Tunnels boost fruit quality, add to berry season Research sheds light on grower experiences for strawberries, raspberries

by RONDA PAYNE ABBOTSFORD – Growers in many countries

produce strawberries and raspberries in tunnels, but the practice hasn’t caught on to the same degree in North America. To help growers determine if the option is a viable one, Kathy Demchak, a senior extension associate in the plant science department at Penn State University and a member of the TunnelBerries research team, has been studying high tunnels for raspberries and fresh-market strawberries. High tunnels are hoop frame structures

covered with six to eight mil clear plastic that lasts about three growing seasons. The tunnels are approximately 24 feet wide and 200 to 300 feet long. They can be single or multi-bay structures that protect workers and plants from the elements while enhancing growing conditions. Multi-bay structures are created from single-bay units that are attached together, providing more structural integrity. Proper installation is the prime determinant

of how long the plastic covering lasts. Snow loads and wind may require taking the plastic down in some regions, but single-bay tunnels can usually stay in place year-round. A great way to manage environmental variables, high tunnels have a significant cost. “Pay-off depends on crop management skills.

On the downside, strawberry roots were exposed to higher levels of salt, perhaps due to the lack of snow or rain leaching salt away. A lack of leaching can also be an issue, leaving behind diseases that will harm strawberries. Several years may need to pass between certain crops. “You won’t want to grow strawberries [in a tunnel] after something like tomatoes,” she says, adding, “We do need to work out the production systems.”

Demchak said pesticide-free and organic

growing is easier in tunnels, but integrated pest management systems would be a good addition. Some growers had issues with spider mites. “Our recommendation for that is to release

There is a cost to the constant maintenance and temperature management,” Demchak says. Demchak surveyed experienced strawberry growers with an interest or experience with the cropping system. Growers produced both June-bearing berries and everbearing varieties. “Fruit appearance was the number one reason,” says Demchak of why

Crop tunnels can extend the growing season and provide more crop protection for berry growers. FILE PHOTO

predatory mites when first seen and just keep scouting,” she says. Some growers felt the benefits didn’t justify the costs and switched to higher value crops as a result. Producing off-season berries was a plus, but finding a market for them was challenging because consumers weren’t expecting locally grown berries out of season. Raspberry growers were also surveyed about their use of high-tunnels. Reasons for using the structures included increased yield, improved appearance and ability to harvest in the rain. While the tunnels delivered a larger berry and fungicide-free fruit, spotted-wing drosophila (SWD) impacted shelf life and eliminated any pesticide-free pitch. Very few raspberry growers planned to scale

growers were using tunnels for berry production. June-bearing growers also appreciated the ability to harvest the fruit while it was raining. The second best reason for everbearing growers was increased yield. But the

survey found that June-bearing varieties, typically grown in single-bay structures, didn’t justify the expense of high tunnels. Many everbearing growers indicated plans to increase tunneled acreage. Most everbearing growers reported payback in two to three years thanks to a longer harvest season, increased yields and a higher percentage of marketable fruit with a longer shelf life.

back their tunnel acreage. “The number of growers planning to increase their acreage significantly outpaced those planning to decrease acreage,” Demchak says. In Philadelphia, growers saw tunnel yields two to four times the average. “When you’ve got them in a tunnel, you’ve really got them in an optimal

growing season for 50% of the time,” Demchak notes. “We get a higher yield that first year and it will go up from there.” The optimal growing condition means plants grow faster and larger. Disease diminishes significantly and harvests come two to three weeks earlier. “Keep a minimum of seven feet between rows,” notes Demchak. “Plants will

get away from you. We use a simple support trellis or like a V row. We’re finding generally if [a variety] works good in the field, it’s good for a tunnel in your area. We never had anything do worse in a tunnel.”

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