For years, climate change was primarily addressed as an environmental phenomenon associated with rising global temperatures. However, for the blueberry industry, the real challenge begins long before the thermometer hits a record high.

This was the argument put forward by the international researcher and consultant Jorge Retamales, who during the XLII International Blueberry Seminar Trujillo 2026 He presented one of the most comprehensive presentations of the meeting, proposing a perspective that transcends meteorology to focus on plant physiology.

Retamales emphasized that the industry cannot turn a blind eye to climate change. “There is a problem that we have to try to address,” he stated.

That idea set the tone for a conference that combined scientific evidence, international studies, and experimental results to explain how rising temperatures are already altering the growth, flowering, productivity, and quality of the blueberries.

A problem that goes beyond agriculture

Before delving into the physiology of the crop, Retamales placed the phenomenon within a broader context.

“The real challenge is that we are a fossil fuel-dependent civilization. Our quality of life and our productivity are based on burning large quantities of fossil carbon,” he noted.

From his perspective, agriculture faces the consequences of a global energy model whose transformation will be slow. “There is a lot of interest, but little decisive action,” he warned, referring to the difficulties in reducing emissions and the sustained increase in atmospheric carbon dioxide concentrations.

But the problem isn't just that the planet is getting warmer. For Retamales, the risk also lies in the increased frequency of extreme weather events.

“Not only will there be a higher average temperature; there will also be a greater number of days with extreme temperatures,” he explained.

And it is precisely these intense heat events that can most severely compromise the physiological functioning of the blueberry.

The climate changes much more than the temperature.

Retamales explained that climate change simultaneously modifies multiple environmental variables. Average temperatures rise, rainfall patterns change, water availability is altered, salinity increases in some irrigation systems, and the biological cycles of insects, diseases, and soil microorganisms are changed. Even pollinators can have their activity affected.

All of this has a direct impact on crop development.

In Peru, he recalled, the effects of El Niño 2023 already allowed us to observe some of these consequences, such as smaller fruit size, reduced flowering, accelerated ripening and a more fragile post-harvest condition.

Jorge Retamales International Blueberries Seminar Trujillo 2026 © Blueberries Consulting

Physiology explains the crop response

One of the key contributions of the conference was explaining why heat produces these effects. Retamales reminded attendees that plant growth depends, among other factors, on the balance between photosynthesis and respiration.

Photosynthesis allows plants to generate the carbohydrates that sustain their growth and development. Respiration, on the other hand, consumes some of that energy to maintain their metabolism. When the temperature rises, this balance is disrupted.

As Retamales explained, photosynthesis of blueberry It reaches its highest efficiency in moderate temperature ranges, while respiration increases with heat. In practical terms, the plant has fewer carbohydrates available to grow, support active leaves, and nourish the fruit.

This imbalance helps explain some of the reduction in growth, yield, and quality observed under heat stress conditions.

When the plant stops defending itself

The conference showed that the blueberry It has natural mechanisms to cope with heat. It produces waxes that reflect some of the radiation, modifies the orientation of its leaves to reduce direct sun exposure, and regulates the opening of its stomata to decrease water loss.

However, these mechanisms have a limit.

“Above 38 degrees Celsius, the plant is no longer able to respond. The transpiration rate is insufficient to control the leaf temperature, and it simply gets damaged,” Retamales noted.

The researcher illustrated this situation with images taken in Morocco after an episode of extreme heat, where plants exposed for just a few hours to temperatures exceeding 38°C exhibited leaf necrosis and a significant loss of photosynthetic surface area. Although they subsequently produced new shoots, the physiological damage had already compromised a significant portion of the growing season.

The roots also suffer

The effects of heat are not limited to the aboveground parts of the plant. Soil temperature modifies root growth, alters the architecture of the root system, and affects the absorption of water and nutrients. Furthermore, it reduces the production of hormones synthesized in the root, such as cytokinins and gibberellins, which are essential for vegetative development.

Retamales emphasized that a vigorous root system is one of the main tools for dealing with climate stress.

“Each increase in temperature reduces the size of the root system, reduces its length, and reduces its vigor,” he said.

This loss of roots subsequently limits the plant's ability to absorb water and regulate its temperature through transpiration.

Jorge Retamales International Blueberries Seminar Trujillo 2026 © Blueberries Consulting

Flowering also changes

Another sensitive aspect relates to the reproductive process. Exposure to temperatures above 30 °C directly affects pollen tube growth.

“Above 30 degrees Celsius, the pollen tube practically stops growing,” he explained.

The consequence is direct: even if pollination occurs, the pollen may not reach the ovary to complete fertilization, reducing seed formation and compromising fruit development.

Quality begins long before the harvest

Retamales also demonstrated how heat stress affects commercial quality. Fruit exposed to the sun can reach temperatures far exceeding those of the surrounding air. While a typical day might register around 22°C ambient temperature, fruit directly exposed to sunlight can easily surpass 34 or 35°C.

This heating affects firmness, size, soluble solids content, and post-harvest life.

In addition, during episodes of high temperature, the plant tends to prioritize vegetative growth over fruit filling.

“Water and carbohydrates go to the vegetative organs and not to the fruits,” Retamales pointed out.

The result can be smaller, dehydrated fruit with less firmness and lower commercial potential.

Genetics is starting to make a difference

A significant portion of the conference was dedicated to the role of genetic improvement. Retamales explained that the tall shrub varieties from the south, widely used in Peru, exhibit greater heat tolerance than the traditional tall shrub varieties from the north. This is due, in part, to the incorporation of species naturally adapted to warm environments into breeding programs.

“Developing heat-adapted varieties has been a recent emphasis in genetic improvement programs,” he said.

However, he noted that there is still much to understand regarding the genetic composition of the new materials, whose information remains protected by the breeding companies.

Jorge Retamales International Blueberries Seminar Trujillo 2026 © Blueberries Consulting

Adapt the environment

Beyond genetics, Retamales presented several strategies to reduce the impact of heat stress. Among them, he highlighted the use of shade netting. Trials demonstrated that certain types of netting can reduce leaf temperature by up to three degrees and significantly increase productivity.

“The nets generated higher yields, except for the black net, which yielded 50%. This increase occurred mainly because they reduced fruit drop,” he explained.

The results showed yield increases of nearly 60% in some treatments, without affecting soluble solids or fruit size. The use of reflective netting to reduce soil temperature and protect the root system was also highlighted.

Management can also build resilience

The researcher emphasized that adaptation does not depend solely on new varieties or infrastructure. Daily field management also plays a crucial role.

Irrigation scheduling, oxygen conservation in the rhizosphere, the use of biostimulants, growth regulators and thermotolerant microorganisms are tools capable of strengthening the physiological response of the plant.

In studies conducted with bacteria adapted to high temperatures, inoculation allowed for an increase in leaf area and the maintenance of a higher photosynthetic rate under stress conditions.

Resilience is born from integration

Towards the end of the conference, Retamales summarized his proposal in one central idea: adaptation to climate change does not depend on a single technology.

“To manage the effects of climate change, we depend on the interaction between genetics, management, and the environment,” he said.

This balance is one of the main challenges for the blueberry industry. Simply producing more will no longer be enough. A better understanding of how the plant functions will be essential to anticipate a rapidly changing climate that demands more resilient production systems.

Read also:

• Luis Miguel Vegas: Peru doubles blueberry production, but El Niño forces cautious projections
• Jessica Rodriguez: Reducing the time between harvesting and cooling will be key to protecting the firmness of blueberries
• Climate change, genetics and efficiency marked the first day of the International Blueberries Seminar Trujillo 2026
• International Blueberry Seminars 2026: Blueberries travel through Peru, Chile, Mexico, Morocco and China