Comparison of Microenvironment between Caterpillar Tunnels and Permanent High Tunnels – Vegetable Crops Hotline

Comparison of Microenvironment between Caterpillar Tunnels and Permanent High Tunnels

Over the past year, we conducted a comparative study on microclimate conditions within caterpillar tunnels and high tunnels at five farms in Indiana. This initiative was prompted by the growing interest in employing caterpillar tunnels for season-extension vegetable production among small and diversified farms.

Caterpillar tunnels, typically lower in height than permanent high tunnels, stand at around 5 to 6 feet tall at the center of the hoops. They are varied in length with some extending up to 200 feet. Most caterpillar tunnels are narrower in width compared to permanent high tunnels. Unlike permanent high tunnels, caterpillar tunnels may lack end walls, with their covers either tied off to stakes at both ends or left open for ventilation.

Compared with permanent high tunnels, caterpillar tunnels are more affordable and easier to assemble and relocate. They offer some of the same benefits as permanent high tunnels but provide more flexibility in addressing various crop needs. During summer, the structure can be adapted for specific crops by using shade cloth or insect netting, enhancing versatility.

Although caterpillar tunnels have numerous advantages, it’s crucial to acknowledge the limitations of caterpillar tunnels in environmental control compared to permanent high tunnels. Caterpillar tunnels have little effect in improving minimum temperatures in the winter, similar to unheated high tunnels. When the tunnels are fully closed, the temperatures in caterpillar tunnels tend to increase faster and reach higher levels than those in high tunnels on sunny days, which may create more significant temperature fluctuations inside caterpillar tunnels than high tunnels in the winter, potentially posing challenges to winter crop production. Moreover, we observed prolonged periods of high relative humidity within caterpillar tunnels, attributed to limited ventilation compared to permanent high tunnels, which may include supplemental ventilation or air circulation fans. The prolonged periods of high relative humidity favor diseases. Higher light intensity was monitored inside caterpillar tunnels compared to permanent high tunnels. Although the same type of plastic was used, reduced usage of the plastic on caterpillar tunnels may potentially extend the plastic lifespan.

Looking ahead, we aim to continue this project, focusing on evaluating how different structures and modified environments impact the production of various crops, particularly in the winter.

We welcome suggestions for future research directions. For further information, please contact Wenjing Guan at

This work is supported by the Specialty Crop Research Initiative (SCRI) [grant no. 2021-51181-35858/project accession no. 1027430] from the USDA National Institute of Food and Agriculture

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