High-Temperature Stress in Tomato Production and How to Manage It
Tomatoes are sun-loving crops, but prolonged exposure to high temperatures can lead to problems such as fruit cracking, poor coloration, blossom-end rot, and reduced fruit enlargement—commonly known as heat stress. While measures such as selecting heat-adapted varieties or using greenhouse cultivation can help, these approaches are not always practical due to limitations in feasibility and cost. In contrast, shade nets offer a simple, widely applicable, and cost-effective way to manage heat. However, many conventional shade nets lower temperatures by blocking more light than necessary, which can reduce photosynthetic efficiency.
Our high light-transmission, heat-focused shade nets overcome this traditional trade-off between shading and cooling, providing an ideal solution for growers. In this article, we highlight the characteristics of heat stress, effective mitigation strategies, and the benefits and considerations of using shade nets in crop production.
Are you facing any of these challenges?
These are common examples of how outdoor temperature can affect tomato growth. This type of problem is generally called heat stress, and it’s one of the biggest factors that can reduce tomato yields. Heat stress occurs when high temperatures cause unfavorable physiological reactions in the plant. The exact temperature range that triggers stress can vary depending on the tomato variety.
Research shows that the ideal temperature for tomato growth is around 77–86°F (25–30°C) during the day and about 68°F (20°C) at night. When daytime temperatures exceed 90°F (32°C), or when nighttime temperatures stay above 70°F (21°C) for several days in a row, tomatoes begin to show signs of heat stress—resulting in poor fruit set and lower overall yields.
Symptoms can appear as early as the seedling stage. If your plants are becoming tall and spindly, heat stress may be to blame. Of course, heat isn’t the only factor affecting tomato growth. Overwatering, sunscald, lack of sunlight, wilting diseases, tomato yellow leaf curl virus, and bacterial wilt are also common problems to watch for. As a general rule, if the upper leaves curl or roll up, heat stress may be one of the causes.
How to Manage Heat Stress
The most effective way to combat heat stress is to choose heat-tolerant tomato varieties developed through selective breeding. Major tomato-producing regions such as California and Florida have hot climates year-round, yet they remain leaders in both processing and fresh-market tomato production. This success comes largely from developing and adopting improved varieties that can handle the heat. However, not all growers can easily find or develop new varieties, and that option isn’t always practical.
Another effective solution is to grow tomatoes in greenhouses or high tunnels, where the growing environment can be controlled more precisely. This allows for year-round production and greater flexibility in variety selection. The downside is that greenhouse construction requires a large upfront investment, and operating costs can become significant for large-scale production. It’s important to carefully evaluate the return on investment before committing to this approach.
Using Shade Nets
A more affordable and practical option is to use shade nets. For tomato production, shade nets with 30–50% shading are typically recommended, though the best level depends on your local climate and field conditions. Because tomatoes are sun-loving plants, too much shading can reduce growth and yield. That said, higher shading can help retain soil moisture and reduce the need for frequent irrigation—though this benefit comes with a trade-off in photosynthesis.
Shade nets come in a variety of types, each designed for different environments and crops. The most common type reduces heat through shading—higher shading generally means stronger cooling. If you want to reduce heat without losing too much light, choose a product that has high visible light transmission while still offering strong heat reduction.
Since tomatoes thrive under sunlight, we recommend our BHL Series, which provides excellent heat reduction with low shading rates. University trials have shown that using this product can increase yield per plant by about 25% compared with no shading.
Shade nets are also known for being highly cost-effective. They’re affordable, require no electricity, can be reused multiple times, and can be easily installed in open fields or over structures such as cold frames. This makes them a great option for improving conditions without major infrastructure changes. You can also use them as retractable or sliding curtains, allowing flexible shading control to respond to daily changes in sunlight and temperature.
Things to Watch Out For
While shade nets don’t block airflow completely like heat films, they still reduce ventilation to some extent. The higher the shading rate, the lower the air circulation—so make sure your fields or greenhouses have adequate ventilation.
Since shading increases soil moisture retention, it’s also important to avoid overwatering. Using the same irrigation schedule as before can lead to root rot or disease outbreaks under shaded conditions.
Finally, the right shade net depends on both your growing environment and tomato variety. Unnecessary shading can reduce photosynthesis and harm plant growth.
Our Products
We manufacture a wide range of shade nets designed for different growing conditions. Thanks to our fully integrated in-house production system, we’re proud to offer some of the highest quality products available in Japan. We’re confident you’ll find the perfect fit for your fields. Please feel free to contact us anytime for advice or product information.