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.

Unique Insect Feeding Damage on Peppers

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

The growing season is never without challenges, and this summer is no exception- especially for our high tunnel bell pepper research! On June 13 we noticed some unique feeding damage on the stems of our pepper plants. This damage was isolated to the stem area beneath the mulch layer.

The stems appear to be completely girdled, but the vascular system of the pepper seems to still be functioning at some level. A week and a half later and many of the damaged plants are beginning to fall over. Some have snapped off completely at the weakened point, but many are still trying to press on and flower. Unfortunately, these plants will likely not be viable much longer either. 

We are working with ISU Professor and Extension Entomologist, Dr. Donald Lewis, to narrow down the source of the damage. Dr. Lewis agrees that this doesn't look like the normal feeding damage for the typical cutworm that plagues vegetable production in Iowa. 

Have you ever seen damage like this in your production system? We would love to hear from you!

Sweet Pea Harvest in Central Iowa

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

Yesterday we were invited to check out the harvest of 100 acres of sweet peas on a farm in Central Iowa. The harvest began at 5:00 a.m. and would be completed by early afternoon. The crew included 7 harvesters, 2 transport carts, 2 teams of mechanical support, and a crew of 10 semi trucks on a continuous rotation. The drivers were transporting the peas 180 miles to a processing plant in southern Minnesota; each semi truck load contained approximately 28,000 lbs of shelled peas.

Rye Cultivar Trial - Anthesis and Roller Crimping

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


Cereal rye plots at anthesis on May 21, 2016.

Early summer has kept us busy with our cereal rye cultivar trial located at the ISU Horticulture Research Station near Gilbert, IA. This study is comparing five cultivars of cereal rye (Aroostook, Elbon, Prima, Wheeler, and Wrens Abruzzi) for their performance as a cover crop in a roller crimping system. Each cultivar was planted on two dates last fall - September 16 and October 13. 

Pollen being shed at anthesis.

One of our primary questions of interest is, "When does each cultivar reach anthesis?" This question is important because cereal rye cannot be successfully killed with a roller crimper until it has reach flowering stage, also known as anthesis. We saw Aroostook reaching anthesis on May 17 with Elbon and Wrens Abruzzi following two days later. Prima and Wheeler both reached anthesis on May 21.

Cereal rye being terminated with the roller crimper.

   










Due to recent rain our roller crimping was slightly delayed, and all plots were terminated with the roller crimper on Friday, June 3. The plots were evaluated on Tuesday, June 7 to assess the success of the kill with the roller crimper. Aroostook and Wrens Abruzzi appear to have the best rate of kill and would be ready for strip tilling and planting of a vegetable crop. Wheeler and Prima appear to be standing back up, and would require another round of roller crimping to be a viable mulch bed.

Prima (left) and Aroostook (right) on June 7.

For more information on cereal rye and roller crimping, please visit reference our extension publication Strip Tillage in Vegetable Production.