The heat wave which has affected the Italian olive-growing areas during this phase of initial olive growth represents a danger for their development.
Le temperatures exceeding 33-34°C, often accompanied by hot, dry winds, they put the entire plant-soil-atmosphere system under stress, with significant repercussions on the physiology of the olive tree and on final productivity.
The combined effect of heat and wind
Under normal conditions, olive trees are able to cope with moderate drought thanks to adaptive physiological mechanisms that reduce water loss.
The combination of high temperatures and strong ventilation, however, accelerates evapotranspiration, or the sum of transpiration from the leaves and evaporation from the soil, causing a rapid decrease in the humidity available in the layer explored by the roots.
Even if, initially, the soils were moderately well hydrated, the intense evaporation and transpiration caused by heat and wind could quickly exhaust the water reserves available to the roots, compromising the water and energy balance of the plant.
Le leaves, in an attempt to protect themselves from dehydration, they close the stomata, compromising photosynthesis and reducing the production of assimilates essential for fruit growth. High temperatures then modify the fluidity of cell membranes, mainly made up of lipids, which become unstable and lose their barrier function. This leads to greater water loss and, in the most critical cases, to localized necrosis.
Small and sensitive olives: the risk of dehydration
At this stage, olives are small in size and very exposed to direct sunlight. When temperatures exceed 33-34°C, the surface of the olive can reach even higher values and, in conditions of strong sunlight, the temperature of its surface can reach and exceed 40°C, with harmful effects on the epidermal tissues.
The drupes lose turgescence and, in some cases, may show wrinkling and phenomena of accelerated senescence or necrosis of the exposed tissues.
Agronomic techniques to mitigate heat stress
To deal with these stresses, olive growers can adopt different protection strategies which strengthen the physiological defenses of plants and limit water loss:
- glycine betaine based tonics: this natural osmoprotectant helps cells retain water, stabilizing membranes and improving drought tolerance;
- seaweed extracts: rich in phytohormones, polysaccharides and trace elements, they stimulate the plant's natural defenses and increase its resistance to environmental stress;
- wood distillates: derived from the pyrolysis of woody biomass, they act as bioactivators, improving the general vitality of plants and their metabolic efficiency;
- rock powders (kaolin, bentonite, zeolite, talc, agricultural lime): applied to the foliage, they reflect part of the solar radiation and lower the temperature of the leaf and fruit surfaces, helping to reduce transpiration and protect the tissues from thermal damage.
The importance of water management
In addition to foliar strategies, rational water management is essential.
Targeted emergency irrigation can help the plant overcome the hottest phases, avoiding water stress and ensuring more balanced production. Monitor soil moisture and intervene promptly can make the difference in maintaining the vitality of the olive grove, especially in the most critical seasons.
AIPO Director
Interregional Association
Olive producers
