Problem

I have a couple of olive trees with a bark problem.  This particular tree is a bit stressed from lace bug I believe, I'm not sure they've had their full care for the last couple of years due to the transition. It needs a bit of a prune too which I will take care of before I spray it. But will wait for your comments first.  See image below.

About Sunburn Damage

Sunburn can occur in olive trees as damage to bark, foliage, fruit which is caused by excessive solar radiation exposure and seriously affect growth.

Sunburn can cause the tree the olive tree to be more susceptible to borers.  Olive trees affected by sunburn are typically poor in health and if severe enough can result in premature death.

Sunburn in olive trees is usually associated with warm weather coupled with water deficit.

Although olive trees are well adapted to hot and dry conditions, too much heat can result in lower yields, leaf wilt, and reduced photosynthesis as the olive tree shuts down critical functions to respond to heat stress.

Older trees can be damaged when the bark is newly exposed to the sun because of pruning or premature leaf drop. Heavy pruning of olive trees can lead to increase reflected light or radiate heat around established trees can also lead to sunburn.

Identification

Sunburn to trunks can leave the tissue dried, cracked and sunken and the bark may peel away leaving the wood susceptible for borer attack or fungal infections to enter the bark for further damage to the exposed hardwood underneath.

Foliage may be brown and necrosis begins at leaf tips, margins and between veins. 

Heat stress usually results in fruit drop if an olive crop is present.

Solutions

Encourage good soil health and moisture-holding capacity.  Encourage branch structure with proper pruning and plant training.  Retain branches that will help to shade the trunk and be beneficial for cropping.

Give trees adequate irrigation to reduce stress and do not overwater trees.

For olive trees and fruit to reduce the risk of sunburn use Kaolin clay applied as a foliar film to help offer protection in reducing heat stress and intense solar radiation.

Whitewashing trunks may help prevent sunburn which is usually seen as an application of rubberised tree sealant.  Sometimes water-based paints are used.

If leaves have not already been killed, sunburn injury to foliage can often be remedied by adequate irrigation, adding shade or shelter, and improving soil conditions.

Sunburn Olive Tree

Bark has been affected by intense sun radiation exposure and also water deficit.

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).