Managing Stress in High Tunnels: Shade Cloth

Kristine Neu and Ajay Nair,
Department of Horticulture,
Iowa State University

The early onset of high temperatures in June has kept us on our toes as we manage our high tunnel production systems at the ISU Horticulture Research Station. While high tunnels bring many benefits to high value crop production, including season extension and increased produce quality, we find that one major downfall is the increase of heat stress. 

Last year, after blossom abortion due to heat stress and severe sun scald damage on tomatoes within our high tunnel, a 30% light reducing shade cloth was purchased to alleviate some of these issues.When the predicted highs reached over 90 degrees early this month, we knew it was once again time to place the shade cloth on our high tunnel, and there was an audible sigh of relief from the tomatoes.

On June 24 we applied shade cloth to small high tunnels that are being used to trial seven colored bell pepper cultivars. In addition to trialing the cultivars, we are examining the response of the plants and fruit to three different shade treatments- no shade, 30% shade, and 50% shade. Our hope is to hone in on the best production methods for colored bell peppers in high tunnels.

A shade cloth may be a valuable tool to utilize in your high tunnel production system, but we understand that cost is a huge decision factor. Here is a short breakdown of approximate costs taken from a large grower supply company:

• 30% polyethylene knitted shade cloth = $0.20 / square foot
• 1000' spool of polyester curtain cord = $30
• Shade Clip (suggested placement is 2' spacing) = $0.47 / clip

Cost to cover a 30' x 96' structure with a 30% shade cloth = $500 + shipping

Please watch for updates throughout the season regarding our high tunnel production of tomatoes and colored bell peppers.