually or biennially, rather than severe pruning at long intervals, tends to promote more regular yields.        
• Bud dormancy and chilling: Unlike many fruit trees, olive buds do not require deep winter chilling to break dormancy – they can grow if conditions are favourable (hence olives can fruit in warm climates with mild winters). However, cool winter temperatures are still important to induce olive floral buds. Insufficient chilling or an excessively warm winter can lead to delayed or incomplete flower differentiation. This is more relevant to certain Australian regions (e.g. subtropical areas) where winters are mild. While growers cannot change the weather, they should be aware that a healthy complement of buds might still fail to bloom if winter conditions are suboptimal. Good orchard practices (nutrition, pest control, pruning) ensure the tree has plenty of viable buds ready; the weather then decides how many of those convert to flowers. If a spring shows poor bloom despite many new shoots, lack of chilling or even a heat shock could be factors. In such cases, focus on tree health and wait for next season – overreacting with drastic pruning is not advised.

Takeaway: Productive fruiting wood arises from a balance – neither too vegetative nor too weak – and it needs sunlight. Pruning is the tool to create that balance by removing what’s unproductive and making space for fruitful shoots under the right environmental conditions.

Pruning Techniques to Promote Renewal Wood

Having set the physiological context, we now turn to pruning methods that encourage renewal of fruiting wood. The approach will vary with the age of the tree and the orchard system (traditional vs. high-density), but several general principles apply: 

• Prune after harvest during dormancy: In Australian conditions, this usually means late autumn to late winter (e.g. June–August, depending on region). Pruning right after harvest is a common practice – for oil cultivars harvested in autumn, growers often prune in winter before the next spring growth. This timing allows the tree to heal cuts before spring sap flow, and any stimulated shoot growth will occur as the weather warms (when it can actually develop). It’s important not to prune so early that a warm spell triggers regrowth in mid-winter, which could be damaged by frost. Generally, prune by late winter, after the risk of heavy rain or frost, if possible. For table olive varieties harvested earlier, pruning might begin in early winter (June/July in Australia). Always avoid pruning in wet conditions – cutting on a rainy day can spread diseases like bacterial olive knot to fresh wounds. 
• Use mostly thinning cuts, minimise heading: A thinning cut removes a branch at its origin, opening space but not excessively stimulating regrowth. A heading cut (tipping a branch) can trigger multiple shoots at that point. While some heading is useful to lower height or induce laterals, indiscriminate heading leads to bushy water-sprout growth at the canopy tops. These vigorous shoots often won’t fruit the next year and just consume resources. The best practice is to thin out entire limbs or large shoots that are unproductive or overcrowding, and lightly head only where necessary for shape. A rule of thumb: “cut to a lateral” – i.e. remove a branch back to a fork where a healthy lateral branch can take over, rather than stub-cutting it mid-way. Thinning cuts preserve the natural balance and direct growth into existing shoots that have better light. This results in more fruitful wood and less wasted vigour. 
• Renew in stages – avoid stripping all old wood at once: Particularly on older trees, do renewal pruning gradually. Remove one major old limb (or a few) each year rather than all in one year. Avoid severe, total canopy pruning whenever possible, as it causes a huge flush of vegetative suckers and a loss of a cropping year. Research confirms that severe pruning drastically reduces the next crop and prompts excessive regrowth. Instead, practice selective renewal: identify 20–30% of the canopy (by volume) that is oldest or least productive and remove that, leaving younger wood intact to fruit. The tree will channel energy into emerging new shoots near the cuts while still fruiting on the remaining wood that year. Over 2–3 seasons, this phased approach can completely refresh an old canopy with minimal yield loss in any given year. Even in low-density traditional orchards, renewal of aged trees is commonly done piecemeal because old olive wood can still sprout if some foliage is left to “pull” sap into the limbs. In very extreme cases where trees must be cut hard (storm damage, disease recovery, or neglected groves), expect a 1–2 year recovery period before normal yields return. Fortunately, olives are resilient – with adequate water and nutrients, they can refoliate and produce on new wood by the second or third year after even a brutal topping.
• Alternate pruning zones or sides: In hedgerow (SHD/HD) systems and even large free-standing trees, it’s wise not to prune the entire tree uniformly in one go. In hedgerows, an established practice is alternate-side pruning: trim one side of the hedgerow (or every other row) in one year and the opposite side the next year. This way, each side always has some younger fruiting shoots while the opposite side is regenerating. The same concept can apply to big trees – for instance, prune some main branches this winter, and others next winter. The unpruned parts will bear fruit to compensate, while the pruned parts regrow. Never “lion-tail” a tree (stripping out all interior branches and leaving a tuft at branch ends) – instead, maintain a balance of interior and exterior growth. By alternating pruning areas, you optimise production while renewing wood. Ferguson et al. (2012) reported that this method in SHD orchards led to better annual yields versus pruning both sides in one year. 
• Remove water sprouts and suckers judiciously: After pruning (especially if heavy), olives respond with vigorous shoots from latent buds – these can be watershoots (upright epicormic shoots along trunk or branches) or suckers from the rootstock/base. These are generally nonproductive in their first year and compete with desirable growth. It’s advisable to remove most of them in summer when they are green and soft (“summer pruning” or suckering). However, note that not all watershoots are bad – if a large limb was removed, some of the resulting watersprouts near the cut can be selected and managed to become the next fruiting branches. Typically, you’d thin out the excess shoots, leaving a few well-placed ones (avoid clusters of shoots all in one spot) and maybe pinch their tips to encourage them to harden and form flower buds. A study in Argentina found that thinning vigorous watersprouts about 3 months after winter pruning improved return bloom and yield compared to just heading them. By removing the most rampant suckers and keeping moderate shoots, you tame the regrowth flush into productive wood. Root suckers (from below the graft or ground) should usually be removed entirely, as they are often from the rootstock (if grafted) or will not form part of the canopy. 
• Aim for a vase or hedgerow form with open centres: In traditional trees, the classic shape is a vase (open-centre) with 3–5 main scaffold limbs. Keeping the centre free of clutter ensures light can reach the middle of the tree. The same logic applies to hedgerows – though they are a “wall” of foliage, they must be kept porous. A Spanish study on olive crown porosity showed that different pruning treatments did not always change overall porosity dramatically, but removing inner branches and lowering canopy density are key to light penetration. An open canopy also reduces disease (more on that below). Therefore, prune with the mindset of creating windows for light and air. One practical tip is to stand inside the tree’s canopy (for big trees) or look through a hedgerow wall – you should see patches of daylight through the canopy. If you can’t, more thinning is needed. Conversely, if you can see too much daylight (the tree looks skeletal), you pruned too much, which can lead to sunburn on bark and excessive suckering. Strive for a balanced canopy – about 50% interior light interception as a rough guide, meaning a mix of sun and dappled shade internally. 

By applying these pruning techniques, growers encourage a continuous supply of young fruiting wood while avoiding the pitfalls of over-pruning. The result is a tree that renews itself gradually: always plenty of 1-year shoots ready for the next crop, and no big shocks to the tree’s system. 

Tailoring Practices to Different Orchard Systems

Olive orchards in Australia range from traditional low-density plantings to modern high-density (HD) and super-high-density (SHD) groves. The principles of fruiting wood renewal apply to all, but the methods and intensity of pruning are adjusted to each system’s needs :

• Traditional (low-density) groves: These are widely spaced trees (e.g. 6m × 6m or more) often grown as large vase-shaped forms. Here, the challenge is managing tree size and rejuvenation over decades. Typically, traditional trees are pruned lightly every year or two, with a more severe renewal pruning maybe every 5–10 years on very old wood. The focus is on opening the centre, removing dead wood, and keeping height reachable (often below ~5–6m for ease of harvest). Growers might remove a few big limbs each winter (to stimulate new shoots inside), but avoid depleting the canopy too much in one go. Because these trees can get very large, sometimes entire sections are “stumped” in rotation – e.g. cut one scaffold back to a low knob to force new shoots, while leaving other scaffolds untouched that year. Over a cycle, the whole tree gets renewed. Traditional hand-pruning is labour-intensive, so it’s done strategically where needed. In these systems, sunlight is usually not a limiting factor around the outer canopy due to wide spacing; the main shading concern is the tree’s own interior. Thus, pruning concentrates on thinning the inside and top. Also, older trees may have hollow or leggy interiors – one objective is to populate those with new shoots by cutting back into those areas (“bringing the tree back in”). This not only produces fruiting wood closer to the trunk (improving harvest efficiency) but also reduces reliance on long, drooping peripheral branches that can break. 
• High-Density (HD) orchards: These are intermediate (e.g. 200–400 trees/ha, perhaps 5m × 3m spacing). Trees are smaller than traditional but larger than SHD hedgerows. Often a central leader or vase hybrid form is used, sometimes trained to ~3–4m height. Pruning in HD systems seeks to maximise light to all sides of the tree while controlling vigour. Mechanical aids may be used (like topping or skirt pruning with saws), but hand pruning is still important to thin out centres. One practice is selective limb removal every couple of years to prevent crowding between trees. In hedgerow-like HD plantings (if trees are aligned in rows but not a continuous hedge), you ensure each tree has its space: branches extending into tractor alleys or too close to neighbours are cut back. Prune to a cone shape (wider base, narrower top) so that lower branches aren’t heavily shaded. If mechanical harvesters like trunk shakers are used, maintaining some clear trunk and strong primary branches is important (so pruning off low suckers and very weak branches that won’t withstand shaking). HD systems might adopt some SHD techniques, like mechanical topping annually to a set height, combined with periodic hand thinning. The key is regular moderate pruning – because these trees are managed for efficiency, you can’t afford the massive alternate bearing swings or overgrowth. In fact, studies suggest annual light pruning in small orchards yields better cumulative production than infrequent heavy cuts. 
• Super-High-Density (SHD) hedgerows: These are very tightly spaced rows (e.g. 4m between rows × 1.5m between trees, ~1600+ trees/ha) pruned into narrow hedges ~2.5–3m tall. Cultivars like Arbequina, Koroneiki, and Leccino are common for SHD due to their naturally compact habit. Mechanical pruning is standard – typically, oscillating blade machines trim the sides and tops annually or biennially to maintain a harvestable “wall” for over-the-row harvesters. While mechanical hedging is efficient, it can lead to shaded interior wood and a decline in fruitful shoots deep in the canopy if done improperly. To counter this, SHD management includes: alternate-side pruning (don’t cut both sides of the hedge in the same year), and occasional, more severe “skimming” or renewal. For example, some growers, every 3–4 years, will do a heavy hedge cut on one side of the row (or remove every second tree, then replant) to renew the wall of foliage. Research by Gómez-del-Campo et al. noted that horizontal canopy porosity in tightly spaced hedges can be as low as 15% in mid-canopy, versus ~37% in the less crowded upper canopy. This highlights how dense these hedges can get. Maintaining porosity (gaps for light) through pruning is thus crucial. Connor et al. (2014) advise that both sides of an SHD hedgerow should never be heavily pruned simultaneously, and that light, frequent pruning is preferable to avoid big yield losses. In practice, this might mean yearly trimming plus a rotational renewal (e.g. flail pruning one side or topping lower than usual, but staggered). SHD groves also put a premium on controlling vegetative vigour – since trees are so close, excessive growth quickly leads to shading. Growers often use regulated deficit irrigation (RDI) and moderate nitrogen regimes to keep shoot growth in check. The pruning then accentuates this, ensuring the hedge doesn’t exceed the bounds (commonly hedged to ~2m wide at base, 1m at top, like an inverted “V”). The reward for this intensive care is early and high yields, but it requires disciplined pruning to sustain. 
• Very old or neglected trees: A note on abandoned or oversized trees (sometimes found in older groves): rejuvenating these requires a special plan. Often, the best course is heavy structural pruning in stages. For instance, cut back extremely tall trees to ~3m height by removing the top third of the canopy (one portion each year over 2–3 years). Simultaneously, thin out interior suckers and apply fertiliser and water to stimulate new shoot formation. This process can essentially “reset” an old tree into a productive, smaller framework. As pointed out in the literature, renewal of olive trees is a traditional practice even in low-density orchards – old wood retains sprouting capacity if given a chance. Farmers in the Mediterranean have for centuries rehabilitated ancient trees by pollarding or scaffold replacement, proving the olive’s remarkable ability to bounce back. Just remember to sanitise tools and perhaps apply protective copper spray on large cuts (to prevent disease in those big pruning wounds, especially important in older trees that may have existing infections). 

In summary, the pruning strategy must fit the system: gentle but regular for intensive hedges, somewhat heavier but less frequent for large traditional trees, and always aimed at keeping enough young wood in the pipeline. Regardless of system, the fundamentals remain: capture sunlight, encourage new shoots, and remove what’s unproductive. 

Integrated Pruning and Pest Management 

Pruning not only influences yields – it also plays a significant role in Integrated Pest and Disease Management (IPDM). A well-pruned olive canopy is generally healthier and easier to protect. Here’s how encouraging productive wood ties in with pest and disease considerations:

• Canopy density and fungal diseases: Many olive diseases thrive in dark, moist environments. Opening up the canopy allows better air movement and faster drying of foliage, which can substantially reduce disease incidence. For example, fungi like peacock spot (Fusicladium oleagineum) and anthracnose (Colletotrichum spp.) require periods of leaf wetness to infect. A dense canopy that stays humid after rain creates an ideal microclimate for these pathogens. By pruning to increase light and airflow, leaves dry quicker, interrupting fungal spore germination. The Best Practice IPDM Manual notes that speeding up evaporation of rain or dew through improved aeration can directly reduce fungal infections. Indeed, researchers observed higher anthracnose severity in very dense SHD plantings compared to more open canopies – underscoring that porosity matters. Growers are advised to prune out overly crowded branches and perhaps even lower canopy height to what their local climate can accommodate (e.g. in humid coastal regions, a shorter tree with a very open centre will suffer less disease than a tall, bushy tree). Additionally, better light penetration enhances bud health – weak, shaded buds are more susceptible to infections like botryosphaeria (which can cause dieback). Thus, a pruning program that keeps fruiting wood in the light not only improves fruiting but also inherently defends against disease. 
• Scale insects and other pests: Pests such as black scale (Saissetia oleae) and olive lace bug (Froggattia olivinia) often reach higher populations in dense, shady canopies. The IPDM manual explains that the immature “crawler” stages of scale and lace bug survive better in cool, humid microclimates inside unpruned trees. Hot, dry conditions are detrimental to these pests (many scales desiccate in sun-exposed positions). By pruning the inner canopy and letting sunlight in, growers create less hospitable conditions for scale infestations. In effect, judicious pruning is a cultural control method: it can significantly cut down pest survival rates, reducing the need for chemical intervention. Similarly, good pruning reduces the hiding spots for other insects and allows natural enemies (parasitoid wasps, lady beetles, etc.) to move more freely through the tree. Spray penetration is also vastly improved – when you do need to apply an oil or insecticide for scale, an open canopy lets the spray reach inner leaves and branches where pests harbour. Many organic or soft pesticides (like soaps, oils, copper, and pyrethrum) rely on contact action, so coverage is critical. Pruning ensures that sprays can “cover” the target surfaces. 
• Olive knot and wound management: One downside of pruning is the creation of wounds, which can be entry points for pathogens – notably olive knot disease, caused by the bacterium Pseudomonas savastanoi. Olive knot can invade fresh pruning cuts, especially during wet weather, forming galls on limbs. To mitigate this, avoid pruning in the rain and consider protective measures for large cuts. A common practice is to spray copper-based bactericide/ fungicide right after pruning or before the next rain. Some growers also apply tree wound dressing or a latex paint on big limb cuts as a physical barrier. These precautions help limit infection. It’s also wise to sanitise pruning tools between trees (a quick dip in disinfectant) if diseases like knot or Verticillium wilt are present, to avoid spreading them. In an IPM context, pruning is timed and executed carefully: e.g. in high rainfall areas, prune in late winter when rains are easing, and treat wounds. Fortunately, productive fruiting wood tends to be smaller diameter cuts (when you renew regularly), which heal faster and pose less risk than chopping massive old limbs. So keeping up with pruning not only fosters new fruit wood but also means you’ll have fewer huge wounds at any one time.  
• Linking pruning to disease management strategies: Some cultural IPM tips explicitly involve pruning. For instance, with anthracnose, aside from fungicides, recommended actions are early harvest (to avoid autumn rains) and pruning trees to a more open canopy. With peacock spot, pruning to allow sunlight on leaves helps because UV light can suppress the fungus, and dry leaves don’t get infected as easily. Even bacterial diseases like olive knot are indirectly suppressed by faster drying (the bacteria thrive in moisture on plant surfaces). Thus, a grower focusing on productive wood (which implies a less crowded canopy) gains a double benefit: better fruiting and fewer disease issues. The Connor et al. review (2014) notes that in traditional low-density orchards, free air movement helps prevent humid microclimates, whereas hedgerow systems require careful pruning/irrigation control to avoid humidity-related disease buildup. They highlight that “narrow and porous hedgerows” achieved by pruning plus controlled water can reduce fungal problems like peacock spot and anthracnose. This aligns perfectly with IPM advice – integrate your pruning program with your pest/disease monitoring. If you notice heavy scale or sooty mould inside trees, it’s a signal to thin those canopies. If fungal outbreaks occur, consider that a sign to increase porosity and maybe lower tree density or height during the next pruning cycle. 
• Pruning and beneficial insects: Keeping some openness in the grove (and not having a tangle of watershoots) also aids beneficial insects and mites. They can navigate and locate pests more effectively in a well-structured tree. Some predators, like lacewings, prefer slightly open trees. Additionally, if you combine pruning with cover crops or intercrops for natural enemies (as mentioned in IPDM manuals ), you create an overall environment where pests are less likely to flare up. 

In summary, a sound pruning regimen is a cornerstone of IPM in olives. It reduces pest and disease pressure naturally by altering the micro-environment and improving the efficacy of other controls. Always balance the need for opening the canopy with the tree’s productive capacity – a healthy medium density (not too sparse) is the target, so that you don’t invite sunscald or stress. With those caveats, pruning is one of the most cost-effective pest management tools a grower has.

Environmental and Management Factors Affecting Wood Renewal

Beyond pruning itself, several environmental and cultural factors influence how well an olive tree can produce new, fruitful wood. Understanding these helps growers create conditions that favour the continual renewal of fruiting shoots: 

• Water availability and irrigation strategy: Olive is drought-tolerant but will not grow new shoots well under severe water stress. Adequate soil moisture during the spring and summer is necessary for shoot extension that becomes next year’s fruiting wood. However, too much water (or untimely irrigation) can fuel overly vigorous vegetative growth that, as noted, may be less fruitful. Modern orchard practice often employs Regulated Deficit Irrigation (RDI) – deliberately stressing the trees mildly at certain times – to manage vigour. For example, some SHD groves impose a dry period during early summer (pit hardening stage of the olive) to slow shoot growth and encourage floral induction. Then, irrigation is increased later to sustain the crop. This technique can result in shorter internodes and more flowering points. Connor et al. (2014) write that sustained or regulated deficit irrigation is useful to ensure high yields without excessive vegetative growth. In essence, water management and pruning go hand in hand: pruning sets the stage for how much the tree will try to regrow, and irrigation fine-tunes that regrowth. In rain-fed groves, the principle is similar – in a very dry year, the tree may barely replace lost wood, so pruning should be lighter; in a wet year (or if supplemental water is available), pruning can be a bit heavier since the tree can respond. Irrigation can also be used post-harvest to boost new shoot growth if needed (e.g. after a heavy crop year, watering after fruit removal can help push some late shoots before winter if the climate allows). 
• Nutrient status: Proper nutrition, especially nitrogen, is crucial for shoot growth and bud formation. Nitrogen applied in late winter through spring supports the development of new shoots and leaves (which ultimately carry next year’s fruit). Nitrogen deficiency will result in short shoots with fewer nodes (hence fewer potential inflorescences). On the other hand, excess nitrogen can cause rank vegetative growth and poor fruiting as the tree stays in a “growth” mode. A balance is needed – typically, commercial growers use foliar and soil tests to guide fertilisation. Phosphorus and potassium are also important for overall tree health and flowering, but N is the main driver of shoot vigour. If heavy pruning is done, a small increase in nitrogen fertiliser can help the tree refill its canopy, but it should be carefully timed (supply N during active growth, not just before dormancy). Zinc and boron foliar spraysare micronutrients worth mentioning: zinc is involved in shoot elongation (zinc deficiency leads to stunted shoots and rosette leaves), and boron is critical for flowering and fruit set. Ensuring these micronutrients are sufficient (via Heat and sunburn if needed) can improve the quality of fruiting wood and subsequent bloom. In short, a well-fed tree can better renew its fruiting wood, but avoid over-fertilising to prevent vegetative bias. Always integrate fertilisation with pruning severity – e.g., after a significant prune, don’t heavily fertilise with N immediately, or you’ll get water sprouts; feed modestly and let the tree rebuild gradually. 
• Climate stress (temperature extremes): Environmental stresses can affect both current fruiting and future wood. For instance, a severe frost can kill one-year-old shoots (either outright or by damaging their cambium), effectively destroying that fruiting wood. If a late spring frost hits just as buds burst, it can wipe out that year’s inflorescences and even the shoots, forcing the tree to push new secondary shoots (which may or may not have time to set buds for the next year). In frost-prone areas, the pruning strategy might include leaving a bit of extra wood as a “backup”. Some growers delay pruning until late winter specifically to assess frost risk – any frost-damaged twigs can then be pruned out, and some fruitful wood might be left untouched to allow a partial crop if frost was light. Mechanical harvesting (shakers or harvesters) are another concern: suddenly exposing older shaded limbs to intense summer sun (through heavy pruning) can scald the bark. This can girdle branches or invite disease. That’s why gradual opening is preferred. If a tree is pruned hard, doing it in winter helps because the summer sun intensity on the new shoots is mitigated by those shoots themselves growing and shading the bark. Also, a whitewash or spray-on kaolin clay can be used on exposed branches to reflect sunlight in the first summer after a hard prune. Wind can break vigorous new shoots if they are too long and unprotected; sheltered orchard design or windbreaks help prevent losing the very shoots you pruned to create. 
• Pests and diseases affecting wood: We’ve touched on how pruning helps prevent pests, but pests can also reduce the formation of productive wood. Defoliation by pests (e.g. a severe peacock spot infection causing leaf drop, or heavy olive lace bug feeding) will weaken shoots and often cause them to die back or fail to form flower buds. For example, if scale insects heavily infest young shoots, the sooty mould and sap loss may stunt those shoots. This reduces fruitful nodes and may require pruning out those damaged twigs. Additionally, wood-boring pests (like olive wood-borer or even trunk diseases) can kill branches, necessitating more renewal. Good IPM to control these problems means the tree retains more healthy shoots to become next year’s fruiting wood. Nutritional disorders (like acute copper deficiency, which can kill shoot tips, or boron toxicity, which can cause twig dieback) similarly affect wood renewal and should be managed via soil and leaf analyses. 
• Cultivar differences: Some olive cultivars naturally produce more or fewer new shoots. For instance, vigorous varieties like Frantoio or Koroneiki tend to sprout readily and may need extra thinning, whereas a slow-growing variety like Manzanillo might require lighter pruning to avoid reducing too much foliage. Cultivars also differ in how strongly they alternate bearing. Research has shown cultivar architecture (branching pattern, shoot length distribution) influences how we should prune. Recognise your cultivar’s habits – a weepy cultivar (drooping branches) might need cuts to upward laterals to prevent all fruit wood from hanging downward and shading itself; an erect cultivar might need opening in the interior. Tailor the pruning severity to how the variety responds. If unsure, trial different pruning levels on a few trees and observe the regrowth and fruiting. 
• Harvest method and timing: Interestingly, how and when you harvest can impact fruiting wood. Mechanical harvesting (shakers or harvesters) can cause some damage to shoots – for example, trunk shakers might break off fruiting twigs, and over-the-row harvesters may knock off branch tips. Pruning can compensate by stimulating regrowth where breakage occurred, but be mindful of harvest injury (make cleaner cuts around damaged areas). Early harvesting (picking fruit earlier in the season) is often recommended to mitigate anthracnose; it can also benefit the tree by giving it a longer post-harvest period to grow new shoots before winter. Late-harvested trees (say, very late May or June picks) have a short window to initiate new growth before cold weather, potentially limiting the next year’s fruit wood. So there’s a trade-off: waiting for maximum ripeness vs. tree recovery time. Many commercial growers find a sweet spot where they harvest as soon as oil accumulation is adequate, then immediately prune and fertilise to maximise the “rest” period for the tree to rebuild. Over the long term, this can increase the consistency of production. 

In summary, productive fruiting wood is not just about cutting branches – it’s the outcome of the whole orchard management system. Pruning is the mechanical stimulus, but water, nutrients, and overall tree stress levels determine how the tree responds. The best results come when pruning is synced with these factors: prune to shape the growth, irrigate and fertilise to support it (but not overdo it), and protect the tree from stresses that could derail the process. By doing so, growers in Australia can maintain olive canopies that are youthful, vigorous, and laden with fruitful shoots year after year.

Conclusion: Practical Takeaways for Growers

Encouraging productive fruiting wood in olives is both an art and a science. The art lies in “reading” the tree – knowing which branches to remove and which to spare – while the science lies in understanding olive physiology and applying evidence-based practices. In this follow-up to Marcelo Berlanda’s pruning guide, we have underlined the key strategies:

• Keep it light and frequent: Regular, moderate pruning (rather than drastic cuts at long intervals) keeps the tree in balance and minimises alternate bearing shocks. Little and often beats all at once. 
• Maximise light, optimise canopy: Ensure every fruitful shoot gets sunlight. Open the centre, manage tree height, and avoid thickets of unproductive wood. A rule: if a bird can’t fly through your tree, it’s too dense! 
• Renew systematically: Remove a portion of old wood each year to stimulate new shoots. Don’t wait until the tree is a solid mass of old branches. Proactive renewal is easier and more productive than drastic rejuvenation. 
• Adapt to your system: Use appropriate techniques for your grove type – whether it’s hand-pruning a gnarly 100-year-old tree or mechanically hedging a super-intensive row. The end goal is the same: a canopy architecture that supports new growth and fruiting. 
• Integrate health with pruning: Remember that pruning is also a sanitation and IPM tool. Dispose of pruned material that contains diseases or pests (don’t leave it on the orchard floor if it’s infested). Consider timing pruning after major disease periods (e.g., prune after the wet season to remove fungus-infected twigs). Always make clean cuts and protect the tree as needed. 
• Monitor and adjust: Finally, observe how your trees respond. If you pruned a block and next spring you see an overly vegetative response (excess watershoots, low flowering), adjust by pruning a bit lighter or later, or try a growth regulator on vigorous shoots, as researchers have tested (e.g., some use plant growth regulators like paclobutrazol or mepiquat chloride experimentally to temper regrowth ). If you see the opposite – weak regrowth – it might mean the tree lacked resources (perhaps it was an “on” year and depleted, or needs more nutrition/irrigation). By following these guidelines, Australian olive growers can improve the productivity and longevity of their groves. The essence of Berlanda’s message, now enriched with current scientific insights, is that pruning for production is about forward-thinking – cultivating next year’s crop wood while harvesting this year’s crop. With a sound renewal strategy, your olive trees will reward you with consistent yields of high-quality fruit and remain robust against pests, diseases, and the vagaries of climate. As always, combine advice with on-ground experience, and happy pruning for productive wood! 

Sources: This article integrates findings from peer-reviewed studies and reputable industry publications, including research by Gómez-del-Campo et al. on light and yield distribution, Tombesi and Connor on pruning and olive physiology, Rousseaux et al. on bud dormancy and flowering, and Australian olive industry resources (NSW DPI, AOA IPDM manual) on best practices. These sources reinforce the recommendations above and ensure advice is aligned with the latest understanding of olive tree management. 

In the lead up to flowering, you need to ensure your trees have adequate nutrition, particularly of Boron and Calcium. ?A lack of Boron?and Calcium may lead to decreased fruit set, oil quality and oil stability.

The application of Boron?and?Calcium?can never be overstressed. ?It is a requirement for your trees.

In Brief

A study on olive trees has looked at different application rates of Boron and Calcium and the effects on fruit set, fruit oil and oil chemical characteristics.

The rate of 100ppm of Boron?and 2% Calcium?was applied at full bloom and the 2nd application at 15 days later.  Trees were sprayed with nutrient solution till run off.

Fruit Set %

Trees in this study showed a higher fruit set. ?Results also confirm the role of Boron?and?Calcium?nutrients in improving fruit set of olive flowers.

From the overall data, the two studied nutrients effectively increased fertilisation either through controlling pollen germination on the stigma or growth of pollen tube through the style. ?Therefore, the subsequent increase in fruit set % was observed.

Fruit oil %

Furthermore, the effects could also be seen in increased fruit oil content. ?This increase reached a significant level in most cases.

Oil Chemical Characteristics

Peroxide Value

The study of the application of Boron?and?Calcium?at the same rate noted above greatly decreased the peroxide value in the cultivars studied.